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Message-Id: <20250625153229.f39c1a1a99ce986380769150@kernel.org>
Date: Wed, 25 Jun 2025 15:32:29 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
x86@...nel.org, Song Liu <songliubraving@...com>, Yonghong Song
<yhs@...com>, John Fastabend <john.fastabend@...il.com>, Hao Luo
<haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
<mhiramat@...nel.org>, Alan Maguire <alan.maguire@...cle.com>, David Laight
<David.Laight@...LAB.COM>, Thomas Weißschuh
<thomas@...ch.de>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCHv3 perf/core 06/22] uprobes: Add is_register argument to
uprobe_write and uprobe_write_opcode
On Thu, 5 Jun 2025 15:23:33 +0200
Jiri Olsa <jolsa@...nel.org> wrote:
> The uprobe_write has special path to restore the original page when we
> write original instruction back. This happens when uprobe_write detects
> that we want to write anything else but breakpoint instruction.
>
> Moving the detection away and passing it to uprobe_write as argument,
> so it's possible to write different instructions (other than just
> breakpoint and rest).
Looks good to me.
Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Thanks,
>
> Acked-by: Andrii Nakryiko <andrii@...nel.org>
> Acked-by: Oleg Nesterov <oleg@...hat.com>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
> arch/arm/probes/uprobes/core.c | 2 +-
> include/linux/uprobes.h | 5 +++--
> kernel/events/uprobes.c | 21 +++++++++++----------
> 3 files changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/arch/arm/probes/uprobes/core.c b/arch/arm/probes/uprobes/core.c
> index 885e0c5e8c20..3d96fb41d624 100644
> --- a/arch/arm/probes/uprobes/core.c
> +++ b/arch/arm/probes/uprobes/core.c
> @@ -30,7 +30,7 @@ int set_swbp(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> unsigned long vaddr)
> {
> return uprobe_write_opcode(auprobe, vma, vaddr,
> - __opcode_to_mem_arm(auprobe->bpinsn));
> + __opcode_to_mem_arm(auprobe->bpinsn), true);
> }
>
> bool arch_uprobe_ignore(struct arch_uprobe *auprobe, struct pt_regs *regs)
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 147c4a0a1af9..518b26756469 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -197,9 +197,10 @@ extern bool is_swbp_insn(uprobe_opcode_t *insn);
> extern bool is_trap_insn(uprobe_opcode_t *insn);
> extern unsigned long uprobe_get_swbp_addr(struct pt_regs *regs);
> extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs);
> -extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr, uprobe_opcode_t);
> +extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr, uprobe_opcode_t,
> + bool is_register);
> extern int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, const unsigned long opcode_vaddr,
> - uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify);
> + uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify, bool is_register);
> extern struct uprobe *uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
> extern int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool);
> extern void uprobe_unregister_nosync(struct uprobe *uprobe, struct uprobe_consumer *uc);
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index f7feb7417a2c..1e5dc3b30707 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -402,10 +402,10 @@ static bool orig_page_is_identical(struct vm_area_struct *vma,
>
> static int __uprobe_write(struct vm_area_struct *vma,
> struct folio_walk *fw, struct folio *folio,
> - unsigned long insn_vaddr, uprobe_opcode_t *insn, int nbytes)
> + unsigned long insn_vaddr, uprobe_opcode_t *insn, int nbytes,
> + bool is_register)
> {
> const unsigned long vaddr = insn_vaddr & PAGE_MASK;
> - const bool is_register = !!is_swbp_insn(insn);
> bool pmd_mappable;
>
> /* For now, we'll only handle PTE-mapped folios. */
> @@ -488,26 +488,27 @@ static int __uprobe_write(struct vm_area_struct *vma,
> * Return 0 (success) or a negative errno.
> */
> int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> - const unsigned long opcode_vaddr, uprobe_opcode_t opcode)
> + const unsigned long opcode_vaddr, uprobe_opcode_t opcode,
> + bool is_register)
> {
> - return uprobe_write(auprobe, vma, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE, verify_opcode);
> + return uprobe_write(auprobe, vma, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE,
> + verify_opcode, is_register);
> }
>
> int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> const unsigned long insn_vaddr, uprobe_opcode_t *insn, int nbytes,
> - uprobe_write_verify_t verify)
> + uprobe_write_verify_t verify, bool is_register)
> {
> const unsigned long vaddr = insn_vaddr & PAGE_MASK;
> struct mm_struct *mm = vma->vm_mm;
> struct uprobe *uprobe;
> - int ret, is_register, ref_ctr_updated = 0;
> + int ret, ref_ctr_updated = 0;
> unsigned int gup_flags = FOLL_FORCE;
> struct mmu_notifier_range range;
> struct folio_walk fw;
> struct folio *folio;
> struct page *page;
>
> - is_register = is_swbp_insn(insn);
> uprobe = container_of(auprobe, struct uprobe, arch);
>
> if (WARN_ON_ONCE(!is_cow_mapping(vma->vm_flags)))
> @@ -569,7 +570,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> /* Walk the page tables again, to perform the actual update. */
> if (folio_walk_start(&fw, vma, vaddr, 0)) {
> if (fw.page == page)
> - ret = __uprobe_write(vma, &fw, folio, insn_vaddr, insn, nbytes);
> + ret = __uprobe_write(vma, &fw, folio, insn_vaddr, insn, nbytes, is_register);
> folio_walk_end(&fw, vma);
> }
>
> @@ -611,7 +612,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> int __weak set_swbp(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
> unsigned long vaddr)
> {
> - return uprobe_write_opcode(auprobe, vma, vaddr, UPROBE_SWBP_INSN);
> + return uprobe_write_opcode(auprobe, vma, vaddr, UPROBE_SWBP_INSN, true);
> }
>
> /**
> @@ -627,7 +628,7 @@ int __weak set_orig_insn(struct arch_uprobe *auprobe,
> struct vm_area_struct *vma, unsigned long vaddr)
> {
> return uprobe_write_opcode(auprobe, vma, vaddr,
> - *(uprobe_opcode_t *)&auprobe->insn);
> + *(uprobe_opcode_t *)&auprobe->insn, false);
> }
>
> /* uprobe should have guaranteed positive refcount */
> --
> 2.49.0
>
--
Masami Hiramatsu (Google) <mhiramat@...nel.org>
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