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uprobes: Simplify is_swbp_at_addr(), remove stale comments

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After the previous change is_swbp_at_addr() is always called with
current->mm. Remove this check and move it close to its single caller.

Also, remove the obsolete comment about is_swbp_at_addr() and
uprobe_state.count.

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 21:55:19 +02:00
parent ed6f6a50dc
commit ec75fba93e
1 changed files with 24 additions and 49 deletions
Download patch file Download diff file Expand all files Collapse all files

73
kernel/events/uprobes.c
View file

@ -282,32 +282,6 @@ put_old:
return ret; return ret;
} }
static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
{
struct page *page;
uprobe_opcode_t opcode;
int result;
if (current->mm == mm) {
pagefault_disable();
result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
sizeof(opcode));
pagefault_enable();
if (likely(result == 0))
goto out;
}
result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (result < 0)
return result;
copy_opcode(page, vaddr, &opcode);
put_page(page);
out:
return is_swbp_insn(&opcode);
}
/** /**
* set_swbp - store breakpoint at a given address. * set_swbp - store breakpoint at a given address.
* @auprobe: arch specific probepoint information. * @auprobe: arch specific probepoint information.
@ -589,29 +563,6 @@ static int copy_insn(struct uprobe *uprobe, struct file *filp)
return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset); return __copy_insn(mapping, filp, uprobe->arch.insn, bytes, uprobe->offset);
} }
/*
* How mm->uprobes_state.count gets updated
* uprobe_mmap() increments the count if
* - it successfully adds a breakpoint.
* - it cannot add a breakpoint, but sees that there is a underlying
* breakpoint (via a is_swbp_at_addr()).
*
* uprobe_munmap() decrements the count if
* - it sees a underlying breakpoint, (via is_swbp_at_addr)
* (Subsequent uprobe_unregister wouldnt find the breakpoint
* unless a uprobe_mmap kicks in, since the old vma would be
* dropped just after uprobe_munmap.)
*
* uprobe_register increments the count if:
* - it successfully adds a breakpoint.
*
* uprobe_unregister decrements the count if:
* - it sees a underlying breakpoint and removes successfully.
* (via is_swbp_at_addr)
* (Subsequent uprobe_munmap wouldnt find the breakpoint
* since there is no underlying breakpoint after the
* breakpoint removal.)
*/
static int static int
install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm, install_breakpoint(struct uprobe *uprobe, struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long vaddr) struct vm_area_struct *vma, unsigned long vaddr)
@ -1389,6 +1340,30 @@ static void mmf_recalc_uprobes(struct mm_struct *mm)
clear_bit(MMF_HAS_UPROBES, &mm->flags); clear_bit(MMF_HAS_UPROBES, &mm->flags);
} }
static int is_swbp_at_addr(struct mm_struct *mm, unsigned long vaddr)
{
struct page *page;
uprobe_opcode_t opcode;
int result;
pagefault_disable();
result = __copy_from_user_inatomic(&opcode, (void __user*)vaddr,
sizeof(opcode));
pagefault_enable();
if (likely(result == 0))
goto out;
result = get_user_pages(NULL, mm, vaddr, 1, 0, 1, &page, NULL);
if (result < 0)
return result;
copy_opcode(page, vaddr, &opcode);
put_page(page);
out:
return is_swbp_insn(&opcode);
}
static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp) static struct uprobe *find_active_uprobe(unsigned long bp_vaddr, int *is_swbp)
{ {
struct mm_struct *mm = current->mm; struct mm_struct *mm = current->mm;