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    SubjectRe: [PATCH][GIT PULL] tracing: Fix compile issue for trace_sched_wakeup.c
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    On Fri, 2010-10-22 at 17:42 -0400, Jason Baron wrote:

    > > > this looks potentially like a separate issue from the 'hang' one - I'm wondering
    > > > if this was re-produced with the same .config as the 'hang' case? I haven't been
    > > > able to hit this one yet....
    > >
    > > Not the same config, and it's very spurious - i.e. a slightly different -tip version
    > > with the same config will boot fine. (this suggests some race)
    > >
    > > Something very much not good with the fundamental mechanics of jump labels i'm
    > > afraid. It might be corrupting some memory here, or have some window of
    > > vulnerability in which an IRQ hits (or so) we will crash.
    > >
    > > Thanks,
    > >
    > > Ingo
    >
    > we probably should have more sanity checks in the jump label code. The
    > patch below verifies the the src and target addresses are within the
    > text sections, and checks that we are not jumping to target out of
    > range.
    >
    > comments? it be nice to get these into the tree asap, so that these
    > might indicate what the issue is. Only lightly tested at this point.
    >
    > thanks,
    >

    Note, if you want a patch processed, please send it as a separate thread
    with "[PATCH]" in the subject. Do not embed patches inside of replies,
    because they most likely will be ignored by most people.

    > -Jason
    >
    > Add sanity checks to the jump label code. Check that the src and dest
    > addresses are in the text sections, and that we aren't jump farther than
    > we can reach.
    >
    >
    > Signed-off-by: Jason Baron <jbaron@redhat.com>
    >
    > diff --git a/arch/x86/kernel/jump_label.c b/arch/x86/kernel/jump_label.c
    > index 961b6b3..14b2180 100644
    > --- a/arch/x86/kernel/jump_label.c
    > +++ b/arch/x86/kernel/jump_label.c
    > @@ -28,11 +28,17 @@ void arch_jump_label_transform(struct jump_entry *entry,
    > enum jump_label_type type)
    > {
    > union jump_code_union code;
    > + long diff;
    >
    > if (type == JUMP_LABEL_ENABLE) {
    > code.jump = 0xe9;
    > - code.offset = entry->target -
    > - (entry->code + JUMP_LABEL_NOP_SIZE);
    > + diff = (long)entry->target -
    > + ((long)(entry->code + JUMP_LABEL_NOP_SIZE));
    > + if (abs(diff) > 0x7fffffff) {
    > + printk(KERN_ERR "jump label out of bounds!\n");
    > + BUG();

    Is there a nicer way to fail here? Can we have a:

    if (WARN_ON_ONCE(abs(diff) > 0x7fffffff)
    return;

    ?


    > + }
    > + code.offset = (s32)diff;
    > } else
    > memcpy(&code, ideal_nop5, JUMP_LABEL_NOP_SIZE);
    > get_online_cpus();
    > diff --git a/kernel/jump_label.c b/kernel/jump_label.c
    > index 7be868b..a33b01d 100644
    > --- a/kernel/jump_label.c
    > +++ b/kernel/jump_label.c
    > @@ -78,6 +78,28 @@ static struct jump_label_entry *get_jump_label_entry(jump_label_t key)
    > return NULL;
    > }
    >
    > +static void verify_jump_addresses(struct jump_entry *table, int nr_entries)
    > +{
    > + int count;
    > + struct jump_entry *iter;
    > +
    > + count = nr_entries;
    > + iter = table;
    > + while (count--) {
    > + if (!kernel_text_address(iter->code)) {
    > + printk(KERN_ERR "jump label: invalid src addr: %lx\n",
    > + (unsigned long)iter->code);
    > + BUG();
    > + }
    > + if (!kernel_text_address(iter->target)) {
    > + printk(KERN_ERR "jump label: invalid dest addr: %lx\n",
    > + (unsigned long)iter->target);
    > + BUG();

    Same for these BUG()s.

    -- Steve

    > + }
    > + iter++;
    > + }
    > +}
    > +
    > static struct jump_label_entry *
    > add_jump_label_entry(jump_label_t key, int nr_entries, struct jump_entry *table)
    > {
    > @@ -85,6 +107,9 @@ add_jump_label_entry(jump_label_t key, int nr_entries, struct jump_entry *table)
    > struct jump_label_entry *e;
    > u32 hash;
    >
    > + /* first verify that the addresses are ok */
    > + verify_jump_addresses(table, nr_entries);
    > +
    > e = get_jump_label_entry(key);
    > if (e)
    > return ERR_PTR(-EEXIST);
    > @@ -289,6 +314,8 @@ add_jump_label_module_entry(struct jump_label_entry *entry,
    > {
    > struct jump_label_module_entry *e;
    >
    > + verify_jump_addresses(iter_begin, count);
    > +
    > e = kmalloc(sizeof(struct jump_label_module_entry), GFP_KERNEL);
    > if (!e)
    > return ERR_PTR(-ENOMEM);




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