powerpc: Add a ppc_inst_as_str() helper

There are quite a few places where instructions are printed, this is
done using a '%x' format specifier. With the introduction of prefixed
instructions, this does not work well. Currently in these places,
ppc_inst_val() is used for the value for %x so only the first word of
prefixed instructions are printed.

When the instructions are word instructions, only a single word should
be printed. For prefixed instructions both the prefix and suffix should
be printed. To accommodate both of these situations, instead of a '%x'
specifier use '%s' and introduce a helper, __ppc_inst_as_str() which
returns a char *. The char * __ppc_inst_as_str() returns is buffer that
is passed to it by the caller.

It is cumbersome to require every caller of __ppc_inst_as_str() to now
declare a buffer. To make it more convenient to use __ppc_inst_as_str(),
wrap it in a macro that uses a compound statement to allocate a buffer
on the caller's stack before calling it.

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Acked-by: Segher Boessenkool <segher@kernel.crashing.org>
[mpe: Drop 0x prefix to match most existings uses, especially xmon]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200602052728.18227-1-jniethe5@gmail.com

arch/powerpc/include/asm/inst.h

@@ -122,6 +122,25 @@ static inline u64 ppc_inst_as_u64(struct ppc_inst x)
 #endif
 }
 
+#define PPC_INST_STR_LEN sizeof("00000000 00000000")
+
+static inline char *__ppc_inst_as_str(char str[PPC_INST_STR_LEN], struct ppc_inst x)
+{
+	if (ppc_inst_prefixed(x))
+		sprintf(str, "%08x %08x", ppc_inst_val(x), ppc_inst_suffix(x));
+	else
+		sprintf(str, "%08x", ppc_inst_val(x));
+
+	return str;
+}
+
+#define ppc_inst_as_str(x)		\
+({					\
+	char __str[PPC_INST_STR_LEN];	\
+	__ppc_inst_as_str(__str, x);	\
+	__str;				\
+})
+
 int probe_user_read_inst(struct ppc_inst *inst,
 			 struct ppc_inst __user *nip);
 

arch/powerpc/kernel/kprobes.c

@@ -244,7 +244,7 @@ static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
 		 * So, we should never get here... but, its still
 		 * good to catch them, just in case...
 		 */
-		printk("Can't step on instruction %x\n", ppc_inst_val(insn));
+		printk("Can't step on instruction %s\n", ppc_inst_as_str(insn));
 		BUG();
 	} else {
 		/*

arch/powerpc/kernel/trace/ftrace.c

@@ -73,8 +73,8 @@ ftrace_modify_code(unsigned long ip, struct ppc_inst old, struct ppc_inst new)
 
 	/* Make sure it is what we expect it to be */
 	if (!ppc_inst_equal(replaced, old)) {
-		pr_err("%p: replaced (%#x) != old (%#x)",
-		(void *)ip, ppc_inst_val(replaced), ppc_inst_val(old));
+		pr_err("%p: replaced (%s) != old (%s)",
+		(void *)ip, ppc_inst_as_str(replaced), ppc_inst_as_str(old));
 		return -EINVAL;
 	}
 
@@ -137,7 +137,7 @@ __ftrace_make_nop(struct module *mod,
 
 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
-		pr_err("Not expected bl: opcode is %x\n", ppc_inst_val(op));
+		pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 
@@ -172,8 +172,8 @@ __ftrace_make_nop(struct module *mod,
 	/* We expect either a mflr r0, or a std r0, LRSAVE(r1) */
 	if (!ppc_inst_equal(op, ppc_inst(PPC_INST_MFLR)) &&
 	    !ppc_inst_equal(op, ppc_inst(PPC_INST_STD_LR))) {
-		pr_err("Unexpected instruction %08x around bl _mcount\n",
-		       ppc_inst_val(op));
+		pr_err("Unexpected instruction %s around bl _mcount\n",
+		       ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 #else
@@ -203,7 +203,7 @@ __ftrace_make_nop(struct module *mod,
 	}
 
 	if (!ppc_inst_equal(op,  ppc_inst(PPC_INST_LD_TOC))) {
-		pr_err("Expected %08x found %08x\n", PPC_INST_LD_TOC, ppc_inst_val(op));
+		pr_err("Expected %08x found %s\n", PPC_INST_LD_TOC, ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 #endif /* CONFIG_MPROFILE_KERNEL */
@@ -231,7 +231,7 @@ __ftrace_make_nop(struct module *mod,
 
 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
-		pr_err("Not expected bl: opcode is %x\n", ppc_inst_val(op));
+		pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 
@@ -406,7 +406,7 @@ static int __ftrace_make_nop_kernel(struct dyn_ftrace *rec, unsigned long addr)
 
 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
-		pr_err("Not expected bl: opcode is %x\n", ppc_inst_val(op));
+		pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 
@@ -533,8 +533,8 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 		return -EFAULT;
 
 	if (!expected_nop_sequence(ip, op[0], op[1])) {
-		pr_err("Unexpected call sequence at %p: %x %x\n",
-		ip, ppc_inst_val(op[0]), ppc_inst_val(op[1]));
+		pr_err("Unexpected call sequence at %p: %s %s\n",
+		ip, ppc_inst_as_str(op[0]), ppc_inst_as_str(op[1]));
 		return -EINVAL;
 	}
 
@@ -597,7 +597,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 
 	/* It should be pointing to a nop */
 	if (!ppc_inst_equal(op,  ppc_inst(PPC_INST_NOP))) {
-		pr_err("Expected NOP but have %x\n", ppc_inst_val(op));
+		pr_err("Expected NOP but have %s\n", ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 
@@ -654,7 +654,7 @@ static int __ftrace_make_call_kernel(struct dyn_ftrace *rec, unsigned long addr)
 	}
 
 	if (!ppc_inst_equal(op, ppc_inst(PPC_INST_NOP))) {
-		pr_err("Unexpected call sequence at %p: %x\n", ip, ppc_inst_val(op));
+		pr_err("Unexpected call sequence at %p: %s\n", ip, ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 
@@ -733,7 +733,7 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
 
 	/* Make sure that that this is still a 24bit jump */
 	if (!is_bl_op(op)) {
-		pr_err("Not expected bl: opcode is %x\n", ppc_inst_val(op));
+		pr_err("Not expected bl: opcode is %s\n", ppc_inst_as_str(op));
 		return -EINVAL;
 	}
 

arch/powerpc/lib/test_emulate_step.c

@@ -1147,7 +1147,7 @@ static int __init emulate_compute_instr(struct pt_regs *regs,
 
 	if (analyse_instr(&op, regs, instr) != 1 ||
 	    GETTYPE(op.type) != COMPUTE) {
-		pr_info("emulation failed, instruction = 0x%08x\n", ppc_inst_val(instr));
+		pr_info("execution failed, instruction = %s\n", ppc_inst_as_str(instr));
 		return -EFAULT;
 	}
 
@@ -1167,7 +1167,7 @@ static int __init execute_compute_instr(struct pt_regs *regs,
 	/* Patch the NOP with the actual instruction */
 	patch_instruction_site(&patch__exec_instr, instr);
 	if (exec_instr(regs)) {
-		pr_info("execution failed, instruction = 0x%08x\n", ppc_inst_val(instr));
+		pr_info("execution failed, instruction = %s\n", ppc_inst_as_str(instr));
 		return -EFAULT;
 	}
 

arch/powerpc/xmon/xmon.c

@@ -2977,7 +2977,7 @@ generic_inst_dump(unsigned long adr, long count, int praddr,
 		dotted = 0;
 		last_inst = inst;
 		if (praddr)
-			printf(REG"  %.8x", adr, ppc_inst_val(inst));
+			printf(REG"  %s", adr, ppc_inst_as_str(inst));
 		printf("\t");
 		dump_func(ppc_inst_val(inst), adr);
 		printf("\n");