Re: [PATCH v10 04/10] powerpc/kprobes: Mark newly allocated probes as ROX

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 30/03/2021 à 06:51, Jordan Niethe a écrit :
> From: Russell Currey <ruscur@russell.cc>
> 
> Add the arch specific insn page allocator for powerpc. This allocates
> ROX pages if STRICT_KERNEL_RWX is enabled. These pages are only written
> to with patch_instruction() which is able to write RO pages.
> 
> Reviewed-by: Daniel Axtens <dja@axtens.net>
> Signed-off-by: Russell Currey <ruscur@russell.cc>
> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> [jpn: Reword commit message, switch to __vmalloc_node_range()]
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> ---
> v9: - vmalloc_exec() no longer exists
>      - Set the page to RW before freeing it
> v10: - use __vmalloc_node_range()
> ---
>   arch/powerpc/kernel/kprobes.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
> index 01ab2163659e..3ae27af9b094 100644
> --- a/arch/powerpc/kernel/kprobes.c
> +++ b/arch/powerpc/kernel/kprobes.c
> @@ -25,6 +25,7 @@
>   #include <asm/sections.h>
>   #include <asm/inst.h>
>   #include <linux/uaccess.h>
> +#include <linux/vmalloc.h>
>   
>   DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
>   DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
> @@ -103,6 +104,19 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
>   	return addr;
>   }
>   
> +void *alloc_insn_page(void)
> +{
> +	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) {
> +		return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
> +				GFP_KERNEL, PAGE_KERNEL_ROX, VM_FLUSH_RESET_PERMS,
> +				NUMA_NO_NODE, __builtin_return_address(0));
> +	} else {
> +		return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
> +				GFP_KERNEL, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
> +				NUMA_NO_NODE, __builtin_return_address(0));
> +	}
> +}
> +

What about

void *alloc_insn_page(void)
{
	pgprot_t prot = IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ? PAGE_KERNEL_ROX : PAGE_KERNEL_EXEC;

	return __vmalloc_node_range(PAGE_SIZE, 1, MODULES_VADDR, MODULES_END,
			GFP_KERNEL, prot, VM_FLUSH_RESET_PERMS,
			NUMA_NO_NODE, __builtin_return_address(0));
}

>   int arch_prepare_kprobe(struct kprobe *p)
>   {
>   	int ret = 0;
>