From: Steven Rostedt When modifying text sections for jump labels, a paranoid check is performed. If the check fails, the system "bugs". But why it failed is not shown. The BUG_ON()s in the jump label update code is replaced with bug_at(ip). This is a function that will show what pointer failed, and what was at the location of the failure that made jump label panic. Signed-off-by: Steven Rostedt --- arch/x86/kernel/jump_label.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index 24cf2b2..912a528 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -24,6 +24,18 @@ union jump_code_union { } __attribute__((packed)); }; +static void bug_at(unsigned char *ip, int line) +{ + /* + * The location is not an op that we were expecting. + * Something went wrong. Crash the box, as something could be + * corrupting the kernel. + */ + pr_warning("Unexpected op at %pS [%p] (%02x %02x %02x %02x %02x) %s:%d\n", + ip, ip, ip[0], ip[1], ip[2], ip[3], ip[4], __FILE__, line); + BUG(); +} + static void __jump_label_transform(struct jump_entry *entry, enum jump_label_type type, void *(*poker)(void *, const void *, size_t), @@ -37,7 +49,8 @@ static void __jump_label_transform(struct jump_entry *entry, * We are enabling this jump label. If it is not a nop * then something must have gone wrong. */ - BUG_ON(memcmp((void *)entry->code, ideal_nop, 5) != 0); + if (unlikely(memcmp((void *)entry->code, ideal_nop, 5) != 0)) + bug_at((void *)entry->code, __LINE__); code.jump = 0xe9; code.offset = entry->target - @@ -51,12 +64,14 @@ static void __jump_label_transform(struct jump_entry *entry, */ if (init) { const unsigned char default_nop[] = { STATIC_KEY_INIT_NOP }; - BUG_ON(memcmp((void *)entry->code, default_nop, 5) != 0); + if (unlikely(memcmp((void *)entry->code, default_nop, 5) != 0)) + bug_at((void *)entry->code, __LINE__); } else { code.jump = 0xe9; code.offset = entry->target - (entry->code + JUMP_LABEL_NOP_SIZE); - BUG_ON(memcmp((void *)entry->code, &code, 5) != 0); + if (unlikely(memcmp((void *)entry->code, &code, 5) != 0)) + bug_at((void *)entry->code, __LINE__); } memcpy(&code, ideal_nops[NOP_ATOMIC5], JUMP_LABEL_NOP_SIZE); } -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/