Messages in this thread | | | Date | Tue, 15 Aug 2023 20:41:12 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH] x86/static_call: Fix __static_call_fixup() |
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On Wed, 16 Aug 2023 01:08:09 +0200 Peter Zijlstra <peterz@infradead.org> wrote:
> diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c > index b70670a98597..2e67512d7104 100644 > --- a/arch/x86/kernel/static_call.c > +++ b/arch/x86/kernel/static_call.c > @@ -186,6 +186,16 @@ EXPORT_SYMBOL_GPL(arch_static_call_transform); > */ > bool __static_call_fixup(void *tramp, u8 op, void *dest) > { > + /* > + * Not all .return_sites are a static_call trampoline (most are not). > + * Check if the next 3 bytes are still kernel text, if not, then this > + * definitely is not a trampoline and we need not worry further. > + * > + * This avoids the memcmp() below tripping over pagefaults etc.. > + */ > + if (!kernel_text_address(tramp+7))
The comment says "next 3 bytes" and the test is "tramp+7". Why the magic 7 number?
If the tramp is 5 bytes, shouldn't it be +8?
-- Steve
> + return false; > + > if (memcmp(tramp+5, tramp_ud, 3)) { > /* Not a trampoline site, not our problem. */ > return false;
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