From: Ard Biesheuvel <ardb@kernel.org>
To: linux-efi@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>
Cc: Ard Biesheuvel <ardb@kernel.org>,
linux-kernel@vger.kernel.org,
Anshuman Khandual <anshuman.khandual@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Dan Williams <dan.j.williams@intel.com>,
Dave Young <dyoung@redhat.com>,
Saravana Kannan <saravanak@google.com>
Subject: [PATCH 02/13] efi/libstub/x86: use mandatory 16-byte stack alignment in mixed mode
Date: Mon, 13 Jan 2020 18:22:34 +0100 [thread overview]
Message-ID: <20200113172245.27925-3-ardb@kernel.org> (raw)
In-Reply-To: <20200113172245.27925-1-ardb@kernel.org>
Reduce the stack frame of the EFI stub's mixed mode thunk routine by
8 bytes, by moving the GDT and return addresses to EBP and EBX, which
we need to preserve anyway, since their top halves will be cleared by
the call into 32-bit firmware code. Doing so results in the UEFI code
being entered with a 16 byte aligned stack, as mandated by the UEFI
spec, fixing the last occurrence in the 64-bit kernel where we violate
this requirement.
Also, move the saved GDT from a global variable to an unused part of the
stack frame, and touch up some other parts of the code.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/efi_thunk_64.S | 46 +++++++------------------
1 file changed, 13 insertions(+), 33 deletions(-)
diff --git a/arch/x86/boot/compressed/efi_thunk_64.S b/arch/x86/boot/compressed/efi_thunk_64.S
index d040ff5458e5..8fb7f6799c52 100644
--- a/arch/x86/boot/compressed/efi_thunk_64.S
+++ b/arch/x86/boot/compressed/efi_thunk_64.S
@@ -27,12 +27,9 @@ SYM_FUNC_START(__efi64_thunk)
push %rbp
push %rbx
- subq $8, %rsp
- leaq 1f(%rip), %rax
- movl %eax, 4(%rsp)
- leaq efi_gdt64(%rip), %rax
- movl %eax, (%rsp)
- movl %eax, 2(%rax) /* Fixup the gdt base address */
+ leaq 1f(%rip), %rbp
+ leaq efi_gdt64(%rip), %rbx
+ movl %ebx, 2(%rbx) /* Fixup the gdt base address */
movl %ds, %eax
push %rax
@@ -48,12 +45,10 @@ SYM_FUNC_START(__efi64_thunk)
movl %esi, 0x0(%rsp)
movl %edx, 0x4(%rsp)
movl %ecx, 0x8(%rsp)
- movq %r8, %rsi
- movl %esi, 0xc(%rsp)
- movq %r9, %rsi
- movl %esi, 0x10(%rsp)
+ movl %r8d, 0xc(%rsp)
+ movl %r9d, 0x10(%rsp)
- sgdt save_gdt(%rip)
+ sgdt 0x14(%rsp)
/*
* Switch to gdt with 32-bit segments. This is the firmware GDT
@@ -68,11 +63,10 @@ SYM_FUNC_START(__efi64_thunk)
pushq %rax
lretq
-1: addq $32, %rsp
+1: lgdt 0x14(%rsp)
+ addq $32, %rsp
movq %rdi, %rax
- lgdt save_gdt(%rip)
-
pop %rbx
movl %ebx, %ss
pop %rbx
@@ -83,15 +77,9 @@ SYM_FUNC_START(__efi64_thunk)
/*
* Convert 32-bit status code into 64-bit.
*/
- test %rax, %rax
- jz 1f
- movl %eax, %ecx
- andl $0x0fffffff, %ecx
- andl $0xf0000000, %eax
- shl $32, %rax
- or %rcx, %rax
-1:
- addq $8, %rsp
+ roll $1, %eax
+ rorq $1, %rax
+
pop %rbx
pop %rbp
ret
@@ -135,9 +123,7 @@ SYM_FUNC_START_LOCAL(efi_enter32)
*/
cli
- movl 56(%esp), %eax
- movl %eax, 2(%eax)
- lgdtl (%eax)
+ lgdtl (%ebx)
movl %cr4, %eax
btsl $(X86_CR4_PAE_BIT), %eax
@@ -154,9 +140,8 @@ SYM_FUNC_START_LOCAL(efi_enter32)
xorl %eax, %eax
lldt %ax
- movl 60(%esp), %eax
pushl $__KERNEL_CS
- pushl %eax
+ pushl %ebp
/* Enable paging */
movl %cr0, %eax
@@ -172,11 +157,6 @@ SYM_DATA_START(efi32_boot_gdt)
.quad 0
SYM_DATA_END(efi32_boot_gdt)
-SYM_DATA_START_LOCAL(save_gdt)
- .word 0
- .quad 0
-SYM_DATA_END(save_gdt)
-
SYM_DATA_START(efi_gdt64)
.word efi_gdt64_end - efi_gdt64
.long 0 /* Filled out by user */
--
2.20.1
next prev parent reply other threads:[~2020-01-13 17:23 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-13 17:22 [GIT PULL 00/13] More EFI updates for v5.6 Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 01/13] efi/libstub/x86: use const attribute for efi_is_64bit() Ard Biesheuvel
2020-01-13 17:22 ` Ard Biesheuvel [this message]
2020-01-13 17:22 ` [PATCH 03/13] efi/libstub/x86: fix unused-variable warning Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 04/13] x86/mm: fix NX bit clearing issue in kernel_map_pages_in_pgd Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 05/13] efi/x86: don't map the entire kernel text RW for mixed mode Ard Biesheuvel
2020-04-08 10:42 ` Jiri Slaby
2020-04-08 10:47 ` Ard Biesheuvel
2020-04-08 10:51 ` Jiri Slaby
2020-04-09 7:51 ` Ard Biesheuvel
2020-04-09 8:06 ` Gary Lin
2020-04-09 8:10 ` Jiri Slaby
2020-04-09 8:19 ` Ard Biesheuvel
2020-04-09 8:34 ` Jiri Slaby
2020-04-09 9:09 ` Ard Biesheuvel
2020-04-09 9:45 ` Ard Biesheuvel
2020-04-09 10:09 ` Jiri Slaby
2020-04-09 10:45 ` Ard Biesheuvel
2020-04-09 11:08 ` Ard Biesheuvel
2020-04-09 11:25 ` Ard Biesheuvel
2020-04-09 11:32 ` Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 06/13] efi/x86: avoid RWX mappings for all of DRAM Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 07/13] efi/x86: limit EFI old memory map to SGI UV machines Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 08/13] efi/arm: defer probe of PCIe backed efifb on DT systems Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 09/13] efi: Fix comment for efi_mem_type() wrt absent physical addresses Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 10/13] efi: Add a flags parameter to efi_memory_map Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 11/13] efi: Add tracking for dynamically allocated memmaps Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 12/13] efi: Fix efi_memmap_alloc() leaks Ard Biesheuvel
2020-01-13 17:22 ` [PATCH 13/13] efi: Fix handling of multiple efi_fake_mem= entries Ard Biesheuvel
2020-01-20 8:25 ` [GIT PULL 00/13] More EFI updates for v5.6 Ingo Molnar
2020-01-20 8:45 ` Ard Biesheuvel
2020-01-22 7:03 ` Ingo Molnar
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