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uprobes: Do not play with utask in xol_get_insn_slot() 

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 <oleg@redhat.com>
Acked-by: Anton Arapov <anton@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
This commit is contained in:
Oleg Nesterov 2012-12-31 18:00:06 +01:00
parent 5a2df662aa
commit a6cb3f6d51
1 changed files with 21 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
kernel/events/uprobes.c
View File

@ -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 * xol_get_insn_slot - allocate a slot for xol.
* allocate a slot.
* Returns the allocated slot address or 0. * 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; struct xol_area *area;
unsigned long offset; unsigned long offset;
unsigned long xol_vaddr;
void *vaddr; void *vaddr;
area = get_xol_area(); area = get_xol_area();
if (!area) if (!area)
return 0; return 0;
current->utask->xol_vaddr = xol_take_insn_slot(area); xol_vaddr = xol_take_insn_slot(area);
/* if (unlikely(!xol_vaddr))
* Initialize the slot if xol_vaddr points to valid
* instruction slot.
*/
if (unlikely(!current->utask->xol_vaddr))
return 0; return 0;
current->utask->vaddr = slot_addr; /* Initialize the slot */
offset = current->utask->xol_vaddr & ~PAGE_MASK; offset = xol_vaddr & ~PAGE_MASK;
vaddr = kmap_atomic(area->page); vaddr = kmap_atomic(area->page);
memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES); memcpy(vaddr + offset, uprobe->arch.insn, MAX_UINSN_BYTES);
kunmap_atomic(vaddr); 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); 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. */ /* Prepare to single-step probed instruction out of line. */
static int 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)) struct uprobe_task *utask;
return 0; unsigned long xol_vaddr;
return -EFAULT; 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 arch_uprobe_pre_xol(&uprobe->arch, regs);
} }
/* /*