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This changes linux-procfs.c to use gdb:unordered_set.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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Fix typos:
...
exising ==> existing
afer ==> after
...
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The maximum number of load/store watchpoints and fetch instruction
watchpoints is 14 each according to LoongArch Reference Manual [1],
so extend the maximum number of hardware watchpoints from 8 to 14.
A new struct user_watch_state_v2 was added into uapi in the related
kernel commit 531936dee53e ("LoongArch: Extend the maximum number of
watchpoints") [2], but there may be no struct user_watch_state_v2 in
the system header in time. Modify the struct loongarch_user_watch_state
in GDB which is same with the uapi struct user_watch_state_v2.
As far as I can tell, the only users for this struct in the userspace
are GDB and LLDB, there are no any problems of software compatibility
between the application and kernel according to the analysis.
The compatibility problem has been considered while developing and
testing. When the applications in the userspace get watchpoint state,
the length will be specified which is no bigger than the sizeof struct
user_watch_state or user_watch_state_v2, the actual length is assigned
as the minimal value of the application and kernel in the generic code
of ptrace:
kernel/ptrace.c: ptrace_regset():
kiov->iov_len = min(kiov->iov_len,
(__kernel_size_t) (regset->n * regset->size));
if (req == PTRACE_GETREGSET)
return copy_regset_to_user(task, view, regset_no, 0,
kiov->iov_len, kiov->iov_base);
else
return copy_regset_from_user(task, view, regset_no, 0,
kiov->iov_len, kiov->iov_base);
For example, there are four kind of combinations, all of them work well.
(1) "older kernel + older app", the actual length is 8+(8+8+4+4)*8=200;
(2) "newer kernel + newer app", the actual length is 8+(8+8+4+4)*14=344;
(3) "older kernel + newer app", the actual length is 8+(8+8+4+4)*8=200;
(4) "newer kernel + older app", the actual length is 8+(8+8+4+4)*8=200.
BTW, LLDB also made this change in the related commit ff79d83caeee
("[LLDB][LoongArch] Extend the maximum number of watchpoints") [3]
[1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=531936dee53e
[3] https://github.com/llvm/llvm-project/commit/ff79d83caeee
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
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I (Andrew Burgess) have taken this patch from this series:
https://inbox.sourceware.org/gdb-patches/20211022071933.3478427-1-m.weghorn@posteo.de/
I started off reviewing that series, but wanted to explore some
alternative strategies for solving the problems this series addresses.
However, this patch I think is super useful, so I've taken it mostly
as it was in the original series.
I have made a few minor cleanups, and I've also added some more tests.
Any bugs should be considered mine (Andrew's), but I've left the
original author (Michael Weghorn) in place as the GDB side changes are
mostly their work.
The function execv_argv::init_for_no_shell (gdb/nat/fork-inferior.c),
is passed a single string ALLARGS containing all of the inferior
arguments, and contains some custom code for splitting this argument
string into a vector of separate arguments. This function is used
when startup-with-shell is off (which is not the default).
The algorithm in this function was just splitting on whitespace
characters, and ignoring any quoting, so for example:
(gdb) set startup-with-shell off
(gdb) set args "first arg" second_arg
would result in three arguments ("first), (arg"), and (second_arg)
being passed to the inferior (the parenthesis are not part of the
parsed arguments).
This commit replaces this custom argument splitting with a use of the
existing gdb_argv class (which uses the libiberty buildargv function).
This does a better job of supporting quoting and escaping, so for the
example given above we now pass two arguments (first arg)
and (second_arg), which is certainly what I would have expected as a
GDB user.
This commit changes the 'execv_argv' class accordingly and drops the
optimization to have all the 'char *' in 'm_argv' point to a single
string rather than allocating a separate string for each arg. This is
needed because we are now going to be stripping some escaping from the
arguments, for example:
(gdb) set startup-with-shell off
(gdb) set args "literal \$"
In this case we will pass the single argument (literal $) to the
inferior, the escaping backslash will be removed. This might seem
strange as usually the backslash would be stripped by the shell, and
now we have no shell. However, I think the consistent behaviour is a
good thing; whether we start with a shell or not the escaping will be
removed.
Using gdb_argv will mean that quote characters are also stripped. If
we consider the first example again:
(gdb) set startup-with-shell off
(gdb) set args "first arg" second_arg
This is now going to pass (first arg) and (second_arg), the quotes
have been removed. If the user did want the original behaviour then
they are going to have to now do this:
(gdb) set startup-with-shell off
(gdb) set args \"first arg\" second_arg
or they could do this:
(gdb) set startup-with-shell off
(gdb) set args '"first' 'arg"' second_arg
This commit also extends the three tests that cover inferior argument
passing to cover the case where 'startup-with-shell' is off. All of
these new tests pass for native targets, but there are still problems
when using remote targets.
The remote target problems arise because of how escaping is handled
while passing arguments to remote targets. I have a larger series
that aims to address this issue:
https://inbox.sourceware.org/gdb-patches/cover.1730731085.git.aburgess@redhat.com
This patch was originally part of that series, but getting a 14 patch
series reviewed is not easy, so I've pulled this patch out on its own
for now, and the new tests are (rather crudely) disabled for remote
targets.
My hope is to work through my 14 patch series posting all of the
patches in smaller groups, which will hopefully make reviewing
easier. As more of that series gets merged, the remote argument
handling will improve, before, eventually, no tests will need to be
disabled.
Co-Authored-By: Andrew Burgess <aburgess@redhat.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28392
Tested-By: Guinevere Larsen <guinevere@redhat.com>
Reviewed-By: Keith Seitz <keiths@redhat.com>
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loongarch_stopped_data_address() is a common function and will be used by
gdb and gdbserver, so move its definition from gdb/loongarch-linux-nat.c
to gdb/nat/loongarch-hw-point.c. This is preparation for later gdbserver
patch on LoongArch and is no effect for the current code.
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
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loongarch_{get,remove}_debug_reg_state() are used as helper functions
by loongarch_linux_nat_target. We should move their definitions from
gdb/nat/loongarch-linux-hw-point.c to gdb/loongarch-linux-nat.c.
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
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loongarch_lookup_debug_reg_state() is a unused function, so we
can remove it.
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
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The regcache_register_size function has one implementation in GDB, and
one in gdbserver. Both of them have a gdb::checked_static_cast to their
corresponding regcache class. This can be avoided by defining a
pure virtual register_size method in the
reg_buffer_common class, which is then implemented by the reg_buffer
class in GDB, and by the regcache class in gdbserver.
Calls to the register_size () function from methods of classes in the
reg_buffer_common hierarchy need to be changed to calls to the newly
defined method, otherwise the compiler complains that a matching method
cannot be found.
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Change-Id: I7f4f74a51e96c42604374e87321ca0e569bc07a3
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This patch is the result of running check-include-guards.py on the
current tree. Running it a second time causes no changes.
Reviewed-By: Tom de Vries <tdevries@suse.de>
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Currently we have duplicate code for each place where
windows_thread_info::context is touched, since for WOW64 processes
it has to do the equivalent with wow64_context instead.
For example this code...:
#ifdef __x86_64__
if (windows_process.wow64_process)
{
th->wow64_context.ContextFlags = WOW64_CONTEXT_ALL;
CHECK (Wow64GetThreadContext (th->h, &th->wow64_context));
...
}
else
#endif
{
th->context.ContextFlags = CONTEXT_DEBUGGER_DR;
CHECK (GetThreadContext (th->h, &th->context));
...
}
...changes to look like this instead:
windows_process.with_context (th, [&] (auto *context)
{
context->ContextFlags = WindowsContext<decltype(context)>::all;
CHECK (get_thread_context (th->h, context));
...
}
The actual choice if context or wow64_context are used, is handled by
this new function in windows_process_info:
template<typename Function>
auto with_context (windows_thread_info *th, Function function)
{
#ifdef __x86_64__
if (wow64_process)
return function (th != nullptr ? th->wow64_context : nullptr);
else
#endif
return function (th != nullptr ? th->context : nullptr);
}
The other parts to make this work are the templated WindowsContext class
which give the appropriate ContextFlags for both types.
And there are also overloaded helper functions, like in the case of
get_thread_context here, call either GetThreadContext or
Wow64GetThreadContext.
According git log --stat, this results in 120 lines less code.
Approved-By: Tom Tromey <tom@tromey.com>
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In commit 18d2988e5da ("gdb, gdbserver, gdbsupport: remove includes of early
headers") all includes of gdbsupport/common-defs.h where removed, but
commit c1cdee0e2c1 ("gdb: LoongArch: Add support for hardware watchpoint")
reintroduced some.
Fix this by removing them.
Tested by doing this on x86_64-linux:
...
$ make \
nat/loongarch-hw-point.o \
nat/loongarch-linux.o \
nat/loongarch-linux-hw-point.o
CXX nat/loongarch-hw-point.o
CXX nat/loongarch-linux.o
CXX nat/loongarch-linux-hw-point.o
...
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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Use gdb::waitpid instead of plain waitpid, making sure that EINTR is handled.
Tested on x86_64-linux.
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We have gdb::handle_eintr, which allows us to rewrite:
...
ssize_t ret;
do
{
errno = 0;
ret = ::write (pipe[1], "+", 1);
}
while (ret == -1 && errno == EINTR);
...
into:
...
ssize_t ret = gdb::handle_eintr (-1, ::write, pipe[1], "+", 1);
...
However, the call to write got a bit mangled, requiring effort to decode it
back to its original form.
Instead, add a new function gdb::write that allows us to write:
...
ssize_t ret = gdb::write (pipe[1], "+", 1);
...
Likewise for waitpid, read and close.
Tested on x86_64-linux.
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Run gdb/contrib/spellcheck.sh on directories gdb*.
Fix typo:
...
unkown -> unknown
...
Tested on x86_64-linux.
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In gdb/aarch64-linux-tdep.c we find:
...
gdb::byte_vector za_zeroed (za_bytes, 0);
regcache->raw_supply (tdep->sme_za_regnum, za_zeroed);
...
We can't use reg_buffer::raw_supply_zeroed here because only part of the
register is written.
Add raw_supply_part_zeroed, and use it instead.
Likewise elsewhere in AArch64 tdep code.
Tested on aarch64-linux.
Approved-By: Luis Machado <luis.machado@arm.com>
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GDB deprecated the commands "show/set mpx bound" in GDB 15.1, as Intel
listed Intel(R) Memory Protection Extensions (MPX) as removed in 2019.
MPX is also deprecated in gcc (since v9.1), the linux kernel (since v5.6)
and glibc (since v2.35). Let's now remove MPX support in GDB completely.
This includes the removal of:
- MPX functionality including register support
- deprecated mpx commands
- i386 and amd64 implementation of the hooks report_signal_info and
get_siginfo_type
- tests
- and pretty printer.
We keep MPX register numbers to not break compatibility with old gdbservers.
Approved-By: Felix Willgerodt <felix.willgerodt@intel.com>
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Event tracing allows GDB to show information about interesting asynchronous
events when tracing with Intel PT. Subsequent patches will add support for
displaying each type of event.
Enabling event-tracing unconditionally would result in rather noisy output, as
breakpoints themselves result in interrupt events. Which is why this patch adds
a set/show command to allow the user to enable/disable event-tracing before
starting a recording. The event-tracing setting has no effect on an already
active recording. The default setting is off. As event tracing will use the
auxiliary infrastructure added by ptwrite, the user can still disable printing
events, even when event-tracing was enabled, by using the /a switch for the
record instruction-history/function-call-history commands.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Markus Metzger <markus.t.metzger@intel.com>
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Enable ptwrite in the PT config, if it is supported by the kernel.
Approved-By: Markus Metzger <markus.t.metzger@intel.com>
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Remove uses of VLAs, replace with gdb::byte_vector. There might be more
in files that I can't compile, but it's difficult to tell without
actually compiling on all platforms.
Many thanks to the Linaro pre-commit CI for helping find some problems
with an earlier iteration of this patch.
Change-Id: I3e5e34fcac51f3e6b732bb801c77944e010b162e
Reviewed-by: Keith Seitz <keiths@redhat.com>
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This commit moves aarch64_linux_memtag_matches_p,
aarch64_linux_set_memtags, aarch64_linux_get_memtag, and
aarch64_linux_memtag_to_string hooks (plus the aarch64_mte_get_atag
function used by them), along with the setting of the memtag granule
size, from aarch64-linux-tdep.c to aarch64-tdep.c, making MTE available
on baremetal targets. Since the aarch64-linux-tdep.c layer inherits
these hooks from aarch64-tdep.c, there is no effective change for
aarch64-linux targets.
Helpers used both by aarch64-tdep.c and by aarch64-linux-tdep.c were
moved from arch/aarch64-mte-linux.{c,h} to new arch/aarch64-mte.{c,h}
files.
Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Tested-By: Luis Machado <luis.machado@arm.com>
Approved-By: Luis Machado <luis.machado@arm.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
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C++ 11 has a built-in attribute for this, no need to use a compat macro.
Change-Id: I90e4220d26e8f3949d91761f8a13cd9c37da3875
Reviewed-by: Lancelot Six <lancelot.six@amd.com>
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Like the previous commit, add two overloads of gdb_tilde_expand, one
takes std::string and other takes gdb::unique_xmalloc_ptr<char>. Make
use of these overloads throughout GDB and gdbserver.
There should be no user visible changes after this commit.
Approved-By: Tom Tromey <tom@tromey.com>
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LoongArch defines hardware watchpoint functions for fetch operations.
After the software configures the watchpoints for fetch, the processor
hardware will monitor the access addresses of the fetch operations and
trigger a watchpoint exception when the watchpoint setting conditions
are met.
Hardware watchpoints for fetch operations is used to implement hardware
breakpoint function on LoongArch. Refer to the following document for
hardware breakpoint.
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints
A simple test is as follows:
lihui@bogon:~$ cat test.c
#include <stdio.h>
int a = 0;
int main()
{
printf("start test\n");
a = 1;
printf("a = %d\n", a);
printf("end test\n");
return 0;
}
lihui@bogon:~$ gcc -g test.c -o test
without this patch:
lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5 printf("start test\n");
(gdb) hbreak 8
No hardware breakpoint support in the target.
with this patch:
lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5 printf("start test\n");
(gdb) hbreak 8
Hardware assisted breakpoint 2 at 0x1200006ec: file test.c, line 8.
(gdb) c
Continuing.
start test
a = 1
Breakpoint 2, main () at test.c:8
8 printf("end test\n");
(gdb) c
Continuing.
end test
[Inferior 1 (process 25378) exited normally]
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
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LoongArch defines hardware watchpoint functions for load/store
operations. After the software configures the watchpoints for
load/store, the processor hardware will monitor the access
addresses of the load/store operations and trigger watchpoint
exception when the watchpoint setting conditions are met.
After this patch, watch/rwatch/awatch command are supported. Refer to the
following document for hardware watchpoint.
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html#control-and-status-registers-related-to-watchpoints
A simple test is as follows:
lihui@bogon:~$ cat test.c
#include <stdio.h>
int a = 0;
int main()
{
printf("start test\n");
a = 1;
printf("a = %d\n", a);
printf("end test\n");
return 0;
}
lihui@bogon:~$ gcc -g test.c -o test
without this patch:
lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5 printf("start test\n");
(gdb) awatch a
Target does not support this type of hardware watchpoint.
...
with this patch:
lihui@bogon:~$ gdb test
...
(gdb) start
...
Temporary breakpoint 1, main () at test.c:5
5 printf("start test\n");
(gdb) awatch a
Hardware access (read/write) watchpoint 2: a
(gdb) c
Continuing.
start test
Hardware access (read/write) watchpoint 2: a
Old value = 0
New value = 1
main () at test.c:7
7 printf("a = %d\n", a);
(gdb) c
Continuing.
Hardware access (read/write) watchpoint 2: a
Value = 1
0x00000001200006e0 in main () at test.c:7
7 printf("a = %d\n", a);
(gdb) c
Continuing.
a = 1
end test
[Inferior 1 (process 22250) exited normally]
Signed-off-by: Hui Li <lihui@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
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After the x86 target description changes that I committed recently,
the first commit in the series being:
commit 8a29222b85f28a2201db50a34ac4144f961311db
Date: Sat Jan 27 10:40:35 2024 +0000
gdb/gdbserver: share I386_LINUX_XSAVE_XCR0_OFFSET definition
and the last commit in the series being:
commit 646d754d14c2fe70a492a893506a74b0463b6ae8
Author: Andrew Burgess <aburgess@redhat.com>
Date: Tue Jan 30 15:37:23 2024 +0000
gdb/gdbserver: share x86/linux tdesc caching
The sourceware buildbot highlighted a regression on i386. On the GDB
side we'd see this:
Remote debugging using :54321
warning: Architecture rejected target-supplied description
Remote connection closed
(gdb)
while on the gdbserver side we'd see this:
$ ./gdbserver/gdbserver --once :54321 ~/empty
Process /srv/aburgess/empty created; pid = 31406
Listening on port 54321
Remote debugging from host ::1, port 39488
../../src/gdbserver/regcache.cc:272: A problem internal to GDBserver has been detected.
Unknown register st0 requested
Aborted (core dumped)
When I tried to reproduce this regression on my local i386 VM the
issue would not reproduce.
I eventually tracked the problem down to x86_linux_tdesc_for_tid in
gdb/nat/x86-linux-tdesc.c. In this function we have this line:
/* Check if PTRACE_GETREGSET works. */
if (ptrace (PTRACE_GETREGSET, tid,
(unsigned int) NT_X86_XSTATE, &iov) < 0)
{
... handle failure ...
}
else
{
... handle success ...
}
The problem is that on my VM the PTRACE_GETREGSET feature is
supported, while on sourceware's buildbot machine this feature is not
supported.
I did a quick search and it seems like the 'xsave' feature in
/proc/cpuinfo might be the indicator for whether PTRACE_GETREGSET is
supported or not, and indeed my machine has the 'xsave' feature while
the sourceware machine does not.
The point of divergence then is this ptrace call, on my machine the
call succeeds and we extract the xcr0 value from the iov vector, while
on the sourceware machine the ptrace call fails and we use a default
xcr0 value of 0.
This xcr0 value is then passed to i386_linux_read_description at the
end of x86_linux_tdesc_for_tid.
In gdb/arch/i386-linux-tdesc.c we find i386_linux_read_description
which does some caching but calls i386_create_target_description to
actually create the target descriptions when needed. The xcr0 value
is masked to only the bits that are interesting, but given a value of
0 we'll just pass 0 through to i386_create_target_description.
In gdb/arch/i386.c we find i386_create_target_description which checks
the xcr0 bits and builds the target description. What we can see is
that if no bits are set in the xcr0 value then no features will be
added to the created target description. This featureless target
description is then transmitted back to GDB, which is then rejected
due to lack of essential core registers.
So, how did things work prior to the above commit series? There are
three places of interest, on the GDB side there is
x86_linux_nat_target::read_description and
i386_linux_core_read_description. Then on the gdbserver side there is
x86_linux_read_description.
All of these locations have a call to i386_linux_read_description
followed by a check if the return value was nullptr. If we do get
back nullptr then we perform another call to
i386_linux_read_description with a default xcr0 value.
Looking in i386_linux_read_description we see a specific check for
xcr0 being 0 in which case we return nullptr.
And so, prior to the above series, if xcr0 was 0 due to
PTRACE_GETREGSET being unavailable we'd use a default xcr0 value.
After the above series this is no longer the case, the 'xcr0 == 0'
check has been removed from i386_linux_read_description and the
calling code is streamlined to remove the use of default xcr0 values.
The fix I propose here is to setup the default xcr0 value at the point
where we find that PTRACE_GETREGSET is unavailable. The default value
used is X86_XSTATE_SSE_MASK. This is the default used in
x86_linux_nat_target::read_description (for GDB) and in
x86_linux_read_description (for gdbserver). The above commit series
already fixed i386_linux_core_read_description to ensure that the
correct default xcr0 value was used, this case is a little special in
that it uses different defaults depending on which sections are
present in the core file, so that case always needed to be handled
differently.
The choice of X86_XSTATE_SSE_MASK corresponds to the default used for
i386 before the above series was committed. This mask includes the
X87 and SSE bits only, neither of these bits are checked for on amd64
or x32, so this default doesn't change the behaviour on these targets.
By setting the default xcr0 value at this early stage we ensure that
the cached xcr0 value on the gdbserver side is correct. This is
critical as this cached xcr0 value is passed through to the in process
agent (IPA). If we leave the cached xcr0 value as 0 and apply the
defaults later in the series we also have to encode the knowledge of
the default into the IPA, this just means we have the default encoded
in multiple locations, which seems like a bad idea. The approach used
in this patch means the default is present in just one location.
This commit should fix the i386 regressions seen on the sourceware
buildbot.
In addition to the fix in nat/x86-linux-tdesc.c I've also fixed the
layout of the declaration of x86_linux_tdesc_for_tid in the header
file.
Approved-By: Felix Willgerodt <felix.willgerodt@intel.com>
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This commit is part of a series to share more of the x86 target
description creation code between GDB and gdbserver.
Unlike previous commits which were mostly refactoring, this commit is
the first that makes a real change, though that change should mostly
be for gdbserver; I've largely adopted the "GDB" way of doing things
for gdbserver, and this fixes a real gdbserver bug.
On a x86-64 Linux target, running the test:
gdb.server/connect-with-no-symbol-file.exp
results in two core files being created. Both of these core files are
from the inferior process, created after gdbserver has detached.
In this test a gdbserver process is started and then, after gdbserver
has started, but before GDB attaches, we either delete the inferior
executable, or change its permissions so it can't be read. Only after
doing this do we attempt to connect with GDB.
As GDB connects to gdbserver, gdbserver attempts to figure out the
target description so that it can send the description to GDB, this
involves a call to x86_linux_read_description.
In x86_linux_read_description one of the first things we do is try to
figure out if the process is 32-bit or 64-bit. To do this we look up
the executable via the thread-id, and then attempt to read the
architecture size from the executable. This isn't going to work if
the executable has been deleted, or is no longer readable.
And so, as we can't read the executable, we default to an i386 target
and use an i386 target description.
A consequence of using an i386 target description is that addresses
are assumed to be 32-bits. Here's an example session that shows the
problems this causes. This is run on an x86-64 machine, and the test
binary (xx.x) is a standard 64-bit x86-64 binary:
shell_1$ gdbserver --once localhost :54321 /tmp/xx.x
shell_2$ gdb -q
(gdb) set sysroot
(gdb) shell chmod 000 /tmp/xx.x
(gdb) target remote :54321
Remote debugging using :54321
warning: /tmp/xx.x: Permission denied.
0xf7fd3110 in ?? ()
(gdb) show architecture
The target architecture is set to "auto" (currently "i386").
(gdb) p/x $pc
$1 = 0xf7fd3110
(gdb) info proc mappings
process 2412639
Mapped address spaces:
Start Addr End Addr Size Offset Perms objfile
0x400000 0x401000 0x1000 0x0 r--p /tmp/xx.x
0x401000 0x402000 0x1000 0x1000 r-xp /tmp/xx.x
0x402000 0x403000 0x1000 0x2000 r--p /tmp/xx.x
0x403000 0x405000 0x2000 0x2000 rw-p /tmp/xx.x
0xf7fcb000 0xf7fcf000 0x4000 0x0 r--p [vvar]
0xf7fcf000 0xf7fd1000 0x2000 0x0 r-xp [vdso]
0xf7fd1000 0xf7fd3000 0x2000 0x0 r--p /usr/lib64/ld-2.30.so
0xf7fd3000 0xf7ff3000 0x20000 0x2000 r-xp /usr/lib64/ld-2.30.so
0xf7ff3000 0xf7ffb000 0x8000 0x22000 r--p /usr/lib64/ld-2.30.so
0xf7ffc000 0xf7ffe000 0x2000 0x2a000 rw-p /usr/lib64/ld-2.30.so
0xf7ffe000 0xf7fff000 0x1000 0x0 rw-p
0xfffda000 0xfffff000 0x25000 0x0 rw-p [stack]
0xff600000 0xff601000 0x1000 0x0 r-xp [vsyscall]
(gdb) info inferiors
Num Description Connection Executable
* 1 process 2412639 1 (remote :54321)
(gdb) shell cat /proc/2412639/maps
00400000-00401000 r--p 00000000 fd:03 45907133 /tmp/xx.x
00401000-00402000 r-xp 00001000 fd:03 45907133 /tmp/xx.x
00402000-00403000 r--p 00002000 fd:03 45907133 /tmp/xx.x
00403000-00405000 rw-p 00002000 fd:03 45907133 /tmp/xx.x
7ffff7fcb000-7ffff7fcf000 r--p 00000000 00:00 0 [vvar]
7ffff7fcf000-7ffff7fd1000 r-xp 00000000 00:00 0 [vdso]
7ffff7fd1000-7ffff7fd3000 r--p 00000000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7fd3000-7ffff7ff3000 r-xp 00002000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7ff3000-7ffff7ffb000 r--p 00022000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7ffc000-7ffff7ffe000 rw-p 0002a000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7ffe000-7ffff7fff000 rw-p 00000000 00:00 0
7ffffffda000-7ffffffff000 rw-p 00000000 00:00 0 [stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
(gdb)
Notice the difference between the mappings reported via GDB and those
reported directly from the kernel via /proc/PID/maps, the addresses of
every mapping is clamped to 32-bits for GDB, while the kernel reports
real 64-bit addresses.
Notice also that the $pc value is a 32-bit value. It appears to be
within one of the mappings reported by GDB, but is outside any of the
mappings reported from the kernel.
And this is where the problem arises. When gdbserver detaches from
the inferior we pass the inferior the address from which it should
resume. Due to the 32/64 bit confusion we tell the inferior to resume
from the 32-bit $pc value, which is not within any valid mapping, and
so, as soon as the inferior resumes, it segfaults.
If we look at how GDB (not gdbserver) figures out its target
description then we see an interesting difference. GDB doesn't try to
read the executable. Instead GDB uses ptrace to query the thread's
state, and uses this to figure out the if the thread is 32 or 64 bit.
If we update gdbserver to do it the "GDB" way then the above problem
is resolved, gdbserver now sees the process as 64-bit, and when we
detach from the inferior we give it the correct 64-bit address, and
the inferior no longer segfaults.
Now, I could just update the gdbserver code, but better, I think, to
share one copy of the code between GDB and gdbserver in gdb/nat/.
That is what this commit does.
The cores of x86_linux_read_description from gdbserver and
x86_linux_nat_target::read_description from GDB are moved into a new
file gdb/nat/x86-linux-tdesc.c and combined into a single function
x86_linux_tdesc_for_tid which is called from each location.
This new function does things mostly the GDB way, some changes are
needed to allow for the sharing; we now take some pointers for where
the shared code can cache the xcr0 and xsave layout values.
Another thing to note about this commit is how the functions
i386_linux_read_description and amd64_linux_read_description are
handled. For now I've left these function as implemented separately
in GDB and gdbserver. I've moved the declarations of these functions
into gdb/arch/{i386,amd64}-linux-tdesc.h, but the implementations are
left where they are.
A later commit in this series will make these functions shared too,
but doing this is not trivial, so I've left that for a separate
commit. Merging the declarations as I've done here ensures that
everyone implements the function to the same API, and once these
functions are shared (in a later commit) we'll want a shared
declaration anyway.
Reviewed-By: Felix Willgerodt <felix.willgerodt@intel.com>
Acked-By: John Baldwin <jhb@FreeBSD.org>
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This patch is part of a series that has the aim sharing the x86 Linux
target description creation code between GDB and gdbserver.
Within GDB part of this process involves reading the cs and ds state
from the 'struct user_regs_struct' using a ptrace call.
This isn't done by gdbserver, which is part of the motivation for this
whole series; the approach gdbserver takes is inferior to the approach
GDB takes (gdbserver relies on reading the file being debugged, and
extracting similar information from the file headers).
This commit moves the reading of cs and ds, which is used to figure
out if a thread is 32-bit or 64-bit (or in x32 mode), into the gdb/nat
directory so that the code can be shared with gdbserver, but at this
point I'm not actually using the code in gdbserver, that will come
later.
As such there should be no user visible changes after this commit, GDB
continues to do things as it did before (reading cs/ds), while
gdbserver continues to use its own approach (which doesn't require
reading cs/ds).
Approved-By: John Baldwin <jhb@FreeBSD.org>
Reviewed-By: Felix Willgerodt <felix.willgerodt@intel.com>
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In a later commit I want to access have_ptrace_getregset from a .c
file in the nat/ directory. To achieve this I need access to the
declaration of have_ptrace_getregset.
Currently have_ptrace_getregset is declared (and defined) twice, once
in GDB and once in gdbserver.
This commit moves the declaration into nat/linux-nat.h, but leaves the
two definitions where they are. Now, in my later commit, I can pull
in the declaration from nat/linux-nat.h.
There should be no user visible changes after this commit.
Approved-By: Felix Willgerodt <felix.willgerodt@intel.com>
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The have_ptrace_getfpxregs global tracks whether GDB or gdbserver is
running on a kernel that supports the GETFPXREGS ptrace request.
Currently this global is declared twice (once in GDB and once in
gdbserver), I think it makes sense to move this global into the nat/
directory, and have a single declaration and definition.
While moving this variable I have converted it to a tribool, as that
was what it really was, if even used the same numbering as the tribool
enum (-1, 0, 1). Where have_ptrace_getfpxregs was used I have updated
in the obvious way.
However, while making this change I noticed what I think is a bug in
x86_linux_nat_target::read_description and x86_linux_read_description,
both of these functions can be called multiple times, but in both
cases we only end up calling i386_linux_read_description the first
time through in the event that PTRACE_GETFPXREGS is not supported.
This is because initially have_ptrace_getfpxregs will be
TRIBOOL_UNKNOWN, but after the ptrace call fails we set
have_ptrace_getfpxregs to TRIBOOL_FALSE. The next time we attempt to
read the target description we'll skip the ptrace call, and so skip
the call to i386_linux_read_description.
I've not tried to address this preexisting bug in this commit, this is
purely a refactor, there should be no user visible changes after this
commit. In later commits I'll merge the gdbserver and GDB code
together into the nat/ directory, and after that I'll try to address
this bug.
Reviewed-By: Felix Willgerodt <felix.willgerodt@intel.com>
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I believe that the get_exec_file function is unnecessary, and the code
can be simplified if we remove it.
Consider for instance when you "run" a program on Linux with native
debugging.
1. run_command_1 obtains the executable file from
`current_program_space->exec_filename ()`
2. it passes it to `run_target->create_inferior()`, which is
`inf_ptrace_target::create_inferior()` in this case, which then
passes it to `fork_inferior()`
3. `fork_inferior()` then has a fallback, where if the passed exec file
is nullptr, it gets its from `get_exec_file()`.
4. `get_exec_file()` returns `current_program_space->exec_filename ()`
- just like the things we started with - or errors out if the
current program space doesn't have a specified executable.
If there's no exec filename passed in step 1, there's not going to be
any in step 4, so it seems pointless to call `get_exec_file()`, we could
just error out when `exec_file` is nullptr. But we can't error out
directly in `fork_inferior()`, since the error is GDB-specific, and that
function is shared with GDBserver.
Speaking of GDBserver, all code paths that lead to `fork_inferior()`
provide a non-nullptr exec file.
Therefore, to simplify things:
- Make `fork_inferior()` assume that the passed exec file is not
nullptr, don't call `get_exec_file()`
- Change some targets (darwin-nat, go32-nat, gnu-nat, inf-ptrace,
nto-procfs, procfs) to error out when the exec file passed to their
create_inferior method is nullptr. Some targets are fine with a
nullptr exec file, so we can't check that in `run_command_1()`.
- Add the `no_executable_specified_error()` function, which re-uses the
error message that `get_exec_file()` had.
- Change some targets (go32-nat, nto-procfs) to not call
`get_exec_file()`, since it's pointless for the same reason as in the
example above, if it returns, it's going the be the same value as the
`exec_file` parameter. Just rely on `exec_file`.
- Remove the final use of `get_exec_file()`, in `load_command()`.
- Remove the `get_exec_file()` implementations in GDB and GDBserver and
remove the shared declaration.
Change-Id: I601c16498e455f7baa1f111a179da2f6c913baa3
Approved-By: Tom Tromey <tom@tromey.com>
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`current_program_space->exec_filename ()`
Calls of `get_exec_file (0)` are equivalent to just getting the exec
filename from the current program space. I'm looking to remove
`get_exec_file`, so replace these uses with
`current_program_space->exec_filename ()`.
Remove the `err` parameter of `get_exec_wrapper` since all the calls
that remain pass 1, meaning to error out if no executable is specified.
Change-Id: I7729ea4c7f03dbb046211cc5aa3858ab3a551965
Approved-By: Tom Tromey <tom@tromey.com>
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The `fork_inferior()` function accepts multiple callbacks, making its
signature a bit hard to read. Define some type aliases to make it a bit
clearer. Use function view for all, while at it.
Change-Id: Ide8d1fa533d0c5eaf3249860f8c0d339baa09bce
Approved-By: Tom Tromey <tom@tromey.com>
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Commit 9a03f218 ("Fix gdb.base/watchpoint-unaligned.exp on aarch64")
fixed a watchpoint bug in gdb -- but did not touch the corresponding
code in gdbserver.
This patch moves the gdb code into gdb/nat, so that it can be shared
with gdbserver, and then changes gdbserver to use it, fixing the bug.
This is yet another case where having a single back end would prevent
bugs.
I tested this using the AdaCore internal gdb testsuite.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29423
Approved-By: Luis Machado <luis.machado@arm.com>
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When GDB attaches to a multi-threaded process, it calls
linux_proc_attach_tgid_threads () to go through all threads found in
/proc/PID/task/ and call attach_proc_task_lwp_callback () on each of
them. If it does that twice without the callback reporting that a new
thread was found, then it considers that all inferior threads have been
found and returns.
The problem is that the callback considers any thread that it hasn't
attached to yet as new. This causes problems if the process has one or
more zombie threads, because GDB can't attach to it and the loop will
always "find" a new thread (the zombie one), and get stuck in an
infinite loop.
This is easy to trigger (at least on aarch64-linux and powerpc64le-linux)
with the gdb.threads/attach-many-short-lived-threads.exp testcase, because
its test program constantly creates and finishes joinable threads so the
chance of having zombie threads is high.
This problem causes the following failures:
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: attach (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: no new threads (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: set breakpoint always-inserted on (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: break break_fn (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: break at break_fn: 1 (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: break at break_fn: 2 (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: break at break_fn: 3 (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: reset timer in the inferior (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: print seconds_left (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: detach (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: set breakpoint always-inserted off (timeout)
FAIL: gdb.threads/attach-many-short-lived-threads.exp: iter 8: delete all breakpoints, watchpoints, tracepoints, and catchpoints in delete_breakpoints (timeout)
ERROR: breakpoints not deleted
The iteration number is random, and all tests in the subsequent iterations
fail too, because GDB is stuck in the attach command at the beginning of
the iteration.
The solution is to make linux_proc_attach_tgid_threads () remember when it
has already processed a given LWP and skip it in the subsequent iterations.
PR testsuite/31312
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31312
Reviewed-By: Luis Machado <luis.machado@arm.com>
Approved-By: Pedro Alves <pedro@palves.net>
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The new function will be used in a subsequent patch to read a different
stat field.
The new code is believed to be equivalent to the old code, so there
should be no change in GDB behaviour. The only material change was to
use std::string and string_printf rather than a fixed char array to
build the path to the stat file.
Also, take the opportunity to move the function's documentation comment to
the header file, to conform with GDB practice.
Reviewed-By: Luis Machado <luis.machado@arm.com>
Approved-By: Pedro Alves <pedro@palves.net>
|
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The code and comment reference stat fields by made-up indexes. The
procfs(5) man page, which describes the /proc/PID/stat file, has a numbered
list of these fields so it's more convenient to use those numbers instead.
This is currently an implementation detail inside the function so it's
not really relevant with the code as-is, but a future patch will do some
refactoring which will make the index more prominent.
Therefore, make this change in a separate patch so that it's simpler to
review.
Reviewed-By: Luis Machado <luis.machado@arm.com>
Approved-By: Pedro Alves <pedro@palves.net>
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clangd tells me that the gdb_signals.h include in target/waitstatus.h is
unused. This include was probably to give access to `enum gdb_signal`,
but this is in fact defined in gdb/signals.h. Change the include to
gdb/signals.h. Include gdbsupport/gdb_signals.h in some files that were
relying on the transitive include.
Change-Id: I6f4361b3d801394bf29abe8c1393aff110aa0ad6
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It's been over 9 years (since commit faf09f0119da) since Linux GDB and
GDBserver started relying on SIGTRAP si_code to tell whether a
breakpoint triggered, which is important for non-stop mode. When that
then-new code was added, I had left the then-old code as fallback, in
case some architectured still needed it. Given AFAIK there haven't
been complaints since, this commit finally removes the fallback code,
along with USE_SIGTRAP_SIGINFO.
Change-Id: I140a5333a9fe70e90dbd186aca1f081549b2e63d
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Now that defs.h, server.h and common-defs.h are included via the
`-include` option, it is no longer necessary for source files to include
them. Remove all the inclusions of these files I could find. Update
the generation scripts where relevant.
Change-Id: Ia026cff269c1b7ae7386dd3619bc9bb6a5332837
Approved-By: Pedro Alves <pedro@palves.net>
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This reverts commit 01ed1674d4435aa4e194fd9373b7705e425ef354.
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This reverts commit 7816b81e9b36ea0f57662bfd7446b573bf0c9e54.
|
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This reverts commit cd9b374ffe372dcaf7e4c15548cf53a301d8dcdd.
|
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This reverts commit 198ff6ff819c240545f9fc68b39636fd376d4ba9.
|
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This reverts commit f4c19f89ef43dbce8065532c808e1aeb05d08994.
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This commit:
commit 198ff6ff819c240545f9fc68b39636fd376d4ba9
Date: Tue Jan 30 15:37:23 2024 +0000
gdb/gdbserver: share x86/linux tdesc caching
added some functions which are always defined, but their use is
guarded within various #ifdef blocks. As a result we were seeing
errors about defined, but unused, functions.
I've fixed this problem in this commit by wrapping the function
definitions within #ifdef blocks.
I'm a little worried that there might be too many #ifdef blocks within
this file, however, I'm going to commit this fix for now as this will
fix the build, then I'll think about if there's a better way to split
this file so we might avoid some of these #ifdef blocks.
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This commit builds on the previous series of commits to share the
target description caching code between GDB and gdbserver for
x86/Linux targets.
The objective of this commit is to move the four functions (2 each of)
i386_linux_read_description and amd64_linux_read_description into
gdb/nat/x86-linux-tdesc.c and combine them so we have just a single
copy of each. Then both GDB and gdbserver will link against these
shared functions.
It is worth reading the description of the previous commit to see why
this merging is not as simple as it seems: on the gdbserver side we
actually have two users of these functions, gdbserver itself, and the
in process agent (IPA).
However, the previous commit streamlined the gdbserver code, and so
now it is simple to move the two functions along with all their
support functions from the gdbserver directory into the gdb/nat/
directory, and then GDB is fine to call these functions.
One small curiosity with this patch is the function
x86_linux_post_init_tdesc. On the gdbserver side the two functions
amd64_linux_read_description and i386_linux_read_description have some
functionality that is not present on the GDB side, that is some
additional configuration that is performed as each target description
is created to setup the expedited registers.
To support this I've added the function x86_linux_post_init_tdesc.
This function is called from the two *_linux_read_description
functions, but is implemented separately for GDB and gdbserver.
This does mean adding back some non-shared code when this whole series
has been about sharing code, but now the only non-shared bit is the
single line that is actually different between GDB and gdbserver, all
the rest, which is identical, is now shared.
I did need to add a new rule to the gdbserver Makefile, this is to
allow the nat/x86-linux-tdesc.c file to be compiled for the IPA.
Approved-By: John Baldwin <jhb@FreeBSD.org>
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This commit is part of a series to share more of the x86 target
description creation code between GDB and gdbserver.
Unlike previous commits which were mostly refactoring, this commit is
the first that makes a real change, though that change should mostly
be for gdbserver; I've largely adopted the "GDB" way of doing things
for gdbserver, and this fixes a real gdbserver bug.
On a x86-64 Linux target, running the test:
gdb.server/connect-with-no-symbol-file.exp
results in two core files being created. Both of these core files are
from the inferior process, created after gdbserver has detached.
In this test a gdbserver process is started and then, after gdbserver
has started, but before GDB attaches, we either delete the inferior
executable, or change its permissions so it can't be read. Only after
doing this do we attempt to connect with GDB.
As GDB connects to gdbserver, gdbserver attempts to figure out the
target description so that it can send the description to GDB, this
involves a call to x86_linux_read_description.
In x86_linux_read_description one of the first things we do is try to
figure out if the process is 32-bit or 64-bit. To do this we look up
the executable via the thread-id, and then attempt to read the
architecture size from the executable. This isn't going to work if
the executable has been deleted, or is no longer readable.
And so, as we can't read the executable, we default to an i386 target
and use an i386 target description.
A consequence of using an i386 target description is that addresses
are assumed to be 32-bits. Here's an example session that shows the
problems this causes. This is run on an x86-64 machine, and the test
binary (xx.x) is a standard 64-bit x86-64 binary:
shell_1$ gdbserver --once localhost :54321 /tmp/xx.x
shell_2$ gdb -q
(gdb) set sysroot
(gdb) shell chmod 000 /tmp/xx.x
(gdb) target remote :54321
Remote debugging using :54321
warning: /tmp/xx.x: Permission denied.
0xf7fd3110 in ?? ()
(gdb) show architecture
The target architecture is set to "auto" (currently "i386").
(gdb) p/x $pc
$1 = 0xf7fd3110
(gdb) info proc mappings
process 2412639
Mapped address spaces:
Start Addr End Addr Size Offset Perms objfile
0x400000 0x401000 0x1000 0x0 r--p /tmp/xx.x
0x401000 0x402000 0x1000 0x1000 r-xp /tmp/xx.x
0x402000 0x403000 0x1000 0x2000 r--p /tmp/xx.x
0x403000 0x405000 0x2000 0x2000 rw-p /tmp/xx.x
0xf7fcb000 0xf7fcf000 0x4000 0x0 r--p [vvar]
0xf7fcf000 0xf7fd1000 0x2000 0x0 r-xp [vdso]
0xf7fd1000 0xf7fd3000 0x2000 0x0 r--p /usr/lib64/ld-2.30.so
0xf7fd3000 0xf7ff3000 0x20000 0x2000 r-xp /usr/lib64/ld-2.30.so
0xf7ff3000 0xf7ffb000 0x8000 0x22000 r--p /usr/lib64/ld-2.30.so
0xf7ffc000 0xf7ffe000 0x2000 0x2a000 rw-p /usr/lib64/ld-2.30.so
0xf7ffe000 0xf7fff000 0x1000 0x0 rw-p
0xfffda000 0xfffff000 0x25000 0x0 rw-p [stack]
0xff600000 0xff601000 0x1000 0x0 r-xp [vsyscall]
(gdb) info inferiors
Num Description Connection Executable
* 1 process 2412639 1 (remote :54321)
(gdb) shell cat /proc/2412639/maps
00400000-00401000 r--p 00000000 fd:03 45907133 /tmp/xx.x
00401000-00402000 r-xp 00001000 fd:03 45907133 /tmp/xx.x
00402000-00403000 r--p 00002000 fd:03 45907133 /tmp/xx.x
00403000-00405000 rw-p 00002000 fd:03 45907133 /tmp/xx.x
7ffff7fcb000-7ffff7fcf000 r--p 00000000 00:00 0 [vvar]
7ffff7fcf000-7ffff7fd1000 r-xp 00000000 00:00 0 [vdso]
7ffff7fd1000-7ffff7fd3000 r--p 00000000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7fd3000-7ffff7ff3000 r-xp 00002000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7ff3000-7ffff7ffb000 r--p 00022000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7ffc000-7ffff7ffe000 rw-p 0002a000 fd:00 143904 /usr/lib64/ld-2.30.so
7ffff7ffe000-7ffff7fff000 rw-p 00000000 00:00 0
7ffffffda000-7ffffffff000 rw-p 00000000 00:00 0 [stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
(gdb)
Notice the difference between the mappings reported via GDB and those
reported directly from the kernel via /proc/PID/maps, the addresses of
every mapping is clamped to 32-bits for GDB, while the kernel reports
real 64-bit addresses.
Notice also that the $pc value is a 32-bit value. It appears to be
within one of the mappings reported by GDB, but is outside any of the
mappings reported from the kernel.
And this is where the problem arises. When gdbserver detaches from
the inferior we pass the inferior the address from which it should
resume. Due to the 32/64 bit confusion we tell the inferior to resume
from the 32-bit $pc value, which is not within any valid mapping, and
so, as soon as the inferior resumes, it segfaults.
If we look at how GDB (not gdbserver) figures out its target
description then we see an interesting difference. GDB doesn't try to
read the executable. Instead GDB uses ptrace to query the thread's
state, and uses this to figure out the if the thread is 32 or 64 bit.
If we update gdbserver to do it the "GDB" way then the above problem
is resolved, gdbserver now sees the process as 64-bit, and when we
detach from the inferior we give it the correct 64-bit address, and
the inferior no longer segfaults.
Now, I could just update the gdbserver code, but better, I think, to
share one copy of the code between GDB and gdbserver in gdb/nat/.
That is what this commit does.
The cores of x86_linux_read_description from gdbserver and
x86_linux_nat_target::read_description from GDB are moved into a new
file gdb/nat/x86-linux-tdesc.c and combined into a single function
x86_linux_tdesc_for_tid which is called from each location.
This new function does things the GDB way, the only changes are to
allow for the sharing; we now have a callback function to call the
first time that the xcr0 state is read, this allows for GDB and
gdbserver to perform their own initialisation as needed, and
additionally, the new function takes a pointer for where to cache the
xcr0 value, this isn't needed for this commit, but will be useful in a
later commit where gdbserver will want to read this cached xcr0
value.
Another thing to note about this commit is how the functions
i386_linux_read_description and amd64_linux_read_description are
handled. For now I've left these function as implemented separately
in GDB and gdbserver. I've moved the declarations of these functions
into gdb/nat/x86-linux-tdesc.h, but the implementations are left as
separate.
A later commit in this series will make these functions shared too,
but doing this is not trivial, so I've left that for a separate
commit. Merging the declarations as I've done here ensures that
everyone implements the function to the same API, and once these
functions are shared (in a later commit) we'll want a shared
declaration anyway.
Approved-By: John Baldwin <jhb@FreeBSD.org>
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Share the definition of I386_LINUX_XSAVE_XCR0_OFFSET between GDB and
gdbserver.
This commit is part of a series that aims to share more of the x86
target description creation code between GDB and gdbserver. The
I386_LINUX_XSAVE_XCR0_OFFSET #define is used as part of the target
description creation, and I noticed that this constant is defined
separately for GDB and gdbserver.
This commit moves the definition into gdb/nat/x86-linux.h, which
allows the #define to be shared.
There should be no user visible changes after this commit.
Approved-By: John Baldwin <jhb@FreeBSD.org>
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This patch is part of a series that has the aim of making the code
that, for x86, reads the target description for a native process
shared between GDB and gdbserver.
Within GDB part of this process involves reading the cs and ds state
from the 'struct user_regs_struct' using a ptrace call.
This isn't done by gdbserver, which is part of the motivation for this
whole series; the approach gdbserver takes is inferior to the approach
GDB takes.
This commit moves the reading of cs and ds, which is used to figure
out if a thread is 32-bit or 64-bit (or in x32 mode), into the gdb/nat
directory so that the code could be shared with gdbserver, but at this
point I'm not actually using the code in gdbserver, that will come
later.
As such there should be no user visible changes after this commit, GDB
continues to do things as it did before (reading cs/ds), while
gdbserver continues to use its own approach (which doesn't require
reading cs/ds).
Approved-By: John Baldwin <jhb@FreeBSD.org>
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On aarch64-linux, with test-case gdb.base/watch-bitfields.exp I run into:
...
(gdb) continue^M
Continuing.^M
^M
Hardware watchpoint 2: -location q.a^M
^M
Old value = 1^M
New value = 0^M
main () at watch-bitfields.c:42^M
42 q.h--;^M
(gdb) FAIL: $exp: -location watch against bitfields: q.e: 0->5: continue
...
In a minimal form, if we step past line 37 which sets q.e, and we have a
watchpoint set on q.e, it triggers:
...
$ gdb -q -batch watch-bitfields -ex "b 37" -ex run -ex "watch q.e" -ex step
Breakpoint 1 at 0x410204: file watch-bitfields.c, line 37.
Breakpoint 1, main () at watch-bitfields.c:37
37 q.e = 5;
Hardware watchpoint 2: q.e
Hardware watchpoint 2: q.e
Old value = 0
New value = 5
main () at /home/vries/gdb/src/gdb/testsuite/gdb.base/watch-bitfields.c:38
38 q.f = 6;
...
However, if we set in addition a watchpoint on q.a, the watchpoint on q.e
doesn't trigger.
How does this happen?
Bitfield q.a is just bit 0 of byte 0, and bitfield q.e is bit 4..7 of byte 1
and bit 1 of byte 2. So, watch q.a should watch byte 0, and watch q.e should
watch bytes 1 and 2.
Using "maint set show-debug-regs on" (and some more detailed debug prints) we
get:
...
WP2: addr=0x440028 (orig=0x440029), ctrl=0x000000d5, ref.count=1
ctrl: enabled=1, offset=1, len=2
WP3: addr=0x440028 (orig=0x440028), ctrl=0x00000035, ref.count=1
ctrl: enabled=1, offset=0, len=1
...
which matches that.
When executing line 37, a hardware watchpoint trap triggers and we hit
aarch64_stopped_data_address with addr_trap == 0x440028:
...
(gdb) p /x addr_trap
$1 = 0x440028
....
and since the loop in aarch64_stopped_data_address walks backward, we check
WP3 first, which matches, and consequently target_stopped_by_watchpoint
returns true in watchpoints_triggered.
Likewise for target_stopped_data_address, which also returns addr == 0x440028.
Watchpoints_triggered matches watchpoint q.a to that address, and sets
watch_triggered_yes.
However, subsequently the value of q.a is checked, and it's the same value as
before (becase the insn in line 37 didn't change q.a), so the watchpoint
hardware trap is not reported to the user.
The problem originates from that fact that aarch64_stopped_data_address picked
WP3 instead of WP2.
There's something we can do about this. In the example above, both
target_stopped_by_watchpoint and target_stopped_data_address returned true.
Instead we can return true in target_stopped_by_watchpoint but false in
target_stopped_data_address. This lets watchpoints_triggered known that a
watchpoint was triggered, but we don't know where, and both watchpoints
get set to watch_triggered_unknown.
Subsequently, the values of both q.a and q.e are checked, and since q.e is not
the same value as before, the watchpoint hardware trap is reported to the user.
Note that this works well for regular (write) watchpoints (watch command), but
not for read watchpoints (rwatch command), because for those no value is
checked. Likewise for access watchpoints (awatch command).
So, fix this by:
- passing a nullptr in aarch64_fbsd_nat_target::stopped_by_watchpoint and
aarch64_linux_nat_target::stopped_by_watchpoint to make clear we're not
interested in the stop address,
- introducing a two-phase approach in aarch64_stopped_data_address, where:
- phase one handles access and read watchpoints, as before, and
- phase two handles write watchpoints, where multiple matches cause:
- return true if addr_p == null, and
- return false if addr_p != null.
Tested on aarch64-linux.
Approved-By: Luis Machado <luis.machado@arm.com>
PR tdep/31214
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31214
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