Messages in this thread Patch in this message | | | Date | Thu, 07 Mar 2019 12:45:31 +0100 | From | Peter Zijlstra <> | Subject | [PATCH 20/20] objtool: Add Direction Flag validation |
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Having DF escape is BAD(tm).
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> --- tools/objtool/arch.h | 4 +++- tools/objtool/arch/x86/decode.c | 8 ++++++++ tools/objtool/check.c | 25 +++++++++++++++++++++++++ tools/objtool/check.h | 2 +- 4 files changed, 37 insertions(+), 2 deletions(-)
--- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -35,7 +35,9 @@ #define INSN_NOP 10 #define INSN_STAC 11 #define INSN_CLAC 12 -#define INSN_OTHER 13 +#define INSN_STD 13 +#define INSN_CLD 14 +#define INSN_OTHER 15 #define INSN_LAST INSN_OTHER enum op_dest_type { --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -456,6 +456,14 @@ int arch_decode_instruction(struct elf * *type = INSN_CALL; break; + case 0xfc: + *type = INSN_CLD; + break; + + case 0xfd: + *type = INSN_STD; + break; + case 0xff: if (modrm_reg == 2 || modrm_reg == 3) --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2020,6 +2020,11 @@ static int validate_branch(struct objtoo return 1; } + if (state.df) { + WARN_FUNC("return with DF set", sec, insn->offset); + return 1; + } + if (func && has_modified_stack_frame(&state)) { WARN_FUNC("return with modified stack frame", sec, insn->offset); @@ -2043,6 +2048,12 @@ static int validate_branch(struct objtoo return 1; } + if (state.df) { + WARN_FUNC("call to %s() with DF set", + sec, insn->offset, insn_dest_name(insn)); + return 1; + } + if (insn->type == INSN_JUMP_UNCONDITIONAL || insn->type == INSN_JUMP_DYNAMIC) return 0; @@ -2160,6 +2171,20 @@ static int validate_branch(struct objtoo state.uaccess = false; break; + case INSN_STD: + if (state.df) + WARN_FUNC("recursive STD", sec, insn->offset); + + state.df = true; + break; + + case INSN_CLD: + if (!state.df && insn->func) + WARN_FUNC("redundant CLD", sec, insn->offset); + + state.df = false; + break; + default: break; } --- a/tools/objtool/check.h +++ b/tools/objtool/check.h @@ -31,7 +31,7 @@ struct insn_state { int stack_size; unsigned char type; bool bp_scratch; - bool drap, end, uaccess; + bool drap, end, uaccess, df; unsigned int uaccess_stack; int drap_reg, drap_offset; struct cfi_reg vals[CFI_NUM_REGS];
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