[PATCH 15/18] powerpc/uprobes: Add support for prefixed instructions

@@ -14,18 +14,28 @@
 
 typedef ppc_opcode_t uprobe_opcode_t;
 
+/*
+ * We have to ensure we have enought space for prefixed instructions, which
+ * are double the size of a word instruction, i.e. 8 bytes. However,
+ * sometimes it is simpler to treat a prefixed instruction like 2 word
+ * instructions.
+ */
 #define MAX_UINSN_BYTES		4
-#define UPROBE_XOL_SLOT_BYTES	(MAX_UINSN_BYTES)
+#define UPROBE_XOL_SLOT_BYTES	(2 * MAX_UINSN_BYTES)
 
 /* The following alias is needed for reference from arch-agnostic code */
 #define UPROBE_SWBP_INSN	BREAKPOINT_INSTRUCTION
 #define UPROBE_SWBP_INSN_SIZE	4 /* swbp insn size in bytes */
 
 struct arch_uprobe {
+	 /*
+	  * Ensure there is enough space for prefixed instructions. Prefixed
+	  * instructions must not cross 64-byte boundaries.
+	  */
 	union {
-		u32	insn;
-		u32	ixol;
-	};
+		uprobe_opcode_t	insn[2];
+		uprobe_opcode_t	ixol[2];
+	} __aligned(64);
 };
 
 struct arch_uprobe_task {

@@ -111,7 +111,7 @@ 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 + ((IS_PREFIX(auprobe->insn[0])) ? 8 : 4);
 
 	user_disable_single_step(current);
 	return 0;

@@ -173,7 +173,7 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
 	 * emulate_step() returns 1 if the insn was successfully emulated.
 	 * For all other cases, we need to single-step in hardware.
 	 */
-	ret = emulate_step(regs, auprobe->insn, 0);
+	ret = emulate_step(regs, auprobe->insn[0], auprobe->insn[1]);
 	if (ret > 0)
 		return true;