[PATCH v2] gdb/jit: use correctly-sized array view in deprecated_frame_register_read call

[Thiago Jung Bauermann]

Hello Simon,

simon.marchi@polymtl.ca writes:

> From: GDB Administrator <gdbadmin@sourceware.org>
>
> New in v2:
>
>  - modify gdb/jit-reader.in, instead of the generated file.
>
> 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).
>
> Change-Id: Ie170da438ec9085863e7be8b455a067b531635dc
> ---
>  gdb/jit-reader.in | 2 +-
>  gdb/jit.c         | 9 +++++----
>  2 files changed, 6 insertions(+), 5 deletions(-)

Sorry about this regression. I haven't noticed it because jit-reader.exp
only runs on x86, and I tested only on aarch64. I should have tested
x86_64 as well.

Thanks for fixing the problem.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>

--
Thiago