From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Alexei Starovoitov <ast@fb.com>
Cc: rostedt <rostedt@goodmis.org>,
"David S. Miller" <davem@davemloft.net>,
Daniel Borkmann <daniel@iogearbox.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
netdev <netdev@vger.kernel.org>, kernel-team <kernel-team@fb.com>,
linux-api <linux-api@vger.kernel.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH v6 bpf-next 08/11] bpf: introduce BPF_RAW_TRACEPOINT
Date: Tue, 27 Mar 2018 19:13:37 -0400 (EDT) [thread overview]
Message-ID: <430531879.1792.1522192417816.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <563f7fa0-5fea-00d3-1eb3-fa00d8cf7e29@fb.com>
----- On Mar 27, 2018, at 6:48 PM, Alexei Starovoitov ast@fb.com wrote:
> On 3/27/18 2:04 PM, Steven Rostedt wrote:
>>
>> +#ifdef CONFIG_BPF_EVENTS
>> +#define BPF_RAW_TP() . = ALIGN(8); \
Given that the section consists of a 16-bytes structure elements
on architectures with 8 bytes pointers, this ". = ALIGN(8)" should
be turned into a STRUCT_ALIGN(), especially given that the compiler
is free to up-align the structure on 32 bytes.
This could explain the kasan splat you are experiencing.
Thanks,
Mathieu
>> + VMLINUX_SYMBOL(__start__bpf_raw_tp) = .; \
>> + KEEP(*(__bpf_raw_tp_map)) \
>> + VMLINUX_SYMBOL(__stop__bpf_raw_tp) = .;
>
> that looks to be correct, but something wrong with it.
>
> Can you try your mini test with kasan on ?
>
> I'm seeing this crash:
> test_stacktrace_[ 18.760662] start ffffffff84642438 stop ffffffff84644f60
> map_raw_tp:PASS:[ 18.761467] i 1 btp->tp cccccccccccccccc
> prog_load raw tp[ 18.762064] kasan: CONFIG_KASAN_INLINE enabled
> 0 nsec
> [ 18.762704] kasan: GPF could be caused by NULL-ptr deref or user
> memory access
> [ 18.765125] general protection fault: 0000 [#1] SMP KASAN PTI
> [ 18.765830] Modules linked in:
> [ 18.778358] Call Trace:
> [ 18.778674] bpf_raw_tracepoint_open.isra.27+0x92/0x380
>
> for some reason the start_bpf_raw_tp is off by 8.
> Not sure how it works for you.
>
> (gdb) p &__bpf_trace_tp_map_sys_exit
> $10 = (struct bpf_raw_event_map *) 0xffffffff84642440
> <__bpf_trace_tp_map_sys_exit>
>
> (gdb) p &__start__bpf_raw_tp
> $7 = (<data variable, no debug info> *) 0xffffffff84642438
>
> (gdb) p (void*)(&__start__bpf_raw_tp)+8
> $11 = (void *) 0xffffffff84642440 <__bpf_trace_tp_map_sys_exit>
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2018-03-27 23:13 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-27 2:46 [PATCH v6 bpf-next 00/11] bpf, tracing: introduce bpf raw tracepoints Alexei Starovoitov
2018-03-27 2:46 ` [PATCH v6 bpf-next 01/11] treewide: remove large struct-pass-by-value from tracepoint arguments Alexei Starovoitov
2018-03-27 2:46 ` [PATCH v6 bpf-next 02/11] net/mediatek: disambiguate mt76 vs mt7601u trace events Alexei Starovoitov
2018-03-27 2:46 ` [PATCH v6 bpf-next 03/11] net/mac802154: disambiguate mac80215 vs mac802154 " Alexei Starovoitov
2018-03-27 2:46 ` [PATCH v6 bpf-next 04/11] net/wireless/iwlwifi: fix iwlwifi_dev_ucode_error tracepoint Alexei Starovoitov
2018-03-27 2:47 ` [PATCH v6 bpf-next 05/11] macro: introduce COUNT_ARGS() macro Alexei Starovoitov
2018-03-27 2:47 ` [PATCH v6 bpf-next 06/11] tracepoint: compute num_args at build time Alexei Starovoitov
2018-03-27 15:15 ` Steven Rostedt
2018-03-27 2:47 ` [PATCH v6 bpf-next 07/11] tracepoint: introduce kernel_tracepoint_find_by_name Alexei Starovoitov
2018-03-27 14:07 ` Steven Rostedt
2018-03-27 14:18 ` Mathieu Desnoyers
2018-03-27 14:42 ` Steven Rostedt
2018-03-27 15:53 ` Alexei Starovoitov
2018-03-27 16:09 ` Mathieu Desnoyers
2018-03-27 16:36 ` Daniel Borkmann
2018-03-27 2:47 ` [PATCH v6 bpf-next 08/11] bpf: introduce BPF_RAW_TRACEPOINT Alexei Starovoitov
2018-03-27 17:02 ` Steven Rostedt
2018-03-27 17:11 ` Steven Rostedt
2018-03-27 18:58 ` Steven Rostedt
2018-03-27 21:04 ` Steven Rostedt
2018-03-27 22:48 ` Alexei Starovoitov
2018-03-27 23:13 ` Mathieu Desnoyers [this message]
2018-03-28 0:00 ` Alexei Starovoitov
2018-03-28 0:44 ` Mathieu Desnoyers
2018-03-28 0:51 ` Alexei Starovoitov
2018-03-28 14:06 ` Steven Rostedt
2018-03-27 18:45 ` Alexei Starovoitov
2018-03-27 19:00 ` Steven Rostedt
2018-03-27 19:07 ` Steven Rostedt
2018-03-27 19:10 ` Steven Rostedt
2018-03-27 19:10 ` Mathieu Desnoyers
2018-03-27 2:47 ` [PATCH v6 bpf-next 09/11] libbpf: add bpf_raw_tracepoint_open helper Alexei Starovoitov
2018-03-27 2:47 ` [PATCH v6 bpf-next 10/11] samples/bpf: raw tracepoint test Alexei Starovoitov
2018-03-27 2:47 ` [PATCH v6 bpf-next 11/11] selftests/bpf: test for bpf_get_stackid() from raw tracepoints Alexei Starovoitov
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