https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88954
Bug ID: 88954
Summary: __attribute__((noplt)) doesn't work with function
pointers
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: hjl.tools at gmail dot com
Depends on: 67400
Target Milestone: ---
Target: i386, x86-64
[hjl@gnu-cfl-1 noplt-3]$ make clean
rm -f *.o *.so *.s
[hjl@gnu-cfl-1 noplt-3]$ cat main.c
void f_noplt(void) __attribute__((noplt));
void (*p_noplt)(void) = f_noplt;
void g(void (*)(void));
int main()
{
g(p_noplt); // lazy: linker sets p_noplt to PLT address
g(f_noplt); // lazy: linker sets mov immediate to PLT address
f_noplt(); // non-lazy
return 0;
}
[hjl@gnu-cfl-1 noplt-3]$ cat lib.c
__attribute__((noplt)) void f_noplt(void) {}
void g(void p(void)) {p();}
[hjl@gnu-cfl-1 noplt-3]$ make CC=gcc
gcc -O2 -fno-pic -c -o main.o main.c
gcc -O2 -fno-pic -fPIC -c -o lib.o lib.c
gcc -shared -o lib.so lib.o
gcc -no-pie -o x main.o lib.so -Wl,-R,.
./x
[hjl@gnu-cfl-1 noplt-3]$ readelf -rW x
Relocation section '.rela.dyn' at offset 0x4c8 contains 3 entries:
Offset Info Type Symbol's Value
Symbol's Name + Addend
0000000000403fe8 0000000400000006 R_X86_64_GLOB_DAT 0000000000401030
f_noplt + 0
0000000000403ff0 0000000100000006 R_X86_64_GLOB_DAT 0000000000000000
__libc_start_main@GLIBC_2.2.5 + 0
0000000000403ff8 0000000200000006 R_X86_64_GLOB_DAT 0000000000000000
__gmon_start__ + 0
Relocation section '.rela.plt' at offset 0x510 contains 2 entries:
Offset Info Type Symbol's Value
Symbol's Name + Addend
0000000000404018 0000000400000007 R_X86_64_JUMP_SLOT 0000000000401030
f_noplt + 0
This dynamic relocation shouldn't be here.
0000000000404020 0000000300000007 R_X86_64_JUMP_SLOT 0000000000000000 g +
0
[hjl@gnu-cfl-1 noplt-3]$
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67400
[Bug 67400] -fno-plt doesn't work with function pointers
