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-rw-r--r--arch/s390/kernel/alternative.c110
1 files changed, 110 insertions, 0 deletions
diff --git a/arch/s390/kernel/alternative.c b/arch/s390/kernel/alternative.c
new file mode 100644
index 000000000000..315986a06cf5
--- /dev/null
+++ b/arch/s390/kernel/alternative.c
@@ -0,0 +1,110 @@
+#include <linux/module.h>
+#include <asm/alternative.h>
+#include <asm/facility.h>
+
+#define MAX_PATCH_LEN (255 - 1)
+
+static int __initdata_or_module alt_instr_disabled;
+
+static int __init disable_alternative_instructions(char *str)
+{
+ alt_instr_disabled = 1;
+ return 0;
+}
+
+early_param("noaltinstr", disable_alternative_instructions);
+
+struct brcl_insn {
+ u16 opc;
+ s32 disp;
+} __packed;
+
+static u16 __initdata_or_module nop16 = 0x0700;
+static u32 __initdata_or_module nop32 = 0x47000000;
+static struct brcl_insn __initdata_or_module nop48 = {
+ 0xc004, 0
+};
+
+static const void *nops[] __initdata_or_module = {
+ &nop16,
+ &nop32,
+ &nop48
+};
+
+static void __init_or_module add_jump_padding(void *insns, unsigned int len)
+{
+ struct brcl_insn brcl = {
+ 0xc0f4,
+ len / 2
+ };
+
+ memcpy(insns, &brcl, sizeof(brcl));
+ insns += sizeof(brcl);
+ len -= sizeof(brcl);
+
+ while (len > 0) {
+ memcpy(insns, &nop16, 2);
+ insns += 2;
+ len -= 2;
+ }
+}
+
+static void __init_or_module add_padding(void *insns, unsigned int len)
+{
+ if (len > 6)
+ add_jump_padding(insns, len);
+ else if (len >= 2)
+ memcpy(insns, nops[len / 2 - 1], len);
+}
+
+static void __init_or_module __apply_alternatives(struct alt_instr *start,
+ struct alt_instr *end)
+{
+ struct alt_instr *a;
+ u8 *instr, *replacement;
+ u8 insnbuf[MAX_PATCH_LEN];
+
+ /*
+ * The scan order should be from start to end. A later scanned
+ * alternative code can overwrite previously scanned alternative code.
+ */
+ for (a = start; a < end; a++) {
+ int insnbuf_sz = 0;
+
+ instr = (u8 *)&a->instr_offset + a->instr_offset;
+ replacement = (u8 *)&a->repl_offset + a->repl_offset;
+
+ if (!test_facility(a->facility))
+ continue;
+
+ if (unlikely(a->instrlen % 2 || a->replacementlen % 2)) {
+ WARN_ONCE(1, "cpu alternatives instructions length is "
+ "odd, skipping patching\n");
+ continue;
+ }
+
+ memcpy(insnbuf, replacement, a->replacementlen);
+ insnbuf_sz = a->replacementlen;
+
+ if (a->instrlen > a->replacementlen) {
+ add_padding(insnbuf + a->replacementlen,
+ a->instrlen - a->replacementlen);
+ insnbuf_sz += a->instrlen - a->replacementlen;
+ }
+
+ s390_kernel_write(instr, insnbuf, insnbuf_sz);
+ }
+}
+
+void __init_or_module apply_alternatives(struct alt_instr *start,
+ struct alt_instr *end)
+{
+ if (!alt_instr_disabled)
+ __apply_alternatives(start, end);
+}
+
+extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
+void __init apply_alternative_instructions(void)
+{
+ apply_alternatives(__alt_instructions, __alt_instructions_end);
+}