The UEFI specification requires a 128KiB stack during boot services. On a native mode boot, the EFI stub executes on the firmware stack. However, on a mixed-mode boot, startup_32 switches to the kernel's boot stack, which is only 16KiB, and the EFI stub is executed with this stack. To avoid any potential problems with running out of stack space, save and restore the UEFI stack pointer in the mixed-mode entry, so that the EFI stub can use the firmware stack in this case as well. Signed-off-by: Arvind Sankar <nivedita@xxxxxxxxxxxx> --- arch/x86/boot/compressed/head_64.S | 46 ++++++++++++++++++++---------- 1 file changed, 31 insertions(+), 15 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 4b7ad1dfbea6..923e5c381804 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -237,21 +237,7 @@ SYM_FUNC_START(startup_32) * used to perform that far jump. */ pushl $__KERNEL_CS - leal rva(startup_64)(%ebp), %eax -#ifdef CONFIG_EFI_MIXED - movl rva(efi32_boot_args)(%ebp), %edi - cmp $0, %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 - cmpl $0, %edx - jnz 1f - leal rva(efi_pe_entry)(%ebp), %eax - movl %edi, %ecx // MS calling convention - movl %esi, %edx -1: -#endif + leal rva(.L64bit)(%ebp), %eax pushl %eax /* Enter paged protected Mode, activating Long Mode */ @@ -260,6 +246,31 @@ SYM_FUNC_START(startup_32) /* Jump from 32bit compatibility mode into 64bit mode. */ lret + + .code64 +SYM_INNER_LABEL(.L64bit, SYM_L_LOCAL) +#ifndef CONFIG_EFI_MIXED + jmp startup_64 +#else + movl efi32_boot_args(%rip), %edi + testl %edi, %edi + jz startup_64 + + /* Restore firmware stack pointer */ + movl efi32_boot_sp(%rip), %esp + /* and align it to 8 mod 16 */ + andl $~0xf, %esp + subl $8, %esp + + movl efi32_boot_args+4(%rip), %esi + movl efi32_boot_args+8(%rip), %edx // saved bootparams pointer + testl %edx, %edx + jnz efi64_stub_entry + movl %edi, %ecx // MS calling convention + movl %esi, %edx + jmp efi_pe_entry +#endif + .code32 SYM_FUNC_END(startup_32) #ifdef CONFIG_EFI_MIXED @@ -285,6 +296,9 @@ SYM_INNER_LABEL(efi32_pe_stub_entry, SYM_L_LOCAL) movw %cs, rva(efi32_boot_cs)(%ebp) movw %ds, rva(efi32_boot_ds)(%ebp) + /* Save firmware stack pointer */ + movl %esp, rva(efi32_boot_sp)(%ebp) + /* Disable paging */ movl %cr0, %eax btrl $X86_CR0_PG_BIT, %eax @@ -648,6 +662,7 @@ SYM_DATA(image_offset, .long 0) #ifdef CONFIG_EFI_MIXED SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0, 0) +SYM_DATA_LOCAL(efi32_boot_sp, .long 0) SYM_DATA(efi_is64, .byte 1) #define ST32_boottime 60 // offsetof(efi_system_table_32_t, boottime) @@ -710,6 +725,7 @@ SYM_FUNC_START(efi32_pe_entry) movl 12(%ebp), %edx // sys_table movl -4(%ebp), %esi // loaded_image movl LI32_image_base(%esi), %esi // loaded_image->image_base + leave // clear stack frame movl %ebx, %ebp // startup_32 for efi32_pe_stub_entry /* * We need to set the image_offset variable here since startup_32() will -- 2.26.2
