[PATCH v2 10/11] uprobes: Add the "enum rp_check ctx" arg to arch_uretprobe_is_alive()

[Oleg Nesterov <oleg@redhat.com>]

arch/x86 doesn't care (so far), but as Pratyush Anand pointed out
other architectures might want why arch_uretprobe_is_alive() was
called and use different checks depending on the context. Add the
new argument to distinguish 2 callers.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 arch/x86/kernel/uprobes.c |    3 ++-
 include/linux/uprobes.h   |    7 ++++++-
 kernel/events/uprobes.c   |    9 ++++++---
 3 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 9d5f570..67eb168 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -994,7 +994,8 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs
 	return -1;
 }
 
-bool arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs)
+bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
+				struct pt_regs *regs)
 {
 	return regs->sp <= ret->stack;
 }
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index 7ab6d2c..c0a5402 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -102,6 +102,11 @@ struct return_instance {
 	struct return_instance	*next;		/* keep as stack */
 };
 
+enum rp_check {
+	RP_CHECK_CALL,
+	RP_CHECK_RET,
+};
+
 struct xol_area;
 
 struct uprobes_state {
@@ -138,7 +143,7 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
 extern int  arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
 extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
 extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs);
-extern bool arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs);
+extern bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, struct pt_regs *regs);
 extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs);
 extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
 					 void *src, unsigned long len);
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 7e61c8c..df5661a 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1514,7 +1514,9 @@ static unsigned long get_trampoline_vaddr(void)
 static void cleanup_return_instances(struct uprobe_task *utask, struct pt_regs *regs)
 {
 	struct return_instance *ri = utask->return_instances;
-	while (ri && !arch_uretprobe_is_alive(ri, regs)) {
+	enum rp_check ctx = RP_CHECK_CALL;
+
+	while (ri && !arch_uretprobe_is_alive(ri, ctx, regs)) {
 		ri = free_ret_instance(ri);
 		utask->depth--;
 	}
@@ -1805,7 +1807,7 @@ static void handle_trampoline(struct pt_regs *regs)
 		 * could hit this trampoline on return. TODO: sigaltstack().
 		 */
 		next = find_next_ret_chain(ri);
-		valid = !next || arch_uretprobe_is_alive(next, regs);
+		valid = !next || arch_uretprobe_is_alive(next, RP_CHECK_RET, regs);
 
 		instruction_pointer_set(regs, ri->orig_ret_vaddr);
 		do {
@@ -1830,7 +1832,8 @@ bool __weak arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs)
 	return false;
 }
 
-bool __weak arch_uretprobe_is_alive(struct return_instance *ret, struct pt_regs *regs)
+bool __weak arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
+					struct pt_regs *regs)
 {
 	return true;
 }
-- 
1.5.5.1