From: Peter Zijlstra peterz@infradead.org
commit 1cc1e4c8aab4213bd4e6353dec2620476a233d6d upstream.
Teach objtool to validate the straight-line-speculation constraints:
- speculation trap after indirect calls - speculation trap after RET
Notable: when an instruction is annotated RETPOLINE_SAFE, indicating speculation isn't a problem, also don't care about sls for that instruction.
Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Signed-off-by: Borislav Petkov bp@suse.de Link: https://lore.kernel.org/r/20211204134908.023037659@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org [bwh: Backported to 5.10: adjust filenames, context] Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/objtool/arch.h | 1 + tools/objtool/arch/x86/decode.c | 13 +++++++++---- tools/objtool/builtin-check.c | 4 +++- tools/objtool/builtin.h | 3 ++- tools/objtool/check.c | 14 ++++++++++++++ 5 files changed, 29 insertions(+), 6 deletions(-)
--- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -26,6 +26,7 @@ enum insn_type { INSN_CLAC, INSN_STD, INSN_CLD, + INSN_TRAP, INSN_OTHER, };
--- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -456,6 +456,11 @@ int arch_decode_instruction(const struct
break;
+ case 0xcc: + /* int3 */ + *type = INSN_TRAP; + break; + case 0xe3: /* jecxz/jrcxz */ *type = INSN_JUMP_CONDITIONAL; @@ -592,10 +597,10 @@ const char *arch_ret_insn(int len) { static const char ret[5][5] = { { BYTE_RET }, - { BYTE_RET, 0x90 }, - { BYTE_RET, 0x66, 0x90 }, - { BYTE_RET, 0x0f, 0x1f, 0x00 }, - { BYTE_RET, 0x0f, 0x1f, 0x40, 0x00 }, + { BYTE_RET, 0xcc }, + { BYTE_RET, 0xcc, 0x90 }, + { BYTE_RET, 0xcc, 0x66, 0x90 }, + { BYTE_RET, 0xcc, 0x0f, 0x1f, 0x00 }, };
if (len < 1 || len > 5) { --- a/tools/objtool/builtin-check.c +++ b/tools/objtool/builtin-check.c @@ -18,7 +18,8 @@ #include "builtin.h" #include "objtool.h"
-bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux; +bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, + validate_dup, vmlinux, sls;
static const char * const check_usage[] = { "objtool check [<options>] file.o", @@ -35,6 +36,7 @@ const struct option check_options[] = { OPT_BOOLEAN('s', "stats", &stats, "print statistics"), OPT_BOOLEAN('d', "duplicate", &validate_dup, "duplicate validation for vmlinux.o"), OPT_BOOLEAN('l', "vmlinux", &vmlinux, "vmlinux.o validation"), + OPT_BOOLEAN('S', "sls", &sls, "validate straight-line-speculation"), OPT_END(), };
--- a/tools/objtool/builtin.h +++ b/tools/objtool/builtin.h @@ -8,7 +8,8 @@ #include <subcmd/parse-options.h>
extern const struct option check_options[]; -extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, validate_dup, vmlinux; +extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats, + validate_dup, vmlinux, sls;
extern int cmd_check(int argc, const char **argv); extern int cmd_orc(int argc, const char **argv); --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2775,6 +2775,12 @@ static int validate_branch(struct objtoo switch (insn->type) {
case INSN_RETURN: + if (next_insn && next_insn->type == INSN_TRAP) { + next_insn->ignore = true; + } else if (sls && !insn->retpoline_safe) { + WARN_FUNC("missing int3 after ret", + insn->sec, insn->offset); + } return validate_return(func, insn, &state);
case INSN_CALL: @@ -2818,6 +2824,14 @@ static int validate_branch(struct objtoo break;
case INSN_JUMP_DYNAMIC: + if (next_insn && next_insn->type == INSN_TRAP) { + next_insn->ignore = true; + } else if (sls && !insn->retpoline_safe) { + WARN_FUNC("missing int3 after indirect jump", + insn->sec, insn->offset); + } + + /* fallthrough */ case INSN_JUMP_DYNAMIC_CONDITIONAL: if (is_sibling_call(insn)) { ret = validate_sibling_call(insn, &state);