objtool: Track original function across branches
If 'insn->func' is NULL, objtool skips some important checks, including
sibling call validation. So if some .fixup code does an invalid sibling
call, objtool ignores it.
Treat all code branches (including alts) as part of the original
function by keeping track of the original func value from
validate_functions().
This improves the usefulness of some clang function fallthrough
warnings, and exposes some additional kernel bugs in the process.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/505df630f33c9717e1ccde6e4b64c5303135c25f.1563413318.git.jpoimboe@redhat.com
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f9494ff..d8a1ce8 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1934,13 +1934,12 @@
* each instruction and validate all the rules described in
* tools/objtool/Documentation/stack-validation.txt.
*/
-static int validate_branch(struct objtool_file *file, struct instruction *first,
- struct insn_state state)
+static int validate_branch(struct objtool_file *file, struct symbol *func,
+ struct instruction *first, struct insn_state state)
{
struct alternative *alt;
struct instruction *insn, *next_insn;
struct section *sec;
- struct symbol *func = NULL;
int ret;
insn = first;
@@ -1961,9 +1960,6 @@
return 1;
}
- if (insn->func)
- func = insn->func->pfunc;
-
if (func && insn->ignore) {
WARN_FUNC("BUG: why am I validating an ignored function?",
sec, insn->offset);
@@ -1985,7 +1981,7 @@
i = insn;
save_insn = NULL;
- func_for_each_insn_continue_reverse(file, insn->func, i) {
+ func_for_each_insn_continue_reverse(file, func, i) {
if (i->save) {
save_insn = i;
break;
@@ -2031,7 +2027,7 @@
if (alt->skip_orig)
skip_orig = true;
- ret = validate_branch(file, alt->insn, state);
+ ret = validate_branch(file, func, alt->insn, state);
if (ret) {
if (backtrace)
BT_FUNC("(alt)", insn);
@@ -2069,7 +2065,7 @@
if (state.bp_scratch) {
WARN("%s uses BP as a scratch register",
- insn->func->name);
+ func->name);
return 1;
}
@@ -2109,8 +2105,8 @@
} else if (insn->jump_dest &&
(!func || !insn->jump_dest->func ||
insn->jump_dest->func->pfunc == func)) {
- ret = validate_branch(file, insn->jump_dest,
- state);
+ ret = validate_branch(file, func,
+ insn->jump_dest, state);
if (ret) {
if (backtrace)
BT_FUNC("(branch)", insn);
@@ -2176,7 +2172,7 @@
break;
case INSN_CLAC:
- if (!state.uaccess && insn->func) {
+ if (!state.uaccess && func) {
WARN_FUNC("redundant UACCESS disable", sec, insn->offset);
return 1;
}
@@ -2197,7 +2193,7 @@
break;
case INSN_CLD:
- if (!state.df && insn->func)
+ if (!state.df && func)
WARN_FUNC("redundant CLD", sec, insn->offset);
state.df = false;
@@ -2236,7 +2232,7 @@
for_each_insn(file, insn) {
if (insn->hint && !insn->visited) {
- ret = validate_branch(file, insn, state);
+ ret = validate_branch(file, insn->func, insn, state);
if (ret && backtrace)
BT_FUNC("<=== (hint)", insn);
warnings += ret;
@@ -2363,12 +2359,12 @@
continue;
insn = find_insn(file, sec, func->offset);
- if (!insn || insn->ignore)
+ if (!insn || insn->ignore || insn->visited)
continue;
state.uaccess = func->alias->uaccess_safe;
- ret = validate_branch(file, insn, state);
+ ret = validate_branch(file, func, insn, state);
if (ret && backtrace)
BT_FUNC("<=== (func)", insn);
warnings += ret;
