powerpc: Use a function for reading instructions

Prefixed instructions will mean there are instructions of different
length. As a result dereferencing a pointer to an instruction will not
necessarily give the desired result. Introduce a function for reading
instructions from memory into the instruction data type.

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/20200506034050.24806-13-jniethe5@gmail.com

arch/powerpc/include/asm/inst.h

@@ -27,6 +27,11 @@ static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
 	return ppc_inst(swab32(ppc_inst_val(x)));
 }
 
+static inline struct ppc_inst ppc_inst_read(const struct ppc_inst *ptr)
+{
+	return *ptr;
+}
+
 static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
 {
 	return ppc_inst_val(x) == ppc_inst_val(y);

arch/powerpc/kernel/kprobes.c

@@ -106,7 +106,7 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
 int arch_prepare_kprobe(struct kprobe *p)
 {
 	int ret = 0;
-	struct ppc_inst insn = *(struct ppc_inst *)p->addr;
+	struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr);
 
 	if ((unsigned long)p->addr & 0x03) {
 		printk("Attempt to register kprobe at an unaligned address\n");
@@ -127,7 +127,7 @@ int arch_prepare_kprobe(struct kprobe *p)
 	if (!ret) {
 		memcpy(p->ainsn.insn, p->addr,
 				MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
-		p->opcode = *p->addr;
+		p->opcode = ppc_inst_val(insn);
 		flush_icache_range((unsigned long)p->ainsn.insn,
 			(unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
 	}
@@ -217,7 +217,7 @@ NOKPROBE_SYMBOL(arch_prepare_kretprobe);
 static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
 {
 	int ret;
-	struct ppc_inst insn = *(struct ppc_inst *)p->ainsn.insn;
+	struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
 
 	/* regs->nip is also adjusted if emulate_step returns 1 */
 	ret = emulate_step(regs, insn);

arch/powerpc/kernel/mce_power.c

@@ -378,7 +378,7 @@ static int mce_find_instr_ea_and_phys(struct pt_regs *regs, uint64_t *addr,
 	pfn = addr_to_pfn(regs, regs->nip);
 	if (pfn != ULONG_MAX) {
 		instr_addr = (pfn << PAGE_SHIFT) + (regs->nip & ~PAGE_MASK);
-		instr = *(struct ppc_inst *)(instr_addr);
+		instr = ppc_inst_read((struct ppc_inst *)instr_addr);
 		if (!analyse_instr(&op, &tmp, instr)) {
 			pfn = addr_to_pfn(regs, op.ea);
 			*addr = op.ea;

arch/powerpc/kernel/optprobes.c

@@ -100,9 +100,9 @@ static unsigned long can_optimize(struct kprobe *p)
 	 * Ensure that the instruction is not a conditional branch,
 	 * and that can be emulated.
 	 */
-	if (!is_conditional_branch(*(struct ppc_inst *)p->ainsn.insn) &&
+	if (!is_conditional_branch(ppc_inst_read((struct ppc_inst *)p->ainsn.insn)) &&
 	    analyse_instr(&op, &regs,
-			  *(struct ppc_inst *)p->ainsn.insn) == 1) {
+			  ppc_inst_read((struct ppc_inst *)p->ainsn.insn)) == 1) {
 		emulate_update_regs(&regs, &op);
 		nip = regs.nip;
 	}

arch/powerpc/kernel/trace/ftrace.c

@@ -848,7 +848,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	struct ppc_inst old, new;
 	int ret;
 
-	old = *(struct ppc_inst *)&ftrace_call;
+	old = ppc_inst_read((struct ppc_inst *)&ftrace_call);
 	new = ftrace_call_replace(ip, (unsigned long)func, 1);
 	ret = ftrace_modify_code(ip, old, new);
 
@@ -856,7 +856,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	/* Also update the regs callback function */
 	if (!ret) {
 		ip = (unsigned long)(&ftrace_regs_call);
-		old = *(struct ppc_inst *)&ftrace_regs_call;
+		old = ppc_inst_read((struct ppc_inst *)&ftrace_regs_call);
 		new = ftrace_call_replace(ip, (unsigned long)func, 1);
 		ret = ftrace_modify_code(ip, old, new);
 	}

arch/powerpc/kernel/uprobes.c

@@ -174,7 +174,7 @@ 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);
+	ret = emulate_step(regs, ppc_inst_read(&auprobe->insn));
 	if (ret > 0)
 		return true;
 

arch/powerpc/lib/code-patching.c

@@ -348,9 +348,9 @@ static unsigned long branch_bform_target(const struct ppc_inst *instr)
 
 unsigned long branch_target(const struct ppc_inst *instr)
 {
-	if (instr_is_branch_iform(*instr))
+	if (instr_is_branch_iform(ppc_inst_read(instr)))
 		return branch_iform_target(instr);
-	else if (instr_is_branch_bform(*instr))
+	else if (instr_is_branch_bform(ppc_inst_read(instr)))
 		return branch_bform_target(instr);
 
 	return 0;
@@ -358,7 +358,8 @@ unsigned long branch_target(const struct ppc_inst *instr)
 
 int instr_is_branch_to_addr(const struct ppc_inst *instr, unsigned long addr)
 {
-	if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
+	if (instr_is_branch_iform(ppc_inst_read(instr)) ||
+	    instr_is_branch_bform(ppc_inst_read(instr)))
 		return branch_target(instr) == addr;
 
 	return 0;
@@ -368,13 +369,14 @@ int translate_branch(struct ppc_inst *instr, const struct ppc_inst *dest,
 		     const struct ppc_inst *src)
 {
 	unsigned long target;
-
 	target = branch_target(src);
 
-	if (instr_is_branch_iform(*src))
+	if (instr_is_branch_iform(ppc_inst_read(src)))
-		return create_branch(instr, dest, target, ppc_inst_val(*src));
+		return create_branch(instr, dest, target,
-	else if (instr_is_branch_bform(*src))
+				     ppc_inst_val(ppc_inst_read(src)));
-		return create_cond_branch(instr, dest, target, ppc_inst_val(*src));
+	else if (instr_is_branch_bform(ppc_inst_read(src)))
+		return create_cond_branch(instr, dest, target,
+					  ppc_inst_val(ppc_inst_read(src)));
 
 	return 1;
 }
@@ -598,7 +600,7 @@ static void __init test_translate_branch(void)
 	patch_instruction(q, instr);
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
-	check(ppc_inst_equal(*q, ppc_inst(0x4a000000)));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x4a000000)));
 
 	/* Maximum positive case, move x to x - 32 MB + 4 */
 	p = buf + 0x2000000;
@@ -609,7 +611,7 @@ static void __init test_translate_branch(void)
 	patch_instruction(q, instr);
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
-	check(ppc_inst_equal(*q, ppc_inst(0x49fffffc)));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x49fffffc)));
 
 	/* Jump to x + 16 MB moved to x + 20 MB */
 	p = buf;
@@ -655,7 +657,7 @@ static void __init test_translate_branch(void)
 	patch_instruction(q, instr);
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
-	check(ppc_inst_equal(*q, ppc_inst(0x43ff8000)));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x43ff8000)));
 
 	/* Maximum positive case, move x to x - 32 KB + 4 */
 	p = buf + 0x8000;
@@ -667,7 +669,7 @@ static void __init test_translate_branch(void)
 	patch_instruction(q, instr);
 	check(instr_is_branch_to_addr(p, addr));
 	check(instr_is_branch_to_addr(q, addr));
-	check(ppc_inst_equal(*q, ppc_inst(0x43ff7ffc)));
+	check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x43ff7ffc)));
 
 	/* Jump to x + 12 KB moved to x + 20 KB */
 	p = buf;

arch/powerpc/lib/feature-fixups.c

@@ -48,7 +48,7 @@ static int patch_alt_instruction(struct ppc_inst *src, struct ppc_inst *dest,
 	int err;
 	struct ppc_inst instr;
 
-	instr = *src;
+	instr = ppc_inst_read(src);
 
 	if (instr_is_relative_branch(*src)) {
 		struct ppc_inst *target = (struct ppc_inst *)branch_target(src);
@@ -403,7 +403,7 @@ static void do_final_fixups(void)
 	length = (__end_interrupts - _stext) / sizeof(struct ppc_inst);
 
 	while (length--) {
-		raw_patch_instruction(dest, *src);
+		raw_patch_instruction(dest, ppc_inst_read(src));
 		src++;
 		dest++;
 	}

arch/powerpc/xmon/xmon.c

@@ -702,13 +702,13 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
 	if ((regs->msr & (MSR_IR|MSR_PR|MSR_64BIT)) == (MSR_IR|MSR_64BIT)) {
 		bp = at_breakpoint(regs->nip);
 		if (bp != NULL) {
-			int stepped = emulate_step(regs, bp->instr[0]);
+			int stepped = emulate_step(regs, ppc_inst_read(bp->instr));
 			if (stepped == 0) {
 				regs->nip = (unsigned long) &bp->instr[0];
 				atomic_inc(&bp->ref_count);
 			} else if (stepped < 0) {
 				printf("Couldn't single-step %s instruction\n",
-				    (IS_RFID(bp->instr[0])? "rfid": "mtmsrd"));
+				    IS_RFID(ppc_inst_read(bp->instr))? "rfid": "mtmsrd");
 			}
 		}
 	}
@@ -949,7 +949,7 @@ static void remove_bpts(void)
 		if (mread(bp->address, &instr, 4) == 4
 		    && ppc_inst_equal(instr, ppc_inst(bpinstr))
 		    && patch_instruction(
-			(struct ppc_inst *)bp->address, bp->instr[0]) != 0)
+			(struct ppc_inst *)bp->address, ppc_inst_read(bp->instr)) != 0)
 			printf("Couldn't remove breakpoint at %lx\n",
 			       bp->address);
 	}