[PATCH 1/2] arm64: kprobes: Remove unneeded address sanity check

[Masami Hiramatsu]

Hi Will,

2018-02-06 23:36 GMT+09:00 Will Deacon <will.deacon at arm.com>:
> On Thu, Feb 01, 2018 at 06:34:58PM +0900, AKASHI Takahiro wrote:
>> From: Masami Hiramatsu <mhiramat at kernel.org>
>>
>> Remove unneeded address sanity check in arch_prepare_kprobe().
>> Since do_debug_exception() is already blacklisted for kprobes, no need
>> to reject all __exception functions. Also, since generic kprobe
>> framework already ensures the address is in kernel text, no need to
>> check it is in rodata again.
>>
>> Signed-off-by: Masami Hiramatsu <mhiramat at kernel.org>
>> Reported-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
>> ---
>>  arch/arm64/kernel/probes/kprobes.c | 8 --------
>>  1 file changed, 8 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c
>> index d849d9804011..3c487a389252 100644
>> --- a/arch/arm64/kernel/probes/kprobes.c
>> +++ b/arch/arm64/kernel/probes/kprobes.c
>> @@ -78,8 +78,6 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
>>  int __kprobes arch_prepare_kprobe(struct kprobe *p)
>>  {
>>       unsigned long probe_addr = (unsigned long)p->addr;
>> -     extern char __start_rodata[];
>> -     extern char __end_rodata[];
>>
>>       if (probe_addr & 0x3)
>>               return -EINVAL;
>> @@ -87,12 +85,6 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
>>       /* copy instruction */
>>       p->opcode = le32_to_cpu(*p->addr);
>>
>> -     if (in_exception_text(probe_addr))
>> -             return -EINVAL;
>> -     if (probe_addr >= (unsigned long) __start_rodata &&
>> -         probe_addr <= (unsigned long) __end_rodata)
>> -             return -EINVAL;
>> -
>
> Does this mean we can remove in_exception_text and the corresponding
> __exception annotations from arm64?

Good catch. As far as I can see, there is no other in_exception_text()
user under arch/arm64,
so we can remove it all.

Thank you,

-- 
Masami Hiramatsu