llvm-project/lld/test/ELF/gc-sections-tls.s

# REQUIRES: x86
# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o

## Relocation in a non .debug_* referencing a discarded TLS symbol is invalid.
## If we happen to have no PT_TLS, we will emit an error.
# RUN: not ld.lld %t.o --gc-sections -o /dev/null 2>&1 | FileCheck %s --check-prefix=ERR

# ERR: error: {{.*}}.o has an STT_TLS symbol but doesn't have an SHF_TLS section

## If we happen to have a PT_TLS, we will resolve the relocation to
## an arbitrary value (current implementation uses a negative value).
# RUN: echo '.section .tbss,"awT"; .globl root; root: .long 0' | \
# RUN:   llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
# RUN: ld.lld --gc-sections -u root %t.o %t1.o -o %t
# RUN: llvm-readelf -x .noalloc %t | FileCheck %s

# CHECK:      Hex dump of section '.noalloc':
# CHECK-NEXT: 0x00000000 {{[0-9a-f]+}} ffffffff

.section .tbss,"awT",@nobits
tls:
  .long 0

.section .noalloc,""
  .quad tls+0x8000
[ELF] Resolve R_DTPREL in .debug_* referencing discarded symbols to -1 The location of a TLS variable is encoded as a DW_OP_const4u/DW_OP_const8u followed by a DW_OP_push_tls_address (or DW_OP_GNU_push_tls_address https://sourceware.org/bugzilla/show_bug.cgi?id=11616 ). This change follows up to D81784 and makes relocations types generalized as R_DTPREL (e.g. R_X86_64_DTPOFF{32,64}, R_PPC64_DTPREL64) use -1 as the tombstone value as well. This works for both TLS Variant I and Variant II architectures. * arm: .long tls(tlsldo) # not working currently (R_ARM_TLS_LDO32 is R_ABS) * mips64: .dtpreldword tls+32768 * ppc64: .quad tls@DTPREL+0x8000 * riscv: neither GCC nor clang has implemented DW_AT_location. It is likely .long/.quad tls@dtprel+0x800 * x86-32: .long tls@DTPOFF * x86-64: .long tls@DTPOFF; .quad tls@DTPOFF tls has a non-negative st_value, so such relocations (st_value+addend) never resolve to -1 in a normal (not discarded) case. ``` // clang -fuse-ld=lld -g -ffunction-sections a.c -Wl,--gc-sections // foo and tls will be discarded by --gc-sections. // DW_AT_location [DW_FORM_exprloc] (DW_OP_const8u 0xffffffffffffffff, DW_OP_GNU_push_tls_address) thread_local int tls; int foo() { return ++tls; } int main() {} ``` Also, drop logic added in D26201 intended to address PR30793. It added a test (gc-debuginfo-tls.s) using a non-SHF_ALLOC section and a local symbol, which does not reflect the intended scenario: a relocation in a SHF_ALLOC section referencing a discarded non-local symbol. For such a non .debug_* section, just emit an error. Reviewed By: jhenderson Differential Revision: https://reviews.llvm.org/D82899 2020-07-04 00:50:30 +08:00			`# REQUIRES: x86`
			`# RUN: llvm-mc -filetype=obj -triple=x86_64 %s -o %t.o`

			`## Relocation in a non .debug_* referencing a discarded TLS symbol is invalid.`
			`## If we happen to have no PT_TLS, we will emit an error.`
			`# RUN: not ld.lld %t.o --gc-sections -o /dev/null 2>&1 \| FileCheck %s --check-prefix=ERR`

			`# ERR: error: {{.*}}.o has an STT_TLS symbol but doesn't have an SHF_TLS section`

			`## If we happen to have a PT_TLS, we will resolve the relocation to`
			`## an arbitrary value (current implementation uses a negative value).`
			`# RUN: echo '.section .tbss,"awT"; .globl root; root: .long 0' \| \`
			`# RUN: llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o`
			`# RUN: ld.lld --gc-sections -u root %t.o %t1.o -o %t`
			`# RUN: llvm-readelf -x .noalloc %t \| FileCheck %s`

			`# CHECK: Hex dump of section '.noalloc':`
			`# CHECK-NEXT: 0x00000000 {{[0-9a-f]+}} ffffffff`

			`.section .tbss,"awT",@nobits`
			`tls:`
			`.long 0`

			`.section .noalloc,""`
			`.quad tls+0x8000`