[PATCH perf/core 06/22] uprobes: Add is_register argument to uprobe_write and uprobe_write_opcode

Jiri Olsa
2025-04-21T21:45:45Z

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).

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, 15 insertions(+), 14 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 b86a2f0475a4..6af61e977bfb 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 vm_area_struct *vma, unsigned long vaddr, uprobe_opcode_t opcode);
+extern int uprobe_write_opcode(struct vm_area_struct *vma, unsigned long vaddr,
+ uprobe_opcode_t opcode, bool is_register);
extern int uprobe_write(struct vm_area_struct *vma, const unsigned long insn_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 6dc7f0b2756d..c8d88060dfbf 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. */
@@ -488,25 +488,25 @@ static int __uprobe_write(struct vm_area_struct *vma,
* Return 0 (success) or a negative errno.
*/
int uprobe_write_opcode(struct vm_area_struct *vma, const unsigned long opcode_vaddr,
- uprobe_opcode_t opcode)
+ uprobe_opcode_t opcode, bool is_register)
{
- return uprobe_write(vma, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE, verify_opcode);
+ return uprobe_write(vma, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE,
+ verify_opcode, is_register);
}

int uprobe_write(struct vm_area_struct *vma, const unsigned long insn_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)
{
const unsigned long vaddr = insn_vaddr & PAGE_MASK;
struct mm_struct *mm = vma->vm_mm;
- int ret, is_register;
+ int ret;
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);
-
if (WARN_ON_ONCE(!is_cow_mapping(vma->vm_flags)))
return -EINVAL;

@@ -555,7 +555,7 @@ int uprobe_write(struct vm_area_struct *vma, const unsigned long insn_vaddr,
/* 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);
}

@@ -593,7 +593,7 @@ int uprobe_write(struct vm_area_struct *vma, const unsigned long insn_vaddr,
int __weak set_swbp(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
unsigned long vaddr)
{
- return uprobe_write_opcode(vma, vaddr, UPROBE_SWBP_INSN);
+ return uprobe_write_opcode(vma, vaddr, UPROBE_SWBP_INSN, true);
}

static int set_swbp_refctr(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long vaddr)
@@ -628,7 +628,7 @@ static int set_swbp_refctr(struct uprobe *uprobe, struct vm_area_struct *vma, un
int __weak set_orig_insn(struct arch_uprobe *auprobe,
struct vm_area_struct *vma, unsigned long vaddr)
{
- return uprobe_write_opcode(vma, vaddr, *(uprobe_opcode_t *)&auprobe->insn);
+ return uprobe_write_opcode(vma, vaddr, *(uprobe_opcode_t *)&auprobe->insn, false);
}

static int set_orig_refctr(struct uprobe *uprobe, struct vm_area_struct *vma, unsigned long vaddr)
--
2.49.0