From c22d2021a9f9bdea62398976eea4f0e6ef668b7d Mon Sep 17 00:00:00 2001 From: Kito Cheng Date: Tue, 28 Jun 2022 21:52:19 +0800 Subject: riscv: Use memcpy to handle unaligned access when fixing R_RISCV_RELATIVE Although RISC-V Linux will enable the unaligned memory access handler by default, that is quite expensive in general, using memcpy will be much cheaper - just break down that into several load/store byte instructions. ARM and MIPS has similar issue: ARM: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51456 MIPS: https://gcc.gnu.org/legacy-ml/gcc-help/2005-07/msg00325.html Reviewed-by: Adhemerval Zanella --- sysdeps/riscv/dl-machine.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/sysdeps/riscv/dl-machine.h b/sysdeps/riscv/dl-machine.h index 4bb858a..dfedc98 100644 --- a/sysdeps/riscv/dl-machine.h +++ b/sysdeps/riscv/dl-machine.h @@ -157,7 +157,10 @@ __attribute__ ((always_inline)) elf_machine_rela_relative (ElfW(Addr) l_addr, const ElfW(Rela) *reloc, void *const reloc_addr) { - *(ElfW(Addr) *) reloc_addr = l_addr + reloc->r_addend; + /* R_RISCV_RELATIVE might located in debug info section which might not + aligned to XLEN bytes. Also support relocations on unaligned offsets. */ + ElfW(Addr) value = l_addr + reloc->r_addend; + memcpy (reloc_addr, &value, sizeof value); } /* Perform a relocation described by R_INFO at the location pointed to -- cgit v1.1