linux-stable.git/arch/powerpc/kernel/process.c, branch linux-5.11.y Linux kernel stable tree powerpc/64: Fix stack trace not displaying final frame 2021-03-17T16:11:31+00:00 Michael Ellerman mpe@ellerman.id.au 2021-02-09T13:59:20+00:00 4eb948eff16365d90f07c5d7cd51dd2e943c0a61 [ Upstream commit e3de1e291fa58a1ab0f471a4b458eff2514e4b5f ] In commit bf13718bc57a ("powerpc: show registers when unwinding interrupt frames") we changed our stack dumping logic to show the full registers whenever we find an interrupt frame on the stack. However we didn't notice that on 64-bit this doesn't show the final frame, ie. the interrupt that brought us in from userspace, whereas on 32-bit it does. That is due to confusion about the size of that last frame. The code in show_stack() calls validate_sp(), passing it STACK_INT_FRAME_SIZE to check the sp is at least that far below the top of the stack. However on 64-bit that size is too large for the final frame, because it includes the red zone, but we don't allocate a red zone for the first frame. So add a new define that encodes the correct size for 32-bit and 64-bit, and use it in show_stack(). This results in the full trace being shown on 64-bit, eg: sysrq: Trigger a crash Kernel panic - not syncing: sysrq triggered crash CPU: 0 PID: 83 Comm: sh Not tainted 5.11.0-rc2-gcc-8.2.0-00188-g571abcb96b10-dirty #649 Call Trace: [c00000000a1c3ac0] [c000000000897b70] dump_stack+0xc4/0x114 (unreliable) [c00000000a1c3b00] [c00000000014334c] panic+0x178/0x41c [c00000000a1c3ba0] [c00000000094e600] sysrq_handle_crash+0x40/0x50 [c00000000a1c3c00] [c00000000094ef98] __handle_sysrq+0xd8/0x210 [c00000000a1c3ca0] [c00000000094f820] write_sysrq_trigger+0x100/0x188 [c00000000a1c3ce0] [c0000000005559dc] proc_reg_write+0x10c/0x1b0 [c00000000a1c3d10] [c000000000479950] vfs_write+0xf0/0x360 [c00000000a1c3d60] [c000000000479d9c] ksys_write+0x7c/0x140 [c00000000a1c3db0] [c00000000002bf5c] system_call_exception+0x19c/0x2c0 [c00000000a1c3e10] [c00000000000d35c] system_call_common+0xec/0x278 --- interrupt: c00 at 0x7fff9fbab428 NIP: 00007fff9fbab428 LR: 000000001000b724 CTR: 0000000000000000 REGS: c00000000a1c3e80 TRAP: 0c00 Not tainted (5.11.0-rc2-gcc-8.2.0-00188-g571abcb96b10-dirty) MSR: 900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 22002884 XER: 00000000 IRQMASK: 0 GPR00: 0000000000000004 00007fffc3cb8960 00007fff9fc59900 0000000000000001 GPR04: 000000002a4b32d0 0000000000000002 0000000000000063 0000000000000063 GPR08: 000000002a4b32d0 0000000000000000 0000000000000000 0000000000000000 GPR12: 0000000000000000 00007fff9fcca9a0 0000000000000000 0000000000000000 GPR16: 0000000000000000 0000000000000000 0000000000000000 00000000100b8fd0 GPR20: 000000002a4b3485 00000000100b8f90 0000000000000000 0000000000000000 GPR24: 000000002a4b0440 00000000100e77b8 0000000000000020 000000002a4b32d0 GPR28: 0000000000000001 0000000000000002 000000002a4b32d0 0000000000000001 NIP [00007fff9fbab428] 0x7fff9fbab428 LR [000000001000b724] 0x1000b724 --- interrupt: c00 Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210209141627.2898485-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit e3de1e291fa58a1ab0f471a4b458eff2514e4b5f ]

In commit bf13718bc57a ("powerpc: show registers when unwinding
interrupt frames") we changed our stack dumping logic to show the full
registers whenever we find an interrupt frame on the stack.

However we didn't notice that on 64-bit this doesn't show the final
frame, ie. the interrupt that brought us in from userspace, whereas on
32-bit it does.

That is due to confusion about the size of that last frame. The code
in show_stack() calls validate_sp(), passing it STACK_INT_FRAME_SIZE
to check the sp is at least that far below the top of the stack.

However on 64-bit that size is too large for the final frame, because
it includes the red zone, but we don't allocate a red zone for the
first frame.

So add a new define that encodes the correct size for 32-bit and
64-bit, and use it in show_stack().

This results in the full trace being shown on 64-bit, eg:

  sysrq: Trigger a crash
  Kernel panic - not syncing: sysrq triggered crash
  CPU: 0 PID: 83 Comm: sh Not tainted 5.11.0-rc2-gcc-8.2.0-00188-g571abcb96b10-dirty #649
  Call Trace:
  [c00000000a1c3ac0] [c000000000897b70] dump_stack+0xc4/0x114 (unreliable)
  [c00000000a1c3b00] [c00000000014334c] panic+0x178/0x41c
  [c00000000a1c3ba0] [c00000000094e600] sysrq_handle_crash+0x40/0x50
  [c00000000a1c3c00] [c00000000094ef98] __handle_sysrq+0xd8/0x210
  [c00000000a1c3ca0] [c00000000094f820] write_sysrq_trigger+0x100/0x188
  [c00000000a1c3ce0] [c0000000005559dc] proc_reg_write+0x10c/0x1b0
  [c00000000a1c3d10] [c000000000479950] vfs_write+0xf0/0x360
  [c00000000a1c3d60] [c000000000479d9c] ksys_write+0x7c/0x140
  [c00000000a1c3db0] [c00000000002bf5c] system_call_exception+0x19c/0x2c0
  [c00000000a1c3e10] [c00000000000d35c] system_call_common+0xec/0x278
  --- interrupt: c00 at 0x7fff9fbab428
  NIP:  00007fff9fbab428 LR: 000000001000b724 CTR: 0000000000000000
  REGS: c00000000a1c3e80 TRAP: 0c00   Not tainted  (5.11.0-rc2-gcc-8.2.0-00188-g571abcb96b10-dirty)
  MSR:  900000000280f033 <SF,HV,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 22002884  XER: 00000000
  IRQMASK: 0
  GPR00: 0000000000000004 00007fffc3cb8960 00007fff9fc59900 0000000000000001
  GPR04: 000000002a4b32d0 0000000000000002 0000000000000063 0000000000000063
  GPR08: 000000002a4b32d0 0000000000000000 0000000000000000 0000000000000000
  GPR12: 0000000000000000 00007fff9fcca9a0 0000000000000000 0000000000000000
  GPR16: 0000000000000000 0000000000000000 0000000000000000 00000000100b8fd0
  GPR20: 000000002a4b3485 00000000100b8f90 0000000000000000 0000000000000000
  GPR24: 000000002a4b0440 00000000100e77b8 0000000000000020 000000002a4b32d0
  GPR28: 0000000000000001 0000000000000002 000000002a4b32d0 0000000000000001
  NIP [00007fff9fbab428] 0x7fff9fbab428
  LR [000000001000b724] 0x1000b724
  --- interrupt: c00

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210209141627.2898485-1-mpe@ellerman.id.au
Signed-off-by: Sasha Levin <sashal@kernel.org>
powerpc/process: Remove target specific __set_dabr() 2020-12-09T06:01:40+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2020-12-04T10:12:51+00:00 ad3ed15cd04b96de7c38204ba7c698cbccd8fe88 __set_dabr() are simple functions that can be inline directly inside set_dabr() and using IS_ENABLED() instead of #ifdef Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/c10b263668e137236c71d76648b03cf2cd1ee66f.1607076733.git.christophe.leroy@csgroup.eu 
__set_dabr() are simple functions that can be inline directly
inside set_dabr() and using IS_ENABLED() instead of #ifdef

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c10b263668e137236c71d76648b03cf2cd1ee66f.1607076733.git.christophe.leroy@csgroup.eu
powerpc/book3s64/pkeys: Don't update SPRN_AMR when in kernel mode. 2020-12-03T14:01:26+00:00 Aneesh Kumar K.V aneesh.kumar@linux.ibm.com 2020-11-27T04:44:16+00:00 48a8ab4eeb8271f2a0e2ca3cf80844a59acca153 Now that kernel correctly store/restore userspace AMR/IAMR values, avoid manipulating AMR and IAMR from the kernel on behalf of userspace. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: Sandipan Das <sandipan@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201127044424.40686-15-aneesh.kumar@linux.ibm.com 
Now that kernel correctly store/restore userspace AMR/IAMR values, avoid
manipulating AMR and IAMR from the kernel on behalf of userspace.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-15-aneesh.kumar@linux.ibm.com
powerpc/book3s64/pkeys: Reset userspace AMR correctly on exec 2020-12-03T14:01:26+00:00 Aneesh Kumar K.V aneesh.kumar@linux.ibm.com 2020-11-27T04:44:14+00:00 d5fa30e6993ffcdd1859d8dab1a07a6f6c6e7c3f On fork, we inherit from the parent and on exec, we should switch to default_amr values. Also, avoid changing the AMR register value within the kernel. The kernel now runs with different AMR values. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: Sandipan Das <sandipan@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201127044424.40686-13-aneesh.kumar@linux.ibm.com 
On fork, we inherit from the parent and on exec, we should switch to default_amr values.

Also, avoid changing the AMR register value within the kernel. The kernel now runs with
different AMR values.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-13-aneesh.kumar@linux.ibm.com
powerpc/book3s64/pkeys: Inherit correctly on fork. 2020-12-03T14:01:25+00:00 Aneesh Kumar K.V aneesh.kumar@linux.ibm.com 2020-11-27T04:44:13+00:00 f643fcab74c005ddfdda68c69909f03bde766ff1 Child thread.kuap value is inherited from the parent in copy_thread_tls. We still need to make sure when the child returns from a fork in the kernel we start with the kernel default AMR value. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reviewed-by: Sandipan Das <sandipan@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201127044424.40686-12-aneesh.kumar@linux.ibm.com 
Child thread.kuap value is inherited from the parent in copy_thread_tls. We still
need to make sure when the child returns from a fork in the kernel we start with the kernel
default AMR value.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-12-aneesh.kumar@linux.ibm.com
powerpc/exec: Set thread.regs early during exec 2020-12-03T14:01:25+00:00 Aneesh Kumar K.V aneesh.kumar@linux.ibm.com 2020-11-27T04:44:11+00:00 d7df77e89039623ededf0ece7b4358f7c9ecbaae In later patches during exec, we would like to access default regs.amr to control access to the user mapping. Having thread.regs set early makes the code changes simpler. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201127044424.40686-10-aneesh.kumar@linux.ibm.com 
In later patches during exec, we would like to access default regs.amr to
control access to the user mapping. Having thread.regs set early makes the
code changes simpler.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201127044424.40686-10-aneesh.kumar@linux.ibm.com
powerpc: show registers when unwinding interrupt frames 2020-12-03T14:01:21+00:00 Nicholas Piggin npiggin@gmail.com 2020-11-07T02:33:05+00:00 bf13718bc57ada25016d9fe80323238d0b94506e It's often useful to know the register state for interrupts in the stack frame. In the below example (with this patch applied), the important information is the state of the page fault. A blatant case like this probably rather should have the page fault regs passed down to the warning, but quite often there are less obvious cases where an interrupt shows up that might give some more clues. The downside is longer and more complex bug output. Bug: Write fault blocked by AMR! WARNING: CPU: 0 PID: 72 at arch/powerpc/include/asm/book3s/64/kup-radix.h:164 __do_page_fault+0x880/0xa90 Modules linked in: CPU: 0 PID: 72 Comm: systemd-gpt-aut Not tainted NIP: c00000000006e2f0 LR: c00000000006e2ec CTR: 0000000000000000 REGS: c00000000a4f3420 TRAP: 0700 MSR: 8000000000021033 <SF,ME,IR,DR,RI,LE> CR: 28002840 XER: 20040000 CFAR: c000000000128be0 IRQMASK: 3 GPR00: c00000000006e2ec c00000000a4f36c0 c0000000014f0700 0000000000000020 GPR04: 0000000000000001 c000000001290f50 0000000000000001 c000000001290f80 GPR08: c000000001612b08 0000000000000000 0000000000000000 00000000ffffe0f7 GPR12: 0000000048002840 c0000000016e0000 c00c000000021c80 c000000000fd6f60 GPR16: 0000000000000000 c00000000a104698 0000000000000003 c0000000087f0000 GPR20: 0000000000000100 c0000000070330b8 0000000000000000 0000000000000004 GPR24: 0000000002000000 0000000000000300 0000000002000000 c00000000a5b0c00 GPR28: 0000000000000000 000000000a000000 00007fffb2a90038 c00000000a4f3820 NIP [c00000000006e2f0] __do_page_fault+0x880/0xa90 LR [c00000000006e2ec] __do_page_fault+0x87c/0xa90 Call Trace: [c00000000a4f36c0] [c00000000006e2ec] __do_page_fault+0x87c/0xa90 (unreliable) [c00000000a4f3780] [c000000000e1c034] do_page_fault+0x34/0x90 [c00000000a4f37b0] [c000000000008908] data_access_common_virt+0x158/0x1b0 --- interrupt: 300 at __copy_tofrom_user_base+0x9c/0x5a4 NIP: c00000000009b028 LR: c000000000802978 CTR: 0000000000000800 REGS: c00000000a4f3820 TRAP: 0300 MSR: 800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE> CR: 24004840 XER: 00000000 CFAR: c00000000009aff4 DAR: 00007fffb2a90038 DSISR: 0a000000 IRQMASK: 0 GPR00: 0000000000000000 c00000000a4f3ac0 c0000000014f0700 00007fffb2a90028 GPR04: c000000008720010 0000000000010000 0000000000000000 0000000000000000 GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000001 GPR12: 0000000000004000 c0000000016e0000 c00c000000021c80 c000000000fd6f60 GPR16: 0000000000000000 c00000000a104698 0000000000000003 c0000000087f0000 GPR20: 0000000000000100 c0000000070330b8 0000000000000000 0000000000000004 GPR24: c00000000a4f3c80 c000000008720000 0000000000010000 0000000000000000 GPR28: 0000000000010000 0000000008720000 0000000000010000 c000000001515b98 NIP [c00000000009b028] __copy_tofrom_user_base+0x9c/0x5a4 LR [c000000000802978] copyout+0x68/0xc0 --- interrupt: 300 [c00000000a4f3af0] [c0000000008074b8] copy_page_to_iter+0x188/0x540 [c00000000a4f3b50] [c00000000035c678] generic_file_buffered_read+0x358/0xd80 [c00000000a4f3c40] [c0000000004c1e90] blkdev_read_iter+0x50/0x80 [c00000000a4f3c60] [c00000000045733c] new_sync_read+0x12c/0x1c0 [c00000000a4f3d00] [c00000000045a1f0] vfs_read+0x1d0/0x240 [c00000000a4f3d50] [c00000000045a7f4] ksys_read+0x84/0x140 [c00000000a4f3da0] [c000000000033a60] system_call_exception+0x100/0x280 [c00000000a4f3e10] [c00000000000c508] system_call_common+0xf8/0x2f8 Instruction dump: eae10078 3be0000b 4bfff890 60420000 792917e1 4182ff18 3c82ffab 3884a5e0 3c62ffab 3863a6e8 480ba891 60000000 <0fe00000> 3be0000b 4bfff860 e93c0938 Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20201107023305.2384874-1-npiggin@gmail.com 
It's often useful to know the register state for interrupts in
the stack frame. In the below example (with this patch applied),
the important information is the state of the page fault.

A blatant case like this probably rather should have the page
fault regs passed down to the warning, but quite often there are
less obvious cases where an interrupt shows up that might give
some more clues.

The downside is longer and more complex bug output.

  Bug: Write fault blocked by AMR!
  WARNING: CPU: 0 PID: 72 at arch/powerpc/include/asm/book3s/64/kup-radix.h:164 __do_page_fault+0x880/0xa90
  Modules linked in:
  CPU: 0 PID: 72 Comm: systemd-gpt-aut Not tainted
  NIP:  c00000000006e2f0 LR: c00000000006e2ec CTR: 0000000000000000
  REGS: c00000000a4f3420 TRAP: 0700
  MSR:  8000000000021033 <SF,ME,IR,DR,RI,LE>  CR: 28002840  XER: 20040000
  CFAR: c000000000128be0 IRQMASK: 3
  GPR00: c00000000006e2ec c00000000a4f36c0 c0000000014f0700 0000000000000020
  GPR04: 0000000000000001 c000000001290f50 0000000000000001 c000000001290f80
  GPR08: c000000001612b08 0000000000000000 0000000000000000 00000000ffffe0f7
  GPR12: 0000000048002840 c0000000016e0000 c00c000000021c80 c000000000fd6f60
  GPR16: 0000000000000000 c00000000a104698 0000000000000003 c0000000087f0000
  GPR20: 0000000000000100 c0000000070330b8 0000000000000000 0000000000000004
  GPR24: 0000000002000000 0000000000000300 0000000002000000 c00000000a5b0c00
  GPR28: 0000000000000000 000000000a000000 00007fffb2a90038 c00000000a4f3820
  NIP [c00000000006e2f0] __do_page_fault+0x880/0xa90
  LR [c00000000006e2ec] __do_page_fault+0x87c/0xa90
  Call Trace:
  [c00000000a4f36c0] [c00000000006e2ec] __do_page_fault+0x87c/0xa90 (unreliable)
  [c00000000a4f3780] [c000000000e1c034] do_page_fault+0x34/0x90
  [c00000000a4f37b0] [c000000000008908] data_access_common_virt+0x158/0x1b0
  --- interrupt: 300 at __copy_tofrom_user_base+0x9c/0x5a4
  NIP:  c00000000009b028 LR: c000000000802978 CTR: 0000000000000800
  REGS: c00000000a4f3820 TRAP: 0300
  MSR:  800000000280b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 24004840  XER: 00000000
  CFAR: c00000000009aff4 DAR: 00007fffb2a90038 DSISR: 0a000000 IRQMASK: 0
  GPR00: 0000000000000000 c00000000a4f3ac0 c0000000014f0700 00007fffb2a90028
  GPR04: c000000008720010 0000000000010000 0000000000000000 0000000000000000
  GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000001
  GPR12: 0000000000004000 c0000000016e0000 c00c000000021c80 c000000000fd6f60
  GPR16: 0000000000000000 c00000000a104698 0000000000000003 c0000000087f0000
  GPR20: 0000000000000100 c0000000070330b8 0000000000000000 0000000000000004
  GPR24: c00000000a4f3c80 c000000008720000 0000000000010000 0000000000000000
  GPR28: 0000000000010000 0000000008720000 0000000000010000 c000000001515b98
  NIP [c00000000009b028] __copy_tofrom_user_base+0x9c/0x5a4
  LR [c000000000802978] copyout+0x68/0xc0
  --- interrupt: 300
  [c00000000a4f3af0] [c0000000008074b8] copy_page_to_iter+0x188/0x540
  [c00000000a4f3b50] [c00000000035c678] generic_file_buffered_read+0x358/0xd80
  [c00000000a4f3c40] [c0000000004c1e90] blkdev_read_iter+0x50/0x80
  [c00000000a4f3c60] [c00000000045733c] new_sync_read+0x12c/0x1c0
  [c00000000a4f3d00] [c00000000045a1f0] vfs_read+0x1d0/0x240
  [c00000000a4f3d50] [c00000000045a7f4] ksys_read+0x84/0x140
  [c00000000a4f3da0] [c000000000033a60] system_call_exception+0x100/0x280
  [c00000000a4f3e10] [c00000000000c508] system_call_common+0xf8/0x2f8
  Instruction dump:
  eae10078 3be0000b 4bfff890 60420000 792917e1 4182ff18 3c82ffab 3884a5e0
  3c62ffab 3863a6e8 480ba891 60000000 <0fe00000> 3be0000b 4bfff860 e93c0938

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201107023305.2384874-1-npiggin@gmail.com
powerpc/signal: Don't manage floating point regs when no FPU 2020-12-03T14:01:11+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2020-08-18T17:19:17+00:00 b6254ced4da6cf28d49fbffe24ee4b3286dcb3f4 There is no point in copying floating point regs when there is no FPU and MATH_EMULATION is not selected. Create a new CONFIG_PPC_FPU_REGS bool that is selected by CONFIG_MATH_EMULATION and CONFIG_PPC_FPU, and use it to opt out everything related to fp_state in thread_struct. The asm const used only by fpu.S are opted out with CONFIG_PPC_FPU as fpu.S build is conditionnal to CONFIG_PPC_FPU. The following app spends approx 8.1 seconds system time on an 8xx without the patch, and 7.0 seconds with the patch (13.5% reduction). On an 832x, it spends approx 2.6 seconds system time without the patch and 2.1 seconds with the patch (19% reduction). void sigusr1(int sig) { } int main(int argc, char **argv) { int i = 100000; signal(SIGUSR1, sigusr1); for (;i--;) raise(SIGUSR1); exit(0); } Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/7569070083e6cd5b279bb5023da601aba3c06f3c.1597770847.git.christophe.leroy@csgroup.eu 
There is no point in copying floating point regs when there
is no FPU and MATH_EMULATION is not selected.

Create a new CONFIG_PPC_FPU_REGS bool that is selected by
CONFIG_MATH_EMULATION and CONFIG_PPC_FPU, and use it to
opt out everything related to fp_state in thread_struct.

The asm const used only by fpu.S are opted out with CONFIG_PPC_FPU
as fpu.S build is conditionnal to CONFIG_PPC_FPU.

The following app spends approx 8.1 seconds system time on an 8xx
without the patch, and 7.0 seconds with the patch (13.5% reduction).

On an 832x, it spends approx 2.6 seconds system time without
the patch and 2.1 seconds with the patch (19% reduction).

	void sigusr1(int sig) { }

	int main(int argc, char **argv)
	{
		int i = 100000;

		signal(SIGUSR1, sigusr1);
		for (;i--;)
			raise(SIGUSR1);
		exit(0);
	}

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/7569070083e6cd5b279bb5023da601aba3c06f3c.1597770847.git.christophe.leroy@csgroup.eu
powerpc/process: Fix uninitialised variable error 2020-09-18T08:12:46+00:00 Michael Ellerman mpe@ellerman.id.au 2020-09-17T02:20:16+00:00 d208e13c6a2277d9fb71fad6a1394c70bdd7b634 Clang, and GCC with -Wmaybe-uninitialized, can't see that val is unused in get_fpexec_mode(): arch/powerpc/kernel/process.c:1940:7: error: variable 'val' is used uninitialized whenever 'if' condition is true if (cpu_has_feature(CPU_FTR_SPE)) { ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ We know that CPU_FTR_SPE will only be true iff CONFIG_SPE is also true, but the compiler doesn't. Avoid it by initialising val to zero. Reported-by: kernel test robot <lkp@intel.com> Fixes: 532ed1900d37 ("powerpc/process: Remove useless #ifdef CONFIG_SPE") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/r/20200917024509.3253837-1-mpe@ellerman.id.au 
Clang, and GCC with -Wmaybe-uninitialized, can't see that val is
unused in get_fpexec_mode():

  arch/powerpc/kernel/process.c:1940:7: error: variable 'val' is used
  uninitialized whenever 'if' condition is true
		  if (cpu_has_feature(CPU_FTR_SPE)) {
		      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

We know that CPU_FTR_SPE will only be true iff CONFIG_SPE is also
true, but the compiler doesn't.

Avoid it by initialising val to zero.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 532ed1900d37 ("powerpc/process: Remove useless #ifdef CONFIG_SPE")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20200917024509.3253837-1-mpe@ellerman.id.au
powerpc/process: Remove useless #ifdef CONFIG_PPC_FPU 2020-09-15T12:13:36+00:00 Christophe Leroy christophe.leroy@csgroup.eu 2020-08-17T05:47:58+00:00 c83c192a6fbb1d4db4144c40296ed059f5eca384 Add a stub for __giveup_fpu() when CONFIG_PPC_FPU is not selected, as done for CONFIG_SPE and CONFIG_ALTIVEC. This allows to remove some #ifdef CONFIG_PPC_FPU. Also change one to IS_ENABLED(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/69c8b7954ceeccc6b849e52e1fa41b3a0f10f6c1.1597643221.git.christophe.leroy@csgroup.eu 
Add a stub for __giveup_fpu() when CONFIG_PPC_FPU is
not selected, as done for CONFIG_SPE and CONFIG_ALTIVEC.

This allows to remove some #ifdef CONFIG_PPC_FPU.

Also change one to IS_ENABLED().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/69c8b7954ceeccc6b849e52e1fa41b3a0f10f6c1.1597643221.git.christophe.leroy@csgroup.eu