Re: [PATCH v3 09/13] powerpc: extend execmem_params for kprobes allocations
From: Christophe Leroy <hidden>
Date: 2023-09-22 10:32:54
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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
quoted hunk ↗ jump to hunk
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; }