1 files changed, 57 insertions, 8 deletions

diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c
index 8d5d0de35de0..90c0e6408992 100644
--- a/arch/s390/kernel/alternative.c
+++ b/arch/s390/kernel/alternative.c
@@ -1,41 +1,90 @@
 // SPDX-License-Identifier: GPL-2.0
 
+#ifndef pr_fmt
+#define pr_fmt(fmt)	"alt: " fmt
+#endif
+
 #include <linux/uaccess.h>
+#include <linux/printk.h>
 #include <asm/nospec-branch.h>
 #include <asm/abs_lowcore.h>
 #include <asm/alternative.h>
 #include <asm/facility.h>
+#include <asm/sections.h>
+#include <asm/machine.h>
+
+#ifndef a_debug
+#define a_debug		pr_debug
+#endif
+
+#ifndef __kernel_va
+#define __kernel_va(x)	(void *)(x)
+#endif
+
+unsigned long __bootdata_preserved(machine_features[1]);
+
+struct alt_debug {
+	unsigned long facilities[MAX_FACILITY_BIT / BITS_PER_LONG];
+	unsigned long mfeatures[MAX_MFEATURE_BIT / BITS_PER_LONG];
+	int spec;
+};
+
+static struct alt_debug __bootdata_preserved(alt_debug);
+
+static void alternative_dump(u8 *old, u8 *new, unsigned int len, unsigned int type, unsigned int data)
+{
+	char oinsn[33], ninsn[33];
+	unsigned long kptr;
+	unsigned int pos;
+
+	for (pos = 0; pos < len && 2 * pos < sizeof(oinsn) - 3; pos++)
+		hex_byte_pack(&oinsn[2 * pos], old[pos]);
+	oinsn[2 * pos] = 0;
+	for (pos = 0; pos < len && 2 * pos < sizeof(ninsn) - 3; pos++)
+		hex_byte_pack(&ninsn[2 * pos], new[pos]);
+	ninsn[2 * pos] = 0;
+	kptr = (unsigned long)__kernel_va(old);
+	a_debug("[%d/%3d] %016lx: %s -> %s\n", type, data, kptr, oinsn, ninsn);
+}
 
 void __apply_alternatives(struct alt_instr *start, struct alt_instr *end, unsigned int ctx)
 {
-	u8 *instr, *replacement;
+	struct alt_debug *d;
 	struct alt_instr *a;
-	bool replace;
+	bool debug, replace;
+	u8 *old, *new;
 
 	/*
 	 * The scan order should be from start to end. A later scanned
 	 * alternative code can overwrite previously scanned alternative code.
 	 */
+	d = &alt_debug;
 	for (a = start; a < end; a++) {
 		if (!(a->ctx & ctx))
 			continue;
 		switch (a->type) {
 		case ALT_TYPE_FACILITY:
 			replace = test_facility(a->data);
+			debug = __test_facility(a->data, d->facilities);
+			break;
+		case ALT_TYPE_FEATURE:
+			replace = test_machine_feature(a->data);
+			debug = __test_machine_feature(a->data, d->mfeatures);
 			break;
 		case ALT_TYPE_SPEC:
 			replace = nobp_enabled();
-			break;
-		case ALT_TYPE_LOWCORE:
-			replace = have_relocated_lowcore();
+			debug = d->spec;
 			break;
 		default:
 			replace = false;
+			debug = false;
 		}
 		if (!replace)
 			continue;
-		instr = (u8 *)&a->instr_offset + a->instr_offset;
-		replacement = (u8 *)&a->repl_offset + a->repl_offset;
-		s390_kernel_write(instr, replacement, a->instrlen);
+		old = (u8 *)&a->instr_offset + a->instr_offset;
+		new = (u8 *)&a->repl_offset + a->repl_offset;
+		if (debug)
+			alternative_dump(old, new, a->instrlen, a->type, a->data);
+		s390_kernel_write(old, new, a->instrlen);
 	}
 }