[PATCH] MIPS: uprobes: Restore thread.trap_nr

[PATCH] MIPS: uprobes: Restore thread.trap_nr

[Tiezhu Yang]

thread.trap_nr is saved in arch_uprobe_pre_xol(), it should be restored
in arch_uprobe_{post,abort}_xol() accordingly, actually it was only done
in the post function, just do it in the abort function too, this change
is similar with x86 and powerpc.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 arch/mips/kernel/uprobes.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/mips/kernel/uprobes.c b/arch/mips/kernel/uprobes.c
index 6b630ed..401b148 100644
--- a/arch/mips/kernel/uprobes.c
+++ b/arch/mips/kernel/uprobes.c
@@ -191,6 +191,7 @@ void arch_uprobe_abort_xol(struct arch_uprobe *aup,
 {
 	struct uprobe_task *utask = current->utask;
 
+	current->thread.trap_nr = utask->autask.saved_trap_nr;
 	instruction_pointer_set(regs, utask->vaddr);
 }
 
-- 
2.1.0

Re: [PATCH] MIPS: uprobes: Restore thread.trap_nr

[Bagas Sanjaya]

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On Sun, Apr 23, 2023 at 09:38:03AM +0800, Tiezhu Yang wrote:
> thread.trap_nr is saved in arch_uprobe_pre_xol(), it should be restored
> in arch_uprobe_{post,abort}_xol() accordingly, actually it was only done
> in the post function, just do it in the abort function too, this change
> is similar with x86 and powerpc.

I'm confused (please fix up grammar, spelling, and punctuation). Can you
explain why thread.trap_nr should be restored somewhere else? Also, what
x86/powerpc changes as reference?

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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Re: [PATCH] MIPS: uprobes: Restore thread.trap_nr

[Tiezhu Yang]

Cc:
Oleg Nesterov <oleg@redhat.com>
Srikar Dronamraju <srikar@linux.vnet.ibm.com>

On 04/23/2023 11:08 AM, Bagas Sanjaya wrote:
> On Sun, Apr 23, 2023 at 09:38:03AM +0800, Tiezhu Yang wrote:
>> thread.trap_nr is saved in arch_uprobe_pre_xol(), it should be restored
>> in arch_uprobe_{post,abort}_xol() accordingly, actually it was only done
>> in the post function, just do it in the abort function too, this change
>> is similar with x86 and powerpc.
>
> I'm confused (please fix up grammar, spelling, and punctuation). Can you
> explain why thread.trap_nr should be restored somewhere else? Also, what
> x86/powerpc changes as reference?
>

Here is the related first commit for x86 in 2012:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0326f5a94dde

When xol insn itself triggers the signal, restart the original insn,
in this case, UTASK_SSTEP_TRAPPED is set [1], it does *abort_xol()
instead of *post_xol() [2], then should do the restore operations.

Maybe Oleg and Srikar could give more detailed backgrounds, thank you.
https://lore.kernel.org/lkml/1682213883-3654-1-git-send-email-yangtiezhu@loongson.cn/

[1] 
https://elixir.bootlin.com/linux/latest/source/kernel/events/uprobes.c#L1980
[2] 
https://elixir.bootlin.com/linux/latest/source/kernel/events/uprobes.c#L2268

Thanks,
Tiezhu

Re: [PATCH] MIPS: uprobes: Restore thread.trap_nr

[Oleg Nesterov]

On 04/23, Tiezhu Yang wrote:
>
> Cc:
> Oleg Nesterov <oleg@redhat.com>
> Srikar Dronamraju <srikar@linux.vnet.ibm.com>
>
> On 04/23/2023 11:08 AM, Bagas Sanjaya wrote:
> >On Sun, Apr 23, 2023 at 09:38:03AM +0800, Tiezhu Yang wrote:
> >>thread.trap_nr is saved in arch_uprobe_pre_xol(), it should be restored
> >>in arch_uprobe_{post,abort}_xol() accordingly, actually it was only done
> >>in the post function, just do it in the abort function too, this change
> >>is similar with x86 and powerpc.
> >
> >I'm confused (please fix up grammar, spelling, and punctuation). Can you
> >explain why thread.trap_nr should be restored somewhere else? Also, what
> >x86/powerpc changes as reference?
> >
>
> Here is the related first commit for x86 in 2012:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0326f5a94dde
>
> When xol insn itself triggers the signal, restart the original insn,
> in this case, UTASK_SSTEP_TRAPPED is set [1], it does *abort_xol()
> instead of *post_xol() [2], then should do the restore operations.

Yes... for example, if the uprobed task was killed abort() should restore
the state and (in particular) change ->trap_nr from UPROBE_TRAP_NR back to
->saved_trap_nr.

So the patch looks fine to me.

Oleg.

Re: [PATCH] MIPS: uprobes: Restore thread.trap_nr

[Thomas Bogendoerfer]

On Sun, Apr 23, 2023 at 09:38:03AM +0800, Tiezhu Yang wrote:
> thread.trap_nr is saved in arch_uprobe_pre_xol(), it should be restored
> in arch_uprobe_{post,abort}_xol() accordingly, actually it was only done
> in the post function, just do it in the abort function too, this change
> is similar with x86 and powerpc.
> 
> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
> ---
>  arch/mips/kernel/uprobes.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/mips/kernel/uprobes.c b/arch/mips/kernel/uprobes.c
> index 6b630ed..401b148 100644
> --- a/arch/mips/kernel/uprobes.c
> +++ b/arch/mips/kernel/uprobes.c
> @@ -191,6 +191,7 @@ void arch_uprobe_abort_xol(struct arch_uprobe *aup,
>  {
>  	struct uprobe_task *utask = current->utask;
>  
> +	current->thread.trap_nr = utask->autask.saved_trap_nr;
>  	instruction_pointer_set(regs, utask->vaddr);
>  }
>  
> -- 
> 2.1.0

applied to mips-next.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]