powerpc: Introduce a function for reporting instruction length

Currently all instructions have the same length, but in preparation for
prefixed instructions introduce a function for returning instruction
length.
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Alistair Popple <alistair@popple.id.au>
Link: https://lore.kernel.org/r/20200506034050.24806-18-jniethe5@gmail.com

arch/powerpc/include/asm/inst.h

@@ -17,6 +17,11 @@ static inline u32 ppc_inst_val(struct ppc_inst x)
 	return x.val;
 }
 
+static inline int ppc_inst_len(struct ppc_inst x)
+{
+	return sizeof(struct ppc_inst);
+}
+
 static inline int ppc_inst_primary_opcode(struct ppc_inst x)
 {
 	return ppc_inst_val(x) >> 26;

arch/powerpc/kernel/kprobes.c

@@ -462,14 +462,16 @@ NOKPROBE_SYMBOL(trampoline_probe_handler);
  */
 int kprobe_post_handler(struct pt_regs *regs)
 {
+	int len;
 	struct kprobe *cur = kprobe_running();
 	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
 
 	if (!cur || user_mode(regs))
 		return 0;
 
+	len = ppc_inst_len(ppc_inst_read((struct ppc_inst *)cur->ainsn.insn));
 	/* make sure we got here for instruction we have a kprobe on */
-	if (((unsigned long)cur->ainsn.insn + 4) != regs->nip)
+	if (((unsigned long)cur->ainsn.insn + len) != regs->nip)
 		return 0;
 
 	if ((kcb->kprobe_status != KPROBE_REENTER) && cur->post_handler) {
@@ -478,7 +480,7 @@ int kprobe_post_handler(struct pt_regs *regs)
 	}
 
 	/* Adjust nip to after the single-stepped instruction */
-	regs->nip = (unsigned long)cur->addr + 4;
+	regs->nip = (unsigned long)cur->addr + len;
 	regs->msr |= kcb->kprobe_saved_msr;
 
 	/*Restore back the original saved kprobes variables and continue. */

arch/powerpc/kernel/uprobes.c

@@ -112,7 +112,7 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 	 * support doesn't exist and have to fix-up the next instruction
 	 * to be executed.
 	 */
-	regs->nip = utask->vaddr + MAX_UINSN_BYTES;
+	regs->nip = utask->vaddr + ppc_inst_len(ppc_inst_read(&auprobe->insn));
 
 	user_disable_single_step(current);
 	return 0;

arch/powerpc/lib/feature-fixups.c

@@ -392,20 +392,20 @@ void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)
 static void do_final_fixups(void)
 {
 #if defined(CONFIG_PPC64) && defined(CONFIG_RELOCATABLE)
-	struct ppc_inst *src, *dest;
-	unsigned long length;
+	struct ppc_inst inst, *src, *dest, *end;
 
 	if (PHYSICAL_START == 0)
 		return;
 
 	src = (struct ppc_inst *)(KERNELBASE + PHYSICAL_START);
 	dest = (struct ppc_inst *)KERNELBASE;
-	length = (__end_interrupts - _stext) / sizeof(struct ppc_inst);
+	end = (void *)src + (__end_interrupts - _stext);
 
-	while (length--) {
-		raw_patch_instruction(dest, ppc_inst_read(src));
-		src++;
-		dest++;
+	while (src < end) {
+		inst = ppc_inst_read(src);
+		raw_patch_instruction(dest, inst);
+		src = (void *)src + ppc_inst_len(inst);
+		dest = (void *)dest + ppc_inst_len(inst);
 	}
 #endif
 }