Re: [tip: x86/boot] x86/boot: Move the EFI mixed mode startup code back under arch/x86, into startup/
From: Aithal, Srikanth
Date: Wed Apr 09 2025 - 07:56:09 EST
On 4/7/2025 3:11 PM, Aithal, Srikanth wrote:
On 4/7/2025 2:00 PM, Ard Biesheuvel wrote:
On Mon, 7 Apr 2025 at 10:38, Aithal, Srikanth <sraithal@xxxxxxx> wrote:
Hello,
This commit breaks the build of next-20250407. The kernel config is
attached here.
Build error:
arch/x86/boot/startup/efi-mixed.o: warning: objtool:
efi32_stub_entry+0x0: unannotated intra-function call
make[3]: *** [scripts/Makefile.build:335:
arch/x86/boot/startup/efi-mixed.o] Error 255
make[3]: *** Deleting file 'arch/x86/boot/startup/efi-mixed.o'
make[3]: *** Waiting for unfinished jobs....
make[2]: *** [scripts/Makefile.build:461: arch/x86/boot/startup] Error 2
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [/home/VT_BUILD/linux/Makefile:2006: .] Error 2
make: *** [Makefile:248: __sub-make] Error 2
Apologies for the breakage.
Does it help to add the following to arch/x86/boot/startup/Makefile:
OBJECT_FILES_NON_STANDARD := y
?
If the above is the solution, could you please let me know how soon it
might be included in the linux-next build?
yes, this fixes the issue.
Reported-by: Srikanth Aithal <sraithal@xxxxxxx>
Tested-by: Srikanth Aithal <sraithal@xxxxxxx>
Thanks,
Srikanth Aithal <sraithal@xxxxxxx>
On 4/7/2025 12:03 AM, tip-bot2 for Ard Biesheuvel wrote:
The following commit has been merged into the x86/boot branch of tip:
Commit-ID: 4f2d1bbc2c92a32fd612e6c3b51832d5c1c3678e
Gitweb: https://git.kernel.org/
tip/4f2d1bbc2c92a32fd612e6c3b51832d5c1c3678e
Author: Ard Biesheuvel <ardb@xxxxxxxxxx>
AuthorDate: Tue, 01 Apr 2025 15:34:20 +02:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Sun, 06 Apr 2025 20:15:14 +02:00
x86/boot: Move the EFI mixed mode startup code back under arch/x86,
into startup/
Linus expressed a strong preference for arch-specific asm code (i.e.,
virtually all of it) to reside under arch/ rather than anywhere else.
So move the EFI mixed mode startup code back, and put it under
arch/x86/boot/startup/ where all shared x86 startup code is going to
live.
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: David Woodhouse <dwmw@xxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20250401133416.1436741-11-
ardb+git@xxxxxxxxxx
---
arch/x86/boot/startup/Makefile | 3 +-
arch/x86/boot/startup/efi-mixed.S | 253 ++++++++++++++++++
++++-
drivers/firmware/efi/libstub/Makefile | 1 +-
drivers/firmware/efi/libstub/x86-mixed.S | 253
+----------------------
4 files changed, 256 insertions(+), 254 deletions(-)
create mode 100644 arch/x86/boot/startup/efi-mixed.S
delete mode 100644 drivers/firmware/efi/libstub/x86-mixed.S
diff --git a/arch/x86/boot/startup/Makefile b/arch/x86/boot/startup/
Makefile
index 03519ef..73946a3 100644
--- a/arch/x86/boot/startup/Makefile
+++ b/arch/x86/boot/startup/Makefile
@@ -1,3 +1,6 @@
# SPDX-License-Identifier: GPL-2.0
+KBUILD_AFLAGS += -D__DISABLE_EXPORTS
+
lib-$(CONFIG_X86_64) += la57toggle.o
+lib-$(CONFIG_EFI_MIXED) += efi-mixed.o
diff --git a/arch/x86/boot/startup/efi-mixed.S b/arch/x86/boot/
startup/efi-mixed.S
new file mode 100644
index 0000000..e04ed99
--- /dev/null
+++ b/arch/x86/boot/startup/efi-mixed.S
@@ -0,0 +1,253 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
+ *
+ * Early support for invoking 32-bit EFI services from a 64-bit
kernel.
+ *
+ * Because this thunking occurs before ExitBootServices() we have to
+ * restore the firmware's 32-bit GDT and IDT before we make EFI
service
+ * calls.
+ *
+ * On the plus side, we don't have to worry about mangling 64-bit
+ * addresses into 32-bits because we're executing with an identity
+ * mapped pagetable and haven't transitioned to 64-bit virtual
addresses
+ * yet.
+ */
+
+#include <linux/linkage.h>
+#include <asm/desc_defs.h>
+#include <asm/msr.h>
+#include <asm/page_types.h>
+#include <asm/pgtable_types.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+
+ .text
+ .code32
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+SYM_FUNC_START(efi32_stub_entry)
+ call 1f
+1: popl %ecx
+
+ /* Clear BSS */
+ xorl %eax, %eax
+ leal (_bss - 1b)(%ecx), %edi
+ leal (_ebss - 1b)(%ecx), %ecx
+ subl %edi, %ecx
+ shrl $2, %ecx
+ cld
+ rep stosl
+
+ add $0x4, %esp /* Discard return address */
+ movl 8(%esp), %ebx /* struct boot_params pointer */
+ jmp efi32_startup
+SYM_FUNC_END(efi32_stub_entry)
+#endif
+
+/*
+ * Called using a far call from __efi64_thunk() below, using the
x86_64 SysV
+ * ABI (except for R8/R9 which are inaccessible to 32-bit code -
EAX/EBX are
+ * used instead). EBP+16 points to the arguments passed via the
stack.
+ *
+ * The first argument (EDI) is a pointer to the boot service or
protocol, to
+ * which the remaining arguments are passed, each truncated to 32
bits.
+ */
+SYM_FUNC_START_LOCAL(efi_enter32)
+ /*
+ * Convert x86-64 SysV ABI params to i386 ABI
+ */
+ pushl 32(%ebp) /* Up to 3 args passed via the stack */
+ pushl 24(%ebp)
+ pushl 16(%ebp)
+ pushl %ebx /* R9 */
+ pushl %eax /* R8 */
+ pushl %ecx
+ pushl %edx
+ pushl %esi
+
+ /* Disable paging */
+ movl %cr0, %eax
+ btrl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+
+ /* Disable long mode via EFER */
+ movl $MSR_EFER, %ecx
+ rdmsr
+ btrl $_EFER_LME, %eax
+ wrmsr
+
+ call *%edi
+
+ /* We must preserve return value */
+ movl %eax, %edi
+
+ call efi32_enable_long_mode
+
+ addl $32, %esp
+ movl %edi, %eax
+ lret
+SYM_FUNC_END(efi_enter32)
+
+ .code64
+SYM_FUNC_START(__efi64_thunk)
+ push %rbp
+ movl %esp, %ebp
+ push %rbx
+
+ /* Move args #5 and #6 into 32-bit accessible registers */
+ movl %r8d, %eax
+ movl %r9d, %ebx
+
+ lcalll *efi32_call(%rip)
+
+ pop %rbx
+ pop %rbp
+ RET
+SYM_FUNC_END(__efi64_thunk)
+
+ .code32
+SYM_FUNC_START_LOCAL(efi32_enable_long_mode)
+ movl %cr4, %eax
+ btsl $(X86_CR4_PAE_BIT), %eax
+ movl %eax, %cr4
+
+ movl $MSR_EFER, %ecx
+ rdmsr
+ btsl $_EFER_LME, %eax
+ wrmsr
+
+ /* Disable interrupts - the firmware's IDT does not work in
long mode */
+ cli
+
+ /* Enable paging */
+ movl %cr0, %eax
+ btsl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+ ret
+SYM_FUNC_END(efi32_enable_long_mode)
+
+/*
+ * This is the common EFI stub entry point for mixed mode. It sets
up the GDT
+ * and page tables needed for 64-bit execution, after which it
calls the
+ * common 64-bit EFI entrypoint efi_stub_entry().
+ *
+ * Arguments: 0(%esp) image handle
+ * 4(%esp) EFI system table pointer
+ * %ebx struct boot_params pointer (or NULL)
+ *
+ * Since this is the point of no return for ordinary execution, no
registers
+ * are considered live except for the function parameters. [Note
that the EFI
+ * stub may still exit and return to the firmware using the Exit()
EFI boot
+ * service.]
+ */
+SYM_FUNC_START_LOCAL(efi32_startup)
+ movl %esp, %ebp
+
+ subl $8, %esp
+ sgdtl (%esp) /* Save GDT descriptor to the
stack */
+ movl 2(%esp), %esi /* Existing GDT pointer */
+ movzwl (%esp), %ecx /* Existing GDT limit */
+ inc %ecx /* Existing GDT size */
+ andl $~7, %ecx /* Ensure size is multiple of
8 */
+
+ subl %ecx, %esp /* Allocate new GDT */
+ andl $~15, %esp /* Realign the stack */
+ movl %esp, %edi /* New GDT address */
+ leal 7(%ecx), %eax /* New GDT limit */
+ pushw %cx /* Push 64-bit CS (for LJMP
below) */
+ pushl %edi /* Push new GDT address */
+ pushw %ax /* Push new GDT limit */
+
+ /* Copy GDT to the stack and add a 64-bit code segment at the
end */
+ movl $GDT_ENTRY(DESC_CODE64, 0, 0xfffff) & 0xffffffff,
(%edi,%ecx)
+ movl $GDT_ENTRY(DESC_CODE64, 0, 0xfffff) >> 32, 4(%edi,%ecx)
+ shrl $2, %ecx
+ cld
+ rep movsl /* Copy the firmware GDT */
+ lgdtl (%esp) /* Switch to the new GDT */
+
+ call 1f
+1: pop %edi
+
+ /* Record mixed mode entry */
+ movb $0x0, (efi_is64 - 1b)(%edi)
+
+ /* Set up indirect far call to re-enter 32-bit mode */
+ leal (efi32_call - 1b)(%edi), %eax
+ addl %eax, (%eax)
+ movw %cs, 4(%eax)
+
+ /* Disable paging */
+ movl %cr0, %eax
+ btrl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+
+ /* Set up 1:1 mapping */
+ leal (pte - 1b)(%edi), %eax
+ movl $_PAGE_PRESENT | _PAGE_RW | _PAGE_PSE, %ecx
+ leal (_PAGE_PRESENT | _PAGE_RW)(%eax), %edx
+2: movl %ecx, (%eax)
+ addl $8, %eax
+ addl $PMD_SIZE, %ecx
+ jnc 2b
+
+ movl $PAGE_SIZE, %ecx
+ .irpc l, 0123
+ movl %edx, \l * 8(%eax)
+ addl %ecx, %edx
+ .endr
+ addl %ecx, %eax
+ movl %edx, (%eax)
+ movl %eax, %cr3
+
+ call efi32_enable_long_mode
+
+ /* Set up far jump to 64-bit mode (CS is already on the stack) */
+ leal (efi_stub_entry - 1b)(%edi), %eax
+ movl %eax, 2(%esp)
+
+ movl 0(%ebp), %edi
+ movl 4(%ebp), %esi
+ movl %ebx, %edx
+ ljmpl *2(%esp)
+SYM_FUNC_END(efi32_startup)
+
+/*
+ * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
+ * efi_system_table_32_t *sys_table)
+ */
+SYM_FUNC_START(efi32_pe_entry)
+ pushl %ebx // save callee-save
registers
+
+ /* Check whether the CPU supports long mode */
+ movl $0x80000001, %eax // assume extended
info support
+ cpuid
+ btl $29, %edx // check long mode bit
+ jnc 1f
+ leal 8(%esp), %esp // preserve stack
alignment
+ xor %ebx, %ebx // no struct
boot_params pointer
+ jmp efi32_startup // only ESP and EBX
remain live
+1: movl $0x80000003, %eax // EFI_UNSUPPORTED
+ popl %ebx
+ RET
+SYM_FUNC_END(efi32_pe_entry)
+
+#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
+ .org efi32_stub_entry + 0x200
+ .code64
+SYM_FUNC_START_NOALIGN(efi64_stub_entry)
+ jmp efi_handover_entry
+SYM_FUNC_END(efi64_stub_entry)
+#endif
+
+ .data
+ .balign 8
+SYM_DATA_START_LOCAL(efi32_call)
+ .long efi_enter32 - .
+ .word 0x0
+SYM_DATA_END(efi32_call)
+SYM_DATA(efi_is64, .byte 1)
+
+ .bss
+ .balign PAGE_SIZE
+SYM_DATA_LOCAL(pte, .fill 6 * PAGE_SIZE, 1, 0)
diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/
firmware/efi/libstub/Makefile
index d23a1b9..2f17339 100644
--- a/drivers/firmware/efi/libstub/Makefile
+++ b/drivers/firmware/efi/libstub/Makefile
@@ -85,7 +85,6 @@ lib-$(CONFIG_EFI_GENERIC_STUB) += efi-stub.o
string.o intrinsics.o systable.o \
lib-$(CONFIG_ARM) += arm32-stub.o
lib-$(CONFIG_ARM64) += kaslr.o arm64.o arm64-stub.o smbios.o
lib-$(CONFIG_X86) += x86-stub.o smbios.o
-lib-$(CONFIG_EFI_MIXED) += x86-mixed.o
lib-$(CONFIG_X86_64) += x86-5lvl.o
lib-$(CONFIG_RISCV) += kaslr.o riscv.o riscv-stub.o
lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
diff --git a/drivers/firmware/efi/libstub/x86-mixed.S b/drivers/
firmware/efi/libstub/x86-mixed.S
deleted file mode 100644
index e04ed99..0000000
--- a/drivers/firmware/efi/libstub/x86-mixed.S
+++ /dev/null
@@ -1,253 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Copyright (C) 2014, 2015 Intel Corporation; author Matt Fleming
- *
- * Early support for invoking 32-bit EFI services from a 64-bit
kernel.
- *
- * Because this thunking occurs before ExitBootServices() we have to
- * restore the firmware's 32-bit GDT and IDT before we make EFI
service
- * calls.
- *
- * On the plus side, we don't have to worry about mangling 64-bit
- * addresses into 32-bits because we're executing with an identity
- * mapped pagetable and haven't transitioned to 64-bit virtual
addresses
- * yet.
- */
-
-#include <linux/linkage.h>
-#include <asm/desc_defs.h>
-#include <asm/msr.h>
-#include <asm/page_types.h>
-#include <asm/pgtable_types.h>
-#include <asm/processor-flags.h>
-#include <asm/segment.h>
-
- .text
- .code32
-#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
-SYM_FUNC_START(efi32_stub_entry)
- call 1f
-1: popl %ecx
-
- /* Clear BSS */
- xorl %eax, %eax
- leal (_bss - 1b)(%ecx), %edi
- leal (_ebss - 1b)(%ecx), %ecx
- subl %edi, %ecx
- shrl $2, %ecx
- cld
- rep stosl
-
- add $0x4, %esp /* Discard return address */
- movl 8(%esp), %ebx /* struct boot_params pointer */
- jmp efi32_startup
-SYM_FUNC_END(efi32_stub_entry)
-#endif
-
-/*
- * Called using a far call from __efi64_thunk() below, using the
x86_64 SysV
- * ABI (except for R8/R9 which are inaccessible to 32-bit code -
EAX/EBX are
- * used instead). EBP+16 points to the arguments passed via the
stack.
- *
- * The first argument (EDI) is a pointer to the boot service or
protocol, to
- * which the remaining arguments are passed, each truncated to 32
bits.
- */
-SYM_FUNC_START_LOCAL(efi_enter32)
- /*
- * Convert x86-64 SysV ABI params to i386 ABI
- */
- pushl 32(%ebp) /* Up to 3 args passed via the stack */
- pushl 24(%ebp)
- pushl 16(%ebp)
- pushl %ebx /* R9 */
- pushl %eax /* R8 */
- pushl %ecx
- pushl %edx
- pushl %esi
-
- /* Disable paging */
- movl %cr0, %eax
- btrl $X86_CR0_PG_BIT, %eax
- movl %eax, %cr0
-
- /* Disable long mode via EFER */
- movl $MSR_EFER, %ecx
- rdmsr
- btrl $_EFER_LME, %eax
- wrmsr
-
- call *%edi
-
- /* We must preserve return value */
- movl %eax, %edi
-
- call efi32_enable_long_mode
-
- addl $32, %esp
- movl %edi, %eax
- lret
-SYM_FUNC_END(efi_enter32)
-
- .code64
-SYM_FUNC_START(__efi64_thunk)
- push %rbp
- movl %esp, %ebp
- push %rbx
-
- /* Move args #5 and #6 into 32-bit accessible registers */
- movl %r8d, %eax
- movl %r9d, %ebx
-
- lcalll *efi32_call(%rip)
-
- pop %rbx
- pop %rbp
- RET
-SYM_FUNC_END(__efi64_thunk)
-
- .code32
-SYM_FUNC_START_LOCAL(efi32_enable_long_mode)
- movl %cr4, %eax
- btsl $(X86_CR4_PAE_BIT), %eax
- movl %eax, %cr4
-
- movl $MSR_EFER, %ecx
- rdmsr
- btsl $_EFER_LME, %eax
- wrmsr
-
- /* Disable interrupts - the firmware's IDT does not work in
long mode */
- cli
-
- /* Enable paging */
- movl %cr0, %eax
- btsl $X86_CR0_PG_BIT, %eax
- movl %eax, %cr0
- ret
-SYM_FUNC_END(efi32_enable_long_mode)
-
-/*
- * This is the common EFI stub entry point for mixed mode. It sets
up the GDT
- * and page tables needed for 64-bit execution, after which it
calls the
- * common 64-bit EFI entrypoint efi_stub_entry().
- *
- * Arguments: 0(%esp) image handle
- * 4(%esp) EFI system table pointer
- * %ebx struct boot_params pointer (or NULL)
- *
- * Since this is the point of no return for ordinary execution, no
registers
- * are considered live except for the function parameters. [Note
that the EFI
- * stub may still exit and return to the firmware using the Exit()
EFI boot
- * service.]
- */
-SYM_FUNC_START_LOCAL(efi32_startup)
- movl %esp, %ebp
-
- subl $8, %esp
- sgdtl (%esp) /* Save GDT descriptor to the
stack */
- movl 2(%esp), %esi /* Existing GDT pointer */
- movzwl (%esp), %ecx /* Existing GDT limit */
- inc %ecx /* Existing GDT size */
- andl $~7, %ecx /* Ensure size is multiple of
8 */
-
- subl %ecx, %esp /* Allocate new GDT */
- andl $~15, %esp /* Realign the stack */
- movl %esp, %edi /* New GDT address */
- leal 7(%ecx), %eax /* New GDT limit */
- pushw %cx /* Push 64-bit CS (for LJMP
below) */
- pushl %edi /* Push new GDT address */
- pushw %ax /* Push new GDT limit */
-
- /* Copy GDT to the stack and add a 64-bit code segment at the
end */
- movl $GDT_ENTRY(DESC_CODE64, 0, 0xfffff) & 0xffffffff,
(%edi,%ecx)
- movl $GDT_ENTRY(DESC_CODE64, 0, 0xfffff) >> 32, 4(%edi,%ecx)
- shrl $2, %ecx
- cld
- rep movsl /* Copy the firmware GDT */
- lgdtl (%esp) /* Switch to the new GDT */
-
- call 1f
-1: pop %edi
-
- /* Record mixed mode entry */
- movb $0x0, (efi_is64 - 1b)(%edi)
-
- /* Set up indirect far call to re-enter 32-bit mode */
- leal (efi32_call - 1b)(%edi), %eax
- addl %eax, (%eax)
- movw %cs, 4(%eax)
-
- /* Disable paging */
- movl %cr0, %eax
- btrl $X86_CR0_PG_BIT, %eax
- movl %eax, %cr0
-
- /* Set up 1:1 mapping */
- leal (pte - 1b)(%edi), %eax
- movl $_PAGE_PRESENT | _PAGE_RW | _PAGE_PSE, %ecx
- leal (_PAGE_PRESENT | _PAGE_RW)(%eax), %edx
-2: movl %ecx, (%eax)
- addl $8, %eax
- addl $PMD_SIZE, %ecx
- jnc 2b
-
- movl $PAGE_SIZE, %ecx
- .irpc l, 0123
- movl %edx, \l * 8(%eax)
- addl %ecx, %edx
- .endr
- addl %ecx, %eax
- movl %edx, (%eax)
- movl %eax, %cr3
-
- call efi32_enable_long_mode
-
- /* Set up far jump to 64-bit mode (CS is already on the stack) */
- leal (efi_stub_entry - 1b)(%edi), %eax
- movl %eax, 2(%esp)
-
- movl 0(%ebp), %edi
- movl 4(%ebp), %esi
- movl %ebx, %edx
- ljmpl *2(%esp)
-SYM_FUNC_END(efi32_startup)
-
-/*
- * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
- * efi_system_table_32_t *sys_table)
- */
-SYM_FUNC_START(efi32_pe_entry)
- pushl %ebx // save callee-save
registers
-
- /* Check whether the CPU supports long mode */
- movl $0x80000001, %eax // assume extended
info support
- cpuid
- btl $29, %edx // check long mode bit
- jnc 1f
- leal 8(%esp), %esp // preserve stack
alignment
- xor %ebx, %ebx // no struct
boot_params pointer
- jmp efi32_startup // only ESP and EBX
remain live
-1: movl $0x80000003, %eax // EFI_UNSUPPORTED
- popl %ebx
- RET
-SYM_FUNC_END(efi32_pe_entry)
-
-#ifdef CONFIG_EFI_HANDOVER_PROTOCOL
- .org efi32_stub_entry + 0x200
- .code64
-SYM_FUNC_START_NOALIGN(efi64_stub_entry)
- jmp efi_handover_entry
-SYM_FUNC_END(efi64_stub_entry)
-#endif
-
- .data
- .balign 8
-SYM_DATA_START_LOCAL(efi32_call)
- .long efi_enter32 - .
- .word 0x0
-SYM_DATA_END(efi32_call)
-SYM_DATA(efi_is64, .byte 1)
-
- .bss
- .balign PAGE_SIZE
-SYM_DATA_LOCAL(pte, .fill 6 * PAGE_SIZE, 1, 0)