Re: [PATCH v3 09/13] powerpc: extend execmem_params for kprobes allocations
On Mon, Sep 18, 2023 at 12:31 AM Mike Rapoport 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 > >
Re: [PATCH v3 09/13] powerpc: extend execmem_params for kprobes allocations
Hi Mike,
Le 18/09/2023 à 09:29, Mike Rapoport a écrit :
> From: "Mike Rapoport (IBM)"
>
> 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)
> ---
> 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;
> }
Re: [PATCH v3 09/13] powerpc: extend execmem_params for kprobes allocations
On Thu, Sep 21, 2023 at 03:30:46PM -0700, Song Liu wrote: > On Mon, Sep 18, 2023 at 12:31 AM Mike Rapoport 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 > > > > -- Sincerely yours, Mike.
Re: [PATCH v3 09/13] powerpc: extend execmem_params for kprobes allocations
Hi Christophe,
On Fri, Sep 22, 2023 at 10:32:46AM +, Christophe Leroy wrote:
> Hi Mike,
>
> Le 18/09/2023 à 09:29, Mike Rapoport a écrit :
> > From: "Mike Rapoport (IBM)"
> >
> > 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)
> > ---
> > 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;
> > }
--
Sincerely yours,
Mike.
