The first time a uprobe with return consumer is hit for a process, a
trampoline slot is obtained in the xol_area and initialized with a
breakpoint instruction. This slot is subsequently used by all
uretprobes.
todo:
unify with xol_take_insn_slot()
Signed-off-by: Anton Arapov <an...@redhat.com>
---
include/linux/uprobes.h | 1 +
kernel/events/uprobes.c | 33 +++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 95d0002..bddfad6 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -91,6 +91,7 @@ struct xol_area {
* the vma go away, and we must handle that reasonably gracefully.
*/
unsigned long vaddr; /* Page(s) of instruction slots
*/
+ unsigned long rp_trampoline_vaddr; /* address of trampolines
*/
};
struct uprobes_state {
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 473db3f..0ad2ac3 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1208,6 +1208,39 @@ static unsigned long xol_get_insn_slot(struct uprobe
*uprobe)
return xol_vaddr;
}
+/*
+ * xol_get_trampoline_slot - A trampoline slot is obtained the first
+ * time a uprobe with return consumer is hit for a process. Use one
+ * trampoline slot for all probes pertaining to a process, i.e.
+ * one per xol_area.
+ */
+static unsigned long xol_get_trampoline_slot(void)
+{
+ struct xol_area *area;
+ unsigned long offset;
+ uprobe_opcode_t bp_insn = UPROBE_SWBP_INSN;
+ void *vaddr;
+
+ area = get_xol_area();
+ if (!area)
+ return 0;
+
+ if (!area->rp_trampoline_vaddr)
+ area->rp_trampoline_vaddr = xol_take_insn_slot(area);
+
+ if (unlikely(!area->rp_trampoline_vaddr))
+ return 0;
+
+ offset = area->rp_trampoline_vaddr & ~PAGE_MASK;
+ vaddr = kmap_atomic(area->page);
+ memcpy(vaddr + offset, &bp_insn, UPROBE_SWBP_INSN_SIZE);
+ kunmap_atomic(vaddr);
+
+ flush_dcache_page(area->page);
+
+ return area->rp_trampoline_vaddr;
+}
+
/*
* xol_free_insn_slot - If slot was earlier allocated by
* @xol_get_insn_slot(), make the slot available for
--
1.8.0.2
--
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