From nobody Fri Oct 10 20:53:40 2025 Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 3F266223339; Thu, 12 Jun 2025 10:50:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=93.17.236.30 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749725443; cv=none; b=eIJATGpBiN1UbmkJVA/gbMCoaZM3dPM1h2G5noQgrEU7cFdbgVUKrp1LXgyWY+bR0x+2aPde2T3IOEhRS4+kjYjP6+3hBnmDCxIGBDA2G3jzmIS+ZGCFz59TR0MLFcD7g+T/mjmyEH+ECg3Vo2ORXiu41T5GNl0+GxTfKpouVcU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749725443; c=relaxed/simple; bh=SQUtuRhE2BAVHn8Mafr9cwFS7bLSZxdCosfeA4mmwDg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=eurQ+c9Mx30fqvk8RLE2PYv0fN5EmPxEgQkcMm0S9U/EFGzKNAeukPEQ8LEtawhNOizXjNduvG9jvTCqGnTn9EoBgI9pRWXu/qaWcVo4BqXqluGyK5E12wGA2cEpHhkssRlHVl+joBvR4eGzgl0LsSu2D5KVmIWY0vasFWys1Gs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu; spf=pass smtp.mailfrom=csgroup.eu; arc=none smtp.client-ip=93.17.236.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=csgroup.eu Received: from localhost (mailhub3.si.c-s.fr [192.168.12.233]) by localhost (Postfix) with ESMTP id 4bHzYb73gyz9tHF; Thu, 12 Jun 2025 12:39:47 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id k2wwbyyyP6lu; Thu, 12 Jun 2025 12:39:47 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4bHzYb6LqLz9tFS; Thu, 12 Jun 2025 12:39:47 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id D48D28B77B; Thu, 12 Jun 2025 12:39:47 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id QnMofMfdk0mU; Thu, 12 Jun 2025 12:39:47 +0200 (CEST) Received: from PO20335.idsi0.si.c-s.fr (unknown [192.168.235.99]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 502998B769; Thu, 12 Jun 2025 12:39:47 +0200 (CEST) From: Christophe Leroy To: Jaroslav Kysela , Takashi Iwai Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sound@vger.kernel.org, Herve Codina , Mark Brown Subject: [PATCH] ALSA: pcm: Convert snd_pcm_ioctl_sync_ptr_{compat/x32} to user_access_begin/user_access_end() Date: Thu, 12 Jun 2025 12:39:39 +0200 Message-ID: <8df11af98033e4cb4d9b0f16d6e9d5b69110b036.1749724057.git.christophe.leroy@csgroup.eu> X-Mailer: git-send-email 2.47.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1749724779; l=8808; i=christophe.leroy@csgroup.eu; s=20211009; h=from:subject:message-id; bh=SQUtuRhE2BAVHn8Mafr9cwFS7bLSZxdCosfeA4mmwDg=; b=JuAnvGdXpCM7km35w05+tUvPA0w1w1jX1C5T0Ty88h3Q2iIkdcGF+rdmyTdi/k6rxrXDkZJBR C1Zu00NQkFTChNEZcJu80cDHnrGGebl28WMqrKj25RtnZM/hcJptrSk X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" With user access protection (Called SMAP on x86 or KUAP on powerpc) each and every call to get_user() or put_user() performs heavy operations to unlock and lock kernel access to userspace. SNDRV_PCM_IOCTL_SYNC_PTR ioctl is a hot path that needs to be optimised. To do that, perform user accesses by blocks using user_access_begin/user_access_end() and unsafe_get_user()/ unsafe_put_user() and alike. Before the patch the 9 calls to put_user() at the end of snd_pcm_ioctl_sync_ptr_compat() imply the following set of instructions about 9 times (access_ok - enable user - write - disable user): 0.00 : c057f858: 3d 20 7f ff lis r9,32767 0.29 : c057f85c: 39 5e 00 14 addi r10,r30,20 0.77 : c057f860: 61 29 ff fc ori r9,r9,65532 0.32 : c057f864: 7c 0a 48 40 cmplw r10,r9 0.36 : c057f868: 41 a1 fb 58 bgt c057f3c0 0.30 : c057f86c: 3d 20 dc 00 lis r9,-9216 1.95 : c057f870: 7d 3a c3 a6 mtspr 794,r9 0.33 : c057f874: 92 8a 00 00 stw r20,0(r10) 0.27 : c057f878: 3d 20 de 00 lis r9,-8704 0.28 : c057f87c: 7d 3a c3 a6 mtspr 794,r9 ... A perf profile shows that in total the 9 put_user() represent 36% of the time spent in snd_pcm_ioctl() and about 80 instructions. With this patch everything is done in 13 instructions and represent only 15% of the time spent in snd_pcm_ioctl(): 0.57 : c057f5dc: 3d 20 dc 00 lis r9,-9216 0.98 : c057f5e0: 7d 3a c3 a6 mtspr 794,r9 0.16 : c057f5e4: 92 7f 00 04 stw r19,4(r31) 0.63 : c057f5e8: 93 df 00 0c stw r30,12(r31) 0.16 : c057f5ec: 93 9f 00 10 stw r28,16(r31) 4.95 : c057f5f0: 92 9f 00 14 stw r20,20(r31) 0.19 : c057f5f4: 92 5f 00 18 stw r18,24(r31) 0.49 : c057f5f8: 92 bf 00 1c stw r21,28(r31) 0.27 : c057f5fc: 93 7f 00 20 stw r27,32(r31) 5.88 : c057f600: 93 36 00 00 stw r25,0(r22) 0.11 : c057f604: 93 17 00 00 stw r24,0(r23) 0.00 : c057f608: 3d 20 de 00 lis r9,-8704 0.79 : c057f60c: 7d 3a c3 a6 mtspr 794,r9 Note that here the access_ok() in user_write_access_begin() is skipped because the exact same verification has already been performed at the beginning of the fonction with the call to user_read_access_begin(). Signed-off-by: Christophe Leroy --- This is a lighter version of previous patch "[PATCH v2] ALSA: pcm: Convert = multiple {get/put}_user to user_access_begin/user_access_end()" focussing o= n identified hot path. Moved and nested the failure labels closer in order to increase readability Link: https://patchwork.ozlabs.org/project/linuxppc-dev/patch/d2609397eafc2= b55ec1f44a3f30ccec00e0c7f6e.1749455639.git.christophe.leroy@csgroup.eu/ sound/core/pcm_compat.c | 40 +++++++++++++++++++++++++++------------- sound/core/pcm_native.c | 40 +++++++++++++++++++++++++++------------- 2 files changed, 54 insertions(+), 26 deletions(-) diff --git a/sound/core/pcm_compat.c b/sound/core/pcm_compat.c index a42ec7f5a1da..348a72e6499e 100644 --- a/sound/core/pcm_compat.c +++ b/sound/core/pcm_compat.c @@ -418,10 +418,18 @@ static int snd_pcm_ioctl_sync_ptr_x32(struct snd_pcm_= substream *substream, if (snd_BUG_ON(!runtime)) return -EINVAL; =20 - if (get_user(sflags, &src->flags) || - get_user(scontrol.appl_ptr, &src->c.control.appl_ptr) || - get_user(scontrol.avail_min, &src->c.control.avail_min)) + if (!user_read_access_begin(src, sizeof(*src))) return -EFAULT; + err =3D -EFAULT; + unsafe_get_user(sflags, &src->flags, Efault_rd); + unsafe_get_user(scontrol.appl_ptr, &src->c.control.appl_ptr, Efault_rd); + unsafe_get_user(scontrol.avail_min, &src->c.control.avail_min, Efault_rd); + err =3D 0; +Efault_rd: + user_read_access_end(); + if (err) + return err; + if (sflags & SNDRV_PCM_SYNC_PTR_HWSYNC) { err =3D snd_pcm_hwsync(substream); if (err < 0) @@ -450,18 +458,24 @@ static int snd_pcm_ioctl_sync_ptr_x32(struct snd_pcm_= substream *substream, } if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL)) snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE); - if (put_user(sstatus.state, &src->s.status.state) || - put_user(sstatus.hw_ptr, &src->s.status.hw_ptr) || - put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp_sec) || - put_user(sstatus.tstamp.tv_nsec, &src->s.status.tstamp_nsec) || - put_user(sstatus.suspended_state, &src->s.status.suspended_state) || - put_user(sstatus.audio_tstamp.tv_sec, &src->s.status.audio_tstamp_sec= ) || - put_user(sstatus.audio_tstamp.tv_nsec, &src->s.status.audio_tstamp_ns= ec) || - put_user(scontrol.appl_ptr, &src->c.control.appl_ptr) || - put_user(scontrol.avail_min, &src->c.control.avail_min)) + + if (!user_write_access_begin(src, sizeof(*src))) return -EFAULT; + err =3D -EFAULT; + unsafe_put_user(sstatus.state, &src->s.status.state, Efault_wr); + unsafe_put_user(sstatus.hw_ptr, &src->s.status.hw_ptr, Efault_wr); + unsafe_put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp_sec, Efault_= wr); + unsafe_put_user(sstatus.tstamp.tv_nsec, &src->s.status.tstamp_nsec, Efaul= t_wr); + unsafe_put_user(sstatus.suspended_state, &src->s.status.suspended_state, = Efault_wr); + unsafe_put_user(sstatus.audio_tstamp.tv_sec, &src->s.status.audio_tstamp_= sec, Efault_wr); + unsafe_put_user(sstatus.audio_tstamp.tv_nsec, &src->s.status.audio_tstamp= _nsec, Efault_wr); + unsafe_put_user(scontrol.appl_ptr, &src->c.control.appl_ptr, Efault_wr); + unsafe_put_user(scontrol.avail_min, &src->c.control.avail_min), Efault_wr= ); + err =3D 0; +Efault_wr: + user_write_access_end(); =20 - return 0; + return err; } #endif /* CONFIG_X86_X32_ABI */ =20 diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index ecb71bf1859d..b104faddb6e3 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -3165,10 +3165,18 @@ static int snd_pcm_ioctl_sync_ptr_compat(struct snd= _pcm_substream *substream, if (snd_BUG_ON(!runtime)) return -EINVAL; =20 - if (get_user(sflags, &src->flags) || - get_user(scontrol.appl_ptr, &src->c.control.appl_ptr) || - get_user(scontrol.avail_min, &src->c.control.avail_min)) + if (!user_read_access_begin(src, sizeof(*src))) return -EFAULT; + err =3D -EFAULT; + unsafe_get_user(sflags, &src->flags, Efault_rd); + unsafe_get_user(scontrol.appl_ptr, &src->c.control.appl_ptr, Efault_rd); + unsafe_get_user(scontrol.avail_min, &src->c.control.avail_min, Efault_rd); + err =3D 0; +Efault_rd: + user_read_access_end(); + if (err) + return err; + if (sflags & SNDRV_PCM_SYNC_PTR_HWSYNC) { err =3D snd_pcm_hwsync(substream); if (err < 0) @@ -3200,18 +3208,24 @@ static int snd_pcm_ioctl_sync_ptr_compat(struct snd= _pcm_substream *substream, } if (!(sflags & SNDRV_PCM_SYNC_PTR_APPL)) snd_pcm_dma_buffer_sync(substream, SNDRV_DMA_SYNC_DEVICE); - if (put_user(sstatus.state, &src->s.status.state) || - put_user(sstatus.hw_ptr, &src->s.status.hw_ptr) || - put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp_sec) || - put_user(sstatus.tstamp.tv_nsec, &src->s.status.tstamp_nsec) || - put_user(sstatus.suspended_state, &src->s.status.suspended_state) || - put_user(sstatus.audio_tstamp.tv_sec, &src->s.status.audio_tstamp_sec= ) || - put_user(sstatus.audio_tstamp.tv_nsec, &src->s.status.audio_tstamp_ns= ec) || - put_user(scontrol.appl_ptr, &src->c.control.appl_ptr) || - put_user(scontrol.avail_min, &src->c.control.avail_min)) + + if (!user_write_access_begin(src, sizeof(*src))) return -EFAULT; + err =3D -EFAULT; + unsafe_put_user(sstatus.state, &src->s.status.state, Efault_wr); + unsafe_put_user(sstatus.hw_ptr, &src->s.status.hw_ptr, Efault_wr); + unsafe_put_user(sstatus.tstamp.tv_sec, &src->s.status.tstamp_sec, Efault_= wr); + unsafe_put_user(sstatus.tstamp.tv_nsec, &src->s.status.tstamp_nsec, Efaul= t_wr); + unsafe_put_user(sstatus.suspended_state, &src->s.status.suspended_state, = Efault_wr); + unsafe_put_user(sstatus.audio_tstamp.tv_sec, &src->s.status.audio_tstamp_= sec, Efault_wr); + unsafe_put_user(sstatus.audio_tstamp.tv_nsec, &src->s.status.audio_tstamp= _nsec, Efault_wr); + unsafe_put_user(scontrol.appl_ptr, &src->c.control.appl_ptr, Efault_wr); + unsafe_put_user(scontrol.avail_min, &src->c.control.avail_min, Efault_wr); + err =3D 0; +Efault_wr: + user_write_access_end(); =20 - return 0; + return err; } #define __SNDRV_PCM_IOCTL_SYNC_PTR32 _IOWR('A', 0x23, struct snd_pcm_sync_= ptr32) =20 --=20 2.47.0