Re: [PATCH bpf-next 04/13] uprobes: Add arch_uprobe_verify_opcode function

Andrii Nakryiko
2024-12-13T00:48:17Z

On Wed, Dec 11, 2024 at 5:34 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Adding arch_uprobe_verify_opcode function, so we can overload
> verification for each architecture in following changes.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
> include/linux/uprobes.h | 5 +++++
> kernel/events/uprobes.c | 19 ++++++++++++++++---
> 2 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index cc723bc48c1d..8843b7f99ed0 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -215,6 +215,11 @@ extern void uprobe_handle_trampoline(struct pt_regs *regs);
> extern void *arch_uretprobe_trampoline(unsigned long *psize);
> extern unsigned long uprobe_get_trampoline_vaddr(void);
> extern void uprobe_copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len);
> +extern int uprobe_verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode);
> +extern int arch_uprobe_verify_opcode(struct arch_uprobe *auprobe, struct page *page,
> + unsigned long vaddr, uprobe_opcode_t *new_opcode,
> + int nbytes);
> +extern bool arch_uprobe_is_register(uprobe_opcode_t *insn, int nbytes);
> #else /* !CONFIG_UPROBES */
> struct uprobes_state {
> };
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index 7c2ecf11a573..8068f91de9e3 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -263,7 +263,13 @@ static void uprobe_copy_to_page(struct page *page, unsigned long vaddr, const vo
> kunmap_atomic(kaddr);
> }
>
> -static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
> +__weak bool arch_uprobe_is_register(uprobe_opcode_t *insn, int nbytes)
> +{
> + return is_swbp_insn(insn);

a bit weird that we ignore nbytes here... should we have nbytes ==
UPROBE_SWBP_INSN_SIZE check somewhere here or inside is_swbp_insn()?

> +}
> +
> +int uprobe_verify_opcode(struct page *page, unsigned long vaddr,
> + uprobe_opcode_t *new_opcode)
> {
> uprobe_opcode_t old_opcode;
> bool is_swbp;
> @@ -291,6 +297,13 @@ static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
> return 1;
> }
>
> +__weak int arch_uprobe_verify_opcode(struct arch_uprobe *auprobe, struct page *page,
> + unsigned long vaddr, uprobe_opcode_t *new_opcode,
> + int nbytes)
> +{
> + return uprobe_verify_opcode(page, vaddr, new_opcode);

again, dropping nbytes on the floor here

> +}
> +
> static struct delayed_uprobe *
> delayed_uprobe_check(struct uprobe *uprobe, struct mm_struct *mm)
> {
> @@ -479,7 +492,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
> bool orig_page_huge = false;
> unsigned int gup_flags = FOLL_FORCE;
>
> - is_register = is_swbp_insn(insn);
> + is_register = arch_uprobe_is_register(insn, nbytes);
> uprobe = container_of(auprobe, struct uprobe, arch);
>
> retry:
> @@ -490,7 +503,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
> if (IS_ERR(old_page))
> return PTR_ERR(old_page);
>
> - ret = verify_opcode(old_page, vaddr, insn);
> + ret = arch_uprobe_verify_opcode(auprobe, old_page, vaddr, insn, nbytes);
> if (ret <= 0)
> goto put_old;
>
> --
> 2.47.0
>