lkml.org 
[lkml]   [2020]   [Jan]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 09/20] efi/x86: simplify 64-bit EFI firmware call wrapper
Date
The efi_call() wrapper used to invoke EFI runtime services serves
a number of purposes:
- realign the stack to 16 bytes
- preserve FP and CR0 register state
- translate from SysV to MS calling convention.

Preserving CR0.TS is no longer necessary in Linux, and preserving the
FP register state is also redundant in most cases, since efi_call() is
almost always used from within the scope of a pair of kernel_fpu_begin()/
kernel_fpu_end() calls, with the exception of the early call to
SetVirtualAddressMap() and the SGI UV support code.

So let's add a pair of kernel_fpu_begin()/_end() calls there as well,
and remove the unnecessary code from the assembly implementation of
efi_call(), and only keep the pieces that deal with the stack
alignment and the ABI translation.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/platform/efi/Makefile | 1 -
arch/x86/platform/efi/efi_64.c | 3 +++
arch/x86/platform/efi/efi_stub_64.S | 39 +++--------------------------
arch/x86/platform/uv/bios_uv.c | 7 ++++--
4 files changed, 12 insertions(+), 38 deletions(-)

diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index fe29f3f5d384..7ec3a8b31f8b 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -1,6 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
OBJECT_FILES_NON_STANDARD_efi_thunk_$(BITS).o := y
-OBJECT_FILES_NON_STANDARD_efi_stub_$(BITS).o := y

obj-$(CONFIG_EFI) += quirks.o efi.o efi_$(BITS).o efi_stub_$(BITS).o
obj-$(CONFIG_EFI_MIXED) += efi_thunk_$(BITS).o
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index a7f11d1ff7c4..03565dad0c4b 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -1019,6 +1019,8 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
efi_switch_mm(&efi_mm);
}

+ kernel_fpu_begin();
+
/* Disable interrupts around EFI calls: */
local_irq_save(flags);
status = efi_call(efi.systab->runtime->set_virtual_address_map,
@@ -1026,6 +1028,7 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
descriptor_version, virtual_map);
local_irq_restore(flags);

+ kernel_fpu_end();

if (save_pgd)
efi_old_memmap_phys_epilog(save_pgd);
diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S
index b1d2313fe3bf..e7e1020f4ccb 100644
--- a/arch/x86/platform/efi/efi_stub_64.S
+++ b/arch/x86/platform/efi/efi_stub_64.S
@@ -8,41 +8,12 @@
*/

#include <linux/linkage.h>
-#include <asm/segment.h>
-#include <asm/msr.h>
-#include <asm/processor-flags.h>
-#include <asm/page_types.h>
-
-#define SAVE_XMM \
- mov %rsp, %rax; \
- subq $0x70, %rsp; \
- and $~0xf, %rsp; \
- mov %rax, (%rsp); \
- mov %cr0, %rax; \
- clts; \
- mov %rax, 0x8(%rsp); \
- movaps %xmm0, 0x60(%rsp); \
- movaps %xmm1, 0x50(%rsp); \
- movaps %xmm2, 0x40(%rsp); \
- movaps %xmm3, 0x30(%rsp); \
- movaps %xmm4, 0x20(%rsp); \
- movaps %xmm5, 0x10(%rsp)
-
-#define RESTORE_XMM \
- movaps 0x60(%rsp), %xmm0; \
- movaps 0x50(%rsp), %xmm1; \
- movaps 0x40(%rsp), %xmm2; \
- movaps 0x30(%rsp), %xmm3; \
- movaps 0x20(%rsp), %xmm4; \
- movaps 0x10(%rsp), %xmm5; \
- mov 0x8(%rsp), %rsi; \
- mov %rsi, %cr0; \
- mov (%rsp), %rsp
+#include <asm/nospec-branch.h>

SYM_FUNC_START(efi_call)
pushq %rbp
movq %rsp, %rbp
- SAVE_XMM
+ and $~0xf, %rsp
mov 16(%rbp), %rax
subq $48, %rsp
mov %r9, 32(%rsp)
@@ -50,9 +21,7 @@ SYM_FUNC_START(efi_call)
mov %r8, %r9
mov %rcx, %r8
mov %rsi, %rcx
- call *%rdi
- addq $48, %rsp
- RESTORE_XMM
- popq %rbp
+ CALL_NOSPEC %rdi
+ leave
ret
SYM_FUNC_END(efi_call)
diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c
index ece9cb9c1189..5c0e2eb5d87c 100644
--- a/arch/x86/platform/uv/bios_uv.c
+++ b/arch/x86/platform/uv/bios_uv.c
@@ -34,10 +34,13 @@ static s64 __uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3,
* If EFI_OLD_MEMMAP is set, we need to fall back to using our old EFI
* callback method, which uses efi_call() directly, with the kernel page tables:
*/
- if (unlikely(efi_enabled(EFI_OLD_MEMMAP)))
+ if (unlikely(efi_enabled(EFI_OLD_MEMMAP))) {
+ kernel_fpu_begin();
ret = efi_call((void *)__va(tab->function), (u64)which, a1, a2, a3, a4, a5);
- else
+ kernel_fpu_end();
+ } else {
ret = efi_call_virt_pointer(tab, function, (u64)which, a1, a2, a3, a4, a5);
+ }

return ret;
}
--
2.20.1
\
 
 \ /
  Last update: 2020-01-03 12:40    [W:0.145 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site