uprobes: Add nbytes argument to uprobe_write

Adding nbytes argument to uprobe_write and related functions as
preparation for writing whole instructions in following changes.

Also renaming opcode arguments to insn, which seems to fit better.

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]

include/linux/uprobes.h

···
 };
 
 typedef int (*uprobe_write_verify_t)(struct page *page, unsigned long vaddr,
-				     uprobe_opcode_t *opcode);
+				     uprobe_opcode_t *insn, int nbytes);
 
 extern void __init uprobes_init(void);
 extern int set_swbp(struct arch_uprobe *aup, struct vm_area_struct *vma, unsigned long vaddr);
···
 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(struct arch_uprobe *auprobe, struct vm_area_struct *vma, const unsigned long opcode_vaddr,
-			uprobe_opcode_t opcode, uprobe_write_verify_t verify);
+			uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify);
 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

···
 	kunmap_atomic(kaddr);
 }
 
-static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
+static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *insn,
+			 int nbytes)
 {
 	uprobe_opcode_t old_opcode;
 	bool is_swbp;
···
 	uprobe_copy_from_page(page, vaddr, &old_opcode, UPROBE_SWBP_INSN_SIZE);
 	is_swbp = is_swbp_insn(&old_opcode);
 
-	if (is_swbp_insn(new_opcode)) {
+	if (is_swbp_insn(insn)) {
 		if (is_swbp)		/* register: already installed? */
 			return 0;
 	} else {
···
 
 static int __uprobe_write(struct vm_area_struct *vma,
 		struct folio_walk *fw, struct folio *folio,
-		unsigned long opcode_vaddr, uprobe_opcode_t opcode)
+		unsigned long insn_vaddr, uprobe_opcode_t *insn, int nbytes)
 {
-	const unsigned long vaddr = opcode_vaddr & PAGE_MASK;
-	const bool is_register = !!is_swbp_insn(&opcode);
+	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. */
···
 	 */
 	flush_cache_page(vma, vaddr, pte_pfn(fw->pte));
 	fw->pte = ptep_clear_flush(vma, vaddr, fw->ptep);
-	copy_to_page(fw->page, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
+	copy_to_page(fw->page, insn_vaddr, insn, nbytes);
 
 	/*
 	 * When unregistering, we may only zap a PTE if uffd is disabled and
···
 int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
 		const unsigned long opcode_vaddr, uprobe_opcode_t opcode)
 {
-	return uprobe_write(auprobe, vma, opcode_vaddr, opcode, verify_opcode);
+	return uprobe_write(auprobe, vma, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE, verify_opcode);
 }
 
 int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma,
-		 const unsigned long opcode_vaddr, uprobe_opcode_t opcode, uprobe_write_verify_t verify)
+		 const unsigned long insn_vaddr, uprobe_opcode_t *insn, int nbytes,
+		 uprobe_write_verify_t verify)
 {
-	const unsigned long vaddr = opcode_vaddr & PAGE_MASK;
+	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;
···
 	struct folio *folio;
 	struct page *page;
 
-	is_register = is_swbp_insn(&opcode);
+	is_register = is_swbp_insn(insn);
 	uprobe = container_of(auprobe, struct uprobe, arch);
 
 	if (WARN_ON_ONCE(!is_cow_mapping(vma->vm_flags)))
···
 		goto out;
 	folio = page_folio(page);
 
-	ret = verify(page, opcode_vaddr, &opcode);
+	ret = verify(page, insn_vaddr, insn, nbytes);
 	if (ret <= 0) {
 		folio_put(folio);
 		goto out;
···
 	/* 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, opcode_vaddr, opcode);
+			ret = __uprobe_write(vma, &fw, folio, insn_vaddr, insn, nbytes);
 		folio_walk_end(&fw, vma);
 	}