2020-06-30 07:44:06

by Xu Wang

Subject: [PATCH] kernel: events: use offset_in_page macro

From: Xu Wang <[email protected]>

Use offset_in_page macro instead of (addr & ~PAGE_MASK).

Signed-off-by: Xu Wang <[email protected]>
---
kernel/events/uprobes.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index bb0862873dba..44d175d81ed6 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -244,14 +244,14 @@ bool __weak is_trap_insn(uprobe_opcode_t *insn)
static void copy_from_page(struct page *page, unsigned long vaddr, void *dst, int len)
{
void *kaddr = kmap_atomic(page);
- memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
+ memcpy(dst, kaddr + offset_in_page(vaddr), len);
kunmap_atomic(kaddr);
}

static void copy_to_page(struct page *page, unsigned long vaddr, const void *src, int len)
{
void *kaddr = kmap_atomic(page);
- memcpy(kaddr + (vaddr & ~PAGE_MASK), src, len);
+ memcpy(kaddr + offset_in_page(vaddr), src, len);
kunmap_atomic(kaddr);
}

@@ -387,7 +387,7 @@ __update_ref_ctr(struct mm_struct *mm, unsigned long vaddr, short d)
}

kaddr = kmap_atomic(page);
- ptr = kaddr + (vaddr & ~PAGE_MASK);
+ ptr = kaddr + offset_in_page(vaddr);

if (unlikely(*ptr + d < 0)) {
pr_warn("ref_ctr going negative. vaddr: 0x%lx, "
--
2.17.1

2020-06-30 07:59:35

by Peter Zijlstra

Subject: Re: [PATCH] kernel: events: use offset_in_page macro

On Tue, Jun 30, 2020 at 07:42:58AM +0000, Chen Ni wrote:

> Use offset_in_page macro instead of (addr & ~PAGE_MASK).

Shees, so now we're replacing a trivial expression with something that's
actually longer to type? How does that make sense?

> - memcpy(dst, kaddr + (vaddr & ~PAGE_MASK), len);
> + memcpy(dst, kaddr + offset_in_page(vaddr), len);