https://sourceware.org/bugzilla/show_bug.cgi?id=30692
Bug ID: 30692
Summary: [RISC-V] Symbol offset in .eh_frame section is not
adjusted after relaxation
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: binutils
Assignee: unassigned at sourceware dot org
Reporter: yanzhang.wang at intel dot com
Target Milestone: ---
When we build the test with option -static -pg, the binary will be segment
fault. This is also a block issue to enable -static-pie for us.
» cat hello.c
int main(void)
{
return 0;
}
» riscv64-unknown-linux-gnu-gcc -static -pg hello.c
(gdb) r
Starting program: /home/riscv/a.out
Program received signal SIGSEGV, Segmentation fault.
classify_object_over_fdes (ob=0x82320 <object>, this_fde=0x100051fba,
range=0x3ffffff380)
at ../../.././gcc/libgcc/unwind-dw2-fde.c:727
727 ../../.././gcc/libgcc/unwind-dw2-fde.c: No such file or directory.
(gdb) bt
#0 classify_object_over_fdes (ob=0x82320 <object>, this_fde=0x100051fba,
range=0x3ffffff380)
at ../../.././gcc/libgcc/unwind-dw2-fde.c:727
#1 0x00000000000513ee in __register_frame_info_bases (dbase=0x0, tbase=0x0,
ob=0x82320 <object>,
begin=<optimized out>) at ../../.././gcc/libgcc/unwind-dw2-fde.c:129
#2 __register_frame_info_bases (dbase=0x0, tbase=0x0, ob=0x82320 <object>,
begin=<optimized out>)
at ../../.././gcc/libgcc/unwind-dw2-fde.c:109
#3 __register_frame_info (begin=<optimized out>, ob=0x82320 <object>)
at ../../.././gcc/libgcc/unwind-dw2-fde.c:145
#4 0x00000000000106d8 in frame_dummy ()
#5 0x0000000000010980 in __libc_start_main_impl ()
#6 0x00000000000105e8 in _start ()
The root cause is the variable __EH_FRAME_BEGIN__ defined in .eh_frame section
has wrong value. Some objdump's output,
00000000000106b6 <frame_dummy>:
106b6: 000517b7 lui a5,0x51
106ba: 3c278793 add a5,a5,962 # 513c2
<__register_frame_info>
106be: c385 beqz a5,106de <frame_dummy+0x28>
106c0: 000825b7 lui a1,0x82
106c4: 0006e537 lui a0,0x6e
106c8: 1141 add sp,sp,-16
106ca: 32058593 add a1,a1,800 # 82320 <object.0>
106ce: 0e050513 add a0,a0,224 # 6e0e0
<__EH_FRAME_BEGIN__>
Disassembly of section .eh_frame:
000000000006e0f0 <__EH_FRAME_BEGIN__+0x10>:
On x86 and ARM, it seems the reference of __EH_FRAME_BEGIN__ will be converted
to section with offset in gas. But on RISC-V, because tc_fix_adjustable was
disabled, so the symbol will not be adjusted.
If we dive deeper, the wrong value comes from the relaxation. The local symbols
in .eh_frame will be adjusted in bfd_elf_discard_info, but will not be adjusted
when and after relaxation. For example, before relaxation, the symbol will be
offset 0x50 due to the alignment requirement; after relaxation, the offset will
be 0x40 because no need to align. That's why .eh_frame start is the
__EH_FRAME_BEGIN__ + 0x10.
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