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SubjectRe: [PATCH v3 3/7] arm: use fixmap for text patching when text is RO
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On Tue, Aug 12, 2014 at 2:39 PM, Stephen Boyd <sboyd@codeaurora.org> wrote:
> On 08/12/14 11:24, Kees Cook wrote:
>> diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
>> index 07314af47733..03dd4e39c833 100644
>> --- a/arch/arm/kernel/patch.c
>> +++ b/arch/arm/kernel/patch.c
>> @@ -13,21 +16,69 @@ struct patch {
>> unsigned int insn;
>> };
>>
>> -void __kprobes __patch_text(void *addr, unsigned int insn)
>> +static DEFINE_SPINLOCK(patch_lock);
>> +
>> +static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
>> +{
>> + unsigned int uintaddr = (uintptr_t) addr;
>> + bool module = !core_kernel_text(uintaddr);
>> + struct page *page;
>> +
>> + if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))
>> + page = vmalloc_to_page(addr);
>> + else if (!module && IS_ENABLED(CONFIG_DEBUG_RODATA))
>> + page = virt_to_page(addr);
>> + else
>> + return addr;
>> +
>> + if (flags)
>> + spin_lock_irqsave(&patch_lock, *flags);
>> +
>> + set_fixmap(fixmap, page_to_phys(page));
>> +
>> + return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
>> +}
>> +
>> +static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
>> +{
>> + clear_fixmap(fixmap);
>> +
>> + if (flags)
>> + spin_unlock_irqrestore(&patch_lock, *flags);
>> +}
>
> Has the kbuildbot complained about this one yet?
>
> CHECK arch/arm/kernel/patch.c
> arch/arm/kernel/patch.c:47:39: warning: context imbalance in
> 'patch_unmap' - unexpected unlock
>
> I guess we're going to ignore it.

No, nothing yet from buildbot, let me do a sparse run -- I think we
can just add annotation and we'll be okay.

-Kees

--
Kees Cook
Chrome OS Security


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