4.4-stable review patch. If anyone has any objections, please let me know.
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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 @@ -116,10 +116,20 @@ ftrace_stub: NESTED(_mcount, PT_SIZE, ra) 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 @@ -128,24 +138,11 @@ NESTED(_mcount, PT_SIZE, ra) 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