x86/alt: Clean up struct alt_instr and its users

* Rename some fields for consistency and clarity, and use standard types.
 * Don't opencode the use of ALT_{ORIG,REPL}_PTR().

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

xen/arch/x86/alternative.c

@@ -163,8 +163,6 @@ void init_or_livepatch apply_alternatives(const struct alt_instr *start,
                                           const struct alt_instr *end)
 {
     const struct alt_instr *a;
-    u8 *instr, *replacement;
-    u8 insnbuf[MAX_PATCH_LEN];
 
     printk(KERN_INFO "alt table %p -> %p\n", start, end);
 
@@ -179,23 +177,25 @@ void init_or_livepatch apply_alternatives(const struct alt_instr *start,
      */
     for ( a = start; a < end; a++ )
     {
-        instr = (u8 *)&a->instr_offset + a->instr_offset;
-        replacement = (u8 *)&a->repl_offset + a->repl_offset;
-        BUG_ON(a->replacementlen > a->instrlen);
-        BUG_ON(a->instrlen > sizeof(insnbuf));
+        uint8_t *orig = ALT_ORIG_PTR(a);
+        uint8_t *repl = ALT_REPL_PTR(a);
+        uint8_t buf[MAX_PATCH_LEN];
+
+        BUG_ON(a->repl_len > a->orig_len);
+        BUG_ON(a->orig_len > sizeof(buf));
         BUG_ON(a->cpuid >= NCAPINTS * 32);
+
         if ( !boot_cpu_has(a->cpuid) )
             continue;
 
-        memcpy(insnbuf, replacement, a->replacementlen);
+        memcpy(buf, repl, a->repl_len);
 
         /* 0xe8/0xe9 are relative branches; fix the offset. */
-        if ( a->replacementlen >= 5 && (*insnbuf & 0xfe) == 0xe8 )
-            *(s32 *)(insnbuf + 1) += replacement - instr;
+        if ( a->repl_len >= 5 && (*buf & 0xfe) == 0xe8 )
+            *(int32_t *)(buf + 1) += repl - orig;
 
-        add_nops(insnbuf + a->replacementlen,
-                 a->instrlen - a->replacementlen);
-        text_poke(instr, insnbuf, a->instrlen);
+        add_nops(buf + a->repl_len, a->orig_len - a->repl_len);
+        text_poke(orig, buf, a->orig_len);
     }
 }
 

xen/include/asm-x86/alternative.h

@@ -9,15 +9,15 @@
 #include <xen/types.h>
 
 struct alt_instr {
-    s32 instr_offset;       /* original instruction */
-    s32 repl_offset;        /* offset to replacement instruction */
-    u16 cpuid;              /* cpuid bit set for replacement */
-    u8  instrlen;           /* length of original instruction */
-    u8  replacementlen;     /* length of new instruction, <= instrlen */
+    int32_t  orig_offset;   /* original instruction */
+    int32_t  repl_offset;   /* offset to replacement instruction */
+    uint16_t cpuid;         /* cpuid bit set for replacement */
+    uint8_t  orig_len;      /* length of original instruction */
+    uint8_t  repl_len;      /* length of new instruction, <= instrlen */
 };
 
-#define __ALT_PTR(a,f)      ((u8 *)((void *)&(a)->f + (a)->f))
-#define ALT_ORIG_PTR(a)     __ALT_PTR(a, instr_offset)
+#define __ALT_PTR(a,f)      ((uint8_t *)((void *)&(a)->f + (a)->f))
+#define ALT_ORIG_PTR(a)     __ALT_PTR(a, orig_offset)
 #define ALT_REPL_PTR(a)     __ALT_PTR(a, repl_offset)
 
 extern void add_nops(void *insns, unsigned int len);