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authorPeter Zijlstra <peterz@infradead.org>2020-04-01 16:38:19 +0200
committerIngo Molnar <mingo@kernel.org>2020-04-22 10:53:50 +0200
commite25eea89bb8853763a22fa2547199cf96b571ba1 (patch)
treef766e439a5bb171c5c71a56943a684f0e6716723 /tools/objtool
parentb746046238bb99b8f703c79f6d95357428fb6476 (diff)
objtool: Introduce HINT_RET_OFFSET
Normally objtool ensures a function keeps the stack layout invariant. But there is a useful exception, it is possible to stuff the return stack in order to 'inject' a 'call': push $fun ret In this case the invariant mentioned above is violated. Add an objtool HINT to annotate this and allow a function exit with a modified stack frame. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lkml.kernel.org/r/20200416115118.690601403@infradead.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/objtool')
-rw-r--r--tools/objtool/check.c24
-rw-r--r--tools/objtool/check.h4
2 files changed, 19 insertions, 9 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 781b3a3c2ba6..93c88ac51f0f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1261,6 +1261,9 @@ static int read_unwind_hints(struct objtool_file *file)
} else if (hint->type == UNWIND_HINT_TYPE_RESTORE) {
insn->restore = true;
insn->hint = true;
+
+ } else if (hint->type == UNWIND_HINT_TYPE_RET_OFFSET) {
+ insn->ret_offset = hint->sp_offset;
continue;
}
@@ -1424,20 +1427,25 @@ static bool is_fentry_call(struct instruction *insn)
return false;
}
-static bool has_modified_stack_frame(struct insn_state *state)
+static bool has_modified_stack_frame(struct instruction *insn, struct insn_state *state)
{
+ u8 ret_offset = insn->ret_offset;
int i;
- if (state->cfa.base != initial_func_cfi.cfa.base ||
- state->cfa.offset != initial_func_cfi.cfa.offset ||
- state->stack_size != initial_func_cfi.cfa.offset ||
- state->drap)
+ if (state->cfa.base != initial_func_cfi.cfa.base || state->drap)
+ return true;
+
+ if (state->cfa.offset != initial_func_cfi.cfa.offset + ret_offset)
return true;
- for (i = 0; i < CFI_NUM_REGS; i++)
+ if (state->stack_size != initial_func_cfi.cfa.offset + ret_offset)
+ return true;
+
+ for (i = 0; i < CFI_NUM_REGS; i++) {
if (state->regs[i].base != initial_func_cfi.regs[i].base ||
state->regs[i].offset != initial_func_cfi.regs[i].offset)
return true;
+ }
return false;
}
@@ -2014,7 +2022,7 @@ static int validate_call(struct instruction *insn, struct insn_state *state)
static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
{
- if (has_modified_stack_frame(state)) {
+ if (has_modified_stack_frame(insn, state)) {
WARN_FUNC("sibling call from callable instruction with modified stack frame",
insn->sec, insn->offset);
return 1;
@@ -2043,7 +2051,7 @@ static int validate_return(struct symbol *func, struct instruction *insn, struct
return 1;
}
- if (func && has_modified_stack_frame(state)) {
+ if (func && has_modified_stack_frame(insn, state)) {
WARN_FUNC("return with modified stack frame",
insn->sec, insn->offset);
return 1;
diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index 2c55f7591443..81ce27e62c04 100644
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -33,9 +33,11 @@ struct instruction {
unsigned int len;
enum insn_type type;
unsigned long immediate;
- bool alt_group, dead_end, ignore, hint, save, restore, ignore_alts;
+ bool alt_group, dead_end, ignore, ignore_alts;
+ bool hint, save, restore;
bool retpoline_safe;
u8 visited;
+ u8 ret_offset;
struct symbol *call_dest;
struct instruction *jump_dest;
struct instruction *first_jump_src;