From: Christophe Leroy <christophe.leroy@csgroup.eu> To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>, npiggin@gmail.com, msuchanek@suse.de Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org Subject: [PATCH v4 19/23] powerpc/syscall: Avoid stack frame in likely part of system_call_exception() Date: Mon, 25 Jan 2021 14:48:32 +0000 (UTC) [thread overview] Message-ID: <cdaf4ac33405e9a00ab277eccc5fd240d95e65b1.1611585031.git.christophe.leroy@csgroup.eu> (raw) In-Reply-To: <cover.1611585031.git.christophe.leroy@csgroup.eu> When r3 is not modified, reload it from regs->orig_r3 to free volatile registers. This avoids a stack frame for the likely part of system_call_exception() Before the patch: c000b4d4 <system_call_exception>: c000b4d4: 7c 08 02 a6 mflr r0 c000b4d8: 94 21 ff e0 stwu r1,-32(r1) c000b4dc: 93 e1 00 1c stw r31,28(r1) c000b4e0: 90 01 00 24 stw r0,36(r1) c000b4e4: 90 6a 00 88 stw r3,136(r10) c000b4e8: 81 6a 00 84 lwz r11,132(r10) c000b4ec: 69 6b 00 02 xori r11,r11,2 c000b4f0: 55 6b ff fe rlwinm r11,r11,31,31,31 c000b4f4: 0f 0b 00 00 twnei r11,0 c000b4f8: 81 6a 00 a0 lwz r11,160(r10) c000b4fc: 55 6b 07 fe clrlwi r11,r11,31 c000b500: 0f 0b 00 00 twnei r11,0 c000b504: 7c 0c 42 e6 mftb r0 c000b508: 83 e2 00 08 lwz r31,8(r2) c000b50c: 81 82 00 28 lwz r12,40(r2) c000b510: 90 02 00 24 stw r0,36(r2) c000b514: 7d 8c f8 50 subf r12,r12,r31 c000b518: 7c 0c 02 14 add r0,r12,r0 c000b51c: 90 02 00 08 stw r0,8(r2) c000b520: 7c 10 13 a6 mtspr 80,r0 c000b524: 81 62 00 70 lwz r11,112(r2) c000b528: 71 60 86 91 andi. r0,r11,34449 c000b52c: 40 82 00 34 bne c000b560 <system_call_exception+0x8c> c000b530: 2b 89 01 b6 cmplwi cr7,r9,438 c000b534: 41 9d 00 64 bgt cr7,c000b598 <system_call_exception+0xc4> c000b538: 3d 40 c0 5c lis r10,-16292 c000b53c: 55 29 10 3a rlwinm r9,r9,2,0,29 c000b540: 39 4a 41 e8 addi r10,r10,16872 c000b544: 80 01 00 24 lwz r0,36(r1) c000b548: 7d 2a 48 2e lwzx r9,r10,r9 c000b54c: 7c 08 03 a6 mtlr r0 c000b550: 7d 29 03 a6 mtctr r9 c000b554: 83 e1 00 1c lwz r31,28(r1) c000b558: 38 21 00 20 addi r1,r1,32 c000b55c: 4e 80 04 20 bctr After the patch: c000b4d4 <system_call_exception>: c000b4d4: 81 6a 00 84 lwz r11,132(r10) c000b4d8: 90 6a 00 88 stw r3,136(r10) c000b4dc: 69 6b 00 02 xori r11,r11,2 c000b4e0: 55 6b ff fe rlwinm r11,r11,31,31,31 c000b4e4: 0f 0b 00 00 twnei r11,0 c000b4e8: 80 6a 00 a0 lwz r3,160(r10) c000b4ec: 54 63 07 fe clrlwi r3,r3,31 c000b4f0: 0f 03 00 00 twnei r3,0 c000b4f4: 7d 6c 42 e6 mftb r11 c000b4f8: 81 82 00 08 lwz r12,8(r2) c000b4fc: 80 02 00 28 lwz r0,40(r2) c000b500: 91 62 00 24 stw r11,36(r2) c000b504: 7c 00 60 50 subf r0,r0,r12 c000b508: 7d 60 5a 14 add r11,r0,r11 c000b50c: 91 62 00 08 stw r11,8(r2) c000b510: 7c 10 13 a6 mtspr 80,r0 c000b514: 80 62 00 70 lwz r3,112(r2) c000b518: 70 6b 86 91 andi. r11,r3,34449 c000b51c: 40 82 00 28 bne c000b544 <system_call_exception+0x70> c000b520: 2b 89 01 b6 cmplwi cr7,r9,438 c000b524: 41 9d 00 84 bgt cr7,c000b5a8 <system_call_exception+0xd4> c000b528: 80 6a 00 88 lwz r3,136(r10) c000b52c: 3d 40 c0 5c lis r10,-16292 c000b530: 55 29 10 3a rlwinm r9,r9,2,0,29 c000b534: 39 4a 41 e4 addi r10,r10,16868 c000b538: 7d 2a 48 2e lwzx r9,r10,r9 c000b53c: 7d 29 03 a6 mtctr r9 c000b540: 4e 80 04 20 bctr Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- arch/powerpc/kernel/syscall.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c index a3510fa4e641..476909b11051 100644 --- a/arch/powerpc/kernel/syscall.c +++ b/arch/powerpc/kernel/syscall.c @@ -115,6 +115,9 @@ notrace long system_call_exception(long r3, long r4, long r5, return regs->gpr[3]; } return -ENOSYS; + } else { + /* Restore r3 from orig_gpr3 to free up a volatile reg */ + r3 = regs->orig_gpr3; } /* May be faster to do array_index_nospec? */ -- 2.25.0
WARNING: multiple messages have this Message-ID (diff)
From: Christophe Leroy <christophe.leroy@csgroup.eu> To: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Michael Ellerman <mpe@ellerman.id.au>, npiggin@gmail.com, msuchanek@suse.de Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 19/23] powerpc/syscall: Avoid stack frame in likely part of system_call_exception() Date: Mon, 25 Jan 2021 14:48:32 +0000 (UTC) [thread overview] Message-ID: <cdaf4ac33405e9a00ab277eccc5fd240d95e65b1.1611585031.git.christophe.leroy@csgroup.eu> (raw) In-Reply-To: <cover.1611585031.git.christophe.leroy@csgroup.eu> When r3 is not modified, reload it from regs->orig_r3 to free volatile registers. This avoids a stack frame for the likely part of system_call_exception() Before the patch: c000b4d4 <system_call_exception>: c000b4d4: 7c 08 02 a6 mflr r0 c000b4d8: 94 21 ff e0 stwu r1,-32(r1) c000b4dc: 93 e1 00 1c stw r31,28(r1) c000b4e0: 90 01 00 24 stw r0,36(r1) c000b4e4: 90 6a 00 88 stw r3,136(r10) c000b4e8: 81 6a 00 84 lwz r11,132(r10) c000b4ec: 69 6b 00 02 xori r11,r11,2 c000b4f0: 55 6b ff fe rlwinm r11,r11,31,31,31 c000b4f4: 0f 0b 00 00 twnei r11,0 c000b4f8: 81 6a 00 a0 lwz r11,160(r10) c000b4fc: 55 6b 07 fe clrlwi r11,r11,31 c000b500: 0f 0b 00 00 twnei r11,0 c000b504: 7c 0c 42 e6 mftb r0 c000b508: 83 e2 00 08 lwz r31,8(r2) c000b50c: 81 82 00 28 lwz r12,40(r2) c000b510: 90 02 00 24 stw r0,36(r2) c000b514: 7d 8c f8 50 subf r12,r12,r31 c000b518: 7c 0c 02 14 add r0,r12,r0 c000b51c: 90 02 00 08 stw r0,8(r2) c000b520: 7c 10 13 a6 mtspr 80,r0 c000b524: 81 62 00 70 lwz r11,112(r2) c000b528: 71 60 86 91 andi. r0,r11,34449 c000b52c: 40 82 00 34 bne c000b560 <system_call_exception+0x8c> c000b530: 2b 89 01 b6 cmplwi cr7,r9,438 c000b534: 41 9d 00 64 bgt cr7,c000b598 <system_call_exception+0xc4> c000b538: 3d 40 c0 5c lis r10,-16292 c000b53c: 55 29 10 3a rlwinm r9,r9,2,0,29 c000b540: 39 4a 41 e8 addi r10,r10,16872 c000b544: 80 01 00 24 lwz r0,36(r1) c000b548: 7d 2a 48 2e lwzx r9,r10,r9 c000b54c: 7c 08 03 a6 mtlr r0 c000b550: 7d 29 03 a6 mtctr r9 c000b554: 83 e1 00 1c lwz r31,28(r1) c000b558: 38 21 00 20 addi r1,r1,32 c000b55c: 4e 80 04 20 bctr After the patch: c000b4d4 <system_call_exception>: c000b4d4: 81 6a 00 84 lwz r11,132(r10) c000b4d8: 90 6a 00 88 stw r3,136(r10) c000b4dc: 69 6b 00 02 xori r11,r11,2 c000b4e0: 55 6b ff fe rlwinm r11,r11,31,31,31 c000b4e4: 0f 0b 00 00 twnei r11,0 c000b4e8: 80 6a 00 a0 lwz r3,160(r10) c000b4ec: 54 63 07 fe clrlwi r3,r3,31 c000b4f0: 0f 03 00 00 twnei r3,0 c000b4f4: 7d 6c 42 e6 mftb r11 c000b4f8: 81 82 00 08 lwz r12,8(r2) c000b4fc: 80 02 00 28 lwz r0,40(r2) c000b500: 91 62 00 24 stw r11,36(r2) c000b504: 7c 00 60 50 subf r0,r0,r12 c000b508: 7d 60 5a 14 add r11,r0,r11 c000b50c: 91 62 00 08 stw r11,8(r2) c000b510: 7c 10 13 a6 mtspr 80,r0 c000b514: 80 62 00 70 lwz r3,112(r2) c000b518: 70 6b 86 91 andi. r11,r3,34449 c000b51c: 40 82 00 28 bne c000b544 <system_call_exception+0x70> c000b520: 2b 89 01 b6 cmplwi cr7,r9,438 c000b524: 41 9d 00 84 bgt cr7,c000b5a8 <system_call_exception+0xd4> c000b528: 80 6a 00 88 lwz r3,136(r10) c000b52c: 3d 40 c0 5c lis r10,-16292 c000b530: 55 29 10 3a rlwinm r9,r9,2,0,29 c000b534: 39 4a 41 e4 addi r10,r10,16868 c000b538: 7d 2a 48 2e lwzx r9,r10,r9 c000b53c: 7d 29 03 a6 mtctr r9 c000b540: 4e 80 04 20 bctr Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> --- arch/powerpc/kernel/syscall.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c index a3510fa4e641..476909b11051 100644 --- a/arch/powerpc/kernel/syscall.c +++ b/arch/powerpc/kernel/syscall.c @@ -115,6 +115,9 @@ notrace long system_call_exception(long r3, long r4, long r5, return regs->gpr[3]; } return -ENOSYS; + } else { + /* Restore r3 from orig_gpr3 to free up a volatile reg */ + r3 = regs->orig_gpr3; } /* May be faster to do array_index_nospec? */ -- 2.25.0
next prev parent reply other threads:[~2021-01-25 15:09 UTC|newest] Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-25 14:48 [PATCH v4 00/23] powerpc/32: Implement C syscall entry/exit Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 01/23] powerpc/32s: Add missing call to kuep_lock on syscall entry Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 02/23] powerpc/32: Always enable data translation " Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 03/23] powerpc/32: On syscall entry, enable instruction translation at the same time as data Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 04/23] powerpc/32: Reorder instructions to avoid using CTR in syscall entry Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 05/23] powerpc/64s: Make kuap_check_amr() and kuap_get_and_check_amr() generic Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 06/23] powerpc/32s: Create C version of kuap_user/kernel_restore() and friends Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 07/23] powerpc/8xx: " Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 08/23] powerpc/irq: Add helper to set regs->softe Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 09/23] powerpc/irq: Rework helpers that manipulate MSR[EE/RI] Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 10/23] powerpc/irq: Add stub irq_soft_mask_return() for PPC32 Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 11/23] powerpc/syscall: Rename syscall_64.c into syscall.c Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-26 10:21 ` Nicholas Piggin 2021-01-26 10:21 ` Nicholas Piggin 2021-01-26 10:28 ` David Laight 2021-01-27 23:50 ` Nicholas Piggin 2021-01-27 23:50 ` Nicholas Piggin 2021-02-02 6:15 ` Christophe Leroy 2021-02-02 6:15 ` Christophe Leroy 2021-02-02 6:38 ` Nicholas Piggin 2021-02-02 6:38 ` Nicholas Piggin 2021-02-02 6:58 ` Christophe Leroy 2021-02-02 6:58 ` Christophe Leroy 2021-02-02 20:10 ` Segher Boessenkool 2021-02-02 20:10 ` Segher Boessenkool 2021-02-08 17:47 ` Christophe Leroy 2021-02-08 17:47 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 12/23] powerpc/syscall: Make syscall.c buildable on PPC32 Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 13/23] powerpc/syscall: Use is_compat_task() Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 14/23] powerpc/syscall: Save r3 in regs->orig_r3 Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-26 10:18 ` Nicholas Piggin 2021-01-26 10:18 ` Nicholas Piggin 2021-02-08 17:47 ` Christophe Leroy 2021-02-08 17:47 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 15/23] powerpc/syscall: Change condition to check MSR_RI Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 16/23] powerpc/32: Always save non volatile GPRs at syscall entry Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 17/23] powerpc/syscall: implement system call entry/exit logic in C for PPC32 Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 18/23] powerpc/32: Remove verification of MSR_PR on syscall in the ASM entry Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy [this message] 2021-01-25 14:48 ` [PATCH v4 19/23] powerpc/syscall: Avoid stack frame in likely part of system_call_exception() Christophe Leroy 2021-01-26 10:14 ` Nicholas Piggin 2021-01-26 10:14 ` Nicholas Piggin 2021-01-25 14:48 ` [PATCH v4 20/23] powerpc/syscall: Do not check unsupported scv vector on PPC32 Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-26 10:16 ` Nicholas Piggin 2021-01-26 10:16 ` Nicholas Piggin 2021-02-08 17:45 ` Christophe Leroy 2021-02-08 17:45 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 21/23] powerpc/syscall: Remove FULL_REGS verification in system_call_exception Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 22/23] powerpc/syscall: Optimise checks in beginning of system_call_exception() Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy 2021-01-25 14:48 ` [PATCH v4 23/23] powerpc/syscall: Avoid storing 'current' in another pointer Christophe Leroy 2021-01-25 14:48 ` Christophe Leroy
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