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[MACH-O] Fix the ASM code generated for __stub_helpers section

Description

[MACH-O] Fix the ASM code generated for __stub_helpers section

Patch by Patricio Villalobos.

I discovered that lld for darwin is generating the wrong code for lazy
bindings in the __stub_helper section (at least for osx 10.12). This is
the way i can reproduce this problem, using this program:

#include <stdio.h>

int main(int argc, char **argv) {
    printf("C: printf!\n");
    puts("C: puts!\n");
    return 0;
}

Then I link it using i have tested it in 3.9, 4.0 and 4.1 versions:

$ clang -c hello.c
$ lld -flavor darwin hello.o -o h1  -lc

When i execute the binary h1 the system gives me the following error:

C: printf!
dyld: lazy symbol binding failed:
BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB
has segment 4 which is too large (0..3)
dyld: BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB has segment 4 which is too
large (0..3)
Trace/BPT trap: 5

Investigating the code, it seems that the problem is that the asm code
generated in the file StubPass.cpp, specifically in the line 323,when it
adds, what it seems an arbitrary number (12) to the offset into the lazy
bind opcodes section, but it should be calculated depending on the
MachONormalizedFileBinaryWrite::lazyBindingInfo result.

I confirmed this bug by patching the code manually in the binary and
writing the right offset in the asm code (__stub_helper).

This patch fixes the content of the atom that contains the assembly code
when the offset is known.

Differential Revision: https://reviews.llvm.org/D35387

Details

Committed
ruiuAug 24 2017, 4:51 PM
Differential Revision
D35387: [MACH-O] Fix the ASM code generated for __stub_helpers section
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