https://bugs.llvm.org/show_bug.cgi?id=47009
Bug ID: 47009
Summary: -z rel breaks aarch64 TLSDESC relocs
Product: lld
Version: unspecified
Hardware: All
OS: All
Status: NEW
Severity: normal
Priority: P
Component: ELF
Assignee: unassignedbugs at nondot.org
Reporter: roland at hack.frob.com
CC: llvm-bugs at lists.llvm.org, maskray at google.com,
phosek at chromium.org, smithp352 at googlemail.com
Take this assembly file:
```
.text
.file "a.c"
.globl foo // -- Begin function foo
.p2align 2
.type foo, at function
foo: // @foo
.cfi_startproc
// %bb.0:
str x30, [x18], #8
stp x29, x30, [sp, #-16]! // 16-byte Folded Spill
mov x29, sp
.cfi_def_cfa w29, 16
.cfi_offset w30, -8
.cfi_offset w29, -16
adrp x0, :tlsdesc:x
ldr x1, [x0, :tlsdesc_lo12:x]
add x0, x0, :tlsdesc_lo12:x
.tlsdesccall x
blr x1
mrs x8, TPIDR_EL0
ldr w9, [x8, x0]
adrp x0, :tlsdesc:y
ldr x1, [x0, :tlsdesc_lo12:y]
add x0, x0, :tlsdesc_lo12:y
.tlsdesccall y
blr x1
ldr w8, [x8, x0]
add w0, w8, w9
ldp x29, x30, [sp], #16 // 16-byte Folded Reload
ldr x30, [x18, #-8]!
ret
.Lfunc_end0:
.size foo, .Lfunc_end0-foo
.cfi_endproc
// -- End function
.hidden x // @x
.type x, at object
.section .tbss,"awT", at nobits
.globl x
.p2align 2
x:
.Lx$local:
.word 0 // 0x0
.size x, 4
.hidden y // @y
.type y, at object
.globl y
.p2align 2
y:
.Ly$local:
.word 0 // 0x0
.size y, 4
```
Compile it with `clang --target=aarch64-fuchsia -c a.s` and then:
```
$ hack/bin/ld.lld -z max-page-size=4096 -z now -z rodynamic -z
separate-loadable-segments --pack-dyn-relocs=relr -z rela --build-id
--hash-style=gnu --eh-frame-hdr -shared -o a.so.rela a.o
$ hack/bin/ld.lld -z max-page-size=4096 -z now -z rodynamic -z
separate-loadable-segments --pack-dyn-relocs=relr -z rel --build-id
--hash-style=gnu --eh-frame-hdr -shared -o a.so.rel a.o
$ readelf -Wr -x.got a.so.rel*
File: a.so.rel
Relocation section '.rel.dyn' at offset 0x390 contains 2 entries:
Offset Info Type Symbol's Value
Symbol's Name
0000000000002000 0000000000000407 R_AARCH64_TLSDESC
0000000000002010 0000000000000407 R_AARCH64_TLSDESC
Hex dump of section '.got':
0x00002000 00000000 00000000 00000000 00000000 ................
0x00002010 00000000 00000000 00000000 00000000 ................
File: a.so.rela
Relocation section '.rela.dyn' at offset 0x390 contains 2 entries:
Offset Info Type Symbol's Value
Symbol's Name + Addend
0000000000002000 0000000000000407 R_AARCH64_TLSDESC 0
0000000000002010 0000000000000407 R_AARCH64_TLSDESC 4
Hex dump of section '.got':
0x00002000 00000000 00000000 00000000 00000000 ................
0x00002010 00000000 00000000 00000000 00000000 ................
```
In the `-z rela` case, the addends survive correctly. In the `-z rel` case,
nonzero addend (4) should be stored in the generated GOT slot at 0x2008 (i.e.
the second word of the two-word TLSDESC GOT slot).
--
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