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Some fixups to the CFI directives for PLT stub entry points.

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The directives I added in r323466 and r323501 did not define a valid
CFA until several instructions into the associated functions.  This
triggers an assertion in GDB when generating a stack trace while
stopped at the first instruction of PLT stub entry point since there
is no valid CFA rule for the first instruction.

This is probably just wrong on my part as the non-simple .cfi_startproc
would have defined a valid CFA.  Instead, define a valid CFA as sp + 0
at the start of the functions and then use .cfa_def_offset to change the
offset when sp is adjusted later in the function.

Sponsored by:	DARPA / AFRL
This commit is contained in:
John Baldwin 2017-11-10 01:17:26 +00:00
parent c3faeef12c
commit a264cb726b
1 changed files with 6 additions and 2 deletions
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8
libexec/rtld-elf/mips/rtld_start.S
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@ -32,6 +32,8 @@
#include <machine/asm.h>
.cfi_sections .debug_frame
.globl _C_LABEL(_rtld_relocate_nonplt_self)
.globl _C_LABEL(_rtld)
@ -107,6 +109,7 @@ END(rtld_start)
_rtld_bind_start:
.frame sp, XCALLFRAME_SIZ, $15
.cfi_startproc simple
.cfi_def_cfa sp, 0
.cfi_register ra, $15
move v1, gp /* save old GP */
#if defined(__mips_o32) || defined(__mips_o64)
@ -114,7 +117,7 @@ _rtld_bind_start:
#endif
SETUP_GP
PTR_SUBU sp, XCALLFRAME_SIZ /* save arguments and sp value in stack */
.cfi_def_cfa sp, XCALLFRAME_SIZ
.cfi_def_cfa_offset XCALLFRAME_SIZ
SETUP_GP64(XCALLFRAME_GP, _rtld_bind_start)
SAVE_GP(XCALLFRAME_GP)
#if defined(__mips_n32) || defined(__mips_n64)
@ -200,6 +203,7 @@ END(_rtld_bind_start)
_rtld_pltbind_start:
.frame sp, XCALLFRAME_SIZ, $15
.cfi_startproc simple
.cfi_def_cfa sp, 0
.cfi_register ra, $15
#if defined(__mips_o32)
move v1, gp /* save pointer to .got.plt */
@ -211,7 +215,7 @@ _rtld_pltbind_start:
#endif
SETUP_GP
PTR_SUBU sp, XCALLFRAME_SIZ /* save arguments and sp value in stack */
.cfi_def_cfa sp, XCALLFRAME_SIZ
.cfi_def_cfa_offset XCALLFRAME_SIZ
SETUP_GP64(XCALLFRAME_GP, _rtld_pltbind_start)
SAVE_GP(XCALLFRAME_GP)
#if defined(__mips_n32) || defined(__mips_n64)