From: Naveen N. Rao <hidden> Date: 2021-05-20 07:30:15
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
I remember running some kprobe tests before submitting the patch, how did I miss that ?
Is there anything special to do to activate the use of optprobes and/or to hit this bug ?
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
Yes, and that was one of the reasons I was reluctant to that new 'struct ppc_inst', as it means
stack frames, copies, etc ... whereas we could have just changed it from 'unsigned int' to 'unsigned
long'.
Ok, now we have it, so let's use it, but use it correctly, see my clean-up series
https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=244719&state=* (v2 on the way).
quoted hunk
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
From: Naveen N. Rao <hidden> Date: 2021-05-20 10:55:17
Christophe Leroy wrote:
Le 20/05/2021 à 09:29, Naveen N. Rao a écrit :
quoted
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
I remember running some kprobe tests before submitting the patch, how did I miss that ?
Is there anything special to do to activate the use of optprobes and/or to hit this bug ?
Yeah, I was surprised when I hit this. One of the requirements we have
for optprobes on powerpc is that the instruction should be a compute
instruction (no load/store -- emulate_update_regs() should be enough)
with the exception of conditional branches. It's possible that you ended
up probing an instruction that couldn't be optimized.
An easy way to confirm if a probe has been optimized is to look at
kprobes/list in debugfs, and to watch out for [OPTIMIZED] flag there.
quoted
diff --git a/arch/powerpc/kernel/optprobes.c
b/arch/powerpc/kernel/optprobes.c
index cdf87086fa33a0..2bc53fa48a1b33 100644
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
I remember running some kprobe tests before submitting the patch, how did I miss that ?
Is there anything special to do to activate the use of optprobes and/or to hit this bug ?
Yeah, I was surprised when I hit this. One of the requirements we have for optprobes on powerpc is
that the instruction should be a compute instruction (no load/store -- emulate_update_regs() should
be enough) with the exception of conditional branches. It's possible that you ended up probing an
instruction that couldn't be optimized.
An easy way to confirm if a probe has been optimized is to look at kprobes/list in debugfs, and to
watch out for [OPTIMIZED] flag there.
I'm not completely sure it is worth reverting, on an other hand it is pointless anyway to have
something to convert to a u64 something that cannot be more than 32 bits on a PPC32, so now that we
have ppc_inst_as_ulong() it is as good I think.
Christophe
I'm not completely sure it is worth reverting, on an other hand it is pointless anyway to have
something to convert to a u64 something that cannot be more than 32 bits on a PPC32, so now that we
have ppc_inst_as_ulong() it is as good I think.
Sure. If necessary, the revert can go in separately as part of your
other cleanup series.
- Naveen
From: Naveen N. Rao <hidden> Date: 2021-06-07 11:35:22
Naveen N. Rao wrote:
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Christophe,
Can you confirm if this patch works for you? It would be good if this
can go in v5.13.
Thanks,
Naveen
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Christophe,
Can you confirm if this patch works for you? It would be good if this can go in v5.13.
I'm trying to use kprobes, but I must be missing something. I have tried to follow the exemple in
kernel's documentation:
# echo 'p:myprobe do_sys_open dfd=%r3' > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable
# cat /sys/kernel/debug/kprobes/list
c00122e4 k kretprobe_trampoline+0x0 [OPTIMIZED]
c018a1b4 k do_sys_open+0x0 [OPTIMIZED]
# cat /sys/kernel/debug/tracing/tracing_on
1
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0 #P:1
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
So it looks like I get no event. I can't believe that do_sys_open() is never hit.
This is without your patch, so it should Oops ?
Then it looks like something is locked up somewhere, because I can't do anything else:
# echo 'p:myprobe2 do_sys_openat2 dfd=%r3' >/sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo '-:myprobe' > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
Christophe
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Christophe,
Can you confirm if this patch works for you? It would be good if this can go in v5.13.
I'm trying to use kprobes, but I must be missing something. I have tried to follow the exemple in
kernel's documentation:
# echo 'p:myprobe do_sys_open dfd=%r3' > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable
# cat /sys/kernel/debug/kprobes/list
c00122e4 k kretprobe_trampoline+0x0 [OPTIMIZED]
c018a1b4 k do_sys_open+0x0 [OPTIMIZED]
# cat /sys/kernel/debug/tracing/tracing_on
1
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0 #P:1
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
So it looks like I get no event. I can't believe that do_sys_open() is never hit.
This is without your patch, so it should Oops ?
Then it looks like something is locked up somewhere, because I can't do anything else:
# echo 'p:myprobe2 do_sys_openat2 dfd=%r3' >/sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo '-:myprobe' > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
Ok, did a new test. Seems like do_sys_open() is really never called.
I set the test at do_sys_openat2 , it was not optimised and was working.
I set the test at do_sys_openat2+0x10 , it was optimised and crashed.
Now I'm going to test the patch.
When I set an event, is that normal that it removes the previous one ? Then we can have only one
event at a time ? And then when that event is enabled we get 'Device or resource busy' when trying
to add a new one ?
Christophe
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Christophe,
Can you confirm if this patch works for you? It would be good if this can go in v5.13.
I'm trying to use kprobes, but I must be missing something. I have tried to follow the exemple in
kernel's documentation:
# echo 'p:myprobe do_sys_open dfd=%r3' > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable
# cat /sys/kernel/debug/kprobes/list
c00122e4 k kretprobe_trampoline+0x0 [OPTIMIZED]
c018a1b4 k do_sys_open+0x0 [OPTIMIZED]
# cat /sys/kernel/debug/tracing/tracing_on
1
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0 #P:1
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
So it looks like I get no event. I can't believe that do_sys_open() is never hit.
This is without your patch, so it should Oops ?
Then it looks like something is locked up somewhere, because I can't do anything else:
# echo 'p:myprobe2 do_sys_openat2 dfd=%r3' >/sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo '-:myprobe' > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
Ok, did a new test. Seems like do_sys_open() is really never called.
I set the test at do_sys_openat2 , it was not optimised and was working.
I set the test at do_sys_openat2+0x10 , it was optimised and crashed.
Now I'm going to test the patch.
When I set an event, is that normal that it removes the previous one ? Then we can have only one
event at a time ? And then when that event is enabled we get 'Device or resource busy' when trying
to add a new one ?
I confirm it doesn't crash anymore and it now works with optimised probes.
Tested-by: Christophe Leroy <redacted>
From: Naveen N. Rao <hidden> Date: 2021-06-08 11:35:09
Christophe Leroy wrote:
Le 07/06/2021 à 19:36, Christophe Leroy a écrit :
quoted
Le 07/06/2021 à 16:31, Christophe Leroy a écrit :
quoted
Le 07/06/2021 à 13:34, Naveen N. Rao a écrit :
quoted
Naveen N. Rao wrote:
quoted
Trying to use a kprobe on ppc32 results in the below splat:
BUG: Unable to handle kernel data access on read at 0x7c0802a6
Faulting instruction address: 0xc002e9f0
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=4K PowerPC 44x Platform
Modules linked in:
CPU: 0 PID: 89 Comm: sh Not tainted 5.13.0-rc1-01824-g3a81c0495fdb #7
NIP: c002e9f0 LR: c0011858 CTR: 00008a47
REGS: c292fd50 TRAP: 0300 Not tainted (5.13.0-rc1-01824-g3a81c0495fdb)
MSR: 00009000 <EE,ME> CR: 24002002 XER: 20000000
DEAR: 7c0802a6 ESR: 00000000
<snip>
NIP [c002e9f0] emulate_step+0x28/0x324
LR [c0011858] optinsn_slot+0x128/0x10000
Call Trace:
opt_pre_handler+0x7c/0xb4 (unreliable)
optinsn_slot+0x128/0x10000
ret_from_syscall+0x0/0x28
The offending instruction is:
81 24 00 00 lwz r9,0(r4)
Here, we are trying to load the second argument to emulate_step():
struct ppc_inst, which is the instruction to be emulated. On ppc64,
structures are passed in registers when passed by value. However, per
the ppc32 ABI, structures are always passed to functions as pointers.
This isn't being adhered to when setting up the call to emulate_step()
in the optprobe trampoline. Fix the same.
Fixes: eacf4c0202654a ("powerpc: Enable OPTPROBES on PPC32")
Signed-off-by: Naveen N. Rao <redacted>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
Christophe,
Can you confirm if this patch works for you? It would be good if this can go in v5.13.
I'm trying to use kprobes, but I must be missing something. I have tried to follow the exemple in
kernel's documentation:
# echo 'p:myprobe do_sys_open dfd=%r3' > /sys/kernel/debug/tracing/kprobe_events
# echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable
# cat /sys/kernel/debug/kprobes/list
c00122e4 k kretprobe_trampoline+0x0 [OPTIMIZED]
c018a1b4 k do_sys_open+0x0 [OPTIMIZED]
# cat /sys/kernel/debug/tracing/tracing_on
1
# cat /sys/kernel/debug/tracing/trace
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0 #P:1
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
So it looks like I get no event. I can't believe that do_sys_open() is never hit.
This is without your patch, so it should Oops ?
Then it looks like something is locked up somewhere, because I can't do anything else:
# echo 'p:myprobe2 do_sys_openat2 dfd=%r3' >/sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo '-:myprobe' > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
# echo > /sys/kernel/debug/tracing/kprobe_events
-sh: can't create /sys/kernel/debug/tracing/kprobe_events: Device or resource busy
These should work if you disable the event. See below...
quoted
quoted
Ok, did a new test. Seems like do_sys_open() is really never called.
I set the test at do_sys_openat2 , it was not optimised and was working.
I set the test at do_sys_openat2+0x10 , it was optimised and crashed.
Now I'm going to test the patch.
When I set an event, is that normal that it removes the previous one ? Then we can have only one
event at a time ? And then when that event is enabled we get 'Device or resource busy' when trying
to add a new one ?
You should append to kprobe_events (i.e., use '>>') when _adding_ an
event, otherwise it is considered a write and it tries to remove the
existing event, which can't be done if the event is enabled.
kprobe_events allows events to be removed only after they are disabled.
quoted
I confirm it doesn't crash anymore and it now works with optimised probes.
Tested-by: Christophe Leroy <redacted>