alternatives: x86 rename and change parameters on ARM

On x86 we squash 'apply_alternatives' in to
'alternative_instructions' (who was its sole user)
and 'apply_alternatives_nocheck' to 'apply_alternatives'.

On ARM we change the parameters for 'apply_alternatives'
to be of 'const struct alt_instr *' instead of void pointer and
size length.

We also add 'const' and make the arguments be on the
proper offset.

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com> [x86 bits]
Reviewed-by: Julien Grall <julien.grall@arm.com> [ARM bits]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/arch/arm/alternative.c

@@ -209,11 +209,11 @@ void __init apply_alternatives_all(void)
     BUG_ON(ret);
 }
 
-int apply_alternatives(void *start, size_t length)
+int apply_alternatives(const struct alt_instr *start, const struct alt_instr *end)
 {
     const struct alt_region region = {
         .begin = start,
-        .end = start + length,
+        .end = end,
     };
 
     return __apply_alternatives(&region);

xen/arch/x86/alternative.c

@@ -144,9 +144,10 @@ static void *init_or_livepatch text_poke(void *addr, const void *opcode, size_t
  * APs have less capabilities than the boot processor are not handled.
  * Tough. Make sure you disable such features by hand.
  */
-void init_or_livepatch apply_alternatives_nocheck(struct alt_instr *start, struct alt_instr *end)
+void init_or_livepatch apply_alternatives(const struct alt_instr *start,
+                                          const struct alt_instr *end)
 {
-    struct alt_instr *a;
+    const struct alt_instr *a;
     u8 *instr, *replacement;
     u8 insnbuf[MAX_PATCH_LEN];
 
@@ -187,24 +188,10 @@ void init_or_livepatch apply_alternatives_nocheck(struct alt_instr *start, struc
  * This routine is called with local interrupt disabled and used during
  * bootup.
  */
-void __init apply_alternatives(struct alt_instr *start, struct alt_instr *end)
-{
-    unsigned long cr0 = read_cr0();
-
-    ASSERT(!local_irq_is_enabled());
-
-    /* Disable WP to allow application of alternatives to read-only pages. */
-    write_cr0(cr0 & ~X86_CR0_WP);
-
-    apply_alternatives_nocheck(start, end);
-
-    /* Reinstate WP. */
-    write_cr0(cr0);
-}
-
 void __init alternative_instructions(void)
 {
     nmi_callback_t *saved_nmi_callback;
+    unsigned long cr0 = read_cr0();
 
     arch_init_ideal_nops();
 
@@ -225,7 +212,15 @@ void __init alternative_instructions(void)
      * expect a machine check to cause undue problems during to code
      * patching.
      */
+    ASSERT(!local_irq_is_enabled());
+
+    /* Disable WP to allow application of alternatives to read-only pages. */
+    write_cr0(cr0 & ~X86_CR0_WP);
+
     apply_alternatives(__alt_instructions, __alt_instructions_end);
 
+    /* Reinstate WP. */
+    write_cr0(cr0);
+
     set_nmi_callback(saved_nmi_callback);
 }

xen/common/livepatch.c

@@ -632,7 +632,7 @@ static int prepare_payload(struct payload *payload,
                 return -EINVAL;
             }
         }
-        apply_alternatives_nocheck(start, end);
+        apply_alternatives(start, end);
     }
 
     sec = livepatch_elf_sec_by_name(elf, ".ex_table");

xen/include/asm-arm/alternative.h

@@ -27,7 +27,7 @@ struct alt_instr {
 #define ALT_REPL_PTR(a)		__ALT_PTR(a, alt_offset)
 
 void __init apply_alternatives_all(void);
-int apply_alternatives(void *start, size_t length);
+int apply_alternatives(const struct alt_instr *start, const struct alt_instr *end);
 
 #define ALTINSTR_ENTRY(feature)						      \
 	" .word 661b - .\n"				/* label           */ \

xen/include/asm-x86/alternative.h

@@ -27,10 +27,9 @@ struct alt_instr {
 #define ALT_ORIG_PTR(a)     __ALT_PTR(a, instr_offset)
 #define ALT_REPL_PTR(a)     __ALT_PTR(a, repl_offset)
 
-/* Similar to apply_alternatives except it can be run with IRQs enabled. */
-extern void apply_alternatives_nocheck(struct alt_instr *start,
-                                       struct alt_instr *end);
-extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
+/* Similar to alternative_instructions except it can be run with IRQs enabled. */
+extern void apply_alternatives(const struct alt_instr *start,
+                               const struct alt_instr *end);
 extern void alternative_instructions(void);
 
 #define OLDINSTR(oldinstr)      "661:\n\t" oldinstr "\n662:\n"