* Oleg Nesterov <o...@redhat.com> [2012-12-31 18:52:23]:
> pre_ssout()->xol_get_insn_slot() path is confusing and buggy. This patch
> cleanups the code, the next one fixes the bug.
>
> Change xol_get_insn_slot() to only allocate the slot and do nothing more,
> move the initialization of utask->xol_vaddr/vaddr into pre_ssout().
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Acked-by: Srikar Dronamraju <sri...@linux.vnet.ibm.com>
> ---
> kernel/events/uprobes.c | 37 +++++++++++++++++++++----------------
> 1 files changed, 21 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index b09b3ba..2ed6239 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -1176,30 +1176,26 @@ static unsigned long xol_take_insn_slot(struct
> xol_area *area)
> }
>
> /*
> - * xol_get_insn_slot - If was not allocated a slot, then
> - * allocate a slot.
> + * xol_get_insn_slot - allocate a slot for xol.
> * Returns the allocated slot address or 0.
> */
> -static unsigned long xol_get_insn_slot(struct uprobe *uprobe, unsigned long
> slot_addr)
> +static unsigned long xol_get_insn_slot(struct uprobe *uprobe)
> {
> struct xol_area *area;
> unsigned long offset;
> + unsigned long xol_vaddr;
> void *vaddr;
>
> area = get_xol_area();
> if (!area)
> return 0;
>
> - current->utask->xol_vaddr = xol_take_insn_slot(area);
> - /*
> - * Initialize the slot if xol_vaddr points to valid
> - * instruction slot.
> - */
> - if (unlikely(!current->utask->xol_vaddr))
> + xol_vaddr = xol_take_insn_slot(area);
> + if (unlikely(!xol_vaddr))
> return 0;
>
> - current->utask->vaddr = slot_addr;
> - offset = current->utask->xol_vaddr & ~PAGE_MASK;
> + /* Initialize the slot */
> + offset = xol_vaddr & ~PAGE_MASK;
> vaddr = kmap_atomic(area->page);
> memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
> kunmap_atomic(vaddr);
> @@ -1209,7 +1205,7 @@ static unsigned long xol_get_insn_slot(struct uprobe
> *uprobe, unsigned long slot
> */
> flush_dcache_page(area->page);
>
> - return current->utask->xol_vaddr;
> + return xol_vaddr;
> }
>
> /*
> @@ -1306,12 +1302,21 @@ static struct uprobe_task *get_utask(void)
>
> /* Prepare to single-step probed instruction out of line. */
> static int
> -pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long vaddr)
> +pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long
> bp_vaddr)
> {
> - if (xol_get_insn_slot(uprobe, vaddr) &&
> !arch_uprobe_pre_xol(&uprobe->arch, regs))
> - return 0;
> + struct uprobe_task *utask;
> + unsigned long xol_vaddr;
> +
> + utask = current->utask;
> +
> + xol_vaddr = xol_get_insn_slot(uprobe);
> + if (!xol_vaddr)
> + return -ENOMEM;
> +
> + utask->xol_vaddr = xol_vaddr;
> + utask->vaddr = bp_vaddr;
>
> - return -EFAULT;
> + return arch_uprobe_pre_xol(&uprobe->arch, regs);
> }
>
> /*
> --
> 1.5.5.1
>
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