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x86/entry, ubsan, objtool: Whitelist __ubsan_handle_*()

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The UBSAN instrumentation only inserts external CALLs when things go
'BAD', much like WARN(). So treat them similar to WARN()s for noinstr,
that is: allow them, at the risk of taking the machine down, to get
their message out.

Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
This commit is contained in:
Peter Zijlstra 2020-06-03 20:09:06 +02:00
parent 14d3b376b6
commit 6b643a07a7
2 changed files with 28 additions and 2 deletions
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2
include/linux/compiler_types.h
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@ -199,7 +199,7 @@ struct ftrace_likely_data {
/* Section for code which can't be instrumented at all */
#define noinstr \
noinline notrace __attribute((__section__(".noinstr.text"))) \
__no_kcsan __no_sanitize_address __no_sanitize_undefined
__no_kcsan __no_sanitize_address
#endif /* __KERNEL__ */

28
tools/objtool/check.c
View File

@ -2190,10 +2190,36 @@ static inline const char *call_dest_name(struct instruction *insn)
return "{dynamic}";
}
static inline bool noinstr_call_dest(struct symbol *func)
{
/*
* We can't deal with indirect function calls at present;
* assume they're instrumented.
*/
if (!func)
return false;
/*
* If the symbol is from a noinstr section; we good.
*/
if (func->sec->noinstr)
return true;
/*
* The __ubsan_handle_*() calls are like WARN(), they only happen when
* something 'BAD' happened. At the risk of taking the machine down,
* let them proceed to get the message out.
*/
if (!strncmp(func->name, "__ubsan_handle_", 15))
return true;
return false;
}
static int validate_call(struct instruction *insn, struct insn_state *state)
{
if (state->noinstr && state->instr <= 0 &&
(!insn->call_dest || !insn->call_dest->sec->noinstr)) {
!noinstr_call_dest(insn->call_dest)) {
WARN_FUNC("call to %s() leaves .noinstr.text section",
insn->sec, insn->offset, call_dest_name(insn));
return 1;