Messages in this thread Patch in this message |  | | Subject | Re: [PATCH 0/5 v2] [GIT PULL] x86/jump label: Paranoid checks and 2 or 5 byte nops | | From | Steven Rostedt <> | | Date | Wed, 01 Feb 2012 10:21:37 -0500 |
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On Wed, 2012-02-01 at 09:05 +0100, Ingo Molnar wrote: > * Steven Rostedt <rostedt@goodmis.org> wrote:
> It would be better to make this a regular commit, this kind of > diagnostics obviously makes sense. That way i could pull in your > updated branch for more testing.
Ingo,
I added the below patch on top of my previous pull request. If you run this on the box that failed, it should give us a little more info.
Thanks!
Please pull the latest tip/perf/jump-label-3 tree, which can be found at:
git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git tip/perf/jump-label-3
Head SHA1: abdefd743e4a28f11bcd38a441253f01dafea03e
Steven Rostedt (1): x86/jump lables: Show where and what was wrong on errors
---- arch/x86/kernel/jump_label.c | 31 +++++++++++++++++++++---------- 1 files changed, 21 insertions(+), 10 deletions(-) --------------------------- commit abdefd743e4a28f11bcd38a441253f01dafea03e Author: Steven Rostedt <srostedt@redhat.com> Date: Wed Feb 1 09:59:24 2012 -0500
x86/jump lables: Show where and what was wrong on errors 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>
diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c index 7112a27..2839524 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);
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