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Problem Description
-------------------
On a Windows machine I built gdbserver, configured for the target
'x86_64-w64-mingw32', then on a GNU/Linux machine I built GDB with
support for all target (--enable-targets=all).
On the Windows machine I start gdbserver with a small test binary:
$ gdbserver 192.168.129.25:54321 C:\some\directory\executable.exe
On the GNU/Linux machine I start GDB without the test binary, and
connect to gdbserver.
As I have not given GDB the test binary, my expectation is that GDB
would connect to gdbserver and then download the file over the remote
protocol, but instead I was presented with this message:
(gdb) target remote 192.168.129.25:54321
Remote debugging using 192.168.129.25:54321
warning: C:\some\directory\executable.exe: No such file or directory.
0x00007ffa3e1e1741 in ?? ()
(gdb)
What I found is that if I told GDB where to find the binary, like
this:
(gdb) file target:C:/some/directory/executable.exe
A program is being debugged already.
Are you sure you want to change the file? (y or n) y
Reading C:/some/directory/executable.exe from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
Reading C:/some/directory/executable.exe from remote target...
Reading symbols from target:C:/some/directory/executable.exe...
(gdb)
then GDB would download the executable.
The Actual Issue
----------------
I tracked the problem down to exec_file_find (solib.c). The remote
target was passing an absolute Windows filename (beginning with "C:/"
in this case), but in exec_file_find GDB was failing the
IS_TARGET_ABSOLUTE_PATH call, and so was treating the filename as
relative.
The IS_TARGET_ABSOLUTE_PATH call was failing because GDB thought that
the file system kind was "unix", and as the filename didn't start with
a "/" it assumed the filename was not absolute.
But I'm connecting to a Windows target and 'target-file-system-kind'
was set to "auto", so GDB should be figuring out that the target
file-system is "dos-based".
Looking in effective_target_file_system_kind (filesystem.c), we find
that the logic of "auto" is delegated to the current gdbarch. However
in windows-tdep.c we see:
set_gdbarch_has_dos_based_file_system (gdbarch, 1);
So if we are using a Windows gdbarch we should have "dos-based"
filesystems. What this means is that after connecting to the remote
target GDB has selected the wrong gdbarch.
What's happening is that the target description sent back by the
remote target only includes the x86-64 registers. There's no
information about which OS we're on. As a consequence, GDB picks the
first x86-64 gdbarch which can handle the provided register set, which
happens to be a GNU/Linux gdbarch.
And indeed, there doesn't appear to be anywhere in gdbserver that sets
the osabi on the target descriptions. Some target descriptions do have
their osabi set when the description is created, e.g. in:
gdb/arch/amd64.c - Sets GNU/Linux osabi when appropriate.
gdb/arch/i386.c - Likewise.
gdb/arch/tic6x.c - Always set GNU/Linux osabi.
There are also some cases in gdb/features/*.c where the tdesc is set,
but these locations are only called from GDB, not from gdbserver.
This means that many target descriptions are created without an osabi,
gdbserver does nothing to fix this, and the description is returned to
GDB without an osabi included. This leaves GDB having to guess what
the target osabi is, and in some cases, GDB can get this wrong.
Proposed Solution
-----------------
I propose to change init_target_desc so that it requires an gdb_osabi
to be passed in, this will then be used to set the target_desc osabi
field.
I believe that within gdbserver init_target_desc is called for every
target_desc, so this should mean that every target_desc has an
opportunity to set the osabi to something sane.
I did consider passing the osabi into the code which creates the
target_desc objects, but that would require updating far more code, as
each target has its own code for creating target descriptions.
The approach taken here requires minimal changes and forces every
user of init_target_desc to think about what the correct osabi is.
In some cases, e.g. amd64, where the osabi is already set when the
target_desc is created, the init_target_desc call will override the
current value, however, we should always be replacing it with the same
actual value. i.e. if the target_desc is created with the osabi set
to GNU/Linux, then this should only happen when gdbserver is built for
GNU/Linux, in which case the init_target_desc should also be setting
the osabi to GNU/Linux.
The Tricky Bits
---------------
Some targets, like amd64, use a features based approach for creating
target_desc objects, there's a function in arch/amd64.c which creates
a target_desc, adds features too it, and returns the new target_desc.
This target_desc is then passed to an init_target_desc call within
gdbserver. This is the easy case to handle.
Then there are other targets which instead have a fixed set of xml
files, each of which is converted into a .dat file, which is then used
to generate a .cc file, which is compiled into gdbserver. The
generated .cc file creates the target_desc object and calls
init_target_desc on it. In this case though the target description
that is sent to GDB isn't generated from the target_desc object, but
is instead the contents of the fixed xml file. For this case the
osabi which we pass to init_target_desc should match the osabi that
exists in the fixed xml file.
Luckily, in the previous commit I copied the osabi information from
the fixed xml files into the .dat files. So in this commit I have
extended regdat.sh to read the osabi from the .dat file and use it in
the generated init_target_desc call.
The problem with some of these .dat base targets is that their fixed
xml files don't currently contain any osabi information, and the file
names don't indicate that they are Linux only (despite them currently
only being used from gdbserver for Linux targets), so I don't
currently feel confident adding any osabi information to these files.
An example would be features/rs6000/powerpc-64.xml. For now I've just
ignored these cases. The init_target_desc will use GDB_OSABI_UNKNOWN
which is the default. This means that for these targets nothing
changes from the current behaviour. But many other targets do now
pass the osabi back. Targets that do pass the osabi back are
improved with this commit.
Conclusion
----------
Now when I connect to the Windows remote the target description
returned includes the osabi name. With this extra information GDB
selects the correct gdbarch object, which means that GDB understands
the target has a "dos-based" file-system. With that correct GDB
understands that the filename it was given is absolute, and so fetches
the file from the remote as we'd like.
Reviewed-By: Kevin Buettner <kevinb@redhat.com>
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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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This function doesn't seem so useful, use `process_info::pid` directly
instead.
Change-Id: I55d592f38b32a197957ed4c569993cd23a818cb4
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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This function doesn't seem so useful, use `thread_info::id::pid`
directly instead.
Change-Id: I7450c4223e5b0bf66788eeb5b070ab6f5287f798
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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This function doesn't seem so useful. Use `thread_info::id::lwp`
directly.
Change-Id: Ib4a86eeeee6c1342bc1c092f083589ce28009be1
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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This function doesn't seem so useful. Use `thread_info::id` directly.
Change-Id: I158cd06a752badd30f68424e329aa42d275e43b7
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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This function doesn't seem so useful. Use `thread_info::id` directly.
Change-Id: I4ae4e7baa44e09704631a1c3a5a66e5b8b5a3594
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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I think it just makes things more obscure. Use `thread_info::id`
directly instead.
Change-Id: I141d5fb08ebf45c13cc32c4bba62773249fcb356
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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Remove the `get_thread_process` function, use `thread_info::process`
instead.
In `server.cc`, use `current_process ()` instead of going through the
current thread.
Change-Id: Ifc61d65852e392d154b854a45d45df584ab3922e
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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Same idea as the previous patch, but for `remove_thread`.
Change-Id: I7e227655be5fcf29a3256e8389eb32051f27882d
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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Since thread_info objects are now basically children of process_info
objects, I think that makes sense.
Change-Id: I7f0a67b921b468e512851cb2f36015d1003412d7
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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In a few spots, we need to get to a process from a thread. Having a
backlink from thread to process is cheap and makes the operation
trivial, add it.
Change-Id: I8a94b2919494b1dcaf954de2246386794308aa82
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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Remove this overload, prefer to use `process_info::for_each_thread`. In
many instances, the `process_info` is already available, so this saves a
map lookup. In other instances, add the `process_info` lookup at the
call site.
In `linux-arm-low.cc` and `win32-i386-low.cc`, use `current_process ()`
instead of `current_thread->id.pid ()`. I presume that if
`current_process ()` and `current_thread` don't match, it's a bug
orthogonal to this change.
Change-Id: I751ed497cb1f313cf937b35125151bee9316fc51
Reviewed-By: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
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Replace the servers global thread list with a process specific thread
list and a ptid -> thread map similar to 'inferior::ptid_thread_map' on
GDB side. Optimize the 'find_thread' and 'find_thread_ptid' functions
to use std::unordered_map::find for faster lookup of threads without
iterating over all processes and threads, if applicable. This becomes
important when debugging applications with a large thread count, e.g.,
in the context of GPU debugging.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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This patch replaces the 'std::list' type of 'all_processes' and
'all_threads' with the more lightweight 'owning_intrusive_list'
type.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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clangd reports gdbsupport/common-gdbthread.h as unused in gdbthread.h,
which seems right, so remove it. Add it to two files that need it, but
were relying on the now-removed include.
Change-Id: I12916a044d0b15f346c4ad0e6527ce99a6d460e4
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Remove newlines after return type in declarations.
Change-Id: I00c6f35e063024cf6674d532454b67e6d0d98a19
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Remove the templated versions of 'find_thread', 'for_each_thread' and
'find_thread_in_random' and replace the template function argument with
'gdb::function_view'. The usage of 'gdb::function_view' produces less
cryptic messages on errors and documents well the types of the
parameters taken by the callback and its return type.
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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As gdbreplay communicates with GDB, it outputs all the remote
protocol communication it reads from the remotelogfile to stderr.
This patch disables this behavior by default but adds the new
--debug-logging option which turns printing the packets
to stderr on again.
The motivation for this change is to make it possible to use
gdbreplay with TCL tests. Printing the whole remotelog file out
seems to overflow the expect cache wich causes gdbreplay to not
to get the packet its expects and results in going out of sync
with GDB. Other motivation is making communication between GDB
and gdbreplay faster as printing bigger remotelogfile takes
considerable amount of time.
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
Approved-By: Tom Tromey <tom@tromey.com>
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Approved-By: Tom Tromey <tom@tromey.com>
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Add handling of '.' in gdb/contrib/spellcheck.sh.
While we're at, simplify the sed invocation by using a single s command
instead of 3 s commands.
Also introduce sed_join and grep_join.
Fix the following common misspellings:
...
bandwith -> bandwidth
emmitted -> emitted
immediatly -> immediately
suprize -> surprise
thru -> through
transfered -> transferred
...
Verified with shellcheck.
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The last use of init_registers_arm_with_neon was removed in this
commit:
commit 7cc17433020a62935e4d91053251fe900d83c7f0
Date: Fri Jul 19 15:04:48 2019 +0100
Arm: Use read_description funcs in gdbserver
But the declaration was left around. Remove the declaration now.
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This reverts commit 98bcde5e268ea7cd54186c5f2c27c65103218fc3. This
commit was causing build problems on at least sparc, ppc, and s390,
though I suspect some other targets might be impacted too.
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On a Windows machine I built gdbserver, configured for the target
'x86_64-w64-mingw32', then on a GNU/Linux machine I built GDB with
support for all target (--enable-targets=all).
On the Windows machine I start gdbserver with a small test binary:
$ gdbserver 192.168.129.25:54321 C:\some\directory\executable.exe
On the GNU/Linux machine I start GDB without the test binary, and
connect to gdbserver.
As I have not given GDB the test binary, my expectation is that GDB
would connect to gdbserver and then download the file over the remote
protocol, but instead I was presented with this message:
(gdb) target remote 192.168.129.25:54321
Remote debugging using 192.168.129.25:54321
warning: C:\some\directory\executable.exe: No such file or directory.
0x00007ffa3e1e1741 in ?? ()
(gdb)
What I found is that if I told GDB where to find the binary, like
this:
(gdb) file target:C:/some/directory/executable.exe
A program is being debugged already.
Are you sure you want to change the file? (y or n) y
Reading C:/some/directory/executable.exe from remote target...
warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.
Reading C:/some/directory/executable.exe from remote target...
Reading symbols from target:C:/some/directory/executable.exe...
(gdb)
then GDB would download the executable.
I eventually tracked the problem down to exec_file_find (solib.c).
The remote target was passing an absolute Windows filename (beginning
with "C:/" in this case), but in exec_file_find GDB was failing the
IS_TARGET_ABSOLUTE_PATH call, and so was treating the filename as
relative.
The IS_TARGET_ABSOLUTE_PATH call was failing because GDB thought that
the file system kind was "unix", and as the filename didn't start with
a "/" it assumed the filename was not absolute.
But I'm connecting to a Windows target, my 'target-file-system-kind'
was set to "auto", so should be figuring out that my file-system is
"dos-based".
Looking in effective_target_file_system_kind (filesystem.c), we find
that the logic of "auto" is delegated to the current gdbarch. However
in windows-tdep.c we see:
set_gdbarch_has_dos_based_file_system (gdbarch, 1);
So if we are using a Windows gdbarch we should have "dos-based"
filesystems. What this means is that after connecting to the remote
target GDB has selected the wrong gdbarch.
What's happening is that the target description sent back by the
remote target only includes the x86-64 registers. There's no
information about which OS we're on. As a consequence, GDB picks the
first x86-64 gdbarch which can handle the provided register set, which
happens to be a GNU/Linux gdbarch.
And indeed, there doesn't appear to be anywhere in gdbserver that sets
the osabi on the target descriptions, though some target descriptions
do have their osabi set when the description is created, e.g. in:
gdb/arch/amd64.c - Sets GNU/Linux osabi when appropriate.
gdb/arch/i386.c - Likewise.
gdb/arch/tic6x.c - Always set GNU/Linux osabi.
Most target descriptions are created without an osabi, gdbserver does
nothing to fix this, and the description is returned to GDB without an
osabi included.
I propose that we always set the osabi name on the target descriptions
returned from gdbserver. We could try to do this when the description
is first created, but that would mean passing extra flags into the
tdesc creation code (or just passing the osabi string in), and I don't
think that's really necessary. If we consider the tdesc creation as
being about figuring out which registers are on the target, then it
makes sense that the osabi information is injected later.
So what I've done is require the osabi name to be passed to the
init_target_desc function. This is called, I believe, for all
targets, in the gdbserver code.
Now when I connect to the Windows remote the target description
returned includes the osabi name. With this extra information GDB
selects the correct gdbarch object, which means that GDB understands
the target has a "dos-based" file-system. With that correct GDB
understands that the filename it was given is absolute, and so fetches
the file from the remote as we'd like.
Approved-By: Luis Machado <luis.machado@arm.com>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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There is a single declaration of set_tdesc_osabi that is shared
between gdbserver/ and gdb/, this declaration takes a 'const char *'
argument which is the string representing an osabi.
Then in gdb/ we have an overload of set_tdesc_osabi which takes an
'enum gdb_osabi'.
In this commit I change the shared set_tdesc_osabi to be the version
which takes an 'enum gdb_osabi', and I remove the version which takes
a 'const char *'. All users of set_tdesc_osabi are updated to pass an
'enum gdb_osabi'.
The features/ code, which is generated from the xml files, requires a
new function to be added to osabi.{c,h} which can return a string
representation of an 'enum gdb_osabi'. With that new function in
place the features/ code is regenerated.
This change is being made to support the next commit. In the next
commit gdbserver will be updated to call set_tdesc_osabi in more
cases. The problem is that gdbserver stores the osabi as a string.
The issue here is that a typo in the gdbserver/ code might go
unnoticed and result in gdbserver sending back an invalid osabi
string.
To fix this we want gdbserver to pass an 'enum gdb_osabi' to the
set_tdesc_osabi function. With that requirement in place it seems to
make sense if all calls to set_tdesc_osabi pass an 'enum gdb_osabi'.
There should be no user visible changes after this commit.
Approved-By: Luis Machado <luis.machado@arm.com>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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Convert target_desc::arch and target_desc::osabi from 'const char*' to
gdb::unique_xmalloc_ptr<char>. This also allows us to remove the user
defined ~target_desc destructor.
I doubt it ever actually occurred, but in theory at least, there was a
memory leak in set_tdesc_architecture and set_tdesc_osabi where the
member variables were assigned without freeing any previous
value... but I suspect that usually these fields are only set once.
There should be no user visible changes after this commit.
Approved-By: Tom Tromey <tom@tromey.com>
Approved-By: Simon Marchi <simon.marchi@efficios.com>
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Add two more separators in spellcheck.sh: colon and comma.
Doing so triggers the "inbetween->between" rule, which gives an incorrect
result. Override this with "inbetween->between, in between, in-between" [1],
in a new file gdb/contrib/common-misspellings.txt.
Fix the following common misspellings:
...
everytime -> every time
sucess -> success
thru -> through
transfered -> transferred
inbetween -> between, in between, in-between
...
Verified with spellcheck.sh. Tested on x86_64-linux.
[1] https://www.grammarly.com/blog/commonly-confused-words/in-between-or-inbetween/
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Fix the following common misspellings:
...
accidently -> accidentally
additonal -> additional
addresing -> addressing
adress -> address
agaisnt -> against
albiet -> albeit
arbitary -> arbitrary
artifical -> artificial
auxillary -> auxiliary
auxilliary -> auxiliary
bcak -> back
begining -> beginning
cannonical -> canonical
compatiblity -> compatibility
completetion -> completion
diferent -> different
emited -> emitted
emiting -> emitting
emmitted -> emitted
everytime -> every time
excercise -> exercise
existance -> existence
fucntion -> function
funtion -> function
guarentee -> guarantee
htis -> this
immediatly -> immediately
layed -> laid
noone -> no one
occurances -> occurrences
occured -> occurred
originaly -> originally
preceeded -> preceded
preceeds -> precedes
propogate -> propagate
publically -> publicly
refering -> referring
substract -> subtract
substracting -> subtracting
substraction -> subtraction
taht -> that
targetting -> targeting
teh -> the
thier -> their
thru -> through
transfered -> transferred
transfering -> transferring
upto -> up to
vincinity -> vicinity
whcih -> which
whereever -> wherever
wierd -> weird
withing -> within
writen -> written
wtih -> with
doesnt -> doesn't
...
Tested on x86_64-linux.
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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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Since this commit:
commit a8651ef51822f91ec86d0d5caffbf2e50b174c23
CommitDate: Fri Jun 14 14:47:38 2024 +0100
gdb/aarch64: prevent crash from in process agent
gdbserver isn't sending expedited registers with its stop reply packets
anymore. The problem is with how the constructor of the
expedited_registers std::vector is called:
The intent of the expedited_registers initialization in
aarch64_linux_read_description is to create a vector with capacity for 6
elements, but that's not how the std::vector constructor works.
Instead it creates a vector pre-populated with 6 elements initialized
with the default value for the type of the elements, and thus the first
6 elements are null pointers. The actual expedited registers are added
starting at the 7th element.
This causes init_target_desc to consider that the expedite_regs list is
empty, since it stops checking at the first nullptr element. The end
result is that gdbserver doesn't send any expedited registers to GDB in
its stop replies.
Fix by not specifying an element count when declaring the vector.
Tested for regressions on aarch64-linux-gnu native-extended-remote.
Approved-By: Andrew Burgess <aburgess@redhat.com>
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Currently, gdbserver hangs after stdin is closed while it tries to
write: "Remote side has terminated connection. GDBserver will reopen
the connection." This hang disappears if --once is also given. Since
the stdin connection won't ever reopen if it's closed, it's safe to
assume --once is desired.
The gdb.server/server-pipe.exp test was also updated to reflect this
change. There is now a second disconnect at the end of the proc,
with a tighter-than-normal timeout to catch if the command hangs as
it used to.
Co-Authored-By: Guinevere Larsen <blarsen@redhat.com>
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29796
Approved-By: Andrew Burgess <aburgess@redhat.com>
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By default GDB will be printing the hex payload of the ptwrite package as
auxiliary information. To customize this, the user can register a ptwrite
filter function in python, that takes the payload and the PC as arguments and
returns a string which will be printed instead. Registering the filter
function is done using a factory pattern to make per-thread filtering easier.
Approved-By: Markus Metzger <markus.t.metzger@intel.com>
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This enables gdb and gdbserver to communicate about ptwrite support. If
ptwrite support would be enabled unconditionally, GDBs with older libipt
versions would break.
Approved-By: Markus Metzger <markus.t.metzger@intel.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>
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Now that all known uses of VLAs within GDB are removed, remove the
`-Wno-vla-cxx-extension` (which was used to silence clang warnings) and
add `-Wvla`, such that any use of a VLA will trigger a warning.
Change-Id: I69a8d7f93f973743165b0ba46f9c2ea8adb89025
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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On an aarch64-linux system with 32-bit userland running in a chroot, and using
target board unix/mthumb I get:
...
(gdb) hbreak hbreak.c:27^M
Hardware assisted breakpoint 2 at 0x4004e2: file hbreak.c, line 27.^M
(gdb) PASS: gdb.base/hbreak.exp: hbreak
continue^M
Continuing.^M
Unexpected error setting breakpoint: Invalid argument.^M
(gdb) XFAIL: gdb.base/hbreak.exp: continue to break-at-exit after hbreak
...
due to this call in arm_linux_nat_target::low_prepare_to_resume:
...
if (ptrace (PTRACE_SETHBPREGS, pid,
(PTRACE_TYPE_ARG3) ((i << 1) + 1), &bpts[i].address) < 0)
perror_with_name (_("Unexpected error setting breakpoint"));
...
This problem does not happen if instead we use a 4-byte aligned address.
This may or may not be a kernel bug.
Work around this by first using an inoffensive address bpts[i].address & ~0x7.
Likewise in arm_target::low_prepare_to_resume, which fixes the same fail on
target board native-gdbserver/mthumb.
While we're at it:
- use arm_hwbp_control_is_initialized in
arm_linux_nat_target::low_prepare_to_resume,
- handle the !arm_hwbp_control_is_initialized case explicitly,
- add missing '_()' in arm_target::low_prepare_to_resume,
- make error messages identical between arm_target::low_prepare_to_resume and
arm_linux_nat_target::low_prepare_to_resume,
- factor out sethbpregs_hwbp_address and sethbpregs_hwbp_control to
make the implementation more readable.
Remove the tentative xfail added in d0af16d5a10 ("[gdb/testsuite] Add xfail in
gdb.base/hbreak.exp") by simply reverting the commit.
Tested on arm-linux.
Approved-By: Luis Machado <luis.machado@arm.com>
Tested-By: Luis Machado <luis.machado@arm.com>
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After the previous two commits, this commit adds support for the
vFile::stat packet to gdbserver. This is pretty similar to the
handling for vFile::fstat, but instead calls 'lstat'.
There's still no users of target_fileio_stat in GDB, that will come in
a later commit.
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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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Add two overloads of gdb_abspath, one which takes std::string and one
which takes gdb::unique_xmalloc_ptr<char>, then 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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This reverts commit e874cbd3879843a83e4bcc4b54cd7107387b1df6.
The patch was wrong. LIBINTL_DEP is needed with an in-tree gettext.
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The intl directory in the source no longer exists. LIBINTL_DEP is
thus always empty. Remove references to it.
config/
* gettext-sister.m4: Don't AC_SUBST LIBINTL_DEP.
bfd/
* Makefile.in: Regenerate.
* configure: Regenerate.
binutils/
* Makefile.am (*_DEPENDENCIES): Remove LIBINTL_DEP.
* Makefile.in: Regenerate.
* configure: Regenerate.
gas/
* Makefile.am (as_new_DEPENDENCIES): Remove LIBINTL_DEP.
* Makefile.in: Regenerate.
* configure: Regenerate.
gdb/
* Makefile.in (INTL_DEPS): Don't set or reference.
* configure: Regenerate.
gdbserver/
* Makefile.in (INTL_DEPS): Don't set or reference.
gdbsupport/
* Makefile.in: Regenerate.
* configure: Regenerate.
gold/
* Makefile.am (deps_var): Remove LIBINTL_DEP.
(incremental_dump_DEPENDENCIES, dwp_DEPENDENCIES): Likewise.
* Makefile.in: Regenerate.
* configure: Regenerate.
* testsuite/Makefile.am (DEPENDENCIES): Remove LIBINTL_DEP.
* testsuite/Makefile.in: Regenerate.
gprof/
* Makefile.am (gprof_DEPENDENCIES): Remove LIBINTL_DEP.
* Makefile.in: Regenerate.
* configure: Regenerate.
ld/
* Makefile.am (ld_new_DEPENDENCIES): Remove LIBINTL_DEP.
* Makefile.in: Regenerate.
* configure: Regenerate.
libctf/
* Makefile.in: Regenerate.
* configure: Regenerate.
opcodes/
* configure.ac (BUILD_LIBS): Remove LIBINTL.
(BUILD_LIB_DEPS): Remove LIBINTL_DEP.
* Makefile.in: Regenerate.
* configure: Regenerate.
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Since this commit:
commit 0ee6b1c511c0e2a6793568692d2e5418cd6bc10d
Date: Wed May 18 13:32:04 2022 -0700
Use aarch64_features to describe register features in target descriptions.
There has been an issue with how aarch64 target descriptions are
cached within gdbserver, and specifically, how this caching impacts
the in process agent (IPA).
The function initialize_tracepoint_ftlib (gdbserver/tracepoint.cc) is
part of the IPA, this function is a constructor function, i.e. is
called as part of the global initialisation process. We can't
guarantee the ordering of when this function is called vs when other
global state is initialised.
Now initialize_tracepoint_ftlib calls initialize_tracepoint, which
calls initialize_low_tracepoint, which for aarch64 calls
aarch64_linux_read_description.
The aarch64_linux_read_description function lives in
linux-aarch64-tdesc.cc and after the above commit, depends on a
std::unordered_map having been initialized.
Prior to the above commit aarch64_linux_read_description used a global
C style array, which obviously requires no runtime initialization.
The consequence of the above is that any inferior linked with the IPA
(for aarch64) will experience undefined behaviour (access to an
uninitialized std::unordered_map) during startup, which for me
manifests as a segfault.
I propose fixing this by moving the std::unordered_map into the
function body, but leaving it static. The map will now be initialized
the first time the function is called, which removes the undefiend
behaviour.
The same problem exists for the expedited_registers global, however
this global can just be made into a function local instead. The
expedited_registers variable is used to build a pointer list which is
then passed to init_target_desc, however init_target_desc copies the
values it is given so expedited_registers does not need to live longer
than its containing function.
On most of the AArch64 machines I have access too tracing is not
supported, and so the gdb.trace/*.exp tests that use the IPA just exit
early reporting unsupported. I've added a test which links an
inferior with the IPA and just starts the inferior. No tracing is
performed. This exposes the current issue even on hosts that don't
support tracing. After this patch the test passes.
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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 the
gdb/arch/ directory and combine them so we have just a single copy of
each. Then GDB, gdbserver, and the in-process-agent (IPA) will link
against these shared functions.
One 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, there 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.
An alternative approach that avoids adding x86_linux_post_init_tdesc
would be to have x86_linux_tdesc_for_tid return a non-const target
description, then in x86_target::low_arch_setup we could inspect the
target description to figure out if it is 64-bit or not, and modify
the target description as needed. In the end I think that adding the
x86_linux_post_init_tdesc function is the simpler solution.
The contents of gdbserver/linux-x86-low.cc have moved to
gdb/arch/x86-linux-tdesc-features.c, and gdbserver/linux-x86-tdesc.h
has moved to gdb/arch/x86-linux-tdesc-features.h, this change leads to
some updates in the #includes in the gdbserver/ directory.
This commit also changes how target descriptions are cached.
Previously both GDB and gdbserver used static C-style arrays to act as
the tdesc cache. This was fine, except for two problems. Either the
C-style arrays would need to be placed in x86-linux-tdesc-features.c,
which would allow us to use the x86_linux_*_tdesc_count_1() functions
to size the arrays for us, or we'd need to hard code the array sizes
using separate #defines, which we'd then have to keep in sync with the
rest of the code in x86-linux-tdesc-features.c.
Given both of these problems I decided a better solution would be to
just switch to using a std::unordered_map to act as the cache. This
will resize automatically, and we can use the xcr0 value as the key.
At first inspection, using xcr0 might seem to be a problem; after all
the {i386,amd64}_create_target_description functions take more than
just the xcr0 value. However, this patch is only for x86/Linux
targets, and for x86/Linux all of the other flags passed to the tdesc
creation functions have constant values and so are irrelevant when we
consider tdesc caching.
For testing I've done the following:
- Built on x86-64 GNU/Linux for all targets, and just for the native
target,
- Build on i386 GNU/Linux for all targets, and just for the native
target,
- Build on a 64-bit, non-x86 GNU/Linux for all targets, just for the
native target, and for targets x86_64-*-linux and i386-*-linux.
Approved-By: Felix Willgerodt <felix.willgerodt@intel.com>
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This commit is part of a series which aims to share more of the target
description creation between GDB and gdbserver for x86/Linux.
After some refactoring earlier in this series the shared
x86_linux_tdesc_for_tid function was added into nat/x86-linux-tdesc.c.
However, this function still relies on amd64_linux_read_description
and i386_linux_read_description which are implemented separately for
both gdbserver and GDB. Given that at their core, all these functions
do is:
1. take an xcr0 value as input,
2. mask out some feature bits,
3. look for a cached pre-generated target description and return it
if found,
4. if no cached target description is found then call either
amd64_create_target_description or
i386_create_target_description to create a new target
description, which is then added to the cache. Return the newly
created target description.
The inner functions amd64_create_target_description and
i386_create_target_description are already shared between GDB and
gdbserver (in the gdb/arch/ directory), so the only thing that
the *_read_description functions really do is add the caching layer,
and it feels like this really could be shared.
However, we have a small problem.
Despite using the same {amd64,i386}_create_target_description
functions in both GDB and gdbserver to create the target descriptions,
on the gdbserver side we cache target descriptions based on a reduced
set of xcr0 feature bits.
What this means is that, in theory, different xcr0 values can map to
the same cache entry, which could result in the wrong target
description being used.
However, I'm not sure if this can actually happen in reality. Within
gdbserver we already split the target description cache based on i386,
amd64, and x32. I suspect within a given gdbserver session we'll only
see at most one target description for each of these.
The cache conflicting problem is caused by xcr0_to_tdesc_idx, which
maps an xcr0 value to a enum x86_linux_tdesc value, and there are only
7 usable values in enum x86_linux_tdesc.
In contrast, on the GDB side there are 64, 32, and 16 cache slots for
i386, amd64, and x32 respectively.
On the GDB side it is much more important to cache things correctly as
a single GDB session might connect to multiple different remote
targets, each of which might have slightly different x86
architectures.
And so, if we want to merge the target description caching between GDB
and gdbserver, then we need to first update gdbserver so that it
caches in the same way as GDB, that is, it needs to adopt a mechanism
that allows for the same number of cache slots of each of i386, amd64,
and x32. In this way, when the caching is shared, GDB's behaviour
will not change.
Unfortunately it's a little more complex than that due to the in
process agent (IPA).
When the IPA is in use, gdbserver sends a target description index to
the IPA, and the IPA uses this to find the correct target description
to use, the IPA having first generated every possible target
description.
Interestingly, there is certainly a bug here which results from only
having 7 values in enum x86_linux_tdesc. As multiple possible target
descriptions in gdbserver map to the same enum x86_linux_tdesc value,
then, when the enum x86_linux_tdesc value is sent to the IPA there is
no way for gdbserver to know that the IPA will select the correct
target description. This bug will get fixed by this commit.
** START OF AN ASIDE **
Back in the day I suspect this approach of sending a target
description index made perfect sense. However since this commit:
commit a8806230241d201f808d856eaae4d44088117b0c
Date: Thu Dec 7 17:07:01 2017 +0000
Initialize target description early in IPA
I think that passing an index was probably a bad idea.
We used to pass the index, and then use that index to lookup which
target description to instantiate and use, the target description was
not generated until the index arrived.
However, the above commit fixed an issue where we can't call malloc()
within (certain parts of) the IPA (apparently), so instead we now
pre-compute _every_ possible target description within the IPA. The
index is only used to lookup which of the (many) pre-computed target
descriptions to use.
It would (I think) have been easier all around if the IPA just
self-inspected, figured out its own xcr0 value, and used that to
create the one target description that is required. So long as the
xcr0 to target description code is shared (at compile time) with
gdbserver, then we can be sure that the IPA will derive the same
target description as gdbserver, and we would avoid all this index
passing business, which has made this commit so very, very painful.
I did look at how a process might derive its own xcr0 value, but I
don't believe this is actually that simple, so for now I've just
doubled down on the index passing approach.
While reviewing earlier iterations of this patch there has been
discussion about the possibility of removing the IPA from GDB. That
would certainly make all of the code touched in this patch much
simpler, but I don't really want to do that as part of this series.
** END OF AN ASIDE **
Currently then for x86/linux, gdbserver sends a number between 0 and 7
to the IPA, and the IPA uses this to create a target description.
However, I am proposing that gdbserver should now create one of (up
to) 64 different target descriptions for i386, so this 0 to 7 index
isn't going to be good enough any more (amd64 and x32 have slightly
fewer possible target descriptions, but still more than 8, so the
problem is the same).
For a while I wondered if I was going to have to try and find some
backward compatible solution for this mess. But after seeing how
lightly the IPA is actually documented, I wonder if it is not the case
that there is a tight coupling between a version of gdbserver and a
version of the IPA? At least I'm hoping so, and that's what I've
assumed in this commit.
In this commit I have thrown out the old IPA target description index
numbering scheme, and switched to a completely new numbering scheme.
Instead of the index that is passed being arbitrary, the index is
instead calculated from the set of xcr0 features that are present on
the target. Within the IPA we can then reverse this logic to recreate
the xcr0 value based on the index, and from the xcr0 value we can
choose the correct target description.
With the gdbserver to IPA numbering scheme issue resolved I have then
update the gdbserver versions of amd64_linux_read_description and
i386_linux_read_description so that they cache target descriptions
using the same set of xcr0 features as GDB itself.
After this gdbserver should now always come up with the same target
description as GDB does on any x86/Linux target.
This commit does not introduce any new code sharing between GDB and
gdbserver as previous commits in this series have done. Instead this
commit is all about bringing GDB and gdbserver into alignment
functionally so that the next commit(s) can merge the GDB and
gdbserver versions of these functions.
Notes On The Implementation
---------------------------
Previously, within gdbserver, target descriptions were cached within
arrays. These arrays were sized based on enum x86_linux_tdesc and
xcr0_to_tdesc_idx returned the array (cache) index.
Now we need different array lengths for each of i386, amd64, and x32.
And the index to use within each array is calculated based on which
xcr0 bits are set and valid for a particular target type.
I really wanted to avoid having fixed array sizes, or having the set
of relevant xcr0 bits encoded in multiple places.
The solution I came up with was to create a single data structure
which would contain a list of xcr0 bits along with flags to indicate
which of the i386, amd64, and x32 targets the bit is relevant for. By
making the table constexpr, and adding some constexpr helper
functions, it is possible to calculate the sizes for the cache arrays
at compile time, as well as the bit masks needed to each target type.
During review it was pointed out[1] that possibly the failure to check
the SSE and X87 bits for amd64/x32 targets might be an error, however,
if this is the case then this is an issue that existed long before
this patch. I'd really like to keep this patch focused on reworking
the existing code and try to avoid changing how target descriptions
are actually created, mostly out of fear that I'll break something.
[1] https://inbox.sourceware.org/gdb-patches/MN2PR11MB4566070607318EE7E669A5E28E1B2@MN2PR11MB4566.namprd11.prod.outlook.com
Approved-By: John Baldwin <jhb@FreeBSD.org>
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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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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This commit is part of a series that aims to share more of the x86
target description reading/generation code between GDB and gdbserver.
There are a huge number of similarities between the code in
gdbserver's x86_linux_read_description function and GDB's
x86_linux_nat_target::read_description function, and it is this
similarity that I plan, in a later commit, to share between GDB and
gdbserver.
However, one thing that is different in x86_linux_read_description is
the code inside the '!use_xml' block. This is the code that handles
the case where gdbserver is not allowed to send an XML target
description back to GDB. In this case gdbserver uses some predefined,
fixed, target descriptions.
First, it's worth noting that I suspect this code is not tested any
more. I couldn't find anything in the testsuite that tries to disable
XML target description support. And the idea of having a single
"fixed" target description really doesn't work well when we think
about all the various x86 extensions that exist. Part of me would
like to rip out the no-xml support in gdbserver (at least for x86),
and if a GDB connects that doesn't support XML target descriptions,
gdbserver can just give an error and drop the connection. GDB has
supported XML target descriptions for 16 years now, I think it would
be reasonable for our shipped gdbserver to drop support for the old
way of doing things.
Anyway.... this commit doesn't do that.
What I did notice was that, over time, the '!use_xml' block appears to
have "drifted" within the x86_linux_read_description function; it's
now not the first check we do. Instead we make some ptrace calls and
return a target description generated based on the result of these
ptrace calls. Surely it only makes sense to generate variable target
descriptions if we can send these back to GDB?
So in this commit I propose to move the '!use_xml' block earlier in
the x86_linux_read_description function.
The benefit of this is that this leaves the later half of
x86_linux_read_description much more similar to the GDB function
x86_linux_nat_target::read_description and sets us up for potentially
sharing code between GDB and gdbserver in a later commit.
Approved-By: John Baldwin <jhb@FreeBSD.org>
Approved-By: Felix Willgerodt <felix.willgerodt@intel.com>
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