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sparc64: Give a stack frame to the ftrace call sites.

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From: Linux Kernel Mailing List
Subject: sparc64: Give a stack frame to the ftrace call sites.
Date: Tuesday, April 13, 2010 - 12:59 pm

Gitweb:     http://git.kernel.org/linus/a71d1d6bb1b26e566e5c06c37857f4cdc1664780
Commit:     a71d1d6bb1b26e566e5c06c37857f4cdc1664780
Parent:     daecbf58a509bc27c112647e825df763c3e3b0f4
Author:     David S. Miller <davem@davemloft.net>
AuthorDate: Tue Apr 6 19:59:46 2010 -0700
Committer:  David S. Miller <davem@davemloft.net>
CommitDate: Mon Apr 12 22:37:15 2010 -0700

    sparc64: Give a stack frame to the ftrace call sites.
    
    It's the only way we'll be able to implement the function
    graph tracer properly.
    
    A positive is that we no longer have to worry about the
    linker over-optimizing the tail call, since we don't
    use a tail call any more.
    
    Signed-off-by: David S. Miller <davem@davemloft.net>
---
 arch/sparc/lib/mcount.S |   31 ++++++++++++++++---------------
 1 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/arch/sparc/lib/mcount.S b/arch/sparc/lib/mcount.S
index 73ed0f3..153c80e 100644
--- a/arch/sparc/lib/mcount.S
+++ b/arch/sparc/lib/mcount.S
@@ -33,9 +33,13 @@ mcount:
 	or		%g2, %lo(ftrace_stub), %g2
 	cmp		%g1, %g2
 	be,pn		%icc, 1f
-	 mov		%i7, %o1
-	jmpl		%g1, %g0
-	 mov		%o7, %o0
+	 mov		%i7, %g2
+	save		%sp, -128, %sp
+	mov		%g2, %o1
+	jmpl		%g1, %o7
+	 mov		%i7, %o0
+	ret
+	 restore
 	/* not reached */
 1:
 #endif
@@ -57,21 +61,18 @@ ftrace_stub:
 	.type		ftrace_caller,#function
 ftrace_caller:
 	sethi		%hi(function_trace_stop), %g1
-	mov		%i7, %o1
-	lduw		[%g1 + %lo(function_trace_stop)], %g2
-	brnz,pn		%g2, ftrace_stub
-	 mov		%o7, %o0
+	mov		%i7, %g2
+	lduw		[%g1 + %lo(function_trace_stop)], %g3
+	brnz,pn		%g3, ftrace_stub
+	 nop
+	save		%sp, -128, %sp
+	mov		%g2, %o1
 	.globl		ftrace_call
 ftrace_call:
-	/* If the final kernel link ever turns on relaxation, we'll need
-	 * to do something about this tail call.  Otherwise the linker
-	 * will rewrite the call into a branch and nop out the move
-	 * instruction.
-	 */
 	call		ftrace_stub
-	 mov		%o0, %o7
-	retl
-	 nop
+	 mov		%i7, %o0
+	ret
+	 restore
 	.size		ftrace_call,.-ftrace_call
 	.size		ftrace_caller,.-ftrace_caller
 #endif
--
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