https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93194
Bug ID: 93194
Summary: -fpatchable-function-entries :
__patchable_function_entries has wrong sh_flags and
sh_addralign
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: i at maskray dot me
Target Milestone: ---
% cat a.c
void f(){}
% gcc -fpatchable-function-entry=3 -c a.c
% readelf -S a.o
...
[Nr] Name Type Address Off Size ES Flg
Lk Inf Al
[ 0] NULL 0000000000000000 000000 000000 00
0 0 0
[ 1] .text PROGBITS 0000000000000000 000040 00000a 00 AX
0 0 1
[ 2] .data PROGBITS 0000000000000000 00004a 000000 00 WA
0 0 1
[ 3] .bss NOBITS 0000000000000000 00004a 000000 00 WA
0 0 1
[ 4] __patchable_function_entries PROGBITS 0000000000000000 00004a
000008 00 A 0 0 1
[ 5] .rela__patchable_function_entries RELA 0000000000000000
0001a0 000018 18 I 10 4 8
sh_addralign of __patchable_function_entries should be 8 on ELF64 platforms, 4
on ELF32 platforms, instead of 1.
__patchable_function_entries should have the SHF_WRITE flag. A
__patchable_function_entries entry is relocated by a symbolic relocation (e.g.
R_X86_64_64, R_AARCH64_ABS64, R_PPC64_ADDR64).
In -shared or -pie mode, the linker will create a dynamic relocation,
* non-preemptible (STB_LOCAL / non-STV_DEFAULT / -Bsymbolic / not-shared /
--dynamic-list excluded / etc): relative relocation (e.g. R_X86_64_RELATIVE)
* preemptible: symbolic relocation (e.g. R_X86_64_64)
(We can't emit an offset relative to the image base (.quad .Lfoo - .Lbase),
because differences across sections are generally not representable. A symbolic
relocation gives the runtime code information about the symbol names, which may
be desirable.)
