From b30e13e8b8ce3b9afa5511b9367023c5061f5a8c Mon Sep 17 00:00:00 2001 From: Tiezhu Yang Date: Fri, 22 Nov 2024 15:47:43 +0800 Subject: [PATCH] objtool: Handle special cases of dead end insn There are some "unreachable instruction" objtool warnings when compiling with Clang on LoongArch, this is because the "break" instruction is set as dead end due to its type is INSN_BUG in decode_instructions() at the beginning, and it does not set insn->dead_end of the "break" instruction as false after checking ".rela.discard.reachable" in add_dead_ends(), so the next instruction of "break" is marked as unreachable. Actually, it can find the reachable instruction after parsing the section ".rela.discard.reachable", in some cases, the "break" instruction may not be the first previous instruction with scheduling by Machine Instruction Scheduler of LLVM, it should find more times and then set insn->dead_end of the "break" instruction as false. This is preparation for later patch on LoongArch, there is no effect for the other archs with this patch. Signed-off-by: Tiezhu Yang Signed-off-by: Huacai Chen Signed-off-by: michael Signed-off-by: maoxiaochuan --- tools/objtool/check.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 9601235e9..191950551 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -22,6 +22,10 @@ #include #include +#ifndef EM_LOONGARCH +#define EM_LOONGARCH 258 +#endif + struct alternative { struct alternative *next; struct instruction *insn; @@ -711,6 +715,18 @@ reachable: } insn->dead_end = false; + + /* Handle the special cases compiled with Clang on LoongArch */ + if (file->elf->ehdr.e_machine == EM_LOONGARCH && + reloc->sym->type == STT_SECTION) { + while (insn && insn_func(insn)) { + insn = prev_insn_same_sym(file, insn); + if (insn && insn->dead_end) { + insn->dead_end = false; + break; + } + } + } } return 0;