[PATCH v7 0/4] Various patches to improve Secure Boot support

[PATCH v7 0/4] Various patches to improve Secure Boot support

[Frediano Ziglio]

These patches improve support for Secure boot.
UEFI CA memory mitigation requires memory pages to be not executable and
writable at the same time. So changing permissions and splitting some section
is required.
Remove multiboot pieces from EFI executable.

Changes since v1:
- improved some comments;
- merged 2 pacthes removing multiboot support in x86 PE;
- removed a patch dealing with SBAT;
- other minor changes (see single patches).

Changes since v2:
- improved some comments.

Changes since v3:
- Added Acked-by;
- Improve commit message.

Changes since v4:
- Messages updates;
- Clean some dependencies cause by code removal;
- Add small commit to remove a possibly unused string.

Changes since v5:
- removed merged commit;
- remove more code/data from xen.efi output.

Changes since v6:
- fix commit message.

Frediano Ziglio (2):
  Align relevant sections to 4KB
  x86: Split .init section to satisfy UEFI CA memory mitigation

Roger Pau Monné (2):
  x86/efi: discard multiboot and PVH support for PE binary
  x86/efi: avoid a relocation in efi_arch_post_exit_boot()

 docs/hypervisor-guide/x86/how-xen-boots.rst |  6 -----
 xen/arch/x86/boot/head.S                    |  8 +++----
 xen/arch/x86/efi/efi-boot.h                 |  7 ++++--
 xen/arch/x86/xen.lds.S                      | 25 ++++++++++++---------
 xen/tools/combine_two_binaries.py           |  2 +-
 5 files changed, 25 insertions(+), 23 deletions(-)

-- 
2.43.0

[PATCH v7 1/4] Align relevant sections to 4KB

[Frediano Ziglio]

From: Frediano Ziglio <frediano.ziglio@cloud.com>

Required by UEFI CA memory mitigation.

It is a requirement for NX_COMPAT so the PE can be loaded with W^X perms
in the pagetables.

NX_COMPAT is a requirement from shim-review,
https://github.com/rhboot/shim-review#do-you-have-the-nx-bit-set-in-your-shim-if-so-is-your-entire-boot-stack-nx-compatible-and-what-testing-have-you-done-to-ensure-such-compatibility

Sections with different permissions must be in separate pages.
In the case of debug sections they are contiguous and have the same
permissions, including the immediately preceding .reloc section, so it's
not an issue if they are not aligned to the page.
Before the .debug sections you could have the .reloc or the SBAT section,
either are permission-compatible.

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
Changes since v1:
- Change subject.

Changes since v2:
- Improved commit message and subject.

Changes since v3:
- Added Acked-by;
- Improved commit message.

Changes since v4:
- Added missing comment;
- Added Acked-by.
---
 xen/arch/x86/xen.lds.S | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index b9e888e596..8e63cf5bc2 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -162,8 +162,8 @@ SECTIONS
        __note_gnu_build_id_end = .;
   } PHDR(note) PHDR(text)
 #elif defined(BUILD_ID_EFI)
-  /* Workaround bug in binutils < 2.36 */
-  . = ALIGN(32);
+  /* Align to satisfy UEFI CA memory mitigation. */
+  . = ALIGN(PAGE_SIZE);
   DECL_SECTION(.buildid) {
        __note_gnu_build_id_start = .;
        *(.buildid)
@@ -330,6 +330,8 @@ SECTIONS
   __2M_rwdata_end = ALIGN(SECTION_ALIGN);
 
 #ifdef EFI
+  /* Align to satisfy UEFI CA memory mitigation. */
+  . = ALIGN(PAGE_SIZE);
   .reloc ALIGN(4) : {
     __base_relocs_start = .;
     *(.reloc)
-- 
2.43.0

[PATCH v7 2/4] x86/efi: discard multiboot and PVH support for PE binary

[Frediano Ziglio]

From: Roger Pau Monné <roger.pau@citrix.com>

Multiboot and PVH booting are not supported for PE, hence discards them
in the linker script when doing a PE build.

That removes some relocations that otherwise appear due to the usage of the
start and __efi64_mb2_start symbols in the multiboot2 header.

Section discarding is not done updating DISCARD_SECTIONS definition as the
change is specific for x86.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
---
Changes since v1:
- improve commit message;
- change section orders to avoid changing code order in final executable;
- merge 2 commits;
- removed deprecated documentation section.

Changes since v2:
- Update commit message, join 2 sentences together.

Changes since v3:
- Added Acked-by.

Changes since v4:
- more clear subject;
- removed more code/data from EFI output;
- removed Acked-by.

Changes since v5:
- simplify section exclusion using more wildcard;
- exclude more multiboot functions.
---
 docs/hypervisor-guide/x86/how-xen-boots.rst | 6 ------
 xen/arch/x86/boot/head.S                    | 8 ++++----
 xen/arch/x86/xen.lds.S                      | 7 +++++++
 xen/tools/combine_two_binaries.py           | 2 +-
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/docs/hypervisor-guide/x86/how-xen-boots.rst b/docs/hypervisor-guide/x86/how-xen-boots.rst
index 8b3229005c..b6d852050a 100644
--- a/docs/hypervisor-guide/x86/how-xen-boots.rst
+++ b/docs/hypervisor-guide/x86/how-xen-boots.rst
@@ -82,12 +82,6 @@ When a PEI-capable toolchain is found, the objects are linked together and a
 PE32+ binary is created.  It can be run directly from the EFI shell, and has
 ``efi_start`` as its entry symbol.
 
-.. note::
-
-   xen.efi does contain all MB1/MB2/PVH tags included in the rest of the
-   build.  However, entry via anything other than the EFI64 protocol is
-   unsupported, and won't work.
-
 
 Boot
 ----
diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 68b963ce6f..981f262b5e 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -126,7 +126,7 @@ multiboot2_header:
         .size multiboot2_header, . - multiboot2_header
         .type multiboot2_header, @object
 
-        .section .init.rodata, "a", @progbits
+        .section .init.rodata.multiboot, "a", @progbits
 
 .Lbad_cpu_msg: .asciz "ERR: Not a 64-bit CPU!"
 .Lbad_ldr_msg: .asciz "ERR: Not a Multiboot bootloader!"
@@ -137,8 +137,7 @@ multiboot2_header:
 .Lno_nx_msg:   .asciz "ERR: Not an NX-capable CPU!"
 #endif
 
-        .section .init.data, "aw", @progbits
-        .subsection 1 /* Put data here after the page tables (in x86_64.S). */
+        .section .init.data.multiboot, "aw", @progbits
         .align 4
 
         .word   0
@@ -154,7 +153,7 @@ vga_text_buffer:
 efi_platform:
         .byte   0
 
-        .section .init.text, "ax", @progbits
+        .section .init.multiboot, "ax", @progbits
 
 early_error: /* Here to improve the disassembly. */
 
@@ -712,6 +711,7 @@ trampoline_setup:
         /* Jump into the relocated trampoline. */
         lret
 
+        .section .init.text, "ax", @progbits
 ENTRY(trampoline_start)
 #include "trampoline.S"
 ENTRY(trampoline_end)
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 8e63cf5bc2..4ed1d2bec1 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -57,6 +57,10 @@ SECTIONS
   __image_base__ = .;
 #else
   . = __image_base__;
+  /DISCARD/ : {
+    *(.text.header)
+    *(.init.*multiboot)
+  }
 #endif
 
 #if 0
@@ -195,6 +199,7 @@ SECTIONS
   DECL_SECTION(.init.text) {
 #endif
        _sinittext = .;
+       *(.init.multiboot)
        *(.init.text)
        *(.text.startup)
        _einittext = .;
@@ -220,6 +225,7 @@ SECTIONS
        *(.init.rodata.cf_clobber)
        __initdata_cf_clobber_end = .;
 
+       *(.init.rodata.multiboot)
        *(.init.rodata)
        *(.init.rodata.*)
 
@@ -234,6 +240,7 @@ SECTIONS
        *(.initcall1.init)
        __initcall_end = .;
 
+       *(.init.data.multiboot)
        *(.init.data)
        *(.init.data.rel)
        *(.init.data.rel.*)
diff --git a/xen/tools/combine_two_binaries.py b/xen/tools/combine_two_binaries.py
index 581e57cbc0..5f0433dcad 100755
--- a/xen/tools/combine_two_binaries.py
+++ b/xen/tools/combine_two_binaries.py
@@ -33,7 +33,7 @@ parser.add_argument('--map', dest='mapfile',
 parser.add_argument('--exports', dest='exports',
                     help='Symbols to export')
 parser.add_argument('--section-header', dest='section_header',
-                    default='.section .init.text, "ax", @progbits',
+                    default='.section .init.multiboot, "ax", @progbits',
                     help='Section header declaration')
 parser.add_argument('-v', '--verbose',
                     action='store_true')
-- 
2.43.0

[PATCH v7 3/4] x86/efi: avoid a relocation in efi_arch_post_exit_boot()

[Frediano Ziglio]

From: Roger Pau Monné <roger.pau@citrix.com>

Instead of using the absolute __start_xen address, calculate it as an
offset from the current instruction pointer.  The relocation would be
problematic if the generated PE binary had .init.text as a standalone
section with just read and execute permissions.

Removing this relocation is necessary to make it safe to split .init.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
Changes since v1:
- Improve commit message.

Changes since v3:
- Added Acked-by.

Changes since v6:
- remove spurious quote.
---
 xen/arch/x86/efi/efi-boot.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h
index d738b839ee..b983f054b5 100644
--- a/xen/arch/x86/efi/efi-boot.h
+++ b/xen/arch/x86/efi/efi-boot.h
@@ -270,7 +270,9 @@ static void __init noreturn efi_arch_post_exit_boot(void)
 
                    /* Jump to higher mappings. */
                    "mov    stack_start(%%rip), %%rsp\n\t"
-                   "movabs $__start_xen, %[rip]\n\t"
+                   "lea    __start_xen(%%rip), %[rip]\n\t"
+                   "add    %[offset], %[rip]\n\t"
+
                    "push   %[cs]\n\t"
                    "push   %[rip]\n\t"
                    "lretq"
@@ -278,7 +280,8 @@ static void __init noreturn efi_arch_post_exit_boot(void)
                      [cr4] "+&r" (cr4)
                    : [cr3] "r" (idle_pg_table),
                      [cs] "i" (__HYPERVISOR_CS),
-                     [ds] "r" (__HYPERVISOR_DS)
+                     [ds] "r" (__HYPERVISOR_DS),
+                     [offset] "r" (__XEN_VIRT_START - xen_phys_start)
                    : "memory" );
     unreachable();
 }
-- 
2.43.0

[PATCH v7 4/4] x86: Split .init section to satisfy UEFI CA memory mitigation

[Frediano Ziglio]

From: Frediano Ziglio <frediano.ziglio@cloud.com>

Currently .init section is both writeable and executable, split data and code
to have 2 sections satisfying W^X rule.

It is a requirement for NX_COMPAT so the PE can be loaded with W^X perms
in the pagetables.

NX_COMPAT is a requirement from shim-review,
https://github.com/rhboot/shim-review#do-you-have-the-nx-bit-set-in-your-shim-if-so-is-your-entire-boot-stack-nx-compatible-and-what-testing-have-you-done-to-ensure-such-compatibility

Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>
Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
Change since v1:
- update comment style.

Changes since v3:
- Added Acked-by.

Changes since v4:
- Added Acked-by.
---
 xen/arch/x86/xen.lds.S | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 4ed1d2bec1..e26e37db13 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -193,11 +193,7 @@ SECTIONS
   __2M_init_start = .;         /* Start of 2M superpages, mapped RWX (boot only). */
   . = ALIGN(PAGE_SIZE);             /* Init code and data */
   __init_begin = .;
-#ifdef EFI /* EFI wants to merge all of .init.*  ELF doesn't. */
-  DECL_SECTION(.init) {
-#else
   DECL_SECTION(.init.text) {
-#endif
        _sinittext = .;
        *(.init.multiboot)
        *(.init.text)
@@ -210,12 +206,12 @@ SECTIONS
         */
        *(.altinstr_replacement)
 
-#ifdef EFI /* EFI wants to merge all of .init.*  ELF doesn't. */
-       . = ALIGN(SMP_CACHE_BYTES);
-#else
   } PHDR(text)
-  DECL_SECTION(.init.data) {
+#ifdef EFI
+  /* Align to satisfy UEFI CA memory mitigation. */
+  . = ALIGN(SECTION_ALIGN);
 #endif
+  DECL_SECTION(.init.data) {
        *(.init.bss.stack_aligned)
        *(.init.data.page_aligned)
 
-- 
2.43.0

Re: [PATCH v7 2/4] x86/efi: discard multiboot and PVH support for PE binary

[Jan Beulich]

On 06.07.2026 12:45, Frediano Ziglio wrote:
> From: Roger Pau Monné <roger.pau@citrix.com>
> 
> Multiboot and PVH booting are not supported for PE, hence discards them
> in the linker script when doing a PE build.
> 
> That removes some relocations that otherwise appear due to the usage of the
> start and __efi64_mb2_start symbols in the multiboot2 header.
> 
> Section discarding is not done updating DISCARD_SECTIONS definition as the
> change is specific for x86.
> 
> No functional change intended.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

Re: [PATCH v7 2/4] x86/efi: discard multiboot and PVH support for PE binary

[Marek Marczykowski-Górecki]

[-- Attachment #1: Type: text/plain, Size: 5575 bytes --]

On Mon, Jul 06, 2026 at 11:45:55AM +0100, Frediano Ziglio wrote:
> From: Roger Pau Monné <roger.pau@citrix.com>
> 
> Multiboot and PVH booting are not supported for PE, hence discards them
> in the linker script when doing a PE build.
> 
> That removes some relocations that otherwise appear due to the usage of the
> start and __efi64_mb2_start symbols in the multiboot2 header.
> 
> Section discarding is not done updating DISCARD_SECTIONS definition as the
> change is specific for x86.
> 
> No functional change intended.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> Signed-off-by: Frediano Ziglio <frediano.ziglio@citrix.com>

Acked-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

> ---
> Changes since v1:
> - improve commit message;
> - change section orders to avoid changing code order in final executable;
> - merge 2 commits;
> - removed deprecated documentation section.
> 
> Changes since v2:
> - Update commit message, join 2 sentences together.
> 
> Changes since v3:
> - Added Acked-by.
> 
> Changes since v4:
> - more clear subject;
> - removed more code/data from EFI output;
> - removed Acked-by.
> 
> Changes since v5:
> - simplify section exclusion using more wildcard;
> - exclude more multiboot functions.
> ---
>  docs/hypervisor-guide/x86/how-xen-boots.rst | 6 ------
>  xen/arch/x86/boot/head.S                    | 8 ++++----
>  xen/arch/x86/xen.lds.S                      | 7 +++++++
>  xen/tools/combine_two_binaries.py           | 2 +-
>  4 files changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/docs/hypervisor-guide/x86/how-xen-boots.rst b/docs/hypervisor-guide/x86/how-xen-boots.rst
> index 8b3229005c..b6d852050a 100644
> --- a/docs/hypervisor-guide/x86/how-xen-boots.rst
> +++ b/docs/hypervisor-guide/x86/how-xen-boots.rst
> @@ -82,12 +82,6 @@ When a PEI-capable toolchain is found, the objects are linked together and a
>  PE32+ binary is created.  It can be run directly from the EFI shell, and has
>  ``efi_start`` as its entry symbol.
>  
> -.. note::
> -
> -   xen.efi does contain all MB1/MB2/PVH tags included in the rest of the
> -   build.  However, entry via anything other than the EFI64 protocol is
> -   unsupported, and won't work.
> -
>  
>  Boot
>  ----
> diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
> index 68b963ce6f..981f262b5e 100644
> --- a/xen/arch/x86/boot/head.S
> +++ b/xen/arch/x86/boot/head.S
> @@ -126,7 +126,7 @@ multiboot2_header:
>          .size multiboot2_header, . - multiboot2_header
>          .type multiboot2_header, @object
>  
> -        .section .init.rodata, "a", @progbits
> +        .section .init.rodata.multiboot, "a", @progbits
>  
>  .Lbad_cpu_msg: .asciz "ERR: Not a 64-bit CPU!"
>  .Lbad_ldr_msg: .asciz "ERR: Not a Multiboot bootloader!"
> @@ -137,8 +137,7 @@ multiboot2_header:
>  .Lno_nx_msg:   .asciz "ERR: Not an NX-capable CPU!"
>  #endif
>  
> -        .section .init.data, "aw", @progbits
> -        .subsection 1 /* Put data here after the page tables (in x86_64.S). */
> +        .section .init.data.multiboot, "aw", @progbits
>          .align 4
>  
>          .word   0
> @@ -154,7 +153,7 @@ vga_text_buffer:
>  efi_platform:
>          .byte   0
>  
> -        .section .init.text, "ax", @progbits
> +        .section .init.multiboot, "ax", @progbits
>  
>  early_error: /* Here to improve the disassembly. */
>  
> @@ -712,6 +711,7 @@ trampoline_setup:
>          /* Jump into the relocated trampoline. */
>          lret
>  
> +        .section .init.text, "ax", @progbits
>  ENTRY(trampoline_start)
>  #include "trampoline.S"
>  ENTRY(trampoline_end)
> diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
> index 8e63cf5bc2..4ed1d2bec1 100644
> --- a/xen/arch/x86/xen.lds.S
> +++ b/xen/arch/x86/xen.lds.S
> @@ -57,6 +57,10 @@ SECTIONS
>    __image_base__ = .;
>  #else
>    . = __image_base__;
> +  /DISCARD/ : {
> +    *(.text.header)
> +    *(.init.*multiboot)
> +  }
>  #endif
>  
>  #if 0
> @@ -195,6 +199,7 @@ SECTIONS
>    DECL_SECTION(.init.text) {
>  #endif
>         _sinittext = .;
> +       *(.init.multiboot)
>         *(.init.text)
>         *(.text.startup)
>         _einittext = .;
> @@ -220,6 +225,7 @@ SECTIONS
>         *(.init.rodata.cf_clobber)
>         __initdata_cf_clobber_end = .;
>  
> +       *(.init.rodata.multiboot)
>         *(.init.rodata)
>         *(.init.rodata.*)
>  
> @@ -234,6 +240,7 @@ SECTIONS
>         *(.initcall1.init)
>         __initcall_end = .;
>  
> +       *(.init.data.multiboot)
>         *(.init.data)
>         *(.init.data.rel)
>         *(.init.data.rel.*)
> diff --git a/xen/tools/combine_two_binaries.py b/xen/tools/combine_two_binaries.py
> index 581e57cbc0..5f0433dcad 100755
> --- a/xen/tools/combine_two_binaries.py
> +++ b/xen/tools/combine_two_binaries.py
> @@ -33,7 +33,7 @@ parser.add_argument('--map', dest='mapfile',
>  parser.add_argument('--exports', dest='exports',
>                      help='Symbols to export')
>  parser.add_argument('--section-header', dest='section_header',
> -                    default='.section .init.text, "ax", @progbits',
> +                    default='.section .init.multiboot, "ax", @progbits',
>                      help='Section header declaration')
>  parser.add_argument('-v', '--verbose',
>                      action='store_true')
> -- 
> 2.43.0
> 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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