[PATCH v2 2/3] arm/alternatives: Rename alt_instr fields which are used in common code

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Alternatives auditing for livepatches is currently broken.  To fix it, the
livepatch code needs to inspect more fields of alt_instr.

Rename ARM's fields to match x86's, because:

 * ARM already exposes alt_offset under the repl name via ALT_REPL_PTR()
 * "alt" is somewhat ambiguous in a structure entirely about alternatives
   already.
 * "repl", being the same number of character as orig leads to slightly neater
   code.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

The other option is to make alt_instr an entirely common structure, but it's
already different between ARM and x86 and I'm not sure the result of doing
this would result in nicer code.
---
 xen/arch/arm/alternative.c             |  6 +++---
 xen/arch/arm/include/asm/alternative.h | 12 ++++++------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/xen/arch/arm/alternative.c b/xen/arch/arm/alternative.c
index f00e3b9b3c11..7366af4ea646 100644
--- a/xen/arch/arm/alternative.c
+++ b/xen/arch/arm/alternative.c
@@ -44,7 +44,7 @@ static bool branch_insn_requires_update(const struct 
alt_instr *alt,
         return true;
 
     replptr = (unsigned long)ALT_REPL_PTR(alt);
-    if ( pc >= replptr && pc <= (replptr + alt->alt_len) )
+    if ( pc >= replptr && pc <= (replptr + alt->repl_len) )
         return false;
 
     /*
@@ -128,9 +128,9 @@ static int __apply_alternatives(const struct alt_region 
*region,
             continue;
 
         if ( alt->cpufeature == ARM_CB_PATCH )
-            BUG_ON(alt->alt_len != 0);
+            BUG_ON(alt->repl_len != 0);
         else
-            BUG_ON(alt->alt_len != alt->orig_len);
+            BUG_ON(alt->repl_len != alt->orig_len);
 
         origptr = ALT_ORIG_PTR(alt);
         updptr = (void *)origptr + update_offset;
diff --git a/xen/arch/arm/include/asm/alternative.h 
b/xen/arch/arm/include/asm/alternative.h
index 1eb4b60fbb3e..d3210e82f9e5 100644
--- a/xen/arch/arm/include/asm/alternative.h
+++ b/xen/arch/arm/include/asm/alternative.h
@@ -13,16 +13,16 @@
 
 struct alt_instr {
        s32 orig_offset;        /* offset to original instruction */
-       s32 alt_offset;         /* offset to replacement instruction */
+       s32 repl_offset;        /* offset to replacement instruction */
        u16 cpufeature;         /* cpufeature bit set for replacement */
        u8  orig_len;           /* size of original instruction(s) */
-       u8  alt_len;            /* size of new instruction(s), <= orig_len */
+       u8  repl_len;           /* size of new instruction(s), <= orig_len */
 };
 
 /* Xen: helpers used by common code. */
 #define __ALT_PTR(a,f)         ((void *)&(a)->f + (a)->f)
 #define ALT_ORIG_PTR(a)                __ALT_PTR(a, orig_offset)
-#define ALT_REPL_PTR(a)                __ALT_PTR(a, alt_offset)
+#define ALT_REPL_PTR(a)                __ALT_PTR(a, repl_offset)
 
 typedef void (*alternative_cb_t)(const struct alt_instr *alt,
                                 const uint32_t *origptr, uint32_t *updptr,
@@ -90,12 +90,12 @@ int apply_alternatives(const struct alt_instr *start, const 
struct alt_instr *en
 #include <asm/asm_defns.h>
 #include <asm/macros.h>
 
-.macro altinstruction_entry orig_offset alt_offset feature orig_len alt_len
+.macro altinstruction_entry orig_offset repl_offset feature orig_len repl_len
        .word \orig_offset - .
-       .word \alt_offset - .
+       .word \repl_offset - .
        .hword \feature
        .byte \orig_len
-       .byte \alt_len
+       .byte \repl_len
 .endm
 
 .macro alternative_insn insn1, insn2, cap, enable = 1
-- 
2.30.2