| Summary: | ld -r severely broken on 64-bit mingw / pe-x86-64 | ||
|---|---|---|---|
| Product: | binutils | Reporter: | Mikael Pettersson <mikpelinux> |
| Component: | ld | Assignee: | unassigned |
| Status: | RESOLVED FIXED | ||
| Severity: | critical | CC: | bug-binutils |
| Priority: | P2 | ||
| Version: | 2.19 | ||
| Target Milestone: | --- | ||
| Host: | i686-pc-cygwin | Target: | x86_64-pc-mingw32 |
| Build: | Last reconfirmed: | ||
| Attachments: | Do not update the vma's of output sections when performing a relocatable link on COFF objects. | ||
|
Description
Mikael Pettersson
2008-10-06 12:22:07 UTC
Hi Mikael, So - what is the difference between bug.o and bug2.o ? Is it possible to reproduce the bug without using inline assembly ? Cheers Nick (In reply to comment #1) > Hi Mikael, > > So - what is the difference between bug.o and bug2.o ? objdump -h bug*.o bug.o: file format pe-x86-64 Sections: Idx Name Size VMA LMA File off Algn 0 .text 000000a0 0000000000000000 0000000000000000 000000b4 2**4 CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE 1 .data 00000000 0000000000000000 0000000000000000 00000000 2**4 ALLOC, LOAD, DATA 2 .bss 00000000 0000000000000000 0000000000000000 00000000 2**4 ALLOC 3 .rdata 00000050 0000000000000000 0000000000000000 00000154 2**4 CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA bug2.o: file format pe-x86-64 Sections: Idx Name Size VMA LMA File off Algn 0 .text 000000a0 0000000000000000 0000000000000000 000000b4 2**4 CONTENTS, ALLOC, LOAD, RELOC, READONLY, CODE 1 .data 00000000 00000000000000a0 00000000000000a0 00000000 2**4 ALLOC, LOAD, DATA 2 .rdata 00000050 00000000000000a0 00000000000000a0 00000154 2**4 CONTENTS, ALLOC, LOAD, RELOC, READONLY, DATA 3 .bss 00000000 00000000000000f0 00000000000000f0 00000000 2**4 ALLOC The files are the same size, but ld -r changes the order of the sections, and appears to add the size of .text (0x0a) to the VMA/LMA of .data and .rdata. And the offsets in the jump table are also off by 0x0a, but since the code and the jump table haven't moved the jump table targets are now wrong. > Is it possible to reproduce the bug without using inline assembly ? Certainly, it's just a gcc switch() jump table. I used inline asm in order to write a test program that could inspect and verify the jump table instead of crashing. The program below (cbug.c) shows the bug in plain C: x86_64-pc-mingw32-gcc -O -c cbug.c x86_64-pc-mingw32-ld -r -o cbug2.o cbug.o x86_64-pc-mingw32-gcc -o cbug cbug.o x86_64-pc-mingw32-gcc -o cbug2 cbug2.o ./cbug at state 0 at state 1 at state 2 at state 3 at state 4 at state 5 at state 6 at state 7 2173 echo $? 0 ./cbug2 at state 0 echo $? 128 Running cbug2 in gdb confirms that it branches to la-la land the first time it enters the switch(), and then SEGVs. #include <stdio.h> enum state { q0, q1, q2, q3, q4, q5, q6, q7 }; int run(int x) { enum state state = q0; for (;;) { printf("at state %d\n", state); fflush(stdout); switch (state) { case q0: x += 1; state = q1; continue; case q1: x *= 2; state = q2; continue; case q2: x += 3; state = q3; continue; case q3: x *= 4; state = q4; continue; case q4: x += 5; state = q5; continue; case q5: x *= 6; state = q6; continue; case q6: x += 7; state = q7; continue; case q7: return x; } } } int main(void) { printf("%d\n", run(42)); return 0; } Created attachment 3018 [details]
Do not update the vma's of output sections when performing a relocatable link on COFF objects.
Hi Mikael, Please could you try out the uploaded patch and see if it works for you. I think that it does the right thing, although I am not very happy with the method I have chosen. Still it does not seem to introduce any new regressions into the linker testsuite and it does appear to work for the testcase you sent. Cheers Nick (In reply to comment #4) Nick, I've tested your patch and it fixes both the two test cases I posted and the original application where I first noticed the bug. Thanks. /Mikael Hi Mikael, Ok, I have checked the patch in along with this changelog entry. Cheers Nick ld/ChangeLog 2008-10-25 Nick Clifton <nickc@redhat.com> PR 6945 * ldlang.c (lang_size_sections_1): Do not update the VMAs of output sections when performing a relocatable link on COFF objects. |