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[ELF] Don't consider SHF_ALLOC ".debug*" sections debug sections 

Fixes PR48071

* The Rust compiler produces SHF_ALLOC `.debug_gdb_scripts` (which normally does not have the flag)
* `.debug_gdb_scripts` sections are removed from `inputSections` due to --strip-debug/--strip-all
* When processing --gc-sections, pieces of a SHF_MERGE section can be marked live separately

`=>` segfault when marking liveness of a `.debug_gdb_scripts` which is not split into pieces (because it is not in `inputSections`)

This patch circumvents the problem by not treating SHF_ALLOC ".debug*" as debug sections (to prevent --strip-debug's stripping)
(which is still useful on its own).

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D91291
This commit is contained in:
Fangrui Song 2020-11-12 09:59:43 -08:00
parent ac523d2de5
commit 8df4e60945
2 changed files with 19 additions and 1 deletions
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3
lld/ELF/InputSection.h
View File

@ -397,7 +397,8 @@ static_assert(sizeof(InputSection) <= 184, "InputSection is too big");
#endif
inline bool isDebugSection(const InputSectionBase &sec) {
return sec.name.startswith(".debug") || sec.name.startswith(".zdebug");
return (sec.flags & llvm::ELF::SHF_ALLOC) == 0 &&
(sec.name.startswith(".debug") || sec.name.startswith(".zdebug"));
}
// The list of all input sections.

17
lld/test/ELF/gc-sections-strip-debug.s Normal file
View File

@ -0,0 +1,17 @@
# REQUIRES: x86
## Test that we don't strip SHF_ALLOC .debug* or crash (PR48071
## mark liveness of a merge section which has not been split).
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o
# RUN: ld.lld %t.o --gc-sections --strip-debug -o %t
# RUN: llvm-readelf -S %t | FileCheck %s
# CHECK: .debug_gdb_scripts
.globl _start
_start:
leaq .L.str(%rip), %rax
.section .debug_gdb_scripts,"aMS",@progbits,1
.L.str:
.asciz "Rust uses SHF_ALLOC .debug_gdb_scripts"