x86/entry/vdso32: Remove open-coded DWARF in sigreturn.S

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The vdso32 sigreturn.S contains open-coded DWARF bytecode, which
includes a hack for gdb to not try to step back to a previous call
instruction when backtracing from a signal handler.

Neither of those are necessary anymore: the backtracing issue is
handled by ".cfi_entry simple" and ".cfi_signal_frame", both of which
have been supported for a very long time now, which allows the
remaining frame to be built using regular .cfi annotations.

Add a few more register offsets to the signal frame just for good
measure.

Replace the nop on fallthrough of the system call (which should never,
ever happen) with a ud2a trap.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20251216212606.1325678-7-hpa@zytor.com

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This commit is contained in:

H. Peter Anvin 2025-12-16 13:26:00 -08:00 • committed by Dave Hansen

parent 98d3e99651

commit 884961618e

3 changed files with 39 additions and 114 deletions

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146

arch/x86/entry/vdso/vdso32/sigreturn.S

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1

arch/x86/include/asm/dwarf2.h

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6

arch/x86/kernel/asm-offsets.c

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