uprobes: Add uprobe_write function

Adding uprobe_write function that does what uprobe_write_opcode did
so far, but allows to pass verify callback function that checks the
memory location before writing the opcode.

It will be used in following changes to implement specific checking
logic for instruction update.

The uprobe_write_opcode now calls uprobe_write with verify_opcode as
the verify callback.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250720112133.244369-5-jolsa@kernel.org

authored by

Jiri Olsa and committed by

Peter Zijlstra 10 months ago 33d7b2be 82afdd05

+15 -4

2 changed files

expand all

include

linux

uprobes.h

kernel

events

uprobes.c

include/linux/uprobes.h

··· 187 187 struct xol_area *xol_area; 188 188 }; 189 189 190 + typedef int (*uprobe_write_verify_t)(struct page *page, unsigned long vaddr, 191 + uprobe_opcode_t *opcode); 192 + 190 193 extern void __init uprobes_init(void); 191 194 extern int set_swbp(struct arch_uprobe *aup, struct vm_area_struct *vma, unsigned long vaddr); 192 195 extern int set_orig_insn(struct arch_uprobe *aup, struct vm_area_struct *vma, unsigned long vaddr); ··· 198 195 extern unsigned long uprobe_get_swbp_addr(struct pt_regs *regs); 199 196 extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs); 200 197 extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr, uprobe_opcode_t); 198 + extern int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, const unsigned long opcode_vaddr, 199 + uprobe_opcode_t opcode, uprobe_write_verify_t verify); 201 200 extern struct uprobe *uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc); 202 201 extern int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool); 203 202 extern void uprobe_unregister_nosync(struct uprobe *uprobe, struct uprobe_consumer *uc);

+10 -4

kernel/events/uprobes.c

··· 399 399 return identical; 400 400 } 401 401 402 - static int __uprobe_write_opcode(struct vm_area_struct *vma, 402 + static int __uprobe_write(struct vm_area_struct *vma, 403 403 struct folio_walk *fw, struct folio *folio, 404 404 unsigned long opcode_vaddr, uprobe_opcode_t opcode) 405 405 { ··· 488 488 int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma, 489 489 const unsigned long opcode_vaddr, uprobe_opcode_t opcode) 490 490 { 491 + return uprobe_write(auprobe, vma, opcode_vaddr, opcode, verify_opcode); 492 + } 493 + 494 + int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, 495 + const unsigned long opcode_vaddr, uprobe_opcode_t opcode, uprobe_write_verify_t verify) 496 + { 491 497 const unsigned long vaddr = opcode_vaddr & PAGE_MASK; 492 498 struct mm_struct *mm = vma->vm_mm; 493 499 struct uprobe *uprobe; ··· 515 509 * page that we can safely modify. Use FOLL_WRITE to trigger a write 516 510 * fault if required. When unregistering, we might be lucky and the 517 511 * anon page is already gone. So defer write faults until really 518 - * required. Use FOLL_SPLIT_PMD, because __uprobe_write_opcode() 512 + * required. Use FOLL_SPLIT_PMD, because __uprobe_write() 519 513 * cannot deal with PMDs yet. 520 514 */ 521 515 if (is_register) ··· 527 521 goto out; 528 522 folio = page_folio(page); 529 523 530 - ret = verify_opcode(page, opcode_vaddr, &opcode); 524 + ret = verify(page, opcode_vaddr, &opcode); 531 525 if (ret <= 0) { 532 526 folio_put(folio); 533 527 goto out; ··· 566 560 /* Walk the page tables again, to perform the actual update. */ 567 561 if (folio_walk_start(&fw, vma, vaddr, 0)) { 568 562 if (fw.page == page) 569 - ret = __uprobe_write_opcode(vma, &fw, folio, opcode_vaddr, opcode); 563 + ret = __uprobe_write(vma, &fw, folio, opcode_vaddr, opcode); 570 564 folio_walk_end(&fw, vma); 571 565 } 572 566

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