git: e541cf8316bb - main - rtld: Annotate .rtld_start on i386
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Date: Tue, 11 Jul 2023 12:12:18 UTC
The branch main has been updated by dchagin:
URL: https://cgit.FreeBSD.org/src/commit/?id=e541cf8316bb787df0f19c43132c517482cf24a6
commit e541cf8316bb787df0f19c43132c517482cf24a6
Author: Dmitry Chagin <dchagin@FreeBSD.org>
AuthorDate: 2023-07-11 12:10:32 +0000
Commit: Dmitry Chagin <dchagin@FreeBSD.org>
CommitDate: 2023-07-11 12:10:32 +0000
rtld: Annotate .rtld_start on i386
Add a stop indicator to rtld_start to satisfy unwinders:
The right unwinding stop indicator should be CFI-undefined PC.
https://dwarfstd.org/doc/Dwarf3.pdf - page 118:
If a Return Address register is defined in the virtual unwind table,
and its rule is undefined (for example, by DW_CFA_undefined), then
there is no return address and no call address, and the virtual
unwind of stack activations is complete.
That is allows gdb and libunwind successfully stop when unwinding stack
from global constructors and destructors.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D40949
---
libexec/rtld-elf/i386/rtld_start.S | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/libexec/rtld-elf/i386/rtld_start.S b/libexec/rtld-elf/i386/rtld_start.S
index 6dbae220d89c..656ebb13864f 100644
--- a/libexec/rtld-elf/i386/rtld_start.S
+++ b/libexec/rtld-elf/i386/rtld_start.S
@@ -30,8 +30,15 @@
.globl .rtld_start
.type .rtld_start,@function
.rtld_start:
+ .cfi_startproc
+ .cfi_undefined %eip
xorl %ebp,%ebp # Clear frame pointer for good form
movl %esp,%esi # Save initial stack pointer
+ pushl %ebp
+ .cfi_def_cfa_offset 4
+ movl %esp,%ebp
+ .cfi_offset %ebp,-4
+ .cfi_def_cfa_register %ebp
andl $0xfffffff0,%esp # Align stack pointer
subl $16,%esp # A place to store exit procedure addr
movl %esp,%ebx # save address of exit proc
@@ -53,6 +60,7 @@
.globl .rtld_goto_main
.rtld_goto_main: # This symbol exists just to make debugging easier.
jmp *%eax # Enter main program
+ .cfi_endproc
/*