powerpc/ftrace: directly call of function graph tracer by ftrace caller

Modify function graph tracer to be handled directly by the standard
ftrace caller.

This is made possible as powerpc now supports
CONFIG_DYNAMIC_FTRACE_WITH_ARGS.

This change simplifies the call of function graph ftrace.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/04d196585ff81bde06a000bd9c633a33a5b21130.1640017960.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/ftrace.h

@@ -38,6 +38,12 @@ static __always_inline void ftrace_instruction_pointer_set(struct ftrace_regs *f
 {
 	regs_set_return_ip(&fregs->regs, ip);
 }
+
+struct ftrace_ops;
+
+#define ftrace_graph_func ftrace_graph_func
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs);
 #endif
 #endif /* __ASSEMBLY__ */
 

arch/powerpc/kernel/trace/ftrace.c

@@ -917,6 +917,9 @@ static int ftrace_modify_ftrace_graph_caller(bool enable)
 	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
 	ppc_inst_t old, new;
 
+	if (IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_ARGS))
+		return 0;
+
 	old = ftrace_call_replace(ip, enable ? stub : addr, 0);
 	new = ftrace_call_replace(ip, enable ? addr : stub, 0);
 
@@ -955,6 +958,14 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip,
 out:
 	return parent;
 }
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS
+void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,
+		       struct ftrace_ops *op, struct ftrace_regs *fregs)
+{
+	fregs->regs.link = prepare_ftrace_return(parent_ip, ip, fregs->regs.gpr[1]);
+}
+#endif
 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 
 #ifdef PPC64_ELF_ABI_v1

arch/powerpc/kernel/trace/ftrace_32.S

@@ -59,13 +59,6 @@ ftrace_call:
 	mtlr	r0
 
 	addi	r1, r1, INT_FRAME_SIZE
-ftrace_caller_common:
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-.globl ftrace_graph_call
-ftrace_graph_call:
-	b	ftrace_graph_stub
-_GLOBAL(ftrace_graph_stub)
-#endif
 	/* old link register ends up in ctr reg */
 	bctr
 
@@ -135,52 +128,10 @@ ftrace_regs_call:
 
 	/* Pop our stack frame */
 	addi r1, r1, INT_FRAME_SIZE
-
-	b	ftrace_caller_common
-
-#ifdef CONFIG_FUNCTION_GRAPH_TRACER
-_GLOBAL(ftrace_graph_caller)
-	stwu	r1,-48(r1)
-	stw	r3, 12(r1)
-	stw	r4, 16(r1)
-	stw	r5, 20(r1)
-	stw	r6, 24(r1)
-	stw	r7, 28(r1)
-	stw	r8, 32(r1)
-	stw	r9, 36(r1)
-	stw	r10,40(r1)
-
-	addi	r5, r1, 48
-	mfctr	r4		/* ftrace_caller has moved local addr here */
-	stw	r4, 44(r1)
-	mflr	r3		/* ftrace_caller has restored LR from stack */
-	subi	r4, r4, MCOUNT_INSN_SIZE
-
-	bl	prepare_ftrace_return
-	nop
-
-        /*
-         * prepare_ftrace_return gives us the address we divert to.
-         * Change the LR in the callers stack frame to this.
-         */
-	stw	r3,52(r1)
-	mtlr	r3
-	lwz	r0,44(r1)
-	mtctr	r0
-
-	lwz	r3, 12(r1)
-	lwz	r4, 16(r1)
-	lwz	r5, 20(r1)
-	lwz	r6, 24(r1)
-	lwz	r7, 28(r1)
-	lwz	r8, 32(r1)
-	lwz	r9, 36(r1)
-	lwz	r10,40(r1)
-
-	addi	r1, r1, 48
-
+	/* old link register ends up in ctr reg */
 	bctr
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
 _GLOBAL(return_to_handler)
 	/* need to save return values */
 	stwu	r1, -16(r1)

arch/powerpc/kernel/trace/ftrace_64_mprofile.S

@@ -124,15 +124,6 @@ ftrace_regs_call:
         /* Based on the cmpd above, if the NIP was altered handle livepatch */
 	bne-	livepatch_handler
 #endif
-
-ftrace_caller_common:
-#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)
@@ -216,8 +207,7 @@ ftrace_call:
         /* Based on the cmpd above, if the NIP was altered handle livepatch */
 	bne-	livepatch_handler
 #endif
-	/* Handle function_graph or go back */
-	b	ftrace_caller_common
+	bctr			/* jump after _mcount site */
 
 #ifdef CONFIG_LIVEPATCH
 	/*
@@ -286,55 +276,3 @@ livepatch_handler:
 	/* Return to original caller of live patched function */
 	blr
 #endif /* CONFIG_LIVEPATCH */
-
-#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)
-
-	/* Save callee's TOC in the ABI compliant location */
-	std	r2, 24(r1)
-	ld	r2, PACATOC(r13)	/* get kernel TOC in r2 */
-
-	addi	r5, r1, 112
-	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
-
-	bl	prepare_ftrace_return
-	nop
-
-	/*
-	 * prepare_ftrace_return gives us the address we divert to.
-	 * Change the LR to this.
-	 */
-	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
-	std	r0, LRSAVE(r1)
-	bctr
-#endif /* CONFIG_FUNCTION_GRAPH_TRACER */