[PATCH 4.9] powerpc/ftrace: Pass the correct stack pointer for DYNAMIC_FTRACE_WITH_REGS

[PATCH 4.9] powerpc/ftrace: Pass the correct stack pointer for DYNAMIC_FTRACE_WITH_REGS

[Naveen N. Rao]

For DYNAMIC_FTRACE_WITH_REGS, we should be passing-in the original set
of registers in pt_regs, to capture the state _before_ ftrace_caller.
However, we are instead passing the stack pointer *after* allocating a
stack frame in ftrace_caller. Fix this by saving the proper value of r1
in pt_regs. Also, use SAVE_10GPRS() to simplify the code.

Fixes: 153086644fd1 ("powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI")
Cc: stable@vger.kernel.org # v4.6+
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
---
Hi Greg,
Here is the backported patch for upstream commit a4979a7e71eb8d 
("powerpc/ftrace: Pass the correct stack pointer for 
DYNAMIC_FTRACE_WITH_REGS") for stable kernel v4.9. This has been tested 
by Michael Ellerman. Kindly apply.

Thanks,
Naveen


 arch/powerpc/kernel/entry_64.S | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 767ef6d68c9e..caa659671599 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -1235,10 +1235,14 @@ _GLOBAL(ftrace_caller)
 	stdu	r1,-SWITCH_FRAME_SIZE(r1)
 
 	/* Save all gprs to pt_regs */
-	SAVE_8GPRS(0,r1)
-	SAVE_8GPRS(8,r1)
-	SAVE_8GPRS(16,r1)
-	SAVE_8GPRS(24,r1)
+	SAVE_GPR(0, r1)
+	SAVE_10GPRS(2, r1)
+	SAVE_10GPRS(12, r1)
+	SAVE_10GPRS(22, r1)
+
+	/* Save previous stack pointer (r1) */
+	addi	r8, r1, SWITCH_FRAME_SIZE
+	std	r8, GPR1(r1)
 
 	/* Load special regs for save below */
 	mfmsr   r8
@@ -1292,10 +1296,10 @@ ftrace_call:
 #endif
 
 	/* Restore gprs */
-	REST_8GPRS(0,r1)
-	REST_8GPRS(8,r1)
-	REST_8GPRS(16,r1)
-	REST_8GPRS(24,r1)
+	REST_GPR(0,r1)
+	REST_10GPRS(2,r1)
+	REST_10GPRS(12,r1)
+	REST_10GPRS(22,r1)
 
 	/* Restore callee's TOC */
 	ld	r2, 24(r1)
-- 
2.14.1

Re: [PATCH 4.9] powerpc/ftrace: Pass the correct stack pointer for DYNAMIC_FTRACE_WITH_REGS

[Greg KH]

On Thu, Sep 28, 2017 at 07:10:27PM +0530, Naveen N. Rao wrote:
> For DYNAMIC_FTRACE_WITH_REGS, we should be passing-in the original set
> of registers in pt_regs, to capture the state _before_ ftrace_caller.
> However, we are instead passing the stack pointer *after* allocating a
> stack frame in ftrace_caller. Fix this by saving the proper value of r1
> in pt_regs. Also, use SAVE_10GPRS() to simplify the code.
> 
> Fixes: 153086644fd1 ("powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI")
> Cc: stable@vger.kernel.org # v4.6+
> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> ---
> Hi Greg,
> Here is the backported patch for upstream commit a4979a7e71eb8d 
> ("powerpc/ftrace: Pass the correct stack pointer for 
> DYNAMIC_FTRACE_WITH_REGS") for stable kernel v4.9. This has been tested 
> by Michael Ellerman. Kindly apply.

Thanks for the backport, now applied.

greg k-h