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s390/ftrace: Fix return address recovery of traced function

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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: 7495e179b4 ("s390/tracing: Enable HAVE_FTRACE_GRAPH_FUNC")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Sumanth Korikkar 2025-02-24 12:27:04 +01:00 committed by Vasily Gorbik
parent a22ee38d2e
commit b4a1dec117
1 changed files with 2 additions and 1 deletions
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3
arch/s390/kernel/ftrace.c
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@ -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(&current->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;
}