diff options
author | Ard Biesheuvel <ardb@kernel.org> | 2020-02-13 01:20:54 +0300 |
---|---|---|
committer | Ard Biesheuvel <ardb@kernel.org> | 2020-02-23 23:59:42 +0300 |
commit | 17054f492dfd4d91e093ebb87013807812ec42a4 (patch) | |
tree | 76a0f59fe30fed885de6c1962e49d5c1e0a67340 /arch/x86/boot | |
parent | 3b8f44fc0810d51b58837cf7fdba3f72f8cffcdc (diff) | |
download | linux-17054f492dfd4d91e093ebb87013807812ec42a4.tar.xz |
efi/x86: Implement mixed mode boot without the handover protocol
Add support for booting 64-bit x86 kernels from 32-bit firmware running
on 64-bit capable CPUs without requiring the bootloader to implement
the EFI handover protocol or allocate the setup block, etc etc, all of
which can be done by the stub itself, using code that already exists.
Instead, create an ordinary EFI application entrypoint but implemented
in 32-bit code [so that it can be invoked by 32-bit firmware], and stash
the address of this 32-bit entrypoint in the .compat section where the
bootloader can find it.
Note that we use the setup block embedded in the binary to go through
startup_32(), but it gets reallocated and copied in efi_pe_entry(),
using the same code that runs when the x86 kernel is booted in EFI
mode from native firmware. This requires the loaded image protocol to
be installed on the kernel image's EFI handle, and point to the kernel
image itself and not to its loader. This, in turn, requires the
bootloader to use the LoadImage() boot service to load the 64-bit
image from 32-bit firmware, which is in fact supported by firmware
based on EDK2. (Only StartImage() will fail, and instead, the newly
added entrypoint needs to be invoked)
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'arch/x86/boot')
-rw-r--r-- | arch/x86/boot/compressed/head_64.S | 59 |
1 files changed, 57 insertions, 2 deletions
diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index a4f5561c1c0e..f7bacc4c1494 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -207,8 +207,13 @@ SYM_FUNC_START(startup_32) cmp $0, %edi jz 1f leal efi64_stub_entry(%ebp), %eax - movl %esi, %edx movl efi32_boot_args+4(%ebp), %esi + movl efi32_boot_args+8(%ebp), %edx // saved bootparams pointer + cmpl $0, %edx + jnz 1f + leal efi_pe_entry(%ebp), %eax + movl %edi, %ecx // MS calling convention + movl %esi, %edx 1: #endif pushl %eax @@ -233,6 +238,8 @@ SYM_FUNC_START(efi32_stub_entry) 1: pop %ebp subl $1b, %ebp + movl %esi, efi32_boot_args+8(%ebp) +SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL) movl %ecx, efi32_boot_args(%ebp) movl %edx, efi32_boot_args+4(%ebp) movb $0, efi_is64(%ebp) @@ -641,8 +648,56 @@ SYM_DATA_START_LOCAL(gdt) SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end) #ifdef CONFIG_EFI_MIXED -SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0) +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) + + .text + .code32 +SYM_FUNC_START(efi32_pe_entry) + pushl %ebp + + call verify_cpu // check for long mode support + testl %eax, %eax + movl $0x80000003, %eax // EFI_UNSUPPORTED + jnz 3f + + call 1f +1: pop %ebp + subl $1b, %ebp + + /* Get the loaded image protocol pointer from the image handle */ + subl $12, %esp // space for the loaded image pointer + pushl %esp // pass its address + leal 4f(%ebp), %eax + pushl %eax // pass the GUID address + pushl 28(%esp) // pass the image handle + + movl 36(%esp), %eax // sys_table + movl ST32_boottime(%eax), %eax // sys_table->boottime + call *BS32_handle_protocol(%eax) // sys_table->boottime->handle_protocol + cmp $0, %eax + jnz 2f + + movl 32(%esp), %ecx // image_handle + movl 36(%esp), %edx // sys_table + movl 12(%esp), %esi // loaded_image + movl LI32_image_base(%esi), %esi // loaded_image->image_base + jmp efi32_pe_stub_entry + +2: addl $24, %esp +3: popl %ebp + ret +SYM_FUNC_END(efi32_pe_entry) + + .section ".rodata" + /* EFI loaded image protocol GUID */ +4: .long 0x5B1B31A1 + .word 0x9562, 0x11d2 + .byte 0x8E, 0x3F, 0x00, 0xA0, 0xC9, 0x69, 0x72, 0x3B #endif /* |