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| author | Peter Zijlstra <peterz@infradead.org> | 2021-02-11 13:03:28 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2021-03-06 12:44:22 +0100 |
| commit | d54dba41999498b38a40940e1123019d50b26496 (patch) | |
| tree | c1025dcdb0eb8c6b353913514db3149486b1e535 /tools/objtool | |
| parent | Linux 5.12-rc2 (diff) | |
| download | linux-d54dba41999498b38a40940e1123019d50b26496.tar.xz linux-d54dba41999498b38a40940e1123019d50b26496.zip | |
objtool: Allow UNWIND_HINT to suppress dodgy stack modifications
rewind_stack_do_exit()
UNWIND_HINT_FUNC
/* Prevent any naive code from trying to unwind to our caller. */
xorl %ebp, %ebp
movq PER_CPU_VAR(cpu_current_top_of_stack), %rax
leaq -PTREGS_SIZE(%rax), %rsp
UNWIND_HINT_REGS
call do_exit
Does unspeakable things to the stack, which objtool currently fails to
detect due to a limitation in instruction decoding. This will be
rectified after which the above will result in:
arch/x86/entry/entry_64.o: warning: objtool: .text+0xab: unsupported stack register modification
Allow the UNWIND_HINT on the next instruction to suppress this, it
will overwrite the state anyway.
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lkml.kernel.org/r/20210211173626.918498579@infradead.org
Diffstat (limited to 'tools/objtool')
| -rw-r--r-- | tools/objtool/check.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 068cdb41f76f..12b8f0f01176 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1959,8 +1959,9 @@ static void restore_reg(struct cfi_state *cfi, unsigned char reg) * 41 5d pop %r13 * c3 retq */ -static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, - struct stack_op *op) +static int update_cfi_state(struct instruction *insn, + struct instruction *next_insn, + struct cfi_state *cfi, struct stack_op *op) { struct cfi_reg *cfa = &cfi->cfa; struct cfi_reg *regs = cfi->regs; @@ -2161,7 +2162,7 @@ static int update_cfi_state(struct instruction *insn, struct cfi_state *cfi, break; } - if (op->dest.reg == cfi->cfa.base) { + if (op->dest.reg == cfi->cfa.base && !(next_insn && next_insn->hint)) { WARN_FUNC("unsupported stack register modification", insn->sec, insn->offset); return -1; @@ -2433,13 +2434,15 @@ static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn return 0; } -static int handle_insn_ops(struct instruction *insn, struct insn_state *state) +static int handle_insn_ops(struct instruction *insn, + struct instruction *next_insn, + struct insn_state *state) { struct stack_op *op; list_for_each_entry(op, &insn->stack_ops, list) { - if (update_cfi_state(insn, &state->cfi, op)) + if (update_cfi_state(insn, next_insn, &state->cfi, op)) return 1; if (op->dest.type == OP_DEST_PUSHF) { @@ -2719,7 +2722,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, return 0; } - if (handle_insn_ops(insn, &state)) + if (handle_insn_ops(insn, next_insn, &state)) return 1; switch (insn->type) { |