The patch below does not apply to the 4.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 8712b27c5723c26400a2b350faf1d6d9fd7ffaad Mon Sep 17 00:00:00 2001

From: "Steven Rostedt (VMware)" rostedt@goodmis.org Date: Sun, 18 Nov 2018 17:25:18 -0500 Subject: [PATCH] MIPS: function_graph: Simplify with function_graph_enter()

The function_graph_enter() function does the work of calling the function graph hook function and the management of the shadow stack, simplifying the work done in the architecture dependent prepare_ftrace_return().

Have MIPS use the new code, and remove the shadow stack management as well as having to set up the trace structure.

This is needed to prepare for a fix of a design bug on how the curr_ret_stack is used.

Cc: Ralf Baechle ralf@linux-mips.org Cc: Paul Burton paul.burton@mips.com Cc: James Hogan jhogan@kernel.org Cc: linux-mips@linux-mips.org Cc: stable@kernel.org Fixes: 03274a3ffb449 ("tracing/fgraph: Adjust fgraph depth before calling trace return callback") Reviewed-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org

diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c index 7f3dfdbc3657..b122cbb4aad1 100644 --- a/arch/mips/kernel/ftrace.c +++ b/arch/mips/kernel/ftrace.c @@ -322,7 +322,6 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, unsigned long fp) { unsigned long old_parent_ra; - struct ftrace_graph_ent trace; unsigned long return_hooker = (unsigned long) &return_to_handler; int faulted, insns; @@ -369,12 +368,6 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, if (unlikely(faulted)) goto out;

- if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp, - NULL) == -EBUSY) { - *parent_ra_addr = old_parent_ra; - return; - } - /* * Get the recorded ip of the current mcount calling site in the * __mcount_loc section, which will be used to filter the function @@ -382,13 +375,10 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, */

insns = core_kernel_text(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; - trace.func = self_ra - (MCOUNT_INSN_SIZE * insns); + self_ra -= (MCOUNT_INSN_SIZE * insns);

- /* Only trace if the calling function expects to */ - if (!ftrace_graph_entry(&trace)) { - current->curr_ret_stack--; + if (function_graph_enter(old_parent_ra, self_ra, fp, NULL)) *parent_ra_addr = old_parent_ra; - } return; out: ftrace_graph_stop();