[PATCH] x86: Put trampoline in separate .init.trampoline section

[Frediano Ziglio <frediano.ziglio@xxxxxxxxx>]

This change put the trampoline in a separate, not executable section.
The trampoline contains a mix of code and data (data which
is modified from C code during early start so must be writable).
This is in preparation for W^X patch in order to satisfy UEFI CA
memory mitigation requirements.
At the moment .init.text and .init.data in EFI mode are put together
so they will be in the same final section as before this patch.
Putting in a separate section (even in final executables) allows
to easily disassembly that section.

Signed-off-by: Frediano Ziglio <frediano.ziglio@xxxxxxxxx>
---
Changes since last version:
- use completely separate section even on final executables
  (suggested by Jan Beulich).
---
 xen/arch/x86/boot/head.S | 6 ++++--
 xen/arch/x86/xen.lds.S   | 5 +++++
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 12bbb97f33..61b7b8894c 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -882,8 +882,10 @@ cmdline_parse_early:
 reloc:
         .incbin "reloc.bin"
 
+#include "x86_64.S"
+
+        .section .init.trampoline, "aw", @progbits
+        .align 4
 ENTRY(trampoline_start)
 #include "trampoline.S"
 ENTRY(trampoline_end)
-
-#include "x86_64.S"
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index d48de67cfd..390870e463 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -269,6 +269,11 @@ SECTIONS
        __ctors_end = .;
   } PHDR(text)
 
+  . = ALIGN(PAGE_SIZE);
+  DECL_SECTION(.init.trampoline) {
+       *(.init.trampoline)
+  } PHDR(text)
+
 #ifndef EFI
   /*
    * With --orphan-sections=warn (or =error) we need to handle certain linker
-- 
2.34.1