| From 6fb8656646f996d1eef42e6d56203c4915cb9e08 Mon Sep 17 00:00:00 2001 |
| From: Matthias Schiffer <mschiffer@universe-factory.net> |
| Date: Sat, 24 Mar 2018 17:57:49 +0100 |
| Subject: mips: ftrace: fix static function graph tracing |
| |
| From: Matthias Schiffer <mschiffer@universe-factory.net> |
| |
| commit 6fb8656646f996d1eef42e6d56203c4915cb9e08 upstream. |
| |
| ftrace_graph_caller was never run after calling ftrace_trace_function, |
| breaking the function graph tracer. Fix this, bringing it in line with the |
| x86 implementation. |
| |
| While we're at it, also streamline the control flow of _mcount a bit to |
| reduce the number of branches. |
| |
| This issue was reported before: |
| https://www.linux-mips.org/archives/linux-mips/2014-11/msg00295.html |
| |
| Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net> |
| Tested-by: Matt Redfearn <matt.redfearn@mips.com> |
| Patchwork: https://patchwork.linux-mips.org/patch/18929/ |
| Signed-off-by: Paul Burton <paul.burton@mips.com> |
| Cc: stable@vger.kernel.org # v3.17+ |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/mips/kernel/mcount.S | 27 ++++++++++++--------------- |
| 1 file changed, 12 insertions(+), 15 deletions(-) |
| |
| --- a/arch/mips/kernel/mcount.S |
| +++ b/arch/mips/kernel/mcount.S |
| @@ -119,10 +119,20 @@ NESTED(_mcount, PT_SIZE, ra) |
| EXPORT_SYMBOL(_mcount) |
| PTR_LA t1, ftrace_stub |
| PTR_L t2, ftrace_trace_function /* Prepare t2 for (1) */ |
| - bne t1, t2, static_trace |
| + beq t1, t2, fgraph_trace |
| nop |
| |
| + MCOUNT_SAVE_REGS |
| + |
| + move a0, ra /* arg1: self return address */ |
| + jalr t2 /* (1) call *ftrace_trace_function */ |
| + move a1, AT /* arg2: parent's return address */ |
| + |
| + MCOUNT_RESTORE_REGS |
| + |
| +fgraph_trace: |
| #ifdef CONFIG_FUNCTION_GRAPH_TRACER |
| + PTR_LA t1, ftrace_stub |
| PTR_L t3, ftrace_graph_return |
| bne t1, t3, ftrace_graph_caller |
| nop |
| @@ -131,24 +141,11 @@ EXPORT_SYMBOL(_mcount) |
| bne t1, t3, ftrace_graph_caller |
| nop |
| #endif |
| - b ftrace_stub |
| -#ifdef CONFIG_32BIT |
| - addiu sp, sp, 8 |
| -#else |
| - nop |
| -#endif |
| - |
| -static_trace: |
| - MCOUNT_SAVE_REGS |
| - |
| - move a0, ra /* arg1: self return address */ |
| - jalr t2 /* (1) call *ftrace_trace_function */ |
| - move a1, AT /* arg2: parent's return address */ |
| |
| - MCOUNT_RESTORE_REGS |
| #ifdef CONFIG_32BIT |
| addiu sp, sp, 8 |
| #endif |
| + |
| .globl ftrace_stub |
| ftrace_stub: |
| RETURN_BACK |
