* [PATCH v2] Powerpc/Watchpoint: Restore nvgprs while returning from exception
@ 2019-06-13 3:30 ` Ravi Bangoria
0 siblings, 0 replies; 4+ messages in thread
From: Ravi Bangoria @ 2019-06-13 3:30 UTC (permalink / raw)
To: mpe
Cc: mikey, benh, paulus, npiggin, christophe.leroy, mahesh,
linuxppc-dev, linux-kernel, naveen.n.rao, ravi.bangoria,
aneesh.kumar
Powerpc hw triggers watchpoint before executing the instruction. To
make trigger-after-execute behavior, kernel emulates the instruction.
If the instruction is 'load something into non-volatile register',
exception handler should restore emulated register state while
returning back, otherwise there will be register state corruption.
Ex, Adding a watchpoint on a list can corrput the list:
# cat /proc/kallsyms | grep kthread_create_list
c00000000121c8b8 d kthread_create_list
Add watchpoint on kthread_create_list->prev:
# perf record -e mem:0xc00000000121c8c0
Run some workload such that new kthread gets invoked. Ex, I just
logged out from console:
list_add corruption. next->prev should be prev (c000000001214e00), \
but was c00000000121c8b8. (next=c00000000121c8b8).
WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/0xc0
CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7+ #69
...
NIP __list_add_valid+0xb4/0xc0
LR __list_add_valid+0xb0/0xc0
Call Trace:
__list_add_valid+0xb0/0xc0 (unreliable)
__kthread_create_on_node+0xe0/0x260
kthread_create_on_node+0x34/0x50
create_worker+0xe8/0x260
worker_thread+0x444/0x560
kthread+0x160/0x1a0
ret_from_kernel_thread+0x5c/0x70
List corruption happened because it uses 'load into non-volatile
register' instruction:
Snippet from __kthread_create_on_node:
c000000000136be8: addis r29,r2,-19
c000000000136bec: ld r29,31424(r29)
if (!__list_add_valid(new, prev, next))
c000000000136bf0: mr r3,r30
c000000000136bf4: mr r5,r28
c000000000136bf8: mr r4,r29
c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8>
Register state from WARN_ON():
GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075
GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000
GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa
GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00
GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370
GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000
GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628
GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0
Watchpoint hit at 0xc000000000136bec.
addis r29,r2,-19
=> r29 = 0xc000000001344e00 + (-19 << 16)
=> r29 = 0xc000000001214e00
ld r29,31424(r29)
=> r29 = *(0xc000000001214e00 + 31424)
=> r29 = *(0xc00000000121c8c0)
0xc00000000121c8c0 is where we placed a watchpoint and thus this
instruction was emulated by emulate_step. But because handle_dabr_fault
did not restore emulated register state, r29 still contains stale
value in above register state.
Fixes: 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors")
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: stable@vger.kernel.org # 2.6.36+
---
v1: https://lkml.org/lkml/2019/6/10/1058
v1->v2:
Successful do_page_fault returns using ret_from_except_lite at
the same place where handle_dabr_fault also returns. v1 messed
up with do_page_fault return path. Fix that in v2.
arch/powerpc/kernel/exceptions-64s.S | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 6b86055..2546427 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1746,7 +1746,7 @@ handle_page_fault:
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_page_fault
cmpdi r3,0
- beq+ 12f
+ beq+ ret_from_except_lite
bl save_nvgprs
mr r5,r3
addi r3,r1,STACK_FRAME_OVERHEAD
@@ -1761,7 +1761,12 @@ handle_dabr_fault:
ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_break
-12: b ret_from_except_lite
+ /*
+ * do_break may have changed the nv-gprs while haldling
+ * breakpoint. If so, we need to restore them with their
+ * updated values. Don't use ret_from_except_lite here.
+ */
+ b ret_from_except
#ifdef CONFIG_PPC_BOOK3S_64
--
1.8.3.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH v2] Powerpc/Watchpoint: Restore nvgprs while returning from exception
@ 2019-06-13 3:30 ` Ravi Bangoria
0 siblings, 0 replies; 4+ messages in thread
From: Ravi Bangoria @ 2019-06-13 3:30 UTC (permalink / raw)
To: mpe
Cc: ravi.bangoria, mikey, linux-kernel, npiggin, paulus,
aneesh.kumar, mahesh, naveen.n.rao, linuxppc-dev
Powerpc hw triggers watchpoint before executing the instruction. To
make trigger-after-execute behavior, kernel emulates the instruction.
If the instruction is 'load something into non-volatile register',
exception handler should restore emulated register state while
returning back, otherwise there will be register state corruption.
Ex, Adding a watchpoint on a list can corrput the list:
# cat /proc/kallsyms | grep kthread_create_list
c00000000121c8b8 d kthread_create_list
Add watchpoint on kthread_create_list->prev:
# perf record -e mem:0xc00000000121c8c0
Run some workload such that new kthread gets invoked. Ex, I just
logged out from console:
list_add corruption. next->prev should be prev (c000000001214e00), \
but was c00000000121c8b8. (next=c00000000121c8b8).
WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/0xc0
CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7+ #69
...
NIP __list_add_valid+0xb4/0xc0
LR __list_add_valid+0xb0/0xc0
Call Trace:
__list_add_valid+0xb0/0xc0 (unreliable)
__kthread_create_on_node+0xe0/0x260
kthread_create_on_node+0x34/0x50
create_worker+0xe8/0x260
worker_thread+0x444/0x560
kthread+0x160/0x1a0
ret_from_kernel_thread+0x5c/0x70
List corruption happened because it uses 'load into non-volatile
register' instruction:
Snippet from __kthread_create_on_node:
c000000000136be8: addis r29,r2,-19
c000000000136bec: ld r29,31424(r29)
if (!__list_add_valid(new, prev, next))
c000000000136bf0: mr r3,r30
c000000000136bf4: mr r5,r28
c000000000136bf8: mr r4,r29
c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8>
Register state from WARN_ON():
GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075
GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000
GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa
GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00
GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370
GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000
GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628
GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0
Watchpoint hit at 0xc000000000136bec.
addis r29,r2,-19
=> r29 = 0xc000000001344e00 + (-19 << 16)
=> r29 = 0xc000000001214e00
ld r29,31424(r29)
=> r29 = *(0xc000000001214e00 + 31424)
=> r29 = *(0xc00000000121c8c0)
0xc00000000121c8c0 is where we placed a watchpoint and thus this
instruction was emulated by emulate_step. But because handle_dabr_fault
did not restore emulated register state, r29 still contains stale
value in above register state.
Fixes: 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors")
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Cc: stable@vger.kernel.org # 2.6.36+
---
v1: https://lkml.org/lkml/2019/6/10/1058
v1->v2:
Successful do_page_fault returns using ret_from_except_lite at
the same place where handle_dabr_fault also returns. v1 messed
up with do_page_fault return path. Fix that in v2.
arch/powerpc/kernel/exceptions-64s.S | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 6b86055..2546427 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -1746,7 +1746,7 @@ handle_page_fault:
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_page_fault
cmpdi r3,0
- beq+ 12f
+ beq+ ret_from_except_lite
bl save_nvgprs
mr r5,r3
addi r3,r1,STACK_FRAME_OVERHEAD
@@ -1761,7 +1761,12 @@ handle_dabr_fault:
ld r5,_DSISR(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_break
-12: b ret_from_except_lite
+ /*
+ * do_break may have changed the nv-gprs while haldling
+ * breakpoint. If so, we need to restore them with their
+ * updated values. Don't use ret_from_except_lite here.
+ */
+ b ret_from_except
#ifdef CONFIG_PPC_BOOK3S_64
--
1.8.3.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v2] Powerpc/Watchpoint: Restore nvgprs while returning from exception
2019-06-13 3:30 ` Ravi Bangoria
@ 2019-06-30 8:37 ` Michael Ellerman
-1 siblings, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2019-06-30 8:37 UTC (permalink / raw)
To: Ravi Bangoria
Cc: ravi.bangoria, mikey, linux-kernel, npiggin, paulus,
aneesh.kumar, mahesh, naveen.n.rao, linuxppc-dev
On Thu, 2019-06-13 at 03:30:14 UTC, Ravi Bangoria wrote:
> Powerpc hw triggers watchpoint before executing the instruction. To
> make trigger-after-execute behavior, kernel emulates the instruction.
> If the instruction is 'load something into non-volatile register',
> exception handler should restore emulated register state while
> returning back, otherwise there will be register state corruption.
> Ex, Adding a watchpoint on a list can corrput the list:
>
> # cat /proc/kallsyms | grep kthread_create_list
> c00000000121c8b8 d kthread_create_list
>
> Add watchpoint on kthread_create_list->prev:
>
> # perf record -e mem:0xc00000000121c8c0
>
> Run some workload such that new kthread gets invoked. Ex, I just
> logged out from console:
>
> list_add corruption. next->prev should be prev (c000000001214e00), \
> but was c00000000121c8b8. (next=c00000000121c8b8).
> WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/0xc0
> CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7+ #69
> ...
> NIP __list_add_valid+0xb4/0xc0
> LR __list_add_valid+0xb0/0xc0
> Call Trace:
> __list_add_valid+0xb0/0xc0 (unreliable)
> __kthread_create_on_node+0xe0/0x260
> kthread_create_on_node+0x34/0x50
> create_worker+0xe8/0x260
> worker_thread+0x444/0x560
> kthread+0x160/0x1a0
> ret_from_kernel_thread+0x5c/0x70
>
> List corruption happened because it uses 'load into non-volatile
> register' instruction:
>
> Snippet from __kthread_create_on_node:
>
> c000000000136be8: addis r29,r2,-19
> c000000000136bec: ld r29,31424(r29)
> if (!__list_add_valid(new, prev, next))
> c000000000136bf0: mr r3,r30
> c000000000136bf4: mr r5,r28
> c000000000136bf8: mr r4,r29
> c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8>
>
> Register state from WARN_ON():
>
> GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075
> GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000
> GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa
> GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00
> GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370
> GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000
> GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628
> GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0
>
> Watchpoint hit at 0xc000000000136bec.
>
> addis r29,r2,-19
> => r29 = 0xc000000001344e00 + (-19 << 16)
> => r29 = 0xc000000001214e00
>
> ld r29,31424(r29)
> => r29 = *(0xc000000001214e00 + 31424)
> => r29 = *(0xc00000000121c8c0)
>
> 0xc00000000121c8c0 is where we placed a watchpoint and thus this
> instruction was emulated by emulate_step. But because handle_dabr_fault
> did not restore emulated register state, r29 still contains stale
> value in above register state.
>
> Fixes: 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors")
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
> Cc: stable@vger.kernel.org # 2.6.36+
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/f474c28fbcbe42faca4eb415172c07d76adcb819
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v2] Powerpc/Watchpoint: Restore nvgprs while returning from exception
@ 2019-06-30 8:37 ` Michael Ellerman
0 siblings, 0 replies; 4+ messages in thread
From: Michael Ellerman @ 2019-06-30 8:37 UTC (permalink / raw)
To: Ravi Bangoria
Cc: ravi.bangoria, mikey, aneesh.kumar, linux-kernel, npiggin,
paulus, mahesh, naveen.n.rao, linuxppc-dev
On Thu, 2019-06-13 at 03:30:14 UTC, Ravi Bangoria wrote:
> Powerpc hw triggers watchpoint before executing the instruction. To
> make trigger-after-execute behavior, kernel emulates the instruction.
> If the instruction is 'load something into non-volatile register',
> exception handler should restore emulated register state while
> returning back, otherwise there will be register state corruption.
> Ex, Adding a watchpoint on a list can corrput the list:
>
> # cat /proc/kallsyms | grep kthread_create_list
> c00000000121c8b8 d kthread_create_list
>
> Add watchpoint on kthread_create_list->prev:
>
> # perf record -e mem:0xc00000000121c8c0
>
> Run some workload such that new kthread gets invoked. Ex, I just
> logged out from console:
>
> list_add corruption. next->prev should be prev (c000000001214e00), \
> but was c00000000121c8b8. (next=c00000000121c8b8).
> WARNING: CPU: 59 PID: 309 at lib/list_debug.c:25 __list_add_valid+0xb4/0xc0
> CPU: 59 PID: 309 Comm: kworker/59:0 Kdump: loaded Not tainted 5.1.0-rc7+ #69
> ...
> NIP __list_add_valid+0xb4/0xc0
> LR __list_add_valid+0xb0/0xc0
> Call Trace:
> __list_add_valid+0xb0/0xc0 (unreliable)
> __kthread_create_on_node+0xe0/0x260
> kthread_create_on_node+0x34/0x50
> create_worker+0xe8/0x260
> worker_thread+0x444/0x560
> kthread+0x160/0x1a0
> ret_from_kernel_thread+0x5c/0x70
>
> List corruption happened because it uses 'load into non-volatile
> register' instruction:
>
> Snippet from __kthread_create_on_node:
>
> c000000000136be8: addis r29,r2,-19
> c000000000136bec: ld r29,31424(r29)
> if (!__list_add_valid(new, prev, next))
> c000000000136bf0: mr r3,r30
> c000000000136bf4: mr r5,r28
> c000000000136bf8: mr r4,r29
> c000000000136bfc: bl c00000000059a2f8 <__list_add_valid+0x8>
>
> Register state from WARN_ON():
>
> GPR00: c00000000059a3a0 c000007ff23afb50 c000000001344e00 0000000000000075
> GPR04: 0000000000000000 0000000000000000 0000001852af8bc1 0000000000000000
> GPR08: 0000000000000001 0000000000000007 0000000000000006 00000000000004aa
> GPR12: 0000000000000000 c000007ffffeb080 c000000000137038 c000005ff62aaa00
> GPR16: 0000000000000000 0000000000000000 c000007fffbe7600 c000007fffbe7370
> GPR20: c000007fffbe7320 c000007fffbe7300 c000000001373a00 0000000000000000
> GPR24: fffffffffffffef7 c00000000012e320 c000007ff23afcb0 c000000000cb8628
> GPR28: c00000000121c8b8 c000000001214e00 c000007fef5b17e8 c000007fef5b17c0
>
> Watchpoint hit at 0xc000000000136bec.
>
> addis r29,r2,-19
> => r29 = 0xc000000001344e00 + (-19 << 16)
> => r29 = 0xc000000001214e00
>
> ld r29,31424(r29)
> => r29 = *(0xc000000001214e00 + 31424)
> => r29 = *(0xc00000000121c8c0)
>
> 0xc00000000121c8c0 is where we placed a watchpoint and thus this
> instruction was emulated by emulate_step. But because handle_dabr_fault
> did not restore emulated register state, r29 still contains stale
> value in above register state.
>
> Fixes: 5aae8a5370802 ("powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors")
> Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
> Cc: stable@vger.kernel.org # 2.6.36+
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/f474c28fbcbe42faca4eb415172c07d76adcb819
cheers
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-06-30 8:50 UTC | newest]
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2019-06-13 3:30 [PATCH v2] Powerpc/Watchpoint: Restore nvgprs while returning from exception Ravi Bangoria
2019-06-13 3:30 ` Ravi Bangoria
2019-06-30 8:37 ` Michael Ellerman
2019-06-30 8:37 ` Michael Ellerman
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