From d58854b6dd88e05dbf2a5d1c32c5acb7bd6ea274 Mon Sep 17 00:00:00 2001 From: Fangrui Song Date: Fri, 10 Mar 2023 11:53:32 -0800 Subject: [PATCH] ld: Allow R_X86_64_GOTPCREL for call *__tls_get_addr@GOTPCREL(%rip) _Thread_local int a; int main() { return a; } % gcc -fno-plt -fpic a.c -fuse-ld=bfd -Wa,-mrelax-relocations=no /usr/bin/ld.bfd: /tmp/ccSSBgrg.o: TLS transition from R_X86_64_TLSGD to R_X86_64_GOTTPOFF against `a' at 0xd in section `.text' failed /usr/bin/ld.bfd: failed to set dynamic section sizes: bad value collect2: error: ld returned 1 exit status This commit fixes the issue. There is an argument that the -fno-plt TLS sequence was added after R_X86_64_GOTPCRELX was required for call, so R_X86_64_GOTPCREL was intended to be unsupported. Unfortunately this standpoint has caused interop difficulty: some projects specify -mrelax-relocations=no to build relocatable object files compatible with older linkers (e.g. https://github.com/IHaskell/IHaskell/issues/636) or do so by accident (e.g. https://github.com/rust-lang/rust/pull/106511 not addressed as of today). Many uses have not been cleaned up in practice, and compiling with -fno-plt will lead to the `TLS transition from R_X86_64_TLSGD ...` error which is hard to reason about. There is another argument which may be weaker but relevant to the necessity of -mrelax-relocations=no: HWAddressSanitizer x86-64 will likely need some assembler support to disable relaxation. Without the support and if the compiler needs to support many gas version, the simplest solution would be to use -Wa,-mrelax-relocations=no. PR ld/24784 * bfd/elf64-x86-64.c (elf_x86_64_check_tls_transition): Allow R_X86_64_GOTPCREL. --- bfd/elf64-x86-64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c index 0aa9af5d8fc..dd987ee011b 100644 --- a/bfd/elf64-x86-64.c +++ b/bfd/elf64-x86-64.c @@ -1253,7 +1253,7 @@ elf_x86_64_check_tls_transition (bfd *abfd, if (largepic) return r_type == R_X86_64_PLTOFF64; else if (indirect_call) - return r_type == R_X86_64_GOTPCRELX; + return (r_type == R_X86_64_GOTPCRELX || r_type == R_X86_64_GOTPCREL); else return (r_type == R_X86_64_PC32 || r_type == R_X86_64_PLT32); } -- 2.30.2