From 383e4f53cbd52a0e697a80a3aa7a7ef891ead8b8 Mon Sep 17 00:00:00 2001
From: Sachin Monga <smonga@linux.ibm.com>
Date: Wed, 30 Oct 2024 16:43:37 -0400
Subject: [PATCH] powerpc64: Obviate the need for ROP protection in
 clone/clone3

Save lr in a non-volatile register before scv in clone/clone3.
For clone, the non-volatile register was unused and already
saved/restored.  Remove the dead code from clone.

Signed-off-by: Sachin Monga <smonga@linux.ibm.com>
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>
---
 .../unix/sysv/linux/powerpc/powerpc64/clone.S |  7 ++--
 .../sysv/linux/powerpc/powerpc64/clone3.S     | 35 ++++++++++---------
 2 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S
index 164311d2bd..e57cb6e82e 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S
@@ -56,7 +56,6 @@ ENTRY (__clone)
 
 	/* Save fn, args, stack across syscall.  */
 	mr	r30,r3			/* Function in r30.  */
-	mr	r29,r5			/* Flags in r29.  */
 	mr	r31,r6			/* Argument in r31.  */
 
 	/* 'flags' argument is first parameter to clone syscall.
@@ -77,14 +76,12 @@ ENTRY (__clone)
 	CHECK_SCV_SUPPORT r28 0f
 	/* This is equivalent to DO_CALL_SCV, but we cannot use the macro here
 	because it uses CFI directives and we just called cfi_endproc.  */
-	mflr 	r9
-	std 	r9,FRAME_LR_SAVE(r1)
+	mflr 	r29
 	.machine "push"
 	.machine "power9"
 	scv 	0
 	.machine "pop"
-	ld 	r9,FRAME_LR_SAVE(r1)
-	mtlr 	r9
+	mtlr 	r29
 
 	/* Check for child process.  */
 	/* When using scv, error is indicated by negative r3.  */
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
index 900c354c9c..913f341d7d 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/clone3.S
@@ -39,14 +39,12 @@
    because it uses CFI directives and we just called cfi_endproc.  */
 # define DO_CLONE3_SVC_CALL(jumpfalse)				\
 	CHECK_SCV_SUPPORT r28 jumpfalse;			\
-	mflr 	r9;						\
-	std 	r9, FRAME_LR_SAVE(r1);				\
+	mflr 	r31;						\
 	.machine "push";					\
 	.machine "power9";					\
 	scv 	0;						\
 	.machine "pop";						\
-	ld 	r9, FRAME_LR_SAVE(r1);				\
-	mtlr 	r9;						\
+	mtlr 	r31;						\
 	/* With scv an, an error is a value -4095 <= x < 0.  */	\
 	cmpdi	cr1, r3, 0;					\
 	b	1f;
@@ -66,13 +64,15 @@ ENTRY(__clone3)
 
 	/* Save some regs in the "red zone".  */
 #ifdef USE_PPC_SCV
-	std	r28, -24(r1)
-	cfi_offset (r28, -24)
+	std	r28, -32(r1)
+	cfi_offset (r28, -32)
 #endif
-	std	r29, -16(r1)
-	std	r30, -8(r1)
-	cfi_offset (r29, -16)
-	cfi_offset (r30, -8)
+	std	r29, -24(r1)
+	std	r30, -16(r1)
+	std	r31, -8(r1)
+	cfi_offset (r29, -24)
+	cfi_offset (r30, -16)
+	cfi_offset (r31, -8)
 
 	/* Save func and arg across syscall.  */
 	mr	r30, r5		/* Function in r30.  */
@@ -132,16 +132,19 @@ L(parent):
 
 	/* Parent.  Restore registers & return.  */
 #ifdef USE_PPC_SCV
-	cfi_offset (r28, -24)
-	ld	r28, -24(r1)
+	cfi_offset (r28, -32)
+	ld	r28, -32(r1)
 	cfi_restore (r28)
 #endif
-	cfi_offset (r29,-16)
-	cfi_offset (r30,-8)
-	ld	r29, -16(r1)
-	ld	r30, -8(r1)
+	cfi_offset (r29,-24)
+	cfi_offset (r30,-16)
+	cfi_offset (r31,-8)
+	ld	r29, -24(r1)
+	ld	r30, -16(r1)
+	ld	r31, -8(r1)
 	cfi_restore (r29)
 	cfi_restore (r30)
+	cfi_restore (r31)
 
 #ifdef USE_PPC_SCV
 	beq	cr1, 0f