uprobes: Add is_register argument to uprobe_write and uprobe_write_opcode

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 <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Acked-by: Masami Hiramatsu (Google) <[e-mail]>
Acked-by: Andrii Nakryiko <[e-mail]>
Acked-by: Oleg Nesterov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

arch/arm/probes/uprobes/core.c

···
 	     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)

include/linux/uprobes.h

···
 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);

kernel/events/uprobes.c

···
 
 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. */
···
  * 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)))
···
 	/* 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);
 	}
 
···
 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);
 }
 
 /**
···
 		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 */