6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Ard Biesheuvel ardb@kernel.org
commit 5c3a85f35b583259cf5ca0344cd79c8899ba1bb7 upstream.
Move the logic that chooses between the different EFI entrypoints out of the 32-bit boot path, and into a 64-bit helper that can perform the same task much more cleanly. While at it, document the mixed mode boot flow in a code comment.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Borislav Petkov bp@suse.de Link: https://lore.kernel.org/r/20221122161017.2426828-4-ardb@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/boot/compressed/efi_mixed.S | 43 +++++++++++++++++++++++++++++++++++ arch/x86/boot/compressed/head_64.S | 24 +++---------------- 2 files changed, 47 insertions(+), 20 deletions(-)
--- a/arch/x86/boot/compressed/efi_mixed.S +++ b/arch/x86/boot/compressed/efi_mixed.S @@ -22,6 +22,49 @@
.code64 .text +/* + * When booting in 64-bit mode on 32-bit EFI firmware, startup_64_mixed_mode() + * is the first thing that runs after switching to long mode. Depending on + * whether the EFI handover protocol or the compat entry point was used to + * enter the kernel, it 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 the presence of such a + * pointer is used to disambiguate. + * + * +--------------+ + * +------------------+ +------------+ +------>| efi_pe_entry | + * | efi32_pe_entry |---->| | | +-----------+--+ + * +------------------+ | | +------+----------------+ | + * | startup_32 |---->| startup_64_mixed_mode | | + * +------------------+ | | +------+----------------+ V + * | efi32_stub_entry |---->| | | +------------------+ + * +------------------+ +------------+ +---->| efi64_stub_entry | + * +-------------+----+ + * +------------+ +----------+ | + * | startup_64 |<----| efi_main |<--------------+ + * +------------+ +----------+ + */ +SYM_FUNC_START(startup_64_mixed_mode) + 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_mixed_mode) + SYM_FUNC_START(__efi64_thunk) push %rbp push %rbx --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -261,25 +261,9 @@ SYM_FUNC_START(startup_32) */ 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 + cmpb $1, rva(efi_is64)(%ebp) + je 1f + leal rva(startup_64_mixed_mode)(%ebp), %eax 1: #endif /* Check if the C-bit position is correct when SEV is active */ @@ -795,7 +779,7 @@ SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLO SYM_DATA(image_offset, .long 0) #endif #ifdef CONFIG_EFI_MIXED -SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0) +SYM_DATA(efi32_boot_args, .long 0, 0, 0) SYM_DATA(efi_is64, .byte 1)
#define ST32_boottime 60 // offsetof(efi_system_table_32_t, boottime)