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authorAnton Arapov <anton@redhat.com>2013-04-03 18:00:32 +0200
committerOleg Nesterov <oleg@redhat.com>2013-04-13 15:31:54 +0200
commite78aebfd27256ca59ccd3e6cf62cfad2a80e02d3 (patch)
tree6655e753d20bf964fbdcb6eefb3087dd954e2a1f /kernel/events
parentea024870cf10687b3fded66a9deb6253888f30b7 (diff)
downloadvexpress-lsk-e78aebfd27256ca59ccd3e6cf62cfad2a80e02d3.tar.gz
uretprobes: Reserve the first slot in xol_vma for trampoline
Allocate trampoline page, as the very first one in uprobed task xol area, and fill it with breakpoint opcode. Also introduce get_trampoline_vaddr() helper, to wrap the trampoline address extraction from area->vaddr. That removes confusion and eases the debug experience in case ->vaddr notion will be changed. Signed-off-by: Anton Arapov <anton@redhat.com> Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'kernel/events')
-rw-r--r--kernel/events/uprobes.c25
1 files changed, 25 insertions, 0 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index eb384e90ac9..d345b7c6cb2 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1132,6 +1132,7 @@ static struct xol_area *get_xol_area(void)
{
struct mm_struct *mm = current->mm;
struct xol_area *area;
+ uprobe_opcode_t insn = UPROBE_SWBP_INSN;
area = mm->uprobes_state.xol_area;
if (area)
@@ -1149,7 +1150,12 @@ static struct xol_area *get_xol_area(void)
if (!area->page)
goto free_bitmap;
+ /* allocate first slot of task's xol_area for the return probes */
+ set_bit(0, area->bitmap);
+ copy_to_page(area->page, 0, &insn, UPROBE_SWBP_INSN_SIZE);
+ atomic_set(&area->slot_count, 1);
init_waitqueue_head(&area->wq);
+
if (!xol_add_vma(area))
return area;
@@ -1346,6 +1352,25 @@ static struct uprobe_task *get_utask(void)
return current->utask;
}
+/*
+ * Current area->vaddr notion assume the trampoline address is always
+ * equal area->vaddr.
+ *
+ * Returns -1 in case the xol_area is not allocated.
+ */
+static unsigned long get_trampoline_vaddr(void)
+{
+ struct xol_area *area;
+ unsigned long trampoline_vaddr = -1;
+
+ area = current->mm->uprobes_state.xol_area;
+ smp_read_barrier_depends();
+ if (area)
+ trampoline_vaddr = area->vaddr;
+
+ return trampoline_vaddr;
+}
+
/* Prepare to single-step probed instruction out of line. */
static int
pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)