From: Naveen N. Rao <[email protected]>
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")
Cc: [email protected]
Signed-off-by: Naveen N. Rao <[email protected]>
---
v2: Rebased on powerpc/merge 7f030e9d57b8
Signed-off-by: Christophe Leroy <[email protected]>
---
arch/powerpc/kernel/optprobes.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
index 2b8fe40069ad..53facb4b377f 100644
--- a/arch/powerpc/kernel/optprobes.c
+++ b/arch/powerpc/kernel/optprobes.c
@@ -228,8 +228,12 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *p)
/*
* 3. load instruction to be emulated into relevant register, and
*/
- temp = ppc_inst_read(p->ainsn.insn);
- patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
+ if (IS_ENABLED(CONFIG_PPC64)) {
+ temp = ppc_inst_read(p->ainsn.insn);
+ patch_imm_load_insns(ppc_inst_as_ulong(temp), 4, buff + TMPL_INSN_IDX);
+ } else {
+ patch_imm_load_insns((unsigned long)p->ainsn.insn, 4, buff + TMPL_INSN_IDX);
+ }
/*
* 4. branch back from trampoline
--
2.25.0
Christophe Leroy wrote:
> From: Naveen N. Rao <[email protected]>
>
> 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")
> Cc: [email protected]
> Signed-off-by: Naveen N. Rao <[email protected]>
> ---
> v2: Rebased on powerpc/merge 7f030e9d57b8
> Signed-off-by: Christophe Leroy <[email protected]>
Thanks for rebasing this!
I think git am drops everything after three dashes, so applying this
patch will drop your SOB. The recommended style (*) for adding a
changelog is to include it within [] before the second SOB.
- Naveen
(*) https://www.kernel.org/doc/html/latest/maintainer/modifying-patches.html
Le 24/06/2021 à 12:59, Naveen N. Rao a écrit :
> Christophe Leroy wrote:
>> From: Naveen N. Rao <[email protected]>
>>
>> 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")
>> Cc: [email protected]
>> Signed-off-by: Naveen N. Rao <[email protected]>
>> ---
>> v2: Rebased on powerpc/merge 7f030e9d57b8
>> Signed-off-by: Christophe Leroy <[email protected]>
>
> Thanks for rebasing this!
>
> I think git am drops everything after three dashes, so applying this patch will drop your SOB. The
> recommended style (*) for adding a changelog is to include it within [] before the second SOB.
>
Yes, I saw that after sending the mail. Usually I add a signed-off-by with 'git --amend -s' when I
add the history, so it goes before the '---' I'm adding.
This time I must have forgotten the '-s' so it was added by the 'git format-patch -s' which is in my
submit script, and so it was added at the end.
It's not really a big deal, up to Michael to either move it at the right place or discard it, I
don't really mind. Do the easiest for you.
Thanks
Christophe
Christophe Leroy <[email protected]> writes:
> Le 24/06/2021 à 12:59, Naveen N. Rao a écrit :
>> Christophe Leroy wrote:
>>> From: Naveen N. Rao <[email protected]>
>>>
>>> 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")
>>> Cc: [email protected]
>>> Signed-off-by: Naveen N. Rao <[email protected]>
>>> ---
>>> v2: Rebased on powerpc/merge 7f030e9d57b8
>>> Signed-off-by: Christophe Leroy <[email protected]>
>>
>> Thanks for rebasing this!
>>
>> I think git am drops everything after three dashes, so applying this patch will drop your SOB. The
>> recommended style (*) for adding a changelog is to include it within [] before the second SOB.
>
> Yes, I saw that after sending the mail. Usually I add a signed-off-by with 'git --amend -s' when I
> add the history, so it goes before the '---' I'm adding.
>
> This time I must have forgotten the '-s' so it was added by the 'git format-patch -s' which is in my
> submit script, and so it was added at the end.
>
> It's not really a big deal, up to Michael to either move it at the right place or discard it, I
> don't really mind. Do the easiest for you.
I just added Christophe's SoB.
cheers
On Wed, 23 Jun 2021 05:23:30 +0000 (UTC), Christophe Leroy 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
>
> [...]
Applied to powerpc/next.
[1/1] powerpc/kprobes: Fix Oops by passing ppc_inst as a pointer to emulate_step() on ppc32
https://git.kernel.org/powerpc/c/511eea5e2ccdfdbf3d626bde0314e551f247dd18
cheers