* [PATCH 1/6] x86/head_64: clean up mixed mode 32-bit entry code
2022-08-15 13:42 [PATCH 0/6] x86: head_64.S spring cleaning Ard Biesheuvel
@ 2022-08-15 13:42 ` Ard Biesheuvel
2022-09-20 19:19 ` Borislav Petkov
2022-08-15 13:42 ` [PATCH 2/6] efi/x86: simplify IDT/GDT preserve/restore Ard Biesheuvel
` (5 subsequent siblings)
6 siblings, 1 reply; 9+ messages in thread
From: Ard Biesheuvel @ 2022-08-15 13:42 UTC (permalink / raw)
To: linux-kernel
Cc: linux-efi, Ard Biesheuvel, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, Michael Roth
The x86_64 32-bit entry code is a jumble of EFI and SEV routines, which
is not good for maintainability. Let's isolate the EFI mixed mode code
and combine it with the boot service thunk that lives in another .S
file, so that we can remove it from head_64.S
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/Makefile | 6 +-
arch/x86/boot/compressed/efi_mixed.S | 358 ++++++++++++++++++++
arch/x86/boot/compressed/efi_thunk_64.S | 195 -----------
arch/x86/boot/compressed/head_32.S | 4 -
arch/x86/boot/compressed/head_64.S | 149 +-------
drivers/firmware/efi/libstub/x86-stub.c | 3 +-
6 files changed, 370 insertions(+), 345 deletions(-)
diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 35ce1a64068b..d6dbb46696a2 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -107,11 +107,11 @@ endif
vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o $(obj)/tdcall.o
-vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
-efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a
+vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_mixed.o
+vmlinux-objs-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
-$(obj)/vmlinux: $(vmlinux-objs-y) $(efi-obj-y) FORCE
+$(obj)/vmlinux: $(vmlinux-objs-y) FORCE
$(call if_changed,ld)
OBJCOPYFLAGS_vmlinux.bin := -R .comment -S
diff --git a/arch/x86/boot/compressed/efi_mixed.S b/arch/x86/boot/compressed/efi_mixed.S
new file mode 100644
index 000000000000..6fd7ac517c53
--- /dev/null
+++ b/arch/x86/boot/compressed/efi_mixed.S
@@ -0,0 +1,358 @@
+/* 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/msr.h>
+#include <asm/page_types.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+
+ .text
+ .code64
+/*
+ * This is the first thing that runs after switching to long mode. Depending on
+ * whether we are using the EFI handover protocol or the compat entry point, we
+ * will either branch to the 64-bit EFI handover entrypoint at offset 0x390 in
+ * the image, or to the 64-bit EFI PE/COFF entrypoint efi_pe_entry(). In the
+ * former case, the bootloader must provide a struct bootparams pointer as the
+ * third argument, so we use that to disambiguate.
+ *
+ * +--------------+
+ * +----------------+ +------------+ +---->| efi_pe_entry |
+ * | efi32_pe_entry |---->| | | +-----------+--+
+ * +----------------+ | | +--------+-------------+ |
+ * | startup_32 |---->| startup_64_mixedmode | |
+ * +----------------+ | | +--------+-------------+ V
+ * | efi32_handover |---->| | | +-----------+------+
+ * +----------------+ +------------+ +---->| efi64_stub_entry |
+ * +-----------+------+
+ * +------------+ +----------+ |
+ * | startup_64 |<----| efi_main |<--------------+
+ * +------------+ +----------+
+ */
+SYM_FUNC_START(startup_64_mixedmode)
+ lea efi32_boot_args(%rip), %rdx
+ mov 0(%rdx), %edi
+ mov 4(%rdx), %esi
+ mov 8(%rdx), %edx // saved bootparams pointer
+ test %edx, %edx
+ jnz efi64_stub_entry
+ /*
+ * efi_pe_entry uses MS calling convention, which requires 32 bytes of
+ * shadow space on the stack even if all arguments are passed in
+ * registers. We also need an additional 8 bytes for the space that
+ * would be occupied by the return address, and this also results in
+ * the correct stack alignment for entry.
+ */
+ sub $40, %rsp
+ mov %rdi, %rcx // MS calling convention
+ mov %rsi, %rdx
+ jmp efi_pe_entry
+SYM_FUNC_END(startup_64_mixedmode)
+
+SYM_FUNC_START(__efi64_thunk)
+ push %rbp
+ push %rbx
+
+ movl %ds, %eax
+ push %rax
+ movl %es, %eax
+ push %rax
+ movl %ss, %eax
+ push %rax
+
+ /* Copy args passed on stack */
+ movq 0x30(%rsp), %rbp
+ movq 0x38(%rsp), %rbx
+ movq 0x40(%rsp), %rax
+
+ /*
+ * Convert x86-64 ABI params to i386 ABI
+ */
+ subq $64, %rsp
+ movl %esi, 0x0(%rsp)
+ movl %edx, 0x4(%rsp)
+ movl %ecx, 0x8(%rsp)
+ movl %r8d, 0xc(%rsp)
+ movl %r9d, 0x10(%rsp)
+ movl %ebp, 0x14(%rsp)
+ movl %ebx, 0x18(%rsp)
+ movl %eax, 0x1c(%rsp)
+
+ leaq 0x20(%rsp), %rbx
+ sgdt (%rbx)
+
+ addq $16, %rbx
+ sidt (%rbx)
+
+ leaq 1f(%rip), %rbp
+
+ /*
+ * Switch to IDT and GDT with 32-bit segments. This is the firmware GDT
+ * and IDT that was installed when the kernel started executing. The
+ * pointers were saved at the efi32_stub_handover entry point below.
+ *
+ * Pass the saved DS selector to the 32-bit code, and use far return to
+ * restore the saved CS selector.
+ */
+ leaq efi32_boot_idt(%rip), %rax
+ lidt (%rax)
+ leaq efi32_boot_gdt(%rip), %rax
+ lgdt (%rax)
+
+ movzwl efi32_boot_ds(%rip), %edx
+ movzwq efi32_boot_cs(%rip), %rax
+ pushq %rax
+ leaq efi_enter32(%rip), %rax
+ pushq %rax
+ lretq
+
+1: addq $64, %rsp
+ movq %rdi, %rax
+
+ pop %rbx
+ movl %ebx, %ss
+ pop %rbx
+ movl %ebx, %es
+ pop %rbx
+ movl %ebx, %ds
+ /* Clear out 32-bit selector from FS and GS */
+ xorl %ebx, %ebx
+ movl %ebx, %fs
+ movl %ebx, %gs
+
+ /*
+ * Convert 32-bit status code into 64-bit.
+ */
+ roll $1, %eax
+ rorq $1, %rax
+
+ pop %rbx
+ pop %rbp
+ RET
+SYM_FUNC_END(__efi64_thunk)
+
+ .code32
+/*
+ * EFI service pointer must be in %edi.
+ *
+ * The stack should represent the 32-bit calling convention.
+ */
+SYM_FUNC_START_LOCAL(efi_enter32)
+ /* Load firmware selector into data and stack segment registers */
+ movl %edx, %ds
+ movl %edx, %es
+ movl %edx, %fs
+ movl %edx, %gs
+ movl %edx, %ss
+
+ /* Reload pgtables */
+ movl %cr3, %eax
+ movl %eax, %cr3
+
+ /* 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
+
+ /*
+ * Some firmware will return with interrupts enabled. Be sure to
+ * disable them before we switch GDTs and IDTs.
+ */
+ cli
+
+ lidtl (%ebx)
+ subl $16, %ebx
+
+ lgdtl (%ebx)
+
+ movl %cr4, %eax
+ btsl $(X86_CR4_PAE_BIT), %eax
+ movl %eax, %cr4
+
+ movl %cr3, %eax
+ movl %eax, %cr3
+
+ movl $MSR_EFER, %ecx
+ rdmsr
+ btsl $_EFER_LME, %eax
+ wrmsr
+
+ xorl %eax, %eax
+ lldt %ax
+
+ pushl $__KERNEL_CS
+ pushl %ebp
+
+ /* Enable paging */
+ movl %cr0, %eax
+ btsl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+ lret
+SYM_FUNC_END(efi_enter32)
+
+#define ST32_boottime 60 // offsetof(efi_system_table_32_t, boottime)
+#define BS32_handle_protocol 88 // offsetof(efi_boot_services_32_t, handle_protocol)
+#define LI32_image_base 32 // offsetof(efi_loaded_image_32_t, image_base)
+
+/*
+ * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
+ * efi_system_table_32_t *sys_table)
+ *
+ * This is the EFI compat entrypoint that will be invoked by the 32-bit EFI
+ * firmware directly (provided that it implements support for compat
+ * entrypoints).
+ */
+SYM_FUNC_START(efi32_pe_entry)
+ pushl %ebp
+ movl %esp, %ebp
+ pushl %eax // dummy push to allocate loaded_image
+
+ pushl %ebx // save callee-save registers
+ pushl %edi
+
+ call verify_cpu // check for long mode support
+ testl %eax, %eax
+ movl $0x80000003, %eax // EFI_UNSUPPORTED
+ jnz 2f
+
+ call 1f
+1: pop %ebx
+
+ /* Get the loaded image protocol pointer from the image handle */
+ leal -4(%ebp), %eax
+ pushl %eax // &loaded_image
+ leal (loaded_image_proto - 1b)(%ebx), %eax
+ pushl %eax // pass the GUID address
+ pushl 8(%ebp) // pass the image handle
+
+ /*
+ * Note the alignment of the stack frame.
+ * sys_table
+ * handle <-- 16-byte aligned on entry by ABI
+ * return address
+ * frame pointer
+ * loaded_image <-- local variable
+ * saved %ebx <-- 16-byte aligned here
+ * saved %edi
+ * &loaded_image
+ * &loaded_image_proto
+ * handle <-- 16-byte aligned for call to handle_protocol
+ */
+
+ movl 12(%ebp), %eax // sys_table
+ movl ST32_boottime(%eax), %eax // sys_table->boottime
+ call *BS32_handle_protocol(%eax) // sys_table->boottime->handle_protocol
+ addl $12, %esp // restore argument space
+ testl %eax, %eax
+ jnz 2f
+
+ movl 8(%ebp), %ecx // image_handle
+ movl 12(%ebp), %edx // sys_table
+ movl -4(%ebp), %esi // loaded_image
+ movl LI32_image_base(%esi), %esi // loaded_image->image_base
+ leal (startup_32 - 1b)(%ebx), %ebp // runtime address of startup_32
+ /*
+ * We need to set the image_offset variable here since startup_32() will
+ * use it before we get to the 64-bit efi_pe_entry() in C code.
+ */
+ subl %esi, %ebp
+ movl %ebp, (image_offset - 1b)(%ebx) // save image_offset
+ xorl %esi, %esi
+ jmp efi32_entry
+
+2: popl %edi // restore callee-save registers
+ popl %ebx
+ leave
+ RET
+SYM_FUNC_END(efi32_pe_entry)
+
+/*
+ * This is the EFI handover protocol entrypoint, which is invoked by jumping to
+ * an offset of 0x190 bytes into the kernel image after it has been loaded into
+ * memory by the EFI firmware or the bootloader.
+ */
+SYM_FUNC_START(efi32_handover)
+ add $0x4, %esp // Discard return address
+ popl %ecx
+ popl %edx
+ popl %esi
+ jmp efi32_entry
+SYM_FUNC_END(efi32_handover)
+
+SYM_FUNC_START_LOCAL(efi32_entry)
+ call 3f
+3: pop %ebx
+
+ /* Save firmware GDTR and code/data selectors */
+ sgdtl (efi32_boot_gdt - 3b)(%ebx)
+ movw %cs, (efi32_boot_cs - 3b)(%ebx)
+ movw %ds, (efi32_boot_ds - 3b)(%ebx)
+
+ /* Store firmware IDT descriptor */
+ sidtl (efi32_boot_idt - 3b)(%ebx)
+
+ leal (efi32_boot_args - 3b)(%ebx), %ebx
+ movl %ecx, 0(%ebx)
+ movl %edx, 4(%ebx)
+ movl %esi, 8(%ebx)
+ movb $0x0, 12(%ebx) // efi_is64
+
+ /* Disable paging */
+ movl %cr0, %eax
+ btrl $X86_CR0_PG_BIT, %eax
+ movl %eax, %cr0
+
+ jmp startup_32
+SYM_FUNC_END(efi32_entry)
+
+ .section ".rodata"
+ /* EFI loaded image protocol GUID */
+ .balign 4
+SYM_DATA_START_LOCAL(loaded_image_proto)
+ .long 0x5b1b31a1
+ .word 0x9562, 0x11d2
+ .byte 0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b
+SYM_DATA_END(loaded_image_proto)
+
+ .data
+ .balign 8
+SYM_DATA_START_LOCAL(efi32_boot_gdt)
+ .word 0
+ .quad 0
+SYM_DATA_END(efi32_boot_gdt)
+
+SYM_DATA_START_LOCAL(efi32_boot_idt)
+ .word 0
+ .quad 0
+SYM_DATA_END(efi32_boot_idt)
+
+SYM_DATA_LOCAL(efi32_boot_cs, .word 0)
+SYM_DATA_LOCAL(efi32_boot_ds, .word 0)
+SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
+SYM_DATA(efi_is64, .byte 1)
+
diff --git a/arch/x86/boot/compressed/efi_thunk_64.S b/arch/x86/boot/compressed/efi_thunk_64.S
deleted file mode 100644
index 67e7edcdfea8..000000000000
--- a/arch/x86/boot/compressed/efi_thunk_64.S
+++ /dev/null
@@ -1,195 +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/msr.h>
-#include <asm/page_types.h>
-#include <asm/processor-flags.h>
-#include <asm/segment.h>
-
- .code64
- .text
-SYM_FUNC_START(__efi64_thunk)
- push %rbp
- push %rbx
-
- movl %ds, %eax
- push %rax
- movl %es, %eax
- push %rax
- movl %ss, %eax
- push %rax
-
- /* Copy args passed on stack */
- movq 0x30(%rsp), %rbp
- movq 0x38(%rsp), %rbx
- movq 0x40(%rsp), %rax
-
- /*
- * Convert x86-64 ABI params to i386 ABI
- */
- subq $64, %rsp
- movl %esi, 0x0(%rsp)
- movl %edx, 0x4(%rsp)
- movl %ecx, 0x8(%rsp)
- movl %r8d, 0xc(%rsp)
- movl %r9d, 0x10(%rsp)
- movl %ebp, 0x14(%rsp)
- movl %ebx, 0x18(%rsp)
- movl %eax, 0x1c(%rsp)
-
- leaq 0x20(%rsp), %rbx
- sgdt (%rbx)
-
- addq $16, %rbx
- sidt (%rbx)
-
- leaq 1f(%rip), %rbp
-
- /*
- * Switch to IDT and GDT with 32-bit segments. This is the firmware GDT
- * and IDT that was installed when the kernel started executing. The
- * pointers were saved at the EFI stub entry point in head_64.S.
- *
- * Pass the saved DS selector to the 32-bit code, and use far return to
- * restore the saved CS selector.
- */
- leaq efi32_boot_idt(%rip), %rax
- lidt (%rax)
- leaq efi32_boot_gdt(%rip), %rax
- lgdt (%rax)
-
- movzwl efi32_boot_ds(%rip), %edx
- movzwq efi32_boot_cs(%rip), %rax
- pushq %rax
- leaq efi_enter32(%rip), %rax
- pushq %rax
- lretq
-
-1: addq $64, %rsp
- movq %rdi, %rax
-
- pop %rbx
- movl %ebx, %ss
- pop %rbx
- movl %ebx, %es
- pop %rbx
- movl %ebx, %ds
- /* Clear out 32-bit selector from FS and GS */
- xorl %ebx, %ebx
- movl %ebx, %fs
- movl %ebx, %gs
-
- /*
- * Convert 32-bit status code into 64-bit.
- */
- roll $1, %eax
- rorq $1, %rax
-
- pop %rbx
- pop %rbp
- RET
-SYM_FUNC_END(__efi64_thunk)
-
- .code32
-/*
- * EFI service pointer must be in %edi.
- *
- * The stack should represent the 32-bit calling convention.
- */
-SYM_FUNC_START_LOCAL(efi_enter32)
- /* Load firmware selector into data and stack segment registers */
- movl %edx, %ds
- movl %edx, %es
- movl %edx, %fs
- movl %edx, %gs
- movl %edx, %ss
-
- /* Reload pgtables */
- movl %cr3, %eax
- movl %eax, %cr3
-
- /* 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
-
- /*
- * Some firmware will return with interrupts enabled. Be sure to
- * disable them before we switch GDTs and IDTs.
- */
- cli
-
- lidtl (%ebx)
- subl $16, %ebx
-
- lgdtl (%ebx)
-
- movl %cr4, %eax
- btsl $(X86_CR4_PAE_BIT), %eax
- movl %eax, %cr4
-
- movl %cr3, %eax
- movl %eax, %cr3
-
- movl $MSR_EFER, %ecx
- rdmsr
- btsl $_EFER_LME, %eax
- wrmsr
-
- xorl %eax, %eax
- lldt %ax
-
- pushl $__KERNEL_CS
- pushl %ebp
-
- /* Enable paging */
- movl %cr0, %eax
- btsl $X86_CR0_PG_BIT, %eax
- movl %eax, %cr0
- lret
-SYM_FUNC_END(efi_enter32)
-
- .data
- .balign 8
-SYM_DATA_START(efi32_boot_gdt)
- .word 0
- .quad 0
-SYM_DATA_END(efi32_boot_gdt)
-
-SYM_DATA_START(efi32_boot_idt)
- .word 0
- .quad 0
-SYM_DATA_END(efi32_boot_idt)
-
-SYM_DATA_START(efi32_boot_cs)
- .word 0
-SYM_DATA_END(efi32_boot_cs)
-
-SYM_DATA_START(efi32_boot_ds)
- .word 0
-SYM_DATA_END(efi32_boot_ds)
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index 3b354eb9516d..6589ddd4cfaf 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -208,10 +208,6 @@ SYM_DATA_START_LOCAL(gdt)
.quad 0x00cf92000000ffff /* __KERNEL_DS */
SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end)
-#ifdef CONFIG_EFI_STUB
-SYM_DATA(image_offset, .long 0)
-#endif
-
/*
* Stack and heap for uncompression
*/
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index d33f060900d2..c2cdbd8a3375 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -259,32 +259,16 @@ SYM_FUNC_START(startup_32)
* We place all of the values on our mini stack so lret can
* used to perform that far jump.
*/
- leal rva(startup_64)(%ebp), %eax
#ifdef CONFIG_EFI_MIXED
- movl rva(efi32_boot_args)(%ebp), %edi
- testl %edi, %edi
- jz 1f
- leal rva(efi64_stub_entry)(%ebp), %eax
- movl rva(efi32_boot_args+4)(%ebp), %esi
- movl rva(efi32_boot_args+8)(%ebp), %edx // saved bootparams pointer
- testl %edx, %edx
- jnz 1f
- /*
- * efi_pe_entry uses MS calling convention, which requires 32 bytes of
- * shadow space on the stack even if all arguments are passed in
- * registers. We also need an additional 8 bytes for the space that
- * would be occupied by the return address, and this also results in
- * the correct stack alignment for entry.
- */
- subl $40, %esp
- leal rva(efi_pe_entry)(%ebp), %eax
- movl %edi, %ecx // MS calling convention
- movl %esi, %edx
-1:
+ cmpb $1, rva(efi_is64)(%ebp)
+ leal rva(startup_64_mixedmode)(%ebp), %eax
+ jne 1f
#endif
/* Check if the C-bit position is correct when SEV is active */
call startup32_check_sev_cbit
+ leal rva(startup_64)(%ebp), %eax
+1:
pushl $__KERNEL_CS
pushl %eax
@@ -299,35 +283,7 @@ SYM_FUNC_END(startup_32)
#ifdef CONFIG_EFI_MIXED
.org 0x190
SYM_FUNC_START(efi32_stub_entry)
- add $0x4, %esp /* Discard return address */
- popl %ecx
- popl %edx
- popl %esi
-
- call 1f
-1: pop %ebp
- subl $ rva(1b), %ebp
-
- movl %esi, rva(efi32_boot_args+8)(%ebp)
-SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL)
- movl %ecx, rva(efi32_boot_args)(%ebp)
- movl %edx, rva(efi32_boot_args+4)(%ebp)
- movb $0, rva(efi_is64)(%ebp)
-
- /* Save firmware GDTR and code/data selectors */
- sgdtl rva(efi32_boot_gdt)(%ebp)
- movw %cs, rva(efi32_boot_cs)(%ebp)
- movw %ds, rva(efi32_boot_ds)(%ebp)
-
- /* Store firmware IDT descriptor */
- sidtl rva(efi32_boot_idt)(%ebp)
-
- /* Disable paging */
- movl %cr0, %eax
- btrl $X86_CR0_PG_BIT, %eax
- movl %eax, %cr0
-
- jmp startup_32
+ jmp efi32_handover
SYM_FUNC_END(efi32_stub_entry)
#endif
@@ -713,6 +669,7 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lno_longmode)
jmp 1b
SYM_FUNC_END(.Lno_longmode)
+ .globl verify_cpu
#include "../../kernel/verify_cpu.S"
.data
@@ -757,98 +714,6 @@ SYM_DATA_START(boot32_idt)
SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
#endif
-#ifdef CONFIG_EFI_STUB
-SYM_DATA(image_offset, .long 0)
-#endif
-#ifdef CONFIG_EFI_MIXED
-SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0)
-SYM_DATA(efi_is64, .byte 1)
-
-#define ST32_boottime 60 // offsetof(efi_system_table_32_t, boottime)
-#define BS32_handle_protocol 88 // offsetof(efi_boot_services_32_t, handle_protocol)
-#define LI32_image_base 32 // offsetof(efi_loaded_image_32_t, image_base)
-
- __HEAD
- .code32
-SYM_FUNC_START(efi32_pe_entry)
-/*
- * efi_status_t efi32_pe_entry(efi_handle_t image_handle,
- * efi_system_table_32_t *sys_table)
- */
-
- pushl %ebp
- movl %esp, %ebp
- pushl %eax // dummy push to allocate loaded_image
-
- pushl %ebx // save callee-save registers
- pushl %edi
-
- call verify_cpu // check for long mode support
- testl %eax, %eax
- movl $0x80000003, %eax // EFI_UNSUPPORTED
- jnz 2f
-
- call 1f
-1: pop %ebx
- subl $ rva(1b), %ebx
-
- /* Get the loaded image protocol pointer from the image handle */
- leal -4(%ebp), %eax
- pushl %eax // &loaded_image
- leal rva(loaded_image_proto)(%ebx), %eax
- pushl %eax // pass the GUID address
- pushl 8(%ebp) // pass the image handle
-
- /*
- * Note the alignment of the stack frame.
- * sys_table
- * handle <-- 16-byte aligned on entry by ABI
- * return address
- * frame pointer
- * loaded_image <-- local variable
- * saved %ebx <-- 16-byte aligned here
- * saved %edi
- * &loaded_image
- * &loaded_image_proto
- * handle <-- 16-byte aligned for call to handle_protocol
- */
-
- movl 12(%ebp), %eax // sys_table
- movl ST32_boottime(%eax), %eax // sys_table->boottime
- call *BS32_handle_protocol(%eax) // sys_table->boottime->handle_protocol
- addl $12, %esp // restore argument space
- testl %eax, %eax
- jnz 2f
-
- movl 8(%ebp), %ecx // image_handle
- movl 12(%ebp), %edx // sys_table
- movl -4(%ebp), %esi // loaded_image
- movl LI32_image_base(%esi), %esi // loaded_image->image_base
- movl %ebx, %ebp // startup_32 for efi32_pe_stub_entry
- /*
- * We need to set the image_offset variable here since startup_32() will
- * use it before we get to the 64-bit efi_pe_entry() in C code.
- */
- subl %esi, %ebx
- movl %ebx, rva(image_offset)(%ebp) // save image_offset
- jmp efi32_pe_stub_entry
-
-2: popl %edi // restore callee-save registers
- popl %ebx
- leave
- RET
-SYM_FUNC_END(efi32_pe_entry)
-
- .section ".rodata"
- /* EFI loaded image protocol GUID */
- .balign 4
-SYM_DATA_START_LOCAL(loaded_image_proto)
- .long 0x5b1b31a1
- .word 0x9562, 0x11d2
- .byte 0x8e, 0x3f, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b
-SYM_DATA_END(loaded_image_proto)
-#endif
-
#ifdef CONFIG_AMD_MEM_ENCRYPT
__HEAD
.code32
diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 05ae8bcc9d67..d7b53dec01be 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -23,7 +23,8 @@
const efi_system_table_t *efi_system_table;
const efi_dxe_services_table_t *efi_dxe_table;
-extern u32 image_offset;
+
+u32 image_offset;
static efi_loaded_image_t *image = NULL;
static efi_status_t
--
2.35.1
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH 3/6] x86/compressed: move startup32_load_idt() out of startup code
2022-08-15 13:42 [PATCH 0/6] x86: head_64.S spring cleaning Ard Biesheuvel
2022-08-15 13:42 ` [PATCH 1/6] x86/head_64: clean up mixed mode 32-bit entry code Ard Biesheuvel
2022-08-15 13:42 ` [PATCH 2/6] efi/x86: simplify IDT/GDT preserve/restore Ard Biesheuvel
@ 2022-08-15 13:42 ` Ard Biesheuvel
2022-08-15 13:42 ` [PATCH 4/6] x86/compressed: move startup32_check_sev_cbit " Ard Biesheuvel
` (3 subsequent siblings)
6 siblings, 0 replies; 9+ messages in thread
From: Ard Biesheuvel @ 2022-08-15 13:42 UTC (permalink / raw)
To: linux-kernel
Cc: linux-efi, Ard Biesheuvel, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, Michael Roth
Move the function startup32_load_idt() into mem_encrypt.S, and turn it
into an ordinary function, instead of relying on hidden register
arguments and non-standard calling conventions.
While at it, simplify the arithmetic involved in populating a IDT entry.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/head_64.S | 71 +------------------
arch/x86/boot/compressed/mem_encrypt.S | 72 ++++++++++++++++++--
2 files changed, 69 insertions(+), 74 deletions(-)
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index c2cdbd8a3375..1ca2ed52f93c 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -118,7 +118,9 @@ SYM_FUNC_START(startup_32)
1:
/* Setup Exception handling for SEV-ES */
+#ifdef CONFIG_AMD_MEM_ENCRYPT
call startup32_load_idt
+#endif
/* Make sure cpu supports long mode. */
call verify_cpu
@@ -701,80 +703,11 @@ SYM_DATA_START(boot_idt)
.endr
SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end)
-#ifdef CONFIG_AMD_MEM_ENCRYPT
-SYM_DATA_START(boot32_idt_desc)
- .word boot32_idt_end - boot32_idt - 1
- .long 0
-SYM_DATA_END(boot32_idt_desc)
- .balign 8
-SYM_DATA_START(boot32_idt)
- .rept 32
- .quad 0
- .endr
-SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
-#endif
-
#ifdef CONFIG_AMD_MEM_ENCRYPT
__HEAD
.code32
-/*
- * Write an IDT entry into boot32_idt
- *
- * Parameters:
- *
- * %eax: Handler address
- * %edx: Vector number
- *
- * Physical offset is expected in %ebp
- */
-SYM_FUNC_START(startup32_set_idt_entry)
- push %ebx
- push %ecx
-
- /* IDT entry address to %ebx */
- leal rva(boot32_idt)(%ebp), %ebx
- shl $3, %edx
- addl %edx, %ebx
-
- /* Build IDT entry, lower 4 bytes */
- movl %eax, %edx
- andl $0x0000ffff, %edx # Target code segment offset [15:0]
- movl $__KERNEL32_CS, %ecx # Target code segment selector
- shl $16, %ecx
- orl %ecx, %edx
-
- /* Store lower 4 bytes to IDT */
- movl %edx, (%ebx)
-
- /* Build IDT entry, upper 4 bytes */
- movl %eax, %edx
- andl $0xffff0000, %edx # Target code segment offset [31:16]
- orl $0x00008e00, %edx # Present, Type 32-bit Interrupt Gate
-
- /* Store upper 4 bytes to IDT */
- movl %edx, 4(%ebx)
-
- pop %ecx
- pop %ebx
- RET
-SYM_FUNC_END(startup32_set_idt_entry)
#endif
-SYM_FUNC_START(startup32_load_idt)
-#ifdef CONFIG_AMD_MEM_ENCRYPT
- /* #VC handler */
- leal rva(startup32_vc_handler)(%ebp), %eax
- movl $X86_TRAP_VC, %edx
- call startup32_set_idt_entry
-
- /* Load IDT */
- leal rva(boot32_idt)(%ebp), %eax
- movl %eax, rva(boot32_idt_desc+2)(%ebp)
- lidt rva(boot32_idt_desc)(%ebp)
-#endif
- RET
-SYM_FUNC_END(startup32_load_idt)
-
/*
* Check for the correct C-bit position when the startup_32 boot-path is used.
*
diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
index a73e4d783cae..889450d073ea 100644
--- a/arch/x86/boot/compressed/mem_encrypt.S
+++ b/arch/x86/boot/compressed/mem_encrypt.S
@@ -11,9 +11,14 @@
#include <asm/processor-flags.h>
#include <asm/msr.h>
+#include <asm/segment.h>
+#include <asm/trapnr.h>
#include <asm/asm-offsets.h>
.text
+ .code64
+#include "../../kernel/sev_verify_cbit.S"
+
.code32
SYM_FUNC_START(get_sev_encryption_bit)
xor %eax, %eax
@@ -61,6 +66,8 @@ SYM_FUNC_START(get_sev_encryption_bit)
RET
SYM_FUNC_END(get_sev_encryption_bit)
+#ifdef CONFIG_AMD_MEM_ENCRYPT
+
/**
* sev_es_req_cpuid - Request a CPUID value from the Hypervisor using
* the GHCB MSR protocol
@@ -98,7 +105,7 @@ SYM_CODE_START_LOCAL(sev_es_req_cpuid)
jmp 1b
SYM_CODE_END(sev_es_req_cpuid)
-SYM_CODE_START(startup32_vc_handler)
+SYM_CODE_START_LOCAL(startup32_vc_handler)
pushl %eax
pushl %ebx
pushl %ecx
@@ -184,15 +191,70 @@ SYM_CODE_START(startup32_vc_handler)
jmp .Lfail
SYM_CODE_END(startup32_vc_handler)
- .code64
+/*
+ * Write an IDT entry
+ *
+ * Parameters:
+ *
+ * %eax: Handler address
+ * %edx: Vector number
+ * %ecx: IDT address
+ */
+SYM_FUNC_START_LOCAL(startup32_set_idt_entry)
+ /* IDT entry address to %ecx */
+ leal (%ecx, %edx, 8), %ecx
+
+ /* Build IDT entry */
+ movl %eax, %edx
+ andl $0x0000ffff, %edx # Target code segment offset [15:0]
+ andl $0xffff0000, %eax # Target code segment offset [31:16]
+ orl $(__KERNEL32_CS << 16), %edx # Target code segment selector
+ orl $0x00008e00, %eax # Present, Type 32-bit Interrupt Gate
+
+ /* Store entry to IDT */
+ movl %edx, (%ecx)
+ movl %eax, 4(%ecx)
+ RET
+SYM_FUNC_END(startup32_set_idt_entry)
-#include "../../kernel/sev_verify_cbit.S"
+SYM_FUNC_START(startup32_load_idt)
+ push %ebp
+ push %ebx
- .data
+ call 1f
+1: pop %ebp
+ leal (boot32_idt - 1b)(%ebp), %ebx
-#ifdef CONFIG_AMD_MEM_ENCRYPT
+ /* #VC handler */
+ leal (startup32_vc_handler - 1b)(%ebp), %eax
+ movl $X86_TRAP_VC, %edx
+ movl %ebx, %ecx
+ call startup32_set_idt_entry
+
+ /* Load IDT */
+ leal (boot32_idt_desc - 1b)(%ebp), %ecx
+ movl %ebx, 2(%ecx)
+ lidt (%ecx)
+
+ pop %ebx
+ pop %ebp
+ RET
+SYM_FUNC_END(startup32_load_idt)
+
+ .data
.balign 8
SYM_DATA(sme_me_mask, .quad 0)
SYM_DATA(sev_status, .quad 0)
SYM_DATA(sev_check_data, .quad 0)
+
+SYM_DATA_START_LOCAL(boot32_idt)
+ .rept 32
+ .quad 0
+ .endr
+SYM_DATA_END(boot32_idt)
+
+SYM_DATA_START_LOCAL(boot32_idt_desc)
+ .word . - boot32_idt - 1
+ .long 0
+SYM_DATA_END(boot32_idt_desc)
#endif
--
2.35.1
^ permalink raw reply related [flat|nested] 9+ messages in thread