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authorPeter Zijlstra <peterz@infradead.org>2019-03-06 12:58:15 +0100
committerIngo Molnar <mingo@kernel.org>2019-04-03 11:02:24 +0200
commit54262aa2830151f89699fa8a6c5aa05f0992e672 (patch)
treed0135bbbf7b4ed3e764cfe93b10172d779c51500 /tools/objtool
parent764eef4b109ae11e6c987de9c14fc7c482041be0 (diff)
objtool: Fix sibling call detection
It turned out that we failed to detect some sibling calls; specifically those without relocation records; like: $ ./objdump-func.sh defconfig-build/mm/kasan/generic.o __asan_loadN 0000 0000000000000840 <__asan_loadN>: 0000 840: 48 8b 0c 24 mov (%rsp),%rcx 0004 844: 31 d2 xor %edx,%edx 0006 846: e9 45 fe ff ff jmpq 690 <check_memory_region> So extend the cross-function jump to also consider those that are not between known (or newly detected) parent/child functions, as sibling-cals when they jump to the start of the function. The second part of that condition is to deal with random jumps to the middle of other function, as can be found in arch/x86/lib/copy_user_64.S for example. This then (with later patches applied) makes the above recognise the sibling call: mm/kasan/generic.o: warning: objtool: __asan_loadN()+0x6: call to check_memory_region() with UACCESS enabled Also make sure to set insn->call_dest for sibling calls so we can know who we're calling. This is useful information when printing validation warnings later. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/objtool')
-rw-r--r--tools/objtool/check.c86
1 files changed, 55 insertions, 31 deletions
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5264a305d658..8118361295dd 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -515,7 +515,8 @@ static int add_jump_destinations(struct objtool_file *file)
continue;
} else {
/* sibling call */
- insn->jump_dest = 0;
+ insn->call_dest = rela->sym;
+ insn->jump_dest = NULL;
continue;
}
@@ -537,25 +538,38 @@ static int add_jump_destinations(struct objtool_file *file)
}
/*
- * For GCC 8+, create parent/child links for any cold
- * subfunctions. This is _mostly_ redundant with a similar
- * initialization in read_symbols().
- *
- * If a function has aliases, we want the *first* such function
- * in the symbol table to be the subfunction's parent. In that
- * case we overwrite the initialization done in read_symbols().
- *
- * However this code can't completely replace the
- * read_symbols() code because this doesn't detect the case
- * where the parent function's only reference to a subfunction
- * is through a switch table.
+ * Cross-function jump.
*/
if (insn->func && insn->jump_dest->func &&
- insn->func != insn->jump_dest->func &&
- !strstr(insn->func->name, ".cold.") &&
- strstr(insn->jump_dest->func->name, ".cold.")) {
- insn->func->cfunc = insn->jump_dest->func;
- insn->jump_dest->func->pfunc = insn->func;
+ insn->func != insn->jump_dest->func) {
+
+ /*
+ * For GCC 8+, create parent/child links for any cold
+ * subfunctions. This is _mostly_ redundant with a
+ * similar initialization in read_symbols().
+ *
+ * If a function has aliases, we want the *first* such
+ * function in the symbol table to be the subfunction's
+ * parent. In that case we overwrite the
+ * initialization done in read_symbols().
+ *
+ * However this code can't completely replace the
+ * read_symbols() code because this doesn't detect the
+ * case where the parent function's only reference to a
+ * subfunction is through a switch table.
+ */
+ if (!strstr(insn->func->name, ".cold.") &&
+ strstr(insn->jump_dest->func->name, ".cold.")) {
+ insn->func->cfunc = insn->jump_dest->func;
+ insn->jump_dest->func->pfunc = insn->func;
+
+ } else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&
+ insn->jump_dest->offset == insn->jump_dest->func->offset) {
+
+ /* sibling class */
+ insn->call_dest = insn->jump_dest->func;
+ insn->jump_dest = NULL;
+ }
}
}
@@ -1785,6 +1799,17 @@ static bool insn_state_match(struct instruction *insn, struct insn_state *state)
return false;
}
+static int validate_sibling_call(struct instruction *insn, struct insn_state *state)
+{
+ if (has_modified_stack_frame(state)) {
+ WARN_FUNC("sibling call from callable instruction with modified stack frame",
+ insn->sec, insn->offset);
+ return 1;
+ }
+
+ return 0;
+}
+
/*
* Follow the branch starting at the given instruction, and recursively follow
* any other branches (jumps). Meanwhile, track the frame pointer state at
@@ -1935,9 +1960,14 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
case INSN_JUMP_CONDITIONAL:
case INSN_JUMP_UNCONDITIONAL:
- if (insn->jump_dest &&
- (!func || !insn->jump_dest->func ||
- insn->jump_dest->func->pfunc == func)) {
+ if (func && !insn->jump_dest) {
+ ret = validate_sibling_call(insn, &state);
+ if (ret)
+ return ret;
+
+ } else if (insn->jump_dest &&
+ (!func || !insn->jump_dest->func ||
+ insn->jump_dest->func->pfunc == func)) {
ret = validate_branch(file, insn->jump_dest,
state);
if (ret) {
@@ -1945,11 +1975,6 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
BT_FUNC("(branch)", insn);
return ret;
}
-
- } else if (func && has_modified_stack_frame(&state)) {
- WARN_FUNC("sibling call from callable instruction with modified stack frame",
- sec, insn->offset);
- return 1;
}
if (insn->type == INSN_JUMP_UNCONDITIONAL)
@@ -1958,11 +1983,10 @@ static int validate_branch(struct objtool_file *file, struct instruction *first,
break;
case INSN_JUMP_DYNAMIC:
- if (func && list_empty(&insn->alts) &&
- has_modified_stack_frame(&state)) {
- WARN_FUNC("sibling call from callable instruction with modified stack frame",
- sec, insn->offset);
- return 1;
+ if (func && list_empty(&insn->alts)) {
+ ret = validate_sibling_call(insn, &state);
+ if (ret)
+ return ret;
}
return 0;