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This commit is the result of running the gdb/copyright.py script,
which automated the update of the copyright year range for all
source files managed by the GDB project to be updated to include
year 2023.
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This changes GDB to use frame_info_ptr instead of frame_info *
The substitution was done with multiple sequential `sed` commands:
sed 's/^struct frame_info;/class frame_info_ptr;/'
sed 's/struct frame_info \*/frame_info_ptr /g' - which left some
issues in a few files, that were manually fixed.
sed 's/\<frame_info \*/frame_info_ptr /g'
sed 's/frame_info_ptr $/frame_info_ptr/g' - used to remove whitespace
problems.
The changed files were then manually checked and some 'sed' changes
undone, some constructors and some gets were added, according to what
made sense, and what Tromey originally did
Co-Authored-By: Bruno Larsen <blarsen@redhat.com>
Approved-by: Tom Tomey <tom@tromey.com>
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I built GDB for all targets on a x86-64/GNU-Linux system, and
then (accidentally) passed GDB a RISC-V binary, and asked GDB to "run"
the binary on the native target. I got this error:
(gdb) show architecture
The target architecture is set to "auto" (currently "i386").
(gdb) file /tmp/hello.rv32.exe
Reading symbols from /tmp/hello.rv32.exe...
(gdb) show architecture
The target architecture is set to "auto" (currently "riscv:rv32").
(gdb) run
Starting program: /tmp/hello.rv32.exe
../../src/gdb/i387-tdep.c:596: internal-error: i387_supply_fxsave: Assertion `tdep->st0_regnum >= I386_ST0_REGNUM' failed.
What's going on here is this; initially the architecture is i386, this
is based on the default architecture, which is set based on the native
target. After loading the RISC-V executable the architecture of the
current inferior is updated based on the architecture of the
executable.
When we "run", GDB does a fork & exec, with the inferior being
controlled through ptrace. GDB sees an initial stop from the inferior
as soon as the inferior comes to life. In response to this stop GDB
ends up calling save_stop_reason (linux-nat.c), which ends up trying
to read register from the inferior, to do this we end up calling
target_ops::fetch_registers, which, for the x86-64 native target,
calls amd64_linux_nat_target::fetch_registers.
After this I eventually end up in i387_supply_fxsave, different x86
based targets will end in different functions to fetch registers, but
it doesn't really matter which function we end up in, the problem is
this line, which is repeated in many places:
i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
The problem here is that the ARCH in this line comes from the current
inferior, which, as we discussed above, will be a RISC-V gdbarch, the
tdep field will actually be of type riscv_gdbarch_tdep, not
i386_gdbarch_tdep. After this cast we are relying on undefined
behaviour, in my case I happen to trigger an assert, but this might
not always be the case.
The thing I tried that exposed this problem was of course, trying to
start an executable of the wrong architecture on a native target. I
don't think that the correct solution for this problem is to detect,
at the point of cast, that the gdbarch_tdep object is of the wrong
type, but, I did wonder, is there a way that we could protect
ourselves from incorrectly casting the gdbarch_tdep object?
I think that there is something we can do here, and this commit is the
first step in that direction, though no actual check is added by this
commit.
This commit can be split into two parts:
(1) In gdbarch.h and arch-utils.c. In these files I have modified
gdbarch_tdep (the function) so that it now takes a template argument,
like this:
template<typename TDepType>
static inline TDepType *
gdbarch_tdep (struct gdbarch *gdbarch)
{
struct gdbarch_tdep *tdep = gdbarch_tdep_1 (gdbarch);
return static_cast<TDepType *> (tdep);
}
After this change we are no better protected, but the cast is now
done within the gdbarch_tdep function rather than at the call sites,
this leads to the second, much larger change in this commit,
(2) Everywhere gdbarch_tdep is called, we make changes like this:
- i386_gdbarch_tdep *tdep = (i386_gdbarch_tdep *) gdbarch_tdep (arch);
+ i386_gdbarch_tdep *tdep = gdbarch_tdep<i386_gdbarch_tdep> (arch);
There should be no functional change after this commit.
In the next commit I will build on this change to add an assertion in
gdbarch_tdep that checks we are casting to the correct type.
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This commit started from an observation I made while working on some
other disassembler patches, that is, that the function
gdb_buffered_insn_length, is broken ... sort of.
I noticed that the gdb_buffered_insn_length function doesn't set up
the application data field if the disassemble_info structure.
Further, I noticed that some architectures, for example, ARM, require
that the application_data field be set, see gdb_print_insn_arm in
arm-tdep.c.
And so, if we ever use gdb_buffered_insn_length for ARM, then GDB will
likely crash. Which is why I said only "sort of" broken. Right now
we don't use gdb_buffered_insn_length with ARM, so maybe it isn't
broken yet?
Anyway to prove to myself that there was a problem here I extended the
disassembler self tests in disasm-selftests.c to include a test of
gdb_buffered_insn_length. As I run the test for all architectures, I
do indeed see GDB crash for ARM.
To fix this we need gdb_buffered_insn_length to create a disassembler
that inherits from gdb_disassemble_info, but we also need this new
disassembler to not print anything.
And so, I introduce a new gdb_non_printing_disassembler class, this is
a disassembler that doesn't print anything to the output stream.
I then observed that both ARC and S12Z also create non-printing
disassemblers, but these are slightly different. While the
disassembler in gdb_non_printing_disassembler reads the instruction
from a buffer, the ARC and S12Z disassemblers read from target memory
using target_read_code.
And so, I further split gdb_non_printing_disassembler into two
sub-classes, gdb_non_printing_memory_disassembler and
gdb_non_printing_buffer_disassembler.
The new selftests now pass, but otherwise, there should be no user
visible changes after this commit.
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Remove all macros related to getting and setting some symbol value:
#define SYMBOL_VALUE(symbol) (symbol)->value.ivalue
#define SYMBOL_VALUE_ADDRESS(symbol) \
#define SET_SYMBOL_VALUE_ADDRESS(symbol, new_value) \
#define SYMBOL_VALUE_BYTES(symbol) (symbol)->value.bytes
#define SYMBOL_VALUE_COMMON_BLOCK(symbol) (symbol)->value.common_block
#define SYMBOL_BLOCK_VALUE(symbol) (symbol)->value.block
#define SYMBOL_VALUE_CHAIN(symbol) (symbol)->value.chain
#define MSYMBOL_VALUE(symbol) (symbol)->value.ivalue
#define MSYMBOL_VALUE_RAW_ADDRESS(symbol) ((symbol)->value.address + 0)
#define MSYMBOL_VALUE_ADDRESS(objfile, symbol) \
#define BMSYMBOL_VALUE_ADDRESS(symbol) \
#define SET_MSYMBOL_VALUE_ADDRESS(symbol, new_value) \
#define MSYMBOL_VALUE_BYTES(symbol) (symbol)->value.bytes
#define MSYMBOL_BLOCK_VALUE(symbol) (symbol)->value.block
Replace them with equivalent methods on the appropriate objects.
Change-Id: Iafdab3b8eefc6dc2fd895aa955bf64fafc59ed50
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While working on the disassembler I was getting frustrated. Every
time I touched disasm.h it seemed like every file in GDB would need to
be rebuilt. Surely the disassembler can't be required by that many
parts of GDB, right?
Turns out that disasm.h is included in target.h, so pretty much every
file was being rebuilt!
The only thing from disasm.h that target.h needed is the
gdb_disassembly_flag enum, as this is part of the target_ops api.
In this commit I move gdb_disassembly_flag into its own file. This is
then included in target.h and disasm.h, after which, the number of
files that depend on disasm.h is much reduced.
I also audited all the other includes of disasm.h and found that the
includes in mep-tdep.c and python/py-registers.c are no longer needed,
so I've removed these.
Now, after changing disasm.h, GDB rebuilds much quicker.
There should be no user visible changes after this commit.
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This commit brings all the changes made by running gdb/copyright.py
as per GDB's Start of New Year Procedure.
For the avoidance of doubt, all changes in this commits were
performed by the script.
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I would like to be able to use non-trivial types in gdbarch_tdep types.
This is not possible at the moment (in theory), because of the one
definition rule.
To allow it, rename all gdbarch_tdep types to <arch>_gdbarch_tdep, and
make them inherit from a gdbarch_tdep base class. The inheritance is
necessary to be able to pass pointers to all these <arch>_gdbarch_tdep
objects to gdbarch_alloc, which takes a pointer to gdbarch_tdep.
These objects are never deleted through a base class pointer, so I
didn't include a virtual destructor. In the future, if gdbarch objects
deletable, I could imagine that the gdbarch_tdep objects could become
owned by the gdbarch objects, and then it would become useful to have a
virtual destructor (so that the gdbarch object can delete the owned
gdbarch_tdep object). But that's not necessary right now.
It turns out that RISC-V already has a gdbarch_tdep that is
non-default-constructible, so that provides a good motivation for this
change.
Most changes are fairly straightforward, mostly needing to add some
casts all over the place. There is however the xtensa architecture,
doing its own little weird thing to define its gdbarch_tdep. I did my
best to adapt it, but I can't test those changes.
Change-Id: Ic001903f91ddd106bd6ca09a79dabe8df2d69f3b
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The r_ldsomap field is specific to Solaris (part of librtld_db), and
should never be accessed for Linux. glibc is planning to add a field
to support multiple namespaces. But there will be no r_ldsomap when
r_version is bumped to 2. Add linux_[ilp32|lp64]_fetch_link_map_offsets
to set r_ldsomap_offset to -1 and use them for Linux targets.
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28236
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When stepping over thread-lock related codes (in uClibc), the inferior process
gets stuck and never manages to enter the critical section:
------8<-------
1 size_t fwrite(const void * __restrict ptr, size_t size,
2 size_t nmemb, register FILE * __restrict stream)
3 {
4 size_t retval;
5 __STDIO_AUTO_THREADLOCK_VAR;
6
7 > __STDIO_AUTO_THREADLOCK(stream);
8
9 retval = fwrite_unlocked(ptr, size, nmemb, stream);
10
11 __STDIO_AUTO_THREADUNLOCK(stream);
12
13 return retval;
14 }
------>8-------
Here, we are at line 7. Using the "next" command leads no where.
However, setting a breakpoint on line 9 and issuing "continue" works.
Looking at the assembly instructions reveals that we're dealing with the
critical section entry code [1] that should never be interrupted, in this
case by the debugger's implicit breakpoints:
------8<-------
...
1 add_s r0,r13,0x38
2 mov_s r3,1
3 llock r2,[r0] <-.
4 brne.nt r2,0,14 --. |
5 scond r3,[r0] | |
6 bne -10 --|--'
7 brne_s r2,0,84 <-'
...
------>8-------
Lines 3 until 5 (inclusive) are supposed to be executed atomically.
Therefore, GDB should never (implicitly) insert a breakpoint on lines
4 and 5, else the program will try to acquire the lock again by jumping
back to line 3 and gets stuck in an infinite loop.
The solution is to make GDB aware of these patterns so it inserts
breakpoints after the sequence -- line 6 in this example.
[1]
https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/tree/libc/sysdeps/linux/arc/bits/atomic.h#n46
------8<-------
({ \
__typeof(oldval) prev; \
\
__asm__ __volatile__( \
"1: llock %0, [%1] \n" \
" brne %0, %2, 2f \n" \
" scond %3, [%1] \n" \
" bnz 1b \n" \
"2: \n" \
: "=&r"(prev) \
: "r"(mem), "ir"(oldval), \
"r"(newval) /* can't be "ir". scond can't take limm for "b" */\
: "cc", "memory"); \
\
prev; \
})
------>8-------
"llock" (Load Locked) loads the 32-bit word pointed by the source
operand. If the load is completed without any interruption or
exception, the physical address is remembered, in Lock Physical Address
(LPA), and the Lock Flag (LF) is set to 1. LF is a non-architecturally
visible flag and is cleared whenever an interrupt or exception takes
place. LF is also cleared (atomically) whenever another process writes
to the LPA.
"scond" (Store Conditional) will write to the destination address if
and only if the LF is set to 1. When finished, with or without a write,
it atomically copies the LF value to ZF (Zero Flag).
These two instructions together provide the mechanism for entering a
critical section. The code snippet above comes from uClibc:
-----------------------
v3 (after Tom's remarks[2]):
handle_atomic_sequence()
- no need to initialize the std::vector with "{}"
- fix typo in comments: "conditial" -> "conditional"
- add braces to the body of "if" condition because of the comment line
arc_linux_software_single_step()
- make the performance slightly more efficient by moving a few
variables after the likely "return" point.
v2 (after Simon's remarks[3]):
- handle_atomic_sequence() gets a copy of an instruction instead of
a reference.
- handle_atomic_sequence() asserts if the given instruction is an llock.
[2]
https://sourceware.org/pipermail/gdb-patches/2021-February/175805.html
[3]
https://sourceware.org/pipermail/gdb-patches/2021-January/175487.html
gdb/ChangeLog:
PR tdep/27369
* arc-linux-tdep.c (handle_atomic_sequence): New.
(arc_linux_software_single_step): Call handle_atomic_sequence().
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This patch converts the most obvious functions from gdb/frame.h to use
the gdb::array_view abstraction. I've converted the ones that used buffer +
length.
There are others using only the buffer, with an implicit size. I did not
touch those for now. But it would be nice to pass the size for safety.
Tested with --enable-targets=all on Ubuntu 18.04/20.04 aarch64-linux.
gdb/ChangeLog
2021-01-19 Luis Machado <luis.machado@linaro.org>
* frame.h (get_frame_register_bytes): Pass a gdb::array_view instead
of buffer + length.
(put_frame_register_bytes): Likewise.
Adjust documentation.
(get_frame_memory): Pass a gdb::array_view instead of buffer + length.
(safe_frame_unwind_memory): Likewise.
* frame.c (get_frame_register_bytes, put_frame_register_bytes)
(get_frame_memory, safe_frame_unwind_memory): Adjust to use
gdb::array_view.
* amd64-fbsd-tdep.c (amd64fbsd_sigtramp_p): Likewise.
* amd64-linux-tdep.c (amd64_linux_sigtramp_start): Likewise.
* amd64-obsd-tdep.c (amd64obsd_sigtramp_p): Likewise.
* arc-linux-tdep.c (arc_linux_is_sigtramp): Likewise.
* cris-tdep.c (cris_sigtramp_start, cris_rt_sigtramp_start): Likewise.
* dwarf2/loc.c (rw_pieced_value): Likewise.
* hppa-tdep.c (hppa_frame_cache): Likewise.
* i386-fbsd-tdep.c (i386fbsd_sigtramp_p): Likewise.
* i386-gnu-tdep.c (i386_gnu_sigtramp_start): Likewise.
* i386-linux-tdep.c (i386_linux_sigtramp_start)
(i386_linux_rt_sigtramp_start): Likewise.
* i386-obsd-tdep.c (i386obsd_sigtramp_p): Likewise.
* i386-tdep.c (i386_register_to_value): Likewise.
* i387-tdep.c (i387_register_to_value): Likewise.
* ia64-tdep.c (ia64_register_to_value): Likewise.
* m32r-linux-tdep.c (m32r_linux_sigtramp_start)
(m32r_linux_rt_sigtramp_start): Likewise.
* m68k-linux-tdep.c (m68k_linux_pc_in_sigtramp): Likewise.
* m68k-tdep.c (m68k_register_to_value): Likewise.
* mips-tdep.c (mips_register_to_value)
(mips_value_to_register): Likewise.
* ppc-fbsd-tdep.c (ppcfbsd_sigtramp_frame_sniffer)
(ppcfbsd_sigtramp_frame_cache): Likewise.
* ppc-obsd-tdep.c (ppcobsd_sigtramp_frame_sniffer)
(ppcobsd_sigtramp_frame_cache): Likewise.
* rs6000-tdep.c (rs6000_in_function_epilogue_frame_p)
(rs6000_register_to_value): Likewise.
* tilegx-tdep.c (tilegx_analyze_prologue): Likewise.
* tramp-frame.c (tramp_frame_start): Likewise.
* valops.c (value_assign): Likewise.
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Add the standard arc_debug_printf, but also arc_linux_debug_printf,
arc_linux_nat_debug_printf and arc_newlib_debug_printf to match the
prefixes currently used in the debug messages.
gdb/ChangeLog:
* arc-tdep.h (arc_debug_printf): New.
* arc-tdep.c: Use arc_debug_printf.
* arc-linux-nat.c (arc_linux_nat_debug_printf): Add and use.
* arc-linux-tdep.c (arc_linux_debug_printf): Add and use.
* arc-newlib-tdep.c (arc_newlib_debug_printf): Add and use.
Change-Id: I5d937566ed7a1925f7982e8809802c8f0560d8c6
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This commits the result of running gdb/copyright.py as per our Start
of New Year procedure...
gdb/ChangeLog
Update copyright year range in copyright header of all GDB files.
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The word "regnum" in comments should be uppercase, because it
reflects a variable name in the code.
gdb/ChangeLog
* arc-linux-tdep.c: Replace "regnum" with "REGNUM" in comments.
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All the arc_linux_supply_*() target operations and the
arc_linux_collect_v2_regset() in arc-linux-tdep.c were
supplying/collecting all the registers in regcache as if the
REGNUM was set to -1.
The more efficient behavior is to examine the REGNUM and act
accordingly. That is what this patch does.
gdb/ChangeLog:
* arc-linux-tdep.c (supply_register): New.
(arc_linux_supply_gregset, arc_linux_supply_v2_regset,
arc_linux_collect_v2_regset): Consider REGNUM.
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Implement functions needed to unwind signal frames on ARC Linux targets.
gdb/ChangeLog
* arc-linux-tdep.c (arc_linux_sc_reg_offsets): New static variable.
(arc_linux_is_sigtramp): New function.
(arc_linux_sigcontext_addr): Likewise.
(arc_linux_init_osabi): Use them.
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The displaced_step_buffer class, introduced in the previous patch,
manages access to a single displaced step buffer. Change it into
displaced_step_buffers (note the plural), which manages access to
multiple displaced step buffers.
When preparing a displaced step for a thread, it looks for an unused
buffer.
For now, all users still pass a single displaced step buffer, so no real
behavior change is expected here. The following patch makes a user pass
more than one buffer, so the functionality introduced by this patch is
going to be useful in the next one.
gdb/ChangeLog:
* displaced-stepping.h (struct displaced_step_buffer): Rename
to...
(struct displaced_step_buffers): ... this.
<m_addr, m_current_thread, m_copy_insn_closure>: Remove.
<struct displaced_step_buffer>: New inner class.
<m_buffers>: New.
* displaced-stepping.c (displaced_step_buffer::prepare): Rename
to...
(displaced_step_buffers::prepare): ... this, adjust for multiple
buffers.
(displaced_step_buffer::finish): Rename to...
(displaced_step_buffers::finish): ... this, adjust for multiple
buffers.
(displaced_step_buffer::copy_insn_closure_by_addr): Rename to...
(displaced_step_buffers::copy_insn_closure_by_addr): ... this,
adjust for multiple buffers.
(displaced_step_buffer::restore_in_ptid): Rename to...
(displaced_step_buffers::restore_in_ptid): ... this, adjust for
multiple buffers.
* linux-tdep.h (linux_init_abi): Change supports_displaced_step
for num_disp_step_buffers.
* linux-tdep.c (struct linux_gdbarch_data)
<num_disp_step_buffers>: New field.
(struct linux_info) <disp_step_buf>: Rename to...
<disp_step_bufs>: ... this, change type to
displaced_step_buffers.
(linux_displaced_step_prepare): Use
linux_gdbarch_data::num_disp_step_buffers to create that number
of buffers.
(linux_displaced_step_finish): Adjust.
(linux_displaced_step_copy_insn_closure_by_addr): Adjust.
(linux_displaced_step_restore_all_in_ptid): Adjust.
(linux_init_abi): Change supports_displaced_step parameter for
num_disp_step_buffers, save it in linux_gdbarch_data.
* aarch64-linux-tdep.c (aarch64_linux_init_abi): Adjust.
* alpha-linux-tdep.c (alpha_linux_init_abi): Adjust.
* amd64-linux-tdep.c (amd64_linux_init_abi_common): Change
supports_displaced_step parameter for num_disp_step_buffers.
(amd64_linux_init_abi): Adjust.
(amd64_x32_linux_init_abi): Adjust.
* arc-linux-tdep.c (arc_linux_init_osabi): Adjust.
* arm-linux-tdep.c (arm_linux_init_abi): Adjust.
* bfin-linux-tdep.c (bfin_linux_init_abi): Adjust.
* cris-linux-tdep.c (cris_linux_init_abi): Adjust.
* csky-linux-tdep.c (csky_linux_init_abi): Adjust.
* frv-linux-tdep.c (frv_linux_init_abi): Adjust.
* hppa-linux-tdep.c (hppa_linux_init_abi): Adjust.
* i386-linux-tdep.c (i386_linux_init_abi): Adjust.
* ia64-linux-tdep.c (ia64_linux_init_abi): Adjust.
* m32r-linux-tdep.c (m32r_linux_init_abi): Adjust.
* m68k-linux-tdep.c (m68k_linux_init_abi):
* microblaze-linux-tdep.c (microblaze_linux_init_abi):
* mips-linux-tdep.c (mips_linux_init_abi): Adjust.
* mn10300-linux-tdep.c (am33_linux_init_osabi): Adjust.
* nios2-linux-tdep.c (nios2_linux_init_abi): Adjust.
* or1k-linux-tdep.c (or1k_linux_init_abi): Adjust.
* ppc-linux-tdep.c (ppc_linux_init_abi): Adjust.
* riscv-linux-tdep.c (riscv_linux_init_abi): Adjust.
* rs6000-tdep.c (struct ppc_inferior_data) <disp_step_buf>:
Change type to displaced_step_buffers.
* s390-linux-tdep.c (s390_linux_init_abi_any): Adjust.
* sh-linux-tdep.c (sh_linux_init_abi): Adjust.
* sparc-linux-tdep.c (sparc32_linux_init_abi): Adjust.
* sparc64-linux-tdep.c (sparc64_linux_init_abi): Adjust.
* tic6x-linux-tdep.c (tic6x_uclinux_init_abi): Adjust.
* tilegx-linux-tdep.c (tilegx_linux_init_abi): Adjust.
* xtensa-linux-tdep.c (xtensa_linux_init_abi): Adjust.
Change-Id: Ia9c02f207da2c9e1d9188020139619122392bb70
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displaced steps
Today, GDB only allows a single displaced stepping operation to happen
per inferior at a time. There is a single displaced stepping buffer per
inferior, whose address is fixed (obtained with
gdbarch_displaced_step_location), managed by infrun.c.
In the case of the AMD ROCm target [1] (in the context of which this
work has been done), it is typical to have thousands of threads (or
waves, in SMT terminology) executing the same code, hitting the same
breakpoint (possibly conditional) and needing to to displaced step it at
the same time. The limitation of only one displaced step executing at a
any given time becomes a real bottleneck.
To fix this bottleneck, we want to make it possible for threads of a
same inferior to execute multiple displaced steps in parallel. This
patch builds the foundation for that.
In essence, this patch moves the task of preparing a displaced step and
cleaning up after to gdbarch functions. This allows using different
schemes for allocating and managing displaced stepping buffers for
different platforms. The gdbarch decides how to assign a buffer to a
thread that needs to execute a displaced step.
On the ROCm target, we are able to allocate one displaced stepping
buffer per thread, so a thread will never have to wait to execute a
displaced step.
On Linux, the entry point of the executable if used as the displaced
stepping buffer, since we assume that this code won't get used after
startup. From what I saw (I checked with a binary generated against
glibc and musl), on AMD64 we have enough space there to fit two
displaced stepping buffers. A subsequent patch makes AMD64/Linux use
two buffers.
In addition to having multiple displaced stepping buffers, there is also
the idea of sharing displaced stepping buffers between threads. Two
threads doing displaced steps for the same PC could use the same buffer
at the same time. Two threads stepping over the same instruction (same
opcode) at two different PCs may also be able to share a displaced
stepping buffer. This is an idea for future patches, but the
architecture built by this patch is made to allow this.
Now, the implementation details. The main part of this patch is moving
the responsibility of preparing and finishing a displaced step to the
gdbarch. Before this patch, preparing a displaced step is driven by the
displaced_step_prepare_throw function. It does some calls to the
gdbarch to do some low-level operations, but the high-level logic is
there. The steps are roughly:
- Ask the gdbarch for the displaced step buffer location
- Save the existing bytes in the displaced step buffer
- Ask the gdbarch to copy the instruction into the displaced step buffer
- Set the pc of the thread to the beginning of the displaced step buffer
Similarly, the "fixup" phase, executed after the instruction was
successfully single-stepped, is driven by the infrun code (function
displaced_step_finish). The steps are roughly:
- Restore the original bytes in the displaced stepping buffer
- Ask the gdbarch to fixup the instruction result (adjust the target's
registers or memory to do as if the instruction had been executed in
its original location)
The displaced_step_inferior_state::step_thread field indicates which
thread (if any) is currently using the displaced stepping buffer, so it
is used by displaced_step_prepare_throw to check if the displaced
stepping buffer is free to use or not.
This patch defers the whole task of preparing and cleaning up after a
displaced step to the gdbarch. Two new main gdbarch methods are added,
with the following semantics:
- gdbarch_displaced_step_prepare: Prepare for the given thread to
execute a displaced step of the instruction located at its current PC.
Upon return, everything should be ready for GDB to resume the thread
(with either a single step or continue, as indicated by
gdbarch_displaced_step_hw_singlestep) to make it displaced step the
instruction.
- gdbarch_displaced_step_finish: Called when the thread stopped after
having started a displaced step. Verify if the instruction was
executed, if so apply any fixup required to compensate for the fact
that the instruction was executed at a different place than its
original pc. Release any resources that were allocated for this
displaced step. Upon return, everything should be ready for GDB to
resume the thread in its "normal" code path.
The displaced_step_prepare_throw function now pretty much just offloads
to gdbarch_displaced_step_prepare and the displaced_step_finish function
offloads to gdbarch_displaced_step_finish.
The gdbarch_displaced_step_location method is now unnecessary, so is
removed. Indeed, the core of GDB doesn't know how many displaced step
buffers there are nor where they are.
To keep the existing behavior for existing architectures, the logic that
was previously implemented in infrun.c for preparing and finishing a
displaced step is moved to displaced-stepping.c, to the
displaced_step_buffer class. Architectures are modified to implement
the new gdbarch methods using this class. The behavior is not expected
to change.
The other important change (which arises from the above) is that the
core of GDB no longer prevents concurrent displaced steps. Before this
patch, start_step_over walks the global step over chain and tries to
initiate a step over (whether it is in-line or displaced). It follows
these rules:
- if an in-line step is in progress (in any inferior), don't start any
other step over
- if a displaced step is in progress for an inferior, don't start
another displaced step for that inferior
After starting a displaced step for a given inferior, it won't start
another displaced step for that inferior.
In the new code, start_step_over simply tries to initiate step overs for
all the threads in the list. But because threads may be added back to
the global list as it iterates the global list, trying to initiate step
overs, start_step_over now starts by stealing the global queue into a
local queue and iterates on the local queue. In the typical case, each
thread will either:
- have initiated a displaced step and be resumed
- have been added back by the global step over queue by
displaced_step_prepare_throw, because the gdbarch will have returned
that there aren't enough resources (i.e. buffers) to initiate a
displaced step for that thread
Lastly, if start_step_over initiates an in-line step, it stops
iterating, and moves back whatever remaining threads it had in its local
step over queue to the global step over queue.
Two other gdbarch methods are added, to handle some slightly annoying
corner cases. They feel awkwardly specific to these cases, but I don't
see any way around them:
- gdbarch_displaced_step_copy_insn_closure_by_addr: in
arm_pc_is_thumb, arm-tdep.c wants to get the closure for a given
buffer address.
- gdbarch_displaced_step_restore_all_in_ptid: when a process forks
(at least on Linux), the address space is copied. If some displaced
step buffers were in use at the time of the fork, we need to restore
the original bytes in the child's address space.
These two adjustments are also made in infrun.c:
- prepare_for_detach: there may be multiple threads doing displaced
steps when we detach, so wait until all of them are done
- handle_inferior_event: when we handle a fork event for a given
thread, it's possible that other threads are doing a displaced step at
the same time. Make sure to restore the displaced step buffer
contents in the child for them.
[1] https://github.com/ROCm-Developer-Tools/ROCgdb
gdb/ChangeLog:
* displaced-stepping.h (struct
displaced_step_copy_insn_closure): Adjust comments.
(struct displaced_step_inferior_state) <step_thread,
step_gdbarch, step_closure, step_original, step_copy,
step_saved_copy>: Remove fields.
(struct displaced_step_thread_state): New.
(struct displaced_step_buffer): New.
* displaced-stepping.c (displaced_step_buffer::prepare): New.
(write_memory_ptid): Move from infrun.c.
(displaced_step_instruction_executed_successfully): New,
factored out of displaced_step_finish.
(displaced_step_buffer::finish): New.
(displaced_step_buffer::copy_insn_closure_by_addr): New.
(displaced_step_buffer::restore_in_ptid): New.
* gdbarch.sh (displaced_step_location): Remove.
(displaced_step_prepare, displaced_step_finish,
displaced_step_copy_insn_closure_by_addr,
displaced_step_restore_all_in_ptid): New.
* gdbarch.c: Re-generate.
* gdbarch.h: Re-generate.
* gdbthread.h (class thread_info) <displaced_step_state>: New
field.
(thread_step_over_chain_remove): New declaration.
(thread_step_over_chain_next): New declaration.
(thread_step_over_chain_length): New declaration.
* thread.c (thread_step_over_chain_remove): Make non-static.
(thread_step_over_chain_next): New.
(global_thread_step_over_chain_next): Use
thread_step_over_chain_next.
(thread_step_over_chain_length): New.
(global_thread_step_over_chain_enqueue): Add debug print.
(global_thread_step_over_chain_remove): Add debug print.
* infrun.h (get_displaced_step_copy_insn_closure_by_addr):
Remove.
* infrun.c (get_displaced_stepping_state): New.
(displaced_step_in_progress_any_inferior): Remove.
(displaced_step_in_progress_thread): Adjust.
(displaced_step_in_progress): Adjust.
(displaced_step_in_progress_any_thread): New.
(get_displaced_step_copy_insn_closure_by_addr): Remove.
(gdbarch_supports_displaced_stepping): Use
gdbarch_displaced_step_prepare_p.
(displaced_step_reset): Change parameter from inferior to
thread.
(displaced_step_prepare_throw): Implement using
gdbarch_displaced_step_prepare.
(write_memory_ptid): Move to displaced-step.c.
(displaced_step_restore): Remove.
(displaced_step_finish): Implement using
gdbarch_displaced_step_finish.
(start_step_over): Allow starting more than one displaced step.
(prepare_for_detach): Handle possibly multiple threads doing
displaced steps.
(handle_inferior_event): Handle possibility that fork event
happens while another thread displaced steps.
* linux-tdep.h (linux_displaced_step_prepare): New.
(linux_displaced_step_finish): New.
(linux_displaced_step_copy_insn_closure_by_addr): New.
(linux_displaced_step_restore_all_in_ptid): New.
(linux_init_abi): Add supports_displaced_step parameter.
* linux-tdep.c (struct linux_info) <disp_step_buf>: New field.
(linux_displaced_step_prepare): New.
(linux_displaced_step_finish): New.
(linux_displaced_step_copy_insn_closure_by_addr): New.
(linux_displaced_step_restore_all_in_ptid): New.
(linux_init_abi): Add supports_displaced_step parameter,
register displaced step methods if true.
(_initialize_linux_tdep): Register inferior_execd observer.
* amd64-linux-tdep.c (amd64_linux_init_abi_common): Add
supports_displaced_step parameter, adjust call to
linux_init_abi. Remove call to
set_gdbarch_displaced_step_location.
(amd64_linux_init_abi): Adjust call to
amd64_linux_init_abi_common.
(amd64_x32_linux_init_abi): Likewise.
* aarch64-linux-tdep.c (aarch64_linux_init_abi): Adjust call to
linux_init_abi. Remove call to
set_gdbarch_displaced_step_location.
* arm-linux-tdep.c (arm_linux_init_abi): Likewise.
* i386-linux-tdep.c (i386_linux_init_abi): Likewise.
* alpha-linux-tdep.c (alpha_linux_init_abi): Adjust call to
linux_init_abi.
* arc-linux-tdep.c (arc_linux_init_osabi): Likewise.
* bfin-linux-tdep.c (bfin_linux_init_abi): Likewise.
* cris-linux-tdep.c (cris_linux_init_abi): Likewise.
* csky-linux-tdep.c (csky_linux_init_abi): Likewise.
* frv-linux-tdep.c (frv_linux_init_abi): Likewise.
* hppa-linux-tdep.c (hppa_linux_init_abi): Likewise.
* ia64-linux-tdep.c (ia64_linux_init_abi): Likewise.
* m32r-linux-tdep.c (m32r_linux_init_abi): Likewise.
* m68k-linux-tdep.c (m68k_linux_init_abi): Likewise.
* microblaze-linux-tdep.c (microblaze_linux_init_abi): Likewise.
* mips-linux-tdep.c (mips_linux_init_abi): Likewise.
* mn10300-linux-tdep.c (am33_linux_init_osabi): Likewise.
* nios2-linux-tdep.c (nios2_linux_init_abi): Likewise.
* or1k-linux-tdep.c (or1k_linux_init_abi): Likewise.
* riscv-linux-tdep.c (riscv_linux_init_abi): Likewise.
* s390-linux-tdep.c (s390_linux_init_abi_any): Likewise.
* sh-linux-tdep.c (sh_linux_init_abi): Likewise.
* sparc-linux-tdep.c (sparc32_linux_init_abi): Likewise.
* sparc64-linux-tdep.c (sparc64_linux_init_abi): Likewise.
* tic6x-linux-tdep.c (tic6x_uclinux_init_abi): Likewise.
* tilegx-linux-tdep.c (tilegx_linux_init_abi): Likewise.
* xtensa-linux-tdep.c (xtensa_linux_init_abi): Likewise.
* ppc-linux-tdep.c (ppc_linux_init_abi): Adjust call to
linux_init_abi. Remove call to
set_gdbarch_displaced_step_location.
* arm-tdep.c (arm_pc_is_thumb): Call
gdbarch_displaced_step_copy_insn_closure_by_addr instead of
get_displaced_step_copy_insn_closure_by_addr.
* rs6000-aix-tdep.c (rs6000_aix_init_osabi): Adjust calls to
clear gdbarch methods.
* rs6000-tdep.c (struct ppc_inferior_data): New structure.
(get_ppc_per_inferior): New function.
(ppc_displaced_step_prepare): New function.
(ppc_displaced_step_finish): New function.
(ppc_displaced_step_restore_all_in_ptid): New function.
(rs6000_gdbarch_init): Register new gdbarch methods.
* s390-tdep.c (s390_gdbarch_init): Don't call
set_gdbarch_displaced_step_location, set new gdbarch methods.
gdb/testsuite/ChangeLog:
* gdb.arch/amd64-disp-step-avx.exp: Adjust pattern.
* gdb.threads/forking-threads-plus-breakpoint.exp: Likewise.
* gdb.threads/non-stop-fair-events.exp: Likewise.
Change-Id: I387cd235a442d0620ec43608fd3dc0097fcbf8c8
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I noticed that the ARC print_one_insn selftest was failing. The
problem is that in print_one_insn_test the arc case falls through into
the special case that handles nios2, score, and riscv.
The special case for these targets hard codes the breakpoint kind to
'4'. This is find for bare metal arc (see arc-tdep.c,
arc_sw_breakpoint_from_kind), however, for arc/linux only breakpoint
kind '2' is supported (see arc-linux-tdep.c,
arc_linux_sw_breakpoint_from_kind).
So the code in print_one_insn_test as it is currently written passed
in an invalid breakpoint kind, this leads to GDB trying to disassemble
unexpected memory.
The fix is to reorder the code in print_one_insn_test so that the arc
case falls through into the default case. In the default we no longer
hard code the breakpoint kind, and everything should be good.
Additionally, given the arc code only expects specific breakpoint kind
values, I thought it would be nice to add some gdb_assert to validate
things. This assert would have triggered in this case and made it
easier to find the error.
After this commit, configure GDB with --enable-targets=all, then run
gdb.gdb/unittest.exp, there should no longer be any failures.
gdb/ChangeLog:
* arc-linux-tdep.c (arc_linux_sw_breakpoint_from_kind): Add an
assert.
* arc-tdep.c (arc_breakpoint_kind_from_pc): Likewise.
* disasm-selftests.c (print_one_insn_test): Fall throough from ARC
case to the default.
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In collect_register() function of arc-linux-tdep.c, the "eret"
(exception return) register value was not being reported correctly.
This patch fixes that.
Background:
When asked for the "pc" value, we have to update the "eret" register
with GDB's STOP_PC. The "eret" instructs the kernel code where to
jump back when an instruction has stopped due to a breakpoint. This
is how collect_register() was doing so:
--------------8<--------------
if (regnum == gdbarch_pc_regnum (gdbarch))
regnum = ARC_ERET_REGNUM;
regcache->raw_collect (regnum, buf + arc_linux_core_reg_offsets[regnum]);
-------------->8--------------
Root cause:
Although this is using the correct offset (ERET register's), it is also
changing the REGNUM itself. Therefore, raw_collect (regnum, ...) is
not reading from "pc" anymore.
v2:
- Fix a copy/paste issue as rightfully addressed by Tom [1].
[1]
https://sourceware.org/pipermail/gdb-patches/2020-November/173208.html
gdb/ChangeLog:
* arc-linux-tdep.c (collect_register): Populate "eret" by
"pc" value from the regcache when asked for "pc" value.
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With the implemenations in this patch, ARC gdb can handle
coredump related matters. The binutils counter part of
this patch has already been pushed [1].
v2 [2]:
- arc_linux_collect_gregset: Use "reg <= ARC_LAST_REGNUM" instead of
"reg < ARC_LAST_REGNUM" for the condition check of the for-loop.
- arc-linux-tdep.c: Use "ARC_LAST_REGNUM < ARRAY_SIZE (...)" instead of
"ARC_LAST_REGNUM <= ARRAY_SIZE (...)" for the "asserts".
- Use "buf + arc_linux_core_reg_offsets[ARC_ERET_REGNUM]" instead of
"buf + REG_OFF (6)".
- Fix a few typos/indentation.
v3 [3]:
- Use gdb_assert_not_reached(text) instead of gdb_assert (!text).
- Remove unnecessary braces in the for loop.
[1] arc: Add support for ARC HS extra registers in core files
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=2745674244d6aecddcf636475034bdb9c0a6b4a0
[2] First remarks
https://sourceware.org/pipermail/gdb-patches/2020-September/171912.html
[3] Second remarks
https://sourceware.org/pipermail/gdb-patches/2020-October/172302.html
gdb/ChangeLog:
* arc-linux-tdep.h: New file.
* arc-linux-tdep.c (arc_linux_core_reg_offsets,
arc_linux_supply_gregset, arc_linux_supply_v2_regset,
arc_linux_collect_gregset, arc_linux_collect_v2_regset,
arc_linux_gregset, arc_linux_v2_regset,
arc_linux_iterate_over_regset_sections,
arc_linux_core_read_description): Implement.
(arc_linux_init_osabi): Set iterate_over_regset_sections.
* arc-tdep.h (ARC_OFFSET_NO_REGISTER): Declare.
(arc_gdbarch_features_create): Add.
* arc-tdep.c (arc_gdbarch_features_create): Not static anymore.
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ARC Linux targets differences from baremetal:
- No support for hardware single instruction stepping.
- Different access rules to registers.
- Use of another instruction for breakpoints.
v2: Changes after Tom's remarks [1]
arc-linux-tdep.c
- Use true/false instead of TRUE/FALSE.
- arc_linux_sw_breakpoint_from_kind (): Break long lines into two.
- arc_linux_sw_breakpoint_from_kind (): Remove starting blank line.
- Use explicit number evaluation, e.g: if (a & b) -> if ((a & b) != 0)
arc-tdep.c
- Use explicit number evaluation, e.g: if (a & b) -> if ((a & b) != 0)
gdb/configure.tgt
- arc*-*-linux*): Remove "build_gdbserver=yes".
v3: Changes after Simon's remarks [2]
arc-linux-tdep.c
- Use "return trap_size" instead of cryptic "return 2".
- Removed unnecessary curly braces.
- Removed "void" from "_initialize_arc_linux_tdep (void)".
v5: Changes after Simon's remarks [3]
- Remove unnecessary empty lines.
- Replace "breakpoint uses" with "breakpoints use" in a comment.
- "return condition;" i.s.o. "if (condition) return true; else return false;"
[1] Tom's remarks
https://sourceware.org/pipermail/gdb-patches/2020-April/167887.html
[2] Simon's remarks on v2
https://sourceware.org/pipermail/gdb-patches/2020-May/168513.html
[3] Simon's remarks on v4
https://sourceware.org/pipermail/gdb-patches/2020-August/170994.html
gdb/ChangeLog:
2020-08-25 Anton Kolesov <anton.kolesov@synopsys.com>
* configure.tgt: ARC support for GNU/Linux.
* Makefile.in (ALL_TARGET_OBJS): Likewise.
* arc-linux-tdep.c: New file.
* arc-tdep.h (ARC_STATUS32_L_MASK, ARC_STATUS32_DE_MASK): Declare.
* arc-tdep.c (arc_write_pc): Use it.
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