[PATCH RFCv3 06/23] uprobes: Add orig argument to uprobe_write and uprobe_write_opcode

Jiri Olsa
2025-03-20T11:43:13Z

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.

In following changes we want to use uprobe_write function for multiple
updates, so adding new function argument to denote that this is the
original instruction update. This way uprobe_write can make appropriate
checks and restore the original page when possible.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
arch/arm/probes/uprobes/core.c | 2 +-
include/linux/uprobes.h | 5 +++--
kernel/events/uprobes.c | 22 ++++++++++------------
3 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/arch/arm/probes/uprobes/core.c b/arch/arm/probes/uprobes/core.c
index f5f790c6e5f8..54a90b565285 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 mm_struct *mm,
unsigned long vaddr)
{
return uprobe_write_opcode(auprobe, mm, vaddr,
- __opcode_to_mem_arm(auprobe->bpinsn));
+ __opcode_to_mem_arm(auprobe->bpinsn), false);
}

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 c69a05775394..1b6a4e2b5464 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -196,9 +196,10 @@ 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 mm_struct *mm, unsigned long vaddr, uprobe_opcode_t);
+extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr,
+ uprobe_opcode_t, bool);
extern int uprobe_write(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr,
- uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify);
+ uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify, bool orig);
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 7ff1f07c8f79..92fed5e50ec1 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -471,25 +471,23 @@ static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm,
* Return 0 (success) or a negative errno.
*/
int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
- unsigned long vaddr, uprobe_opcode_t opcode)
+ unsigned long vaddr, uprobe_opcode_t opcode, bool orig)
{
- return uprobe_write(auprobe, mm, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE, verify_opcode);
+ return uprobe_write(auprobe, mm, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE, verify_opcode, orig);
}

int uprobe_write(struct arch_uprobe *auprobe, struct mm_struct *mm,
unsigned long vaddr, uprobe_opcode_t *insn,
- int nbytes, uprobe_write_verify_t verify)
+ int nbytes, uprobe_write_verify_t verify, bool orig)
{
struct page *old_page, *new_page;
struct vm_area_struct *vma;
- int ret, is_register;
+ int ret;
bool orig_page_huge = false;
unsigned int gup_flags = FOLL_FORCE;

- is_register = is_swbp_insn(insn);
-
retry:
- if (is_register)
+ if (!orig)
gup_flags |= FOLL_SPLIT_PMD;
/* Read the page with vaddr into memory */
old_page = get_user_page_vma_remote(mm, vaddr, gup_flags, &vma);
@@ -505,14 +503,14 @@ int uprobe_write(struct arch_uprobe *auprobe, struct mm_struct *mm,
goto put_old;
}

- if (WARN(!is_register && PageCompound(old_page),
+ if (WARN(orig && PageCompound(old_page),
"uprobe unregister should never work on compound page\n")) {
ret = -EINVAL;
goto put_old;
}

ret = 0;
- if (!is_register && !PageAnon(old_page))
+ if (orig && !PageAnon(old_page))
goto put_old;

ret = anon_vma_prepare(vma);
@@ -528,7 +526,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct mm_struct *mm,
copy_highpage(new_page, old_page);
uprobe_copy_to_page(new_page, vaddr, insn, nbytes);

- if (!is_register) {
+ if (orig) {
struct page *orig_page;
pgoff_t index;

@@ -579,7 +577,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct mm_struct *mm,
*/
int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
{
- return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
+ return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN, false);
}

static int set_swbp_refctr(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
@@ -614,7 +612,7 @@ int __weak
set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
{
return uprobe_write_opcode(auprobe, mm, vaddr,
- *(uprobe_opcode_t *)&auprobe->insn);
+ *(uprobe_opcode_t *)&auprobe->insn, true);
}

static int set_orig_refctr(struct uprobe *uprobe, struct mm_struct *mm, unsigned long vaddr)
--
2.49.0