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Message-ID: <534c5e53-07bb-07bd-0435-76a10b55228d@linux.alibaba.com>
Date: Fri, 4 Aug 2023 19:24:33 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Leo Yan <leo.yan@...aro.org>, James Clark <james.clark@....com>,
Peter Zijlstra <peterz@...radead.org>
Cc: alexander.shishkin@...ux.intel.com, mingo@...hat.com,
baolin.wang@...ux.alibaba.com, acme@...nel.org,
mark.rutland@....com, jolsa@...nel.org, namhyung@...nel.org,
irogers@...gle.com, adrian.hunter@...el.com,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
nathan@...nel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v4 1/2] perf/core: Bail out early if the request AUX area
is out of bound
On 2023/8/4 16:59, Leo Yan wrote:
> On Fri, Aug 04, 2023 at 03:29:44PM +0800, Shuai Xue wrote:
>> When perf-record with a large AUX area, e.g 4GB, it fails with:
>>
>> #perf record -C 0 -m ,4G -e arm_spe_0// -- sleep 1
>> failed to mmap with 12 (Cannot allocate memory)
>>
>> and it reveals a WARNING with __alloc_pages():
>>
>> [ 66.595604] ------------[ cut here ]------------
>> [ 66.600206] WARNING: CPU: 44 PID: 17573 at mm/page_alloc.c:5568 __alloc_pages+0x1ec/0x248
>> [ 66.608375] Modules linked in: ip6table_filter(E) ip6_tables(E) iptable_filter(E) ebtable_nat(E) ebtables(E) aes_ce_blk(E) vfat(E) fat(E) aes_ce_cipher(E) crct10dif_ce(E) ghash_ce(E) sm4_ce_cipher(E) sm4(E) sha2_ce(E) sha256_arm64(E) sha1_ce(E) acpi_ipmi(E) sbsa_gwdt(E) sg(E) ipmi_si(E) ipmi_devintf(E) ipmi_msghandler(E) ip_tables(E) sd_mod(E) ast(E) drm_kms_helper(E) syscopyarea(E) sysfillrect(E) nvme(E) sysimgblt(E) i2c_algo_bit(E) nvme_core(E) drm_shmem_helper(E) ahci(E) t10_pi(E) libahci(E) drm(E) crc64_rocksoft(E) i40e(E) crc64(E) libata(E) i2c_core(E)
>> [ 66.657719] CPU: 44 PID: 17573 Comm: perf Kdump: loaded Tainted: G E 6.3.0-rc4+ #58
>> [ 66.666749] Hardware name: Default Default/Default, BIOS 1.2.M1.AL.P.139.00 03/22/2023
>> [ 66.674650] pstate: 23400009 (nzCv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
>> [ 66.681597] pc : __alloc_pages+0x1ec/0x248
>> [ 66.685680] lr : __kmalloc_large_node+0xc0/0x1f8
>> [ 66.690285] sp : ffff800020523980
>> [ 66.693585] pmr_save: 000000e0
>> [ 66.696624] x29: ffff800020523980 x28: ffff000832975800 x27: 0000000000000000
>> [ 66.703746] x26: 0000000000100000 x25: 0000000000100000 x24: ffff8000083615d0
>> [ 66.710866] x23: 0000000000040dc0 x22: ffff000823d6d140 x21: 000000000000000b
>> [ 66.717987] x20: 000000000000000b x19: 0000000000000000 x18: 0000000000000030
>> [ 66.725108] x17: 0000000000000000 x16: ffff800008f05be8 x15: ffff000823d6d6d0
>> [ 66.732229] x14: 0000000000000000 x13: 343373656761705f x12: 726e202c30206574
>> [ 66.739350] x11: 00000000ffff7fff x10: 00000000ffff7fff x9 : ffff8000083af570
>> [ 66.746471] x8 : 00000000000bffe8 x7 : c0000000ffff7fff x6 : 000000000005fff4
>> [ 66.753592] x5 : 0000000000000000 x4 : ffff000823d6d8d8 x3 : 0000000000000000
>> [ 66.760713] x2 : 0000000000000000 x1 : 0000000000000001 x0 : 0000000000040dc0
>> [ 66.767834] Call trace:
>> [ 66.770267] __alloc_pages+0x1ec/0x248
>> [ 66.774003] __kmalloc_large_node+0xc0/0x1f8
>> [ 66.778259] __kmalloc_node+0x134/0x1e8
>> [ 66.782081] rb_alloc_aux+0xe0/0x298
>> [ 66.785643] perf_mmap+0x440/0x660
>> [ 66.789031] mmap_region+0x308/0x8a8
>> [ 66.792593] do_mmap+0x3c0/0x528
>> [ 66.795807] vm_mmap_pgoff+0xf4/0x1b8
>> [ 66.799456] ksys_mmap_pgoff+0x18c/0x218
>> [ 66.803365] __arm64_sys_mmap+0x38/0x58
>> [ 66.807187] invoke_syscall+0x50/0x128
>> [ 66.810922] el0_svc_common.constprop.0+0x58/0x188
>> [ 66.815698] do_el0_svc+0x34/0x50
>> [ 66.818999] el0_svc+0x34/0x108
>> [ 66.822127] el0t_64_sync_handler+0xb8/0xc0
>> [ 66.826296] el0t_64_sync+0x1a4/0x1a8
>> [ 66.829946] ---[ end trace 0000000000000000 ]---
>>
>> 'rb->aux_pages' allocated by kcalloc() is a pointer array which is used to
>> maintains AUX trace pages. The allocated page for this array is physically
>> contiguous (and virtually contiguous) with an order of 0..MAX_ORDER. If the
>> size of pointer array crosses the limitation set by MAX_ORDER, it reveals a
>> WARNING.
>>
>> So bail out early with -ENOMEM if the request AUX area is out of bound,
>> e.g.:
>>
>> #perf record -C 0 -m ,4G -e arm_spe_0// -- sleep 1
>> failed to mmap with 12 (Cannot allocate memory)
>>
>> Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
>> ---
>> kernel/events/ring_buffer.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
>> index a0433f37b024..c445e927368d 100644
>> --- a/kernel/events/ring_buffer.c
>> +++ b/kernel/events/ring_buffer.c
>> @@ -699,6 +699,9 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event,
>> watermark = 0;
>> }
>>
>> + /* Can't allocate more than MAX_ORDER */
>
> The comment is confused. I'd like to refine it as:
>
> /*
> * kcalloc_node() is unable to allocate buffer if the size is larger
> * than: PAGE_SIZE << MAX_ORDER; directly bail out in this case.
> */
Hi, Leo,
Thank you for your quick feedback. The comment is simplified from Peter's reply in v2
version. Your refined comment is more detailed and it makes sense to me, I would like
to adopt it if @Peter has no other opinions.
> To be honest, I am not sure if perf core maintainers like this kind
> thing or not. Please seek their opinion before you move forward.
>
and hi, all perf core maintainers,
I have not received explicit objection from perf core maintainers @Peter or @James so
I moved forward to address their comments. It's fine to me to wait for more opinions from
perf core maintainers.
Best Regards,
Shuai
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