x86/alternatives: build time check feature is in range

Ensure at build time the feature(s) used for the alternative blocks are in
range of the featureset.

No functional change intended, as all current usages are correct.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/include/asm/alternative-asm.h b/xen/arch/x86/include/asm/alternative-asm.h
index 4092f5ba70a6350624bc2a86a9e115fa34c34278..83e8594f0eaf7751c335fdb72e57fa09ac159b28 100644 (file)
--- a/xen/arch/x86/include/asm/alternative-asm.h
+++ b/xen/arch/x86/include/asm/alternative-asm.h
@@ -12,6 +12,9 @@
  * instruction. See apply_alternatives().
  */
 .macro altinstruction_entry orig, repl, feature, orig_len, repl_len, pad_len
+    .if \feature >= NCAPINTS * 32
+        .error "alternative feature outside of featureset range"
+    .endif
     .long \orig - .
     .long \repl - .
     .word \feature

diff --git a/xen/arch/x86/include/asm/alternative.h b/xen/arch/x86/include/asm/alternative.h
index 69555d781ef9093013fb8d814f84bbb425e403b9..38472fb58e2da4e782419f24b99cdccccef00991 100644 (file)
--- a/xen/arch/x86/include/asm/alternative.h
+++ b/xen/arch/x86/include/asm/alternative.h
@@ -7,6 +7,7 @@
 #include <xen/lib.h>
 #include <xen/stringify.h>
 #include <asm/asm-macros.h>
+#include <asm/cpufeatureset.h>
 
 struct __packed alt_instr {
     int32_t  orig_offset;   /* original instruction */
@@ -59,6 +60,9 @@ extern void alternative_branches(void);
                     alt_repl_len(n2)) "-" alt_orig_len)
 
 #define ALTINSTR_ENTRY(feature, num)                                    \
+        " .if " STR(feature) " >= " STR(NCAPINTS * 32) "\n"             \
+        " .error \"alternative feature outside of featureset range\"\n" \
+        " .endif\n"                                                     \
         " .long .LXEN%=_orig_s - .\n"             /* label           */ \
         " .long " alt_repl_s(num)" - .\n"         /* new instruction */ \
         " .word " __stringify(feature) "\n"       /* feature bit     */ \