[PATCH] gdb/jit: use correctly-sized array view in deprecated_frame_register_read call

[Simon Marchi]

On 2025-01-11 06:04, Hannes Domani wrote:
>  Am Samstag, 11. Januar 2025 um 05:46:27 MEZ hat simon.marchi@polymtl.ca <simon.marchi@polymtl.ca> Folgendes geschrieben:
> 
>> From: GDB Administrator <gdbadmin@sourceware.org>
>>
>> Commit 7fcdec025c05 ("GDB: Use gdb::array_view for buffers used in
>> register reading and unwinding") introduces a regression in
>> gdb.base/jit-reader.exp:
>>
>>      $ ./gdb -q -nx --data-directory=data-directory testsuite/outputs/gdb.base/jit-reader/jit-reader -ex 'jit-reader-load /home/simark/build/binutils-gdb/gdb/testsuite/outputs/gdb.base/jit-reader/jit-reader.so' -ex r -batch
>>
>>      This GDB supports auto-downloading debuginfo from the following URLs:
>>        <https://debuginfod.archlinux.org>
>>      Enable debuginfod for this session? (y or [n]) [answered N; input not from terminal]
>>      Debuginfod has been disabled.
>>      To make this setting permanent, add 'set debuginfod enabled off' to .gdbinit.
>>      [Thread debugging using libthread_db enabled]
>>      Using host libthread_db library "/usr/lib/../lib/libthread_db.so.1".
>>
>>      Program received signal SIGTRAP, Trace/breakpoint trap.
>>      Recursive internal problem.
>>
>> The "Recusive internal problem" part is not good, but it's not the point
>> of this patch.  It still means we hit an internal error.
>>
>> The stack trace is:
>>
>>      #0  internal_error_loc (file=0x55555ebefb20 "/home/simark/src/binutils-gdb/gdb/frame.c", line=1207, fmt=0x55555ebef500 "%s: Assertion `%s' failed.") at /home/simark/src/binutils-gdb/gdbsupport/errors.cc:53
>>      #1  0x0000555561604d83 in frame_register_unwind (next_frame=..., regnum=16, optimizedp=0x7ffff12e5a20, unavailablep=0x7ffff12e5a30, lvalp=0x7ffff12e5a40, addrp=0x7ffff12e5a60, realnump=0x7ffff12e5a50, buffer=...)
>>          at /home/simark/src/binutils-gdb/gdb/frame.c:1207
>>      #2  0x0000555561608334 in deprecated_frame_register_read (frame=..., regnum=16, myaddr=...) at /home/simark/src/binutils-gdb/gdb/frame.c:1496
>>      #3  0x0000555561a74259 in jit_unwind_reg_get_impl (cb=0x7ffff1049ca0, regnum=16) at /home/simark/src/binutils-gdb/gdb/jit.c:988
>>      #4  0x00007fffd26e634e in read_register (callbacks=0x7ffff1049ca0, dw_reg=16, value=0x7fffffffb4c8) at /home/simark/src/binutils-gdb/gdb/testsuite/gdb.base/jit-reader.c:100
>>      #5  0x00007fffd26e645f in unwind_frame (self=0x50400000ac10, cbs=0x7ffff1049ca0) at /home/simark/src/binutils-gdb/gdb/testsuite/gdb.base/jit-reader.c:143
>>      #6  0x0000555561a74a12 in jit_frame_sniffer (self=0x55556374d040 <jit_frame_unwind>, this_frame=..., cache=0x5210002905f8) at /home/simark/src/binutils-gdb/gdb/jit.c:1042
>>      #7  0x00005555615f499e in frame_unwind_try_unwinder (this_frame=..., this_cache=0x5210002905f8, unwinder=0x55556374d040 <jit_frame_unwind>) at /home/simark/src/binutils-gdb/gdb/frame-unwind.c:138
>>      #8  0x00005555615f512c in frame_unwind_find_by_frame (this_frame=..., this_cache=0x5210002905f8) at /home/simark/src/binutils-gdb/gdb/frame-unwind.c:209
>>      #9  0x00005555616178d0 in get_frame_type (frame=...) at /home/simark/src/binutils-gdb/gdb/frame.c:2996
>>      #10 0x000055556282db03 in do_print_frame_info (uiout=0x511000027500, fp_opts=..., frame=..., print_level=0, print_what=SRC_AND_LOC, print_args=1, set_current_sal=1) at /home/simark/src/binutils-gdb/gdb/stack.c:1033
>>
>> The problem is that function `jit_unwind_reg_get_impl` passes field
>> `gdb_reg_value::value`, a gdb_byte array of 1 element (used as a
>> flexible array member), as the array view parameter of
>> `deprecated_frame_register_read`.  This results in an array view of size
>> 1.  The assertion in `frame_register_unwind` that verifies the passed in
>> buffer is larger enough to hold the unwound register value then fails.
>>
>> Fix this by explicitly creating an array view of the right size.
>>
>> At the same time, remove the `1` in the array definition, which would
>> have avoided this bug (it wouldn't have compiled).
> 
> Is that part missing?

Ohhh, it's because it's in jit-reader.h, which is generated, and I
modified the generated file.  I'll send a v2.

Simon