From b4a1dec11793936ffe1a9fb811724532ff3b1174 Mon Sep 17 00:00:00 2001 From: Sumanth Korikkar Date: Mon, 24 Feb 2025 12:27:04 +0100 Subject: [PATCH] s390/ftrace: Fix return address recovery of traced function When fgraph is enabled the traced function return address is replaced with trampoline return_to_handler(). The original return address of the traced function is saved in per task return stack along with a stack pointer for reliable stack unwinding via function_graph_enter_regs(). During stack unwinding e.g. for livepatching, ftrace_graph_ret_addr() identifies the original return address of the traced function with the saved stack pointer. With a recent change, the stack pointers passed to ftrace_graph_ret_addr() and function_graph_enter_regs() do not match anymore, and therefore the original return address is not found. Pass the correct stack pointer to function_graph_enter_regs() to fix this. Fixes: 7495e179b478 ("s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC") Reviewed-by: Heiko Carstens Signed-off-by: Sumanth Korikkar Signed-off-by: Vasily Gorbik --- arch/s390/kernel/ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c index 63ba6306632e..e540b022ceb2 100644 --- a/arch/s390/kernel/ftrace.c +++ b/arch/s390/kernel/ftrace.c @@ -266,12 +266,13 @@ void ftrace_graph_func(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) { unsigned long *parent = &arch_ftrace_regs(fregs)->regs.gprs[14]; + unsigned long sp = arch_ftrace_regs(fregs)->regs.gprs[15]; if (unlikely(ftrace_graph_is_dead())) return; if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; - if (!function_graph_enter_regs(*parent, ip, 0, parent, fregs)) + if (!function_graph_enter_regs(*parent, ip, 0, (unsigned long *)sp, fregs)) *parent = (unsigned long)&return_to_handler; }