Re: kprobes broken in linux-next (was Re: [tip:perf/kprobes] kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist)

Masami Hiramatsu
2014-05-02T01:13:52Z

(2014/05/01 14:26), Vineet Gupta wrote:
> On Thursday 24 April 2014 04:28 PM, tip-bot for Masami Hiramatsu wrote:
>> Commit-ID: 376e242429bf8539ef39a080ac113c8799840b13
>> Gitweb: http://git.kernel.org/tip/376e242429bf8539ef39a080ac113c8799840b13
>> Author: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
>> AuthorDate: Thu, 17 Apr 2014 17:17:05 +0900
>> Committer: Ingo Molnar <mingo@kernel.org>
>> CommitDate: Thu, 24 Apr 2014 10:02:56 +0200
>>
>> kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist
>>
>> Introduce NOKPROBE_SYMBOL() macro which builds a kprobes
>> blacklist at kernel build time.
>>
> ....
>
>> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
>> index 146e4ff..40ceb3c 100644
>> --- a/include/asm-generic/vmlinux.lds.h
>> +++ b/include/asm-generic/vmlinux.lds.h
>> @@ -109,6 +109,14 @@
>> #define BRANCH_PROFILE()
>> #endif
>>
>> +#ifdef CONFIG_KPROBES
>> +#define KPROBE_BLACKLIST() VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
>> + *(_kprobe_blacklist) \
>> + VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
>> +#else
>> +#define KPROBE_BLACKLIST()
>> +#endif
>> +
>> #ifdef CONFIG_EVENT_TRACING
>> #define FTRACE_EVENTS() . = ALIGN(8); \
>> VMLINUX_SYMBOL(__start_ftrace_events) = .; \
>> @@ -507,6 +515,7 @@
>> *(.init.rodata) \
>> FTRACE_EVENTS() \
>> TRACE_SYSCALLS() \
>> + KPROBE_BLACKLIST() \
>> MEM_DISCARD(init.rodata) \
>> CLK_OF_TABLES() \
>> RESERVEDMEM_OF_TABLES() \
>
> Linux-next fails to boot on ARC due to misaligned __start_kprobe_blacklist. Patch
> below fixes it.
>
> ------------------------>
>>From c5afc4ebf9c1c094a260e2aaff6c5b3106063039 Mon Sep 17 00:00:00 2001
> From: Vineet Gupta <vgupta@synopsys.com>
> Date: Thu, 1 May 2014 10:47:29 +0530
> Subject: [PATCH] kprobes: Ensure blacklist data is aligned
>
> ARC Linux (not supporting native unaligned access) was failing to boot
> because __start_kprobe_blacklist was not aligned.
>
> This was because per generated vmlinux.lds it was emitted right next
> to .rodata with strings etc hence could be randomly unaligned.
>
> Fix that by ensuring a word alignment. While 4 would suffice for 32bit
> arches and problem at hand, it is probably better to put 8.
>
> | Path: (null) CPU: 0 PID: 1 Comm: swapper Not tainted
> | 3.15.0-rc3-next-20140430 #2
> | task: 8f044000 ti: 8f01e000 task.ti: 8f01e000
> |
> | [ECR ]: 0x00230400 => Misaligned r/w from 0x800fb0d3
> | [EFA ]: 0x800fb0d3
> | [BLINK ]: do_one_initcall+0x86/0x1bc
> | [ERET ]: init_kprobes+0x52/0x120
>
> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Thanks!

> ---
> include/asm-generic/vmlinux.lds.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 40ceb3ceba79..8e0204a68c74 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -110,7 +110,8 @@
> #endif
>
> #ifdef CONFIG_KPROBES
> -#define KPROBE_BLACKLIST() VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
> +#define KPROBE_BLACKLIST() . = ALIGN(8); \
> + VMLINUX_SYMBOL(__start_kprobe_blacklist) = .; \
> *(_kprobe_blacklist) \
> VMLINUX_SYMBOL(__stop_kprobe_blacklist) = .;
> #else
>

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Research Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com