[PATCH 3/7] x86/alt: Clean up the assembly used to generate alternatives

[Andrew Cooper <andrew.cooper3@citrix.com>]

 * On the C side, switch to using local lables rather than hardcoded numbers.
 * Rename parameters and lables to be consistent with alt_instr names, and
   consistent between the the C and asm versions.
 * On the asm side, factor some expressions out into macros to aid clarity.
 * Consistently declare section attributes.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
 xen/include/asm-x86/alternative-asm.h | 57 +++++++++++++++++--------------
 xen/include/asm-x86/alternative.h     | 64 +++++++++++++++++++----------------
 2 files changed, 67 insertions(+), 54 deletions(-)

diff --git a/xen/include/asm-x86/alternative-asm.h b/xen/include/asm-x86/alternative-asm.h
index 6640e85..150bd1a 100644
--- a/xen/include/asm-x86/alternative-asm.h
+++ b/xen/include/asm-x86/alternative-asm.h
@@ -9,60 +9,67 @@
  * enough information for the alternatives patching code to patch an
  * instruction. See apply_alternatives().
  */
-.macro altinstruction_entry orig alt feature orig_len alt_len
+.macro altinstruction_entry orig repl feature orig_len repl_len
     .long \orig - .
-    .long \alt - .
+    .long \repl - .
     .word \feature
     .byte \orig_len
-    .byte \alt_len
+    .byte \repl_len
 .endm
 
+#define orig_len               (.L\@_orig_e       -     .L\@_orig_s)
+#define repl_len(nr)           (.L\@_repl_e\()nr  -     .L\@_repl_s\()nr)
+#define decl_repl(insn, nr)     .L\@_repl_s\()nr: insn; .L\@_repl_e\()nr:
+
 .macro ALTERNATIVE oldinstr, newinstr, feature
-.Lold_start_\@:
+.L\@_orig_s:
     \oldinstr
-.Lold_end_\@:
+.L\@_orig_e:
 
     .pushsection .altinstructions, "a", @progbits
-    altinstruction_entry .Lold_start_\@, .Lnew_start_\@, \feature, \
-        (.Lold_end_\@ - .Lold_start_\@), (.Lnew_end_\@ - .Lnew_start_\@)
+    altinstruction_entry .L\@_orig_s, .L\@_repl_s1, \feature, \
+        orig_len, repl_len(1)
 
     .section .discard, "a", @progbits
     /* Assembler-time check that \newinstr isn't longer than \oldinstr. */
-    .byte 0xff + (.Lnew_end_\@ - .Lnew_start_\@) - (.Lold_end_\@ - .Lold_start_\@)
+    .byte 0xff + repl_len(1) - orig_len
 
     .section .altinstr_replacement, "ax", @progbits
-.Lnew_start_\@:
-    \newinstr
-.Lnew_end_\@:
+
+    decl_repl(\newinstr, 1)
+
     .popsection
 .endm
 
 .macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
-.Lold_start_\@:
+.L\@_orig_s:
     \oldinstr
-.Lold_end_\@:
+.L\@_orig_e:
 
     .pushsection .altinstructions, "a", @progbits
-    altinstruction_entry .Lold_start_\@, .Lnew1_start_\@, \feature1, \
-        (.Lold_end_\@ - .Lold_start_\@), (.Lnew1_end_\@ - .Lnew1_start_\@)
-    altinstruction_entry .Lold_start_\@, .Lnew2_start_\@, \feature2, \
-        (.Lold_end_\@ - .Lold_start_\@), (.Lnew2_end_\@ - .Lnew2_start_\@)
+
+    altinstruction_entry .L\@_orig_s, .L\@_repl_s1, \feature1, \
+        orig_len, repl_len(1)
+    altinstruction_entry .L\@_orig_s, .L\@_repl_s2, \feature2, \
+        orig_len, repl_len(2)
 
     .section .discard, "a", @progbits
     /* Assembler-time check that \newinstr{1,2} aren't longer than \oldinstr. */
-    .byte 0xff + (.Lnew1_end_\@ - .Lnew1_start_\@) - (.Lold_end_\@ - .Lold_start_\@)
-    .byte 0xff + (.Lnew2_end_\@ - .Lnew2_start_\@) - (.Lold_end_\@ - .Lold_start_\@)
+    .byte 0xff + repl_len(1) - orig_len
+    .byte 0xff + repl_len(2) - orig_len
 
     .section .altinstr_replacement, "ax", @progbits
-.Lnew1_start_\@:
-    \newinstr1
-.Lnew1_end_\@:
-.Lnew2_start_\@:
-    \newinstr2
-.Lnew2_end_\@:
+
+    decl_repl(\newinstr1, 1)
+    decl_repl(\newinstr2, 2)
+
     .popsection
 .endm
 
+#undef decl_repl
+#undef repl_len
+#undef orig_len
+
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_ALTERNATIVE_ASM_H_ */
 
diff --git a/xen/include/asm-x86/alternative.h b/xen/include/asm-x86/alternative.h
index fefa87d..1e5cfbd 100644
--- a/xen/include/asm-x86/alternative.h
+++ b/xen/include/asm-x86/alternative.h
@@ -26,44 +26,50 @@ 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"
+#define OLDINSTR(oldinstr)      ".L%=_orig_s:\n\t" oldinstr "\n.L%=_orig_e:\n"
 
-#define b_replacement(number)   "663"#number
-#define e_replacement(number)   "664"#number
+#define repl_s(num)             ".L%=_repl_s"#num
+#define repl_e(num)             ".L%=_repl_e"#num
 
-#define alt_slen "662b-661b"
-#define alt_rlen(number) e_replacement(number)"f-"b_replacement(number)"f"
+#define alt_orig_len            "(.L%=_orig_e - .L%=_orig_s)"
+#define alt_repl_len(num)       "(" repl_e(num) " - " repl_s(num) ")"
 
-#define ALTINSTR_ENTRY(feature, number)                                       \
-        " .long 661b - .\n"                             /* label           */ \
-        " .long " b_replacement(number)"f - .\n"        /* new instruction */ \
-        " .word " __stringify(feature) "\n"             /* feature bit     */ \
-        " .byte " alt_slen "\n"                         /* source len      */ \
-        " .byte " alt_rlen(number) "\n"                 /* replacement len */
+#define ALTINSTR_ENTRY(feature, num)                                    \
+        " .long .L%=_orig_s - .\n"                /* label           */ \
+        " .long " repl_s(num)" - .\n"             /* new instruction */ \
+        " .word " __stringify(feature) "\n"       /* feature bit     */ \
+        " .byte " alt_orig_len "\n"               /* source len      */ \
+        " .byte " alt_repl_len(num) "\n"          /* replacement len */
 
-#define DISCARD_ENTRY(number)                           /* rlen <= slen */    \
-        " .byte 0xff + (" alt_rlen(number) ") - (" alt_slen ")\n"
+#define DISCARD_ENTRY(num)                        /* repl <= orig */    \
+        " .byte 0xff + (" alt_repl_len(num) ") - (" alt_orig_len ")\n"
 
-#define ALTINSTR_REPLACEMENT(newinstr, feature, number) /* replacement */     \
-        b_replacement(number)":\n\t" newinstr "\n" e_replacement(number) ":\n\t"
-
-#define ALTERNATIVE_N(newinstr, feature, number)	\
-	".pushsection .altinstructions,\"a\"\n"		\
-	ALTINSTR_ENTRY(feature, number)			\
-	".section .discard,\"a\",@progbits\n"		\
-	DISCARD_ENTRY(number)				\
-	".section .altinstr_replacement, \"ax\"\n"	\
-	ALTINSTR_REPLACEMENT(newinstr, feature, number)	\
-	".popsection\n"
+#define ALTINSTR_REPLACEMENT(newinstr, num)       /* replacement */     \
+        repl_s(num)":\n\t" newinstr "\n" repl_e(num) ":\n\t"
 
 /* alternative assembly primitive: */
-#define ALTERNATIVE(oldinstr, newinstr, feature)			  \
-	OLDINSTR(oldinstr)						  \
-	ALTERNATIVE_N(newinstr, feature, 1)
+#define ALTERNATIVE(oldinstr, newinstr, feature)                        \
+        OLDINSTR(oldinstr)                                              \
+        ".pushsection .altinstructions, \"a\", @progbits\n"             \
+        ALTINSTR_ENTRY(feature, 1)                                      \
+        ".section .discard, \"a\", @progbits\n"                         \
+        DISCARD_ENTRY(1)                                                \
+        ".section .altinstr_replacement, \"ax\", @progbits\n"           \
+        ALTINSTR_REPLACEMENT(newinstr, 1)                               \
+        ".popsection\n"
 
 #define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
-	ALTERNATIVE(oldinstr, newinstr1, feature1)			  \
-	ALTERNATIVE_N(newinstr2, feature2, 2)
+        OLDINSTR(oldinstr)                                              \
+        ".pushsection .altinstructions, \"a\", @progbits\n"             \
+        ALTINSTR_ENTRY(feature1, 1)                                     \
+        ALTINSTR_ENTRY(feature2, 2)                                     \
+        ".section .discard, \"a\", @progbits\n"                         \
+        DISCARD_ENTRY(1)                                                \
+        DISCARD_ENTRY(2)                                                \
+        ".section .altinstr_replacement, \"ax\", @progbits\n"           \
+        ALTINSTR_REPLACEMENT(newinstr1, 1)                              \
+        ALTINSTR_REPLACEMENT(newinstr2, 2)                              \
+        ".popsection\n"
 
 /*
  * Alternative instructions for different CPU types or capabilities.
-- 
2.1.4


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