Messages in this thread Patch in this message | | | Date | Thu, 08 Mar 2012 17:17:36 -0500 | From | Steven Rostedt <> | Subject | [PATCH 6/7] x86/jump lables: Show where and what was wrong on errors |
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From: Steven Rostedt <srostedt@redhat.com>
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 <rostedt@goodmis.org> --- arch/x86/kernel/jump_label.c | 31 +++++++++++++++++++++---------- 1 files changed, 21 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index d426da6..9bae2c9 100644 --- a/arch/x86/kernel/jump_label.c +++ b/arch/x86/kernel/jump_label.c @@ -32,6 +32,18 @@ union jump_code_union { } __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. + */ + printk("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), @@ -59,12 +71,7 @@ static void __jump_label_transform(struct jump_entry *entry, code.jump = 0xe9; code.offset = entry->target - (entry->code + size); } else - /* - * The location is not a nop that we were expecting, - * something went wrong. Crash the box, as something could be - * corrupting the kernel. - */ - BUG(); + bug_at(ip, __LINE__); } else { /* * We are disabling this jump label. If it is not what @@ -78,7 +85,8 @@ static void __jump_label_transform(struct jump_entry *entry, return; /* We are initializing from the default nop */ - BUG_ON(memcmp(ip, default_nop, 5) != 0); + if (unlikely(memcmp(ip, default_nop, 5) != 0)) + bug_at(ip, __LINE__); /* Set to the ideal nop */ size = JUMP_LABEL_NOP_SIZE; @@ -91,7 +99,9 @@ static void __jump_label_transform(struct jump_entry *entry, code.jump = 0xe9; code.offset = entry->target - (entry->code + JUMP_LABEL_NOP_SIZE); - BUG_ON(memcmp(ip, &code, 5) != 0); + + if (unlikely(memcmp(ip, &code, 5) != 0)) + bug_at(ip, __LINE__); size = JUMP_LABEL_NOP_SIZE; memcpy(&code, ideal_nops[NOP_ATOMIC5], size); @@ -101,13 +111,14 @@ static void __jump_label_transform(struct jump_entry *entry, /* Had better be a 2 byte jmp */ code.jump_short = 0xeb; code.offset = entry->target - (entry->code + 2); - BUG_ON(memcmp(ip, &code, 2) != 0); + if (unlikely(memcmp(ip, &code, 2) != 0)) + bug_at(ip, __LINE__); size = 2; memcpy(&code, nop_short, size); } else /* The code was not what we expected! */ - BUG(); + bug_at(ip, __LINE__); } (*poker)(ip, &code, size); -- 1.7.8.3
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