runtime backtracing: port commit #2e7f8442 to uprobes1

    * runtime/uprobes/uprobes.c (uprobe_get_pc): new function

3 files changed, 46 insertions, 2 deletions

diff --git a/runtime/stack-x86_64.c b/runtime/stack-x86_64.c
index d6c63412..3fc203f7 100644
--- a/runtime/stack-x86_64.c
+++ b/runtime/stack-x86_64.c
@@ -38,7 +38,6 @@ static void __stp_stack_print(struct pt_regs *regs, int verbose, int levels,
 
 	while (levels && (tsk || !arch_unw_user_mode(&info))) {
 		int ret = unwind(&info, tsk);
-#if defined(UPROBES_API_VERSION) && UPROBES_API_VERSION > 1
                 unsigned long maybe_pc = 0;
                 if (ri) {
                         maybe_pc = uprobe_get_pc(ri, UNW_PC(&info),
@@ -48,7 +47,6 @@ static void __stp_stack_print(struct pt_regs *regs, int verbose, int levels,
                         else
                                 UNW_PC(&info) = maybe_pc;
                 }
-#endif
 		dbug_unwind(1, "ret=%d PC=%lx SP=%lx\n", ret, UNW_PC(&info), UNW_SP(&info));
 		if (ret == 0) {
 			_stp_func_print(UNW_PC(&info), verbose, 1, tsk);
diff --git a/runtime/uprobes/uprobes.c b/runtime/uprobes/uprobes.c
index 60c84509..cdb98707 100644
--- a/runtime/uprobes/uprobes.c
+++ b/runtime/uprobes/uprobes.c
@@ -2596,6 +2596,44 @@ static void uretprobe_set_trampoline(struct uprobe_process *uproc,
 	}
 }
 
+unsigned long uprobe_get_pc(struct uretprobe_instance *ri, unsigned long pc,
+			unsigned long sp)
+{
+        struct uretprobe *rp;
+        struct uprobe_kimg *uk;
+        struct uprobe_process *uproc;
+        unsigned long trampoline_addr;
+        struct hlist_node *r;
+        struct uretprobe_instance *ret_inst;
+
+        if (!ri)
+                return 0;
+        rp = ri->rp;
+        uk = (struct uprobe_kimg *)rp->u.kdata;
+        if (!uk)
+                return 0;
+        uproc = uk->ppt->uproc;
+        if (IS_ERR(uproc->uretprobe_trampoline_addr))
+          return pc;
+        trampoline_addr = (unsigned long)uproc->uretprobe_trampoline_addr;
+        if (pc != trampoline_addr)
+                return pc;
+        r = &ri->hlist;
+        hlist_for_each_entry_from(ret_inst, r, hlist) {
+                if (ret_inst->ret_addr == trampoline_addr)
+                        continue;
+                /* First handler with a stack pointer lower than the
+                   address (or equal) must be the one. */
+                if (ret_inst->sp == sp || compare_stack_ptrs(ret_inst->sp, sp))
+                        return ret_inst->ret_addr;
+        }
+        printk(KERN_ERR "Original return address for trampoline not found at "
+               "0x%lx pid/tgid=%d/%d\n", sp, current->pid, current->tgid);
+        return 0;
+}
+
+EXPORT_SYMBOL_GPL(uprobe_get_pc);
+
 #else	/* ! CONFIG_URETPROBES */
 
 static void uretprobe_handle_entry(struct uprobe *u, struct pt_regs *regs,
diff --git a/runtime/uprobes/uprobes.h b/runtime/uprobes/uprobes.h
index d542420d..e888f9e8 100644
--- a/runtime/uprobes/uprobes.h
+++ b/runtime/uprobes/uprobes.h
@@ -95,6 +95,14 @@ extern void unregister_uretprobe(struct uretprobe *rp);
 /* For PRs 9940, 6852... */
 extern void unmap_uprobe(struct uprobe *u);
 extern void unmap_uretprobe(struct uretprobe *rp);
+/*
+ * Given a program counter, translate it back to the original address
+ * if it is the address of the trampoline. sp is the stack pointer for
+ * the frame that corresponds to the address.
+ */
+extern unsigned long uprobe_get_pc(struct uretprobe_instance *ri,
+                                   unsigned long pc,
+                                   unsigned long sp);
 
 #ifdef UPROBES_IMPLEMENTATION