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Handle LLVM-generated TLSDESC code sequence
It had been assumed that the TLSDESC code seqeunce looks like this:
lea 0(%rip), %rax
R_X86_64_GOTPC32_TLSDESC foo
call *(%rax)
R_X86_64_TLSDESC_CALL foo
However, LLVM seems to also emit something like this:
lea 0(%rip), %reg
R_X86_64_GOTPC32_TLSDESC foo
...
mov %reg, %rax
...
call *(%rax)
R_X86_64_TLSDESC_CALL foo
That means when we rewrite the LEA instruction to relax the code
sequence, we need to handle destination registers other than %rax.
The wrong assumption caused a program crash as reported as
https://bugs.gentoo.org/914849.- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,48 @@ | ||
| #!/bin/bash | ||
| . $(dirname $0)/common.inc | ||
|
|
||
| supports_tlsdesc || skip | ||
|
|
||
| cat <<'EOF' | $GCC -c -o $t/a.o -xassembler - | ||
| .globl get_foo | ||
| .type get_foo, @function | ||
| get_foo: | ||
| pushl %ebx | ||
| call __x86.get_pc_thunk.bx | ||
| addl $_GLOBAL_OFFSET_TABLE_, %ebx | ||
| subl $8, %esp | ||
| leal foo@TLSDESC(%ebx), %ebx | ||
| movl %ebx, %eax | ||
| call *foo@TLSCALL(%eax) | ||
| movl %gs:(%eax), %eax | ||
| addl $8, %esp | ||
| popl %ebx | ||
| ret | ||
| EOF | ||
|
|
||
| cat <<EOF | $GCC -fPIC -c -o $t/b.o -xc - $tlsdesc_opt | ||
| #include <stdio.h> | ||
| _Thread_local int foo; | ||
| int get_foo(); | ||
| int main() { | ||
| foo = 42; | ||
| printf("%d\n", get_foo()); | ||
| } | ||
| EOF | ||
|
|
||
| $CC -B. -o $t/exe1 $t/a.o $t/b.o | ||
| $QEMU $t/exe1 | grep -q 42 | ||
|
|
||
| $CC -B. -o $t/exe2 $t/a.o $t/b.o -Wl,-no-relax | ||
| $QEMU $t/exe2 | grep -q 42 | ||
|
|
||
| $CC -B. -shared -o $t/c.so $t/a.o | ||
| $CC -B. -o $t/exe3 $t/b.o $t/c.so | ||
| $QEMU $t/exe3 | grep -q 42 | ||
|
|
||
| $CC -B. -shared -o $t/c.so $t/a.o -Wl,-no-relax | ||
| $CC -B. -o $t/exe4 $t/b.o $t/c.so -Wl,-no-relax | ||
| $QEMU $t/exe4 | grep -q 42 |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,47 @@ | ||
| #!/bin/bash | ||
| . $(dirname $0)/common.inc | ||
|
|
||
| supports_tlsdesc || skip | ||
|
|
||
| cat <<EOF | $GCC -c -o $t/a.o -xassembler - | ||
| .globl get_foo | ||
| .type get_foo, @function | ||
| get_foo: | ||
| pushq %rbp | ||
| movq %rsp, %rbp | ||
| leaq foo@TLSDESC(%rip), %rbx | ||
| movq %rbx, %rax | ||
| call *foo@TLSCALL(%rax) | ||
| movq %fs:0, %rdx | ||
| addq %rdx, %rax | ||
| movl (%rax), %eax | ||
| popq %rbp | ||
| ret | ||
| EOF | ||
|
|
||
| cat <<EOF | $GCC -fPIC -c -o $t/b.o -xc - $tlsdesc_opt | ||
| #include <stdio.h> | ||
| _Thread_local int foo; | ||
| int get_foo(); | ||
| int main() { | ||
| foo = 42; | ||
| printf("%d\n", get_foo()); | ||
| } | ||
| EOF | ||
|
|
||
| $CC -B. -o $t/exe1 $t/a.o $t/b.o | ||
| $QEMU $t/exe1 | grep -q 42 | ||
|
|
||
| $CC -B. -o $t/exe2 $t/a.o $t/b.o -Wl,-no-relax | ||
| $QEMU $t/exe2 | grep -q 42 | ||
|
|
||
| $CC -B. -shared -o $t/c.so $t/a.o | ||
| $CC -B. -o $t/exe3 $t/b.o $t/c.so | ||
| $QEMU $t/exe3 | grep -q 42 | ||
|
|
||
| $CC -B. -shared -o $t/c.so $t/a.o -Wl,-no-relax | ||
| $CC -B. -o $t/exe4 $t/b.o $t/c.so -Wl,-no-relax | ||
| $QEMU $t/exe4 | grep -q 42 |