On Thu, Nov 14, 2024 at 03:41:03PM -0800, Andrii Nakryiko wrote:

On Tue, Nov 5, 2024 at 5:34 AM Jiri Olsa [off-list ref] wrote:

quoted

Adding len argument to uprobe_write_opcode as preparation
fo writing longer instructions in following changes.

typo: for

quoted

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/uprobes.h |  3 ++-
 kernel/events/uprobes.c | 14 ++++++++------
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 28068f9fcdc1..7d23a4fee6f4 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h

@@ -181,7 +181,8 @@ 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 *insn, int len);

is len in sizeof(uprobe_opcode_t) units or in bytes? it would be good
to make this clearer

it feels like passing `void *` for insns would be better, tbh...

good catch, it's meant as bytes, uprobe_opcode_t is u8 on x86, but other archs
treat it differently, void * might solve that in this function, will check

thanks,
jirka

quoted

 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 e9308649bba3..3e275717789b 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c

@@ -471,7 +471,7 @@ 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 *insn, int len)
 {
        struct uprobe *uprobe;
        struct page *old_page, *new_page;

@@ -480,7 +480,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
        bool orig_page_huge = false;
        unsigned int gup_flags = FOLL_FORCE;

-       is_register = is_swbp_insn(&opcode);
+       is_register = is_swbp_insn(insn);
        uprobe = container_of(auprobe, struct uprobe, arch);

 retry:

@@ -491,7 +491,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
        if (IS_ERR(old_page))
                return PTR_ERR(old_page);

-       ret = verify_opcode(old_page, vaddr, &opcode);
+       ret = verify_opcode(old_page, vaddr, insn);
        if (ret <= 0)
                goto put_old;

@@ -525,7 +525,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,

        __SetPageUptodate(new_page);
        copy_highpage(new_page, old_page);
-       copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
+       copy_to_page(new_page, vaddr, insn, len);

        if (!is_register) {
                struct page *orig_page;

@@ -582,7 +582,9 @@ int uprobe_write_opcode(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);
+       uprobe_opcode_t insn = UPROBE_SWBP_INSN;
+
+       return uprobe_write_opcode(auprobe, mm, vaddr, &insn, UPROBE_SWBP_INSN_SIZE);
 }

 /**

@@ -598,7 +600,7 @@ 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, UPROBE_SWBP_INSN_SIZE);
 }

 /* uprobe should have guaranteed positive refcount */
--

2.47.0