diff mbox series

[v3,09/13] powerpc: extend execmem_params for kprobes allocations

Message ID 20230918072955.2507221-10-rppt@kernel.org (mailing list archive)
State Handled Elsewhere
Delegated to: BPF
Headers show
Series mm: jit/text allocator | expand

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Commit Message

Mike Rapoport Sept. 18, 2023, 7:29 a.m. UTC 
From: "Mike Rapoport (IBM)" <rppt@kernel.org>

powerpc overrides kprobes::alloc_insn_page() to remove writable
permissions when STRICT_MODULE_RWX is on.

Add definition of EXECMEM_KRPOBES to execmem_params to allow using the
generic kprobes::alloc_insn_page() with the desired permissions.

As powerpc uses breakpoint instructions to inject kprobes, it does not
need to constrain kprobe allocations to the modules area and can use the
entire vmalloc address space.

Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
---
 arch/powerpc/kernel/kprobes.c | 14 --------------
 arch/powerpc/kernel/module.c  | 11 +++++++++++
 2 files changed, 11 insertions(+), 14 deletions(-)

Comments

Song Liu Sept. 21, 2023, 10:30 p.m. UTC | #1 
On Mon, Sep 18, 2023 at 12:31 AM Mike Rapoport <rppt@kernel.org> wrote:
>
[...]
> @@ -135,5 +138,13 @@ struct execmem_params __init *execmem_arch_params(void)
>
>         range->pgprot = prot;
>
> +       execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_START;
> +       execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_END;

.end = VMALLOC_END.

Thanks,
Song

> +
> +       if (strict_module_rwx_enabled())
> +               execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_ROX;
> +       else
> +               execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_EXEC;
> +
>         return &execmem_params;
>  }
> --
> 2.39.2
>
>
Christophe Leroy Sept. 22, 2023, 10:32 a.m. UTC | #2 
Hi Mike,

Le 18/09/2023 à 09:29, Mike Rapoport a écrit :
> From: "Mike Rapoport (IBM)" <rppt@kernel.org>
> 
> powerpc overrides kprobes::alloc_insn_page() to remove writable
> permissions when STRICT_MODULE_RWX is on.
> 
> Add definition of EXECMEM_KRPOBES to execmem_params to allow using the
> generic kprobes::alloc_insn_page() with the desired permissions.
> 
> As powerpc uses breakpoint instructions to inject kprobes, it does not
> need to constrain kprobe allocations to the modules area and can use the
> entire vmalloc address space.

I don't understand what you mean here. Does it mean kprobe allocation 
doesn't need to be executable ? I don't think so based on the pgprot you 
set.

On powerpc book3s/32, vmalloc space is not executable. Only modules 
space is executable. X/NX cannot be set on a per page basis, it can only 
be set on a 256 Mbytes segment basis.

See commit c49643319715 ("powerpc/32s: Only leave NX unset on segments 
used for modules") and 6ca055322da8 ("powerpc/32s: Use dedicated segment 
for modules with STRICT_KERNEL_RWX") and 7bee31ad8e2f ("powerpc/32s: Fix 
is_module_segment() when MODULES_VADDR is defined").

So if your intention is still to have an executable kprobes, then you 
can't use vmalloc address space.

Christophe

> 
> Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
> ---
>   arch/powerpc/kernel/kprobes.c | 14 --------------
>   arch/powerpc/kernel/module.c  | 11 +++++++++++
>   2 files changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index 62228c7072a2..14c5ddec3056 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -126,20 +126,6 @@ kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offse
>   	return (kprobe_opcode_t *)(addr + offset);
>   }
>   
> -void *alloc_insn_page(void)
> -{
> -	void *page;
> -
> -	page = execmem_text_alloc(EXECMEM_KPROBES, PAGE_SIZE);
> -	if (!page)
> -		return NULL;
> -
> -	if (strict_module_rwx_enabled())
> -		set_memory_rox((unsigned long)page, 1);
> -
> -	return page;
> -}
> -
>   int arch_prepare_kprobe(struct kprobe *p)
>   {
>   	int ret = 0;
> diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
> index 824d9541a310..bf2c62aef628 100644
> --- a/arch/powerpc/kernel/module.c
> +++ b/arch/powerpc/kernel/module.c
> @@ -95,6 +95,9 @@ static struct execmem_params execmem_params __ro_after_init = {
>   		[EXECMEM_DEFAULT] = {
>   			.alignment = 1,
>   		},
> +		[EXECMEM_KPROBES] = {
> +			.alignment = 1,
> +		},
>   		[EXECMEM_MODULE_DATA] = {
>   			.alignment = 1,
>   		},
> @@ -135,5 +138,13 @@ struct execmem_params __init *execmem_arch_params(void)
>   
>   	range->pgprot = prot;
>   
> +	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_START;
> +	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_END;
> +
> +	if (strict_module_rwx_enabled())
> +		execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_ROX;
> +	else
> +		execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_EXEC;
> +
>   	return &execmem_params;
>   }
Mike Rapoport Sept. 23, 2023, 4:25 p.m. UTC | #3 
On Thu, Sep 21, 2023 at 03:30:46PM -0700, Song Liu wrote:
> On Mon, Sep 18, 2023 at 12:31 AM Mike Rapoport <rppt@kernel.org> wrote:
> >
> [...]
> > @@ -135,5 +138,13 @@ struct execmem_params __init *execmem_arch_params(void)
> >
> >         range->pgprot = prot;
> >
> > +       execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_START;
> > +       execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_END;
> 
> .end = VMALLOC_END.

Thanks, this should have been

	execmem_params.ranges[EXECMEM_KPROBES].start = range->start;
	execmem_params.ranges[EXECMEM_KPROBES].end = range->end;

where range points to the same range as EXECMEM_MODULE_TEXT.

 
> Thanks,
> Song
> 
> > +
> > +       if (strict_module_rwx_enabled())
> > +               execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_ROX;
> > +       else
> > +               execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_EXEC;
> > +
> >         return &execmem_params;
> >  }
> > --
> > 2.39.2
> >
> >
Mike Rapoport Sept. 23, 2023, 4:27 p.m. UTC | #4 
Hi Christophe,

On Fri, Sep 22, 2023 at 10:32:46AM +0000, Christophe Leroy wrote:
> Hi Mike,
> 
> Le 18/09/2023 à 09:29, Mike Rapoport a écrit :
> > From: "Mike Rapoport (IBM)" <rppt@kernel.org>
> > 
> > powerpc overrides kprobes::alloc_insn_page() to remove writable
> > permissions when STRICT_MODULE_RWX is on.
> > 
> > Add definition of EXECMEM_KRPOBES to execmem_params to allow using the
> > generic kprobes::alloc_insn_page() with the desired permissions.
> > 
> > As powerpc uses breakpoint instructions to inject kprobes, it does not
> > need to constrain kprobe allocations to the modules area and can use the
> > entire vmalloc address space.
> 
> I don't understand what you mean here. Does it mean kprobe allocation 
> doesn't need to be executable ? I don't think so based on the pgprot you 
> set.
> 
> On powerpc book3s/32, vmalloc space is not executable. Only modules 
> space is executable. X/NX cannot be set on a per page basis, it can only 
> be set on a 256 Mbytes segment basis.
> 
> See commit c49643319715 ("powerpc/32s: Only leave NX unset on segments 
> used for modules") and 6ca055322da8 ("powerpc/32s: Use dedicated segment 
> for modules with STRICT_KERNEL_RWX") and 7bee31ad8e2f ("powerpc/32s: Fix 
> is_module_segment() when MODULES_VADDR is defined").
> 
> So if your intention is still to have an executable kprobes, then you 
> can't use vmalloc address space.

Right, and I've fixed the KPROBES range to uses the same range as MODULES.
The commit message is stale and I need to update it.
 
> Christophe
> 
> > 
> > Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
> > ---
> >   arch/powerpc/kernel/kprobes.c | 14 --------------
> >   arch/powerpc/kernel/module.c  | 11 +++++++++++
> >   2 files changed, 11 insertions(+), 14 deletions(-)
> > 
> > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> > index 62228c7072a2..14c5ddec3056 100644
> > --- a/arch/powerpc/kernel/kprobes.c
> > +++ b/arch/powerpc/kernel/kprobes.c
> > @@ -126,20 +126,6 @@ kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offse
> >   	return (kprobe_opcode_t *)(addr + offset);
> >   }
> >   
> > -void *alloc_insn_page(void)
> > -{
> > -	void *page;
> > -
> > -	page = execmem_text_alloc(EXECMEM_KPROBES, PAGE_SIZE);
> > -	if (!page)
> > -		return NULL;
> > -
> > -	if (strict_module_rwx_enabled())
> > -		set_memory_rox((unsigned long)page, 1);
> > -
> > -	return page;
> > -}
> > -
> >   int arch_prepare_kprobe(struct kprobe *p)
> >   {
> >   	int ret = 0;
> > diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
> > index 824d9541a310..bf2c62aef628 100644
> > --- a/arch/powerpc/kernel/module.c
> > +++ b/arch/powerpc/kernel/module.c
> > @@ -95,6 +95,9 @@ static struct execmem_params execmem_params __ro_after_init = {
> >   		[EXECMEM_DEFAULT] = {
> >   			.alignment = 1,
> >   		},
> > +		[EXECMEM_KPROBES] = {
> > +			.alignment = 1,
> > +		},
> >   		[EXECMEM_MODULE_DATA] = {
> >   			.alignment = 1,
> >   		},
> > @@ -135,5 +138,13 @@ struct execmem_params __init *execmem_arch_params(void)
> >   
> >   	range->pgprot = prot;
> >   
> > +	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_START;
> > +	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_END;
> > +
> > +	if (strict_module_rwx_enabled())
> > +		execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_ROX;
> > +	else
> > +		execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_EXEC;
> > +
> >   	return &execmem_params;
> >   }
diff mbox series

Patch

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 62228c7072a2..14c5ddec3056 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -126,20 +126,6 @@  kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offse
 	return (kprobe_opcode_t *)(addr + offset);
 }
 
-void *alloc_insn_page(void)
-{
-	void *page;
-
-	page = execmem_text_alloc(EXECMEM_KPROBES, PAGE_SIZE);
-	if (!page)
-		return NULL;
-
-	if (strict_module_rwx_enabled())
-		set_memory_rox((unsigned long)page, 1);
-
-	return page;
-}
-
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index 824d9541a310..bf2c62aef628 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c
@@ -95,6 +95,9 @@  static struct execmem_params execmem_params __ro_after_init = {
 		[EXECMEM_DEFAULT] = {
 			.alignment = 1,
 		},
+		[EXECMEM_KPROBES] = {
+			.alignment = 1,
+		},
 		[EXECMEM_MODULE_DATA] = {
 			.alignment = 1,
 		},
@@ -135,5 +138,13 @@  struct execmem_params __init *execmem_arch_params(void)
 
 	range->pgprot = prot;
 
+	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_START;
+	execmem_params.ranges[EXECMEM_KPROBES].start = VMALLOC_END;
+
+	if (strict_module_rwx_enabled())
+		execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_ROX;
+	else
+		execmem_params.ranges[EXECMEM_KPROBES].pgprot = PAGE_KERNEL_EXEC;
+
 	return &execmem_params;
 }