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uprobes: Kill set_orig_insn()->is_swbp_at_addr()

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Unlike set_swbp(), set_orig_insn()->is_swbp_at_addr() makes sense,
although it can't prevent all confusions.

But the usage of is_swbp_at_addr() is equally confusing, and it adds
the extra get_user_pages() we can avoid.

This patch removes set_orig_insn()->is_swbp_at_addr() but changes
write_opcode() to do the necessary checks before replace_page().

Perhaps it also makes sense to ensure PAGE_MAPPING_ANON in unregister
case.

find_active_uprobe() becomes the only user of is_swbp_at_addr(),
we can change its semantics.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-09-23 21:30:44 +02:00
parent cceb55aab7
commit ed6f6a50dc
1 changed files with 23 additions and 9 deletions
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32
kernel/events/uprobes.c
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@ -190,6 +190,25 @@ static void copy_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t
kunmap_atomic(kaddr);
}
static int verify_opcode(struct page *page, unsigned long vaddr, uprobe_opcode_t *new_opcode)
{
uprobe_opcode_t old_opcode;
bool is_swbp;
copy_opcode(page, vaddr, &old_opcode);
is_swbp = is_swbp_insn(&old_opcode);
if (is_swbp_insn(new_opcode)) {
if (is_swbp) /* register: already installed? */
return 0;
} else {
if (!is_swbp) /* unregister: was it changed by us? */
return -EINVAL;
}
return 1;
}
/*
* NOTE:
* Expect the breakpoint instruction to be the smallest size instruction for
@ -226,6 +245,10 @@ static int write_opcode(struct mm_struct *mm, unsigned long vaddr,
if (ret <= 0)
return ret;
ret = verify_opcode(old_page, vaddr, &opcode);
if (ret <= 0)
goto put_old;
ret = -ENOMEM;
new_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vaddr);
if (!new_page)
@ -311,15 +334,6 @@ int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned
int __weak
set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
{
int result;
result = is_swbp_at_addr(mm, vaddr);
if (!result)
return -EINVAL;
if (result != 1)
return result;
return write_opcode(mm, vaddr, *(uprobe_opcode_t *)auprobe->insn);
}