Currently, ftrace_graph_caller() sets up a separate stack frame to save
some state before calling into prepare_ftrace_return(). Eliminate this
by calling into ftrace_graph_caller() right after the ftrace handler.
We make a few changes to accommodate this:
1. Currently, due to where it is present, ftrace_graph_caller() is not
invoked if the NIP is modified by the ftrace handler, indicating either
a livepatched function or a jprobe'd function. To achieve the same
behavior, we now save/compare against original NIP if function graph is
enabled, in addition to CONFIG_LIVEPATCH.
2. We use r14 for saving the original NIP and r15 for storing the
possibly modified NIP. r15 is later used to determine if the function
has been livepatched.
3. To re-use the same stack frame setup/teardown code, we have
ftrace_graph_caller() save the modified LR in pt_regs.
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
arch/powerpc/kernel/trace/ftrace_64_mprofile.S | 70 ++++++++------------------
1 file changed, 21 insertions(+), 49 deletions(-)
diff --git a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
index b1bad68ea6db..981b99dc3029 100644
--- a/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
+++ b/arch/powerpc/kernel/trace/ftrace_64_mprofile.S
@@ -72,9 +72,10 @@ _GLOBAL(ftrace_caller)
addi r3,r3,function_trace_op@toc@l
ld r5,0(r3)
-#ifdef CONFIG_LIVEPATCH
+#if defined(CONFIG_FUNCTION_GRAPH_TRACER) || defined(CONFIG_LIVEPATCH)
mr r14,r7 /* remember old NIP */
#endif
+
/* Calculate ip from nip-4 into r3 for call below */
subi r3, r7, MCOUNT_INSN_SIZE
@@ -97,10 +98,19 @@ ftrace_call:
nop
/* Load ctr with the possibly modified NIP */
- ld r3, _NIP(r1)
- mtctr r3
+ ld r15, _NIP(r1)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+.globl ftrace_graph_call
+ftrace_graph_call:
+ b ftrace_graph_stub
+_GLOBAL(ftrace_graph_stub)
+#endif
+
+ mtctr r15
+
#ifdef CONFIG_LIVEPATCH
- cmpd r14,r3 /* has NIP been altered? */
+ cmpd r14, r15 /* has NIP been altered? */
#endif
/* Restore gprs */
@@ -124,13 +134,6 @@ ftrace_call:
bne- livepatch_handler
#endif
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-.globl ftrace_graph_call
-ftrace_graph_call:
- b ftrace_graph_stub
-_GLOBAL(ftrace_graph_stub)
-#endif
-
bctr /* jump after _mcount site */
_GLOBAL(ftrace_stub)
@@ -233,50 +236,19 @@ livepatch_handler:
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
_GLOBAL(ftrace_graph_caller)
- stdu r1, -112(r1)
- /* with -mprofile-kernel, parameter regs are still alive at _mcount */
- std r10, 104(r1)
- std r9, 96(r1)
- std r8, 88(r1)
- std r7, 80(r1)
- std r6, 72(r1)
- std r5, 64(r1)
- std r4, 56(r1)
- std r3, 48(r1)
+ cmpd r14, r15 /* has NIP been altered? */
+ bne- ftrace_graph_stub
- /* Save callee's TOC in the ABI compliant location */
- std r2, 24(r1)
- ld r2, PACATOC(r13) /* get kernel TOC in r2 */
-
- mfctr r4 /* ftrace_caller has moved local addr here */
- std r4, 40(r1)
- mflr r3 /* ftrace_caller has restored LR from stack */
- subi r4, r4, MCOUNT_INSN_SIZE
+ ld r3, _LINK(r1)
+ subi r4, r14, MCOUNT_INSN_SIZE /* load saved original NIP */
bl prepare_ftrace_return
nop
/*
* prepare_ftrace_return gives us the address we divert to.
- * Change the LR to this.
+ * We save it in pt_regs to be used when we go back.
*/
- mtlr r3
-
- ld r0, 40(r1)
- mtctr r0
- ld r10, 104(r1)
- ld r9, 96(r1)
- ld r8, 88(r1)
- ld r7, 80(r1)
- ld r6, 72(r1)
- ld r5, 64(r1)
- ld r4, 56(r1)
- ld r3, 48(r1)
-
- /* Restore callee's TOC */
- ld r2, 24(r1)
-
- addi r1, r1, 112
- mflr r0
- bctr
+ std r3, _LINK(r1)
+ b ftrace_graph_stub
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
--
2.12.2
