powerpc64le: _init/_fini file changes for ROP

The ROP instructions were added in ISA 3.1 (ie, Power10), however they
were defined so that if executed on older cpus, they would behave as
nops.  This allows us to emit them on older cpus and they'd just be
ignored, but if run on a Power10, then the binary would be ROP protected.

Hash instructions use negative offsets so the default position
of ROP pointer is FRAME_ROP_SAVE from caller's SP.

Modified FRAME_MIN_SIZE_PARM to 112 for ELFv2 to reserve
additional 16 bytes for ROP save slot and padding.

Signed-off-by: Sachin Monga <smonga@linux.ibm.com>
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>

sysdeps/powerpc/powerpc64/crti.S

@@ -68,6 +68,9 @@ BODY_LABEL (_init):
 	LOCALENTRY(_init)
 	mflr 0
 	std 0, FRAME_LR_SAVE(r1)
+#ifdef	__ROP_PROTECT__
+	hashst 0, FRAME_ROP_SAVE(r1)
+#endif
 	stdu r1, -FRAME_MIN_SIZE_PARM(r1)
 #if PREINIT_FUNCTION_WEAK
 	addis r9, r2, .LC0@toc@ha
@@ -87,4 +90,7 @@ BODY_LABEL (_fini):
 	LOCALENTRY(_fini)
 	mflr 0
 	std 0, FRAME_LR_SAVE(r1)
+#ifdef	__ROP_PROTECT__
+	hashst 0, FRAME_ROP_SAVE(r1)
+#endif
 	stdu r1, -FRAME_MIN_SIZE_PARM(r1)

sysdeps/powerpc/powerpc64/crtn.S

@@ -42,10 +42,16 @@
 	addi r1, r1, FRAME_MIN_SIZE_PARM
 	ld r0, FRAME_LR_SAVE(r1)
 	mtlr r0
+#ifdef	__ROP_PROTECT__
+	hashchk 0, FRAME_ROP_SAVE(r1)
+#endif
 	blr
 
 	.section .fini,"ax",@progbits
 	addi r1, r1, FRAME_MIN_SIZE_PARM
 	ld r0, FRAME_LR_SAVE(r1)
 	mtlr r0
+#ifdef	__ROP_PROTECT__
+	hashchk 0, FRAME_ROP_SAVE(r1)
+#endif
 	blr

sysdeps/powerpc/powerpc64/sysdep.h

@@ -31,8 +31,9 @@
 #define FRAME_TOC_SAVE		40
 #define FRAME_PARM_SAVE		48
 #else
+#define FRAME_ROP_SAVE		-8
 #define FRAME_MIN_SIZE		32
-#define FRAME_MIN_SIZE_PARM	96
+#define FRAME_MIN_SIZE_PARM	112 /* Includes space for the ROP save slot */
 #define FRAME_TOC_SAVE		24
 #define FRAME_PARM_SAVE		32
 #endif