https://sourceware.org/bugzilla/show_bug.cgi?id=26902
Bug ID: 26902
Summary: gold powerpc inserts jump to middle of long branch
stub
Product: binutils
Version: 2.36 (HEAD)
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: gold
Assignee: ccoutant at gmail dot com
Reporter: michael.hudson at canonical dot com
CC: ian at airs dot com
Target Milestone: ---
When linking a call to a file in the same module that requires a long branch,
gold inserts a jump to 8 bytes into the stub.
This came up with a ghc update in Ubuntu, but it's possible to recreate by
hand.
Here are my test files:
(hirsute-ppc64el)root@juju-b11c42-ubuntu-26:/build/haskell-network-byte-order-RQo4iL/haskell-network-byte-order-0.1.5/gold-test-case#
cat main.c
void large(void);
void local(void);
int
main(int argc, char** argv)
{
local();
return 0;
}
(hirsute-ppc64el)root@juju-b11c42-ubuntu-26:/build/haskell-network-byte-order-RQo4iL/haskell-network-byte-order-0.1.5/gold-test-case#
cat large.S
.machine power8
.abiversion 2
.section ".text"
.align 2
large:
#include "nops16M.h"
(hirsute-ppc64el)root@juju-b11c42-ubuntu-26:/build/haskell-network-byte-order-RQo4iL/haskell-network-byte-order-0.1.5/gold-test-case#
cat target.c
#include <stdio.h>
void local(void);
int a_global;
void local(void)
{
printf("a_global %d\n", a_global);
}
I made nops16M.h like this:
for x in `seq 1024`; do echo nop >> nops1k.h; done
for x in `seq 1024`; do echo '#include "nops1k.h"' >> nops1M.h; done
for x in `seq 16`; do echo '#include "nops1M.h"' >> nops16M.h; done
Then:
# gcc -c -o main.o main.c
# gcc -c -o large.o large.S
# gcc -c -o target.o target.c
# gcc -fuse-ld=gold -o test-gold main.c large.o target.o
# ./test-gold
Segmentation fault (core dumped)
And from objdump -D test-gold:
000000000000073c <main>:
73c: 02 04 4c 3c addis r2,r12,1026
740: c4 78 42 38 addi r2,r2,30916
744: a6 02 08 7c mflr r0
748: 10 00 01 f8 std r0,16(r1)
74c: f8 ff e1 fb std r31,-8(r1)
750: c1 ff 21 f8 stdu r1,-64(r1)
754: 78 0b 3f 7c mr r31,r1
758: 78 1b 69 7c mr r9,r3
75c: 20 00 9f f8 std r4,32(r31)
760: e6 01 09 7c mtfprwz f0,r9
764: 2c 00 3f 39 addi r9,r31,44
768: ae 4f 00 7c stfiwx f0,0,r9
76c: 9d 00 00 48 bl 808 <00000000.long_branch.4000810+0x8>
770: 00 00 00 60 nop
774: 00 00 20 39 li r9,0
778: 78 4b 23 7d mr r3,r9
77c: 40 00 3f 38 addi r1,r31,64
780: 10 00 01 e8 ld r0,16(r1)
784: a6 03 08 7c mtlr r0
788: f8 ff e1 eb ld r31,-8(r1)
78c: 20 00 80 4e blr
790: 00 00 00 00 .long 0x0
794: 00 00 00 01 .long 0x1000000
798: 80 01 00 01 .long 0x1000180
79c: 00 00 00 00 .long 0x0
and
0000000000000800 <00000000.long_branch.4000810>:
800: 70 80 82 e9 ld r12,-32656(r2)
804: a6 03 89 7d mtctr r12
808: 20 04 80 4e bctr
80c: 00 00 00 00 .long 0x0
This doesn't happen with -fuse-ld=bfd.
There are some recent commits that look like they might address this
(specifically fa40fbe484954c560ab1c0ff4bc1b2eeb1511344 which says in part
(Target_powerpc::Branch_info::make_stub): Don't add local
entry offset to long branch dest passed to
add_long_branch_entry. Do pass st_other bits.
) but I built gold from git and this still happens.
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