https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84574
Bug ID: 84574
Summary: Function return thunks shouldn't be aliased to
indirect branch thunks
Product: gcc
Version: 8.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
Target Milestone: ---
Target: x86-64
Function return thunks shouldn't be aliased to indirect branch thunks
since indirect branch thunks are placed in COMDAT section and a COMDAT
section with indirect branch may not have return thunk:
[hjl@gnu-skx-1 xxx]$ cat x.i
void
foo (void)
{
}
[hjl@gnu-skx-1 xxx]$ cat y.i
extern void foo (void);
int
main ()
{
foo ();
return 0;
}
[hjl@gnu-skx-1 xxx]$ cat thunk.S
.section
.text.__x86_indirect_thunk,"axG",@progbits,__x86_indirect_thunk,comdat
.globl __x86_indirect_thunk
.hidden __x86_indirect_thunk
.type __x86_indirect_thunk, @function
__x86_indirect_thunk:
.LFB1:
.cfi_startproc
call .LIND3
.LIND2:
lfence
jmp .LIND2
.LIND3:
lea 8(%rsp), %rsp
ret
.cfi_endproc
.LFE1:
.section .note.GNU-stack,"",@progbits
[hjl@gnu-skx-1 xxx]$ make
/export/build/gnu/gcc-test/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-test/build-x86_64-linux/gcc/ -c -o thunk.o thunk.S
/export/build/gnu/gcc-test/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-test/build-x86_64-linux/gcc/ -O2
-mindirect-branch=thunk -c y.i
/export/build/gnu/gcc-test/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-test/build-x86_64-linux/gcc/ -O2
-mindirect-branch=thunk -mfunction-return=thunk -c x.i
/export/build/gnu/gcc-test/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-test/build-x86_64-linux/gcc/ -O2
-mindirect-branch=thunk -o x thunk.o y.o x.o
/usr/local/bin/ld: x.o: in function `foo':
x.i:(.text+0x1): undefined reference to `__x86_return_thunk'
collect2: error: ld returned 1 exit status
make: *** [Makefile:30: x] Error 1
[hjl@gnu-skx-1 xxx]$
