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>
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
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)
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
#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