[PATCH v2] Arm: avoid .init.data to be marked as executable

[Jan Beulich <jbeulich@xxxxxxxx>]

This confuses disassemblers, at the very least. Move
.altinstr_replacement to .init.text. The previously redundant ALIGN()
now gets converted to page alignment, such that the hypervisor mapping
won't have this as executable (it'll instead get mapped r/w, which I'm
told is intended to be adjusted at some point).

Note that for the actual patching logic's purposes this part of
.init.text _has_ to live after _einittext (or before _sinittext), or
else branch_insn_requires_update() would produce wrong results.

Also, to have .altinstr_replacement have consistent attributes in the
object files, add "x" to the one instance where it was missing.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
v2: Put past _einittext.

--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -148,6 +148,8 @@ SECTIONS
        _sinittext = .;
        *(.init.text)
        _einittext = .;
+       . = ALIGN(PAGE_SIZE);        /* Avoid mapping alt insns executable */
+       *(.altinstr_replacement)
   } :text
   . = ALIGN(PAGE_SIZE);
   .init.data : {
@@ -169,8 +171,6 @@ SECTIONS
        __alt_instructions = .;
        *(.altinstructions)
        __alt_instructions_end = .;
-       . = ALIGN(4);
-       *(.altinstr_replacement)
 
 #ifdef CONFIG_DEBUG_LOCK_PROFILE
        . = ALIGN(POINTER_ALIGN);
--- a/xen/include/asm-arm/alternative.h
+++ b/xen/include/asm-arm/alternative.h
@@ -67,7 +67,7 @@ int apply_alternatives(const struct alt_
        ALTINSTR_ENTRY(feature,cb)                                      \
        ".popsection\n"                                                 \
        " .if " __stringify(cb) " == 0\n"                               \
-       ".pushsection .altinstr_replacement, \"a\"\n"                   \
+       ".pushsection .altinstr_replacement, \"ax\"\n"                  \
        "663:\n\t"                                                      \
        newinstr "\n"                                                   \
        "664:\n\t"                                                      \