@@ -207,8 +207,8 @@ 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
1:
#endif
pushl %eax
@@ -233,6 +233,8 @@ SYM_FUNC_START(efi32_stub_entry)
1: pop %ebp
subl $1b, %ebp
+ movl %esi, efi32_boot_args+8(%ebp)
+2:
movl %ecx, efi32_boot_args(%ebp)
movl %edx, efi32_boot_args+4(%ebp)
movb $0, efi_is64(%ebp)
@@ -249,6 +251,49 @@ SYM_FUNC_START(efi32_stub_entry)
jmp startup_32
SYM_FUNC_END(efi32_stub_entry)
+
+#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)
+
+ .subsection 1
+ .code32
+SYM_FUNC_START(efi32_pe_entry)
+ pushl %ebp
+
+ call 3f
+3: pop %ebp
+ subl $3b, %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 5f(%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 4f
+
+ 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 2b
+
+4: addl $24, %esp
+ popl %ebp
+ ret
+SYM_FUNC_END(efi32_pe_entry)
+
+ /* EFI loaded image protocol GUID */
+5: .long 0x5B1B31A1
+ .word 0x9562, 0x11d2
+ .byte 0x8E, 0x3F, 0x00, 0xA0, 0xC9, 0x69, 0x72, 0x3B
+ .previous
#endif
.code64
@@ -465,11 +510,23 @@ SYM_CODE_END(startup_64)
SYM_FUNC_START(efi64_stub_entry)
SYM_FUNC_START_ALIAS(efi_stub_entry)
and $~0xf, %rsp /* realign the stack */
+#ifdef CONFIG_EFI_MIXED
+ cmpl $0, %edx
+ jz 0f
+#endif
call efi_main
movq %rax,%rsi
movl BP_code32_start(%esi), %eax
leaq startup_64(%rax), %rax
jmp *%rax
+
+#ifdef CONFIG_EFI_MIXED
+0: movl %edi, %ecx // MS calling convention
+ movl %esi, %edx
+ call efi_pe_entry
+1: hlt
+ jmp 1b
+#endif
SYM_FUNC_END(efi64_stub_entry)
SYM_FUNC_END_ALIAS(efi_stub_entry)
#endif
@@ -641,7 +698,7 @@ 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)
#endif
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, allocate the setup block etc etc, all of which can be done by the stub using code we have already implemented. 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 services 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> --- arch/x86/boot/compressed/head_64.S | 61 +++++++++++++++++++- 1 file changed, 59 insertions(+), 2 deletions(-)