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efi/libstub/x86: Use const attribute for efi_is_64bit()

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Reshuffle the x86 stub code a bit so that we can tag the efi_is_64bit()
function with the 'const' attribute, which permits the compiler to
optimize away any redundant calls. Since we have two different entry
points for 32 and 64 bit firmware in the startup code, this also
simplifies the C code since we'll enter it with the efi_is64 variable
already set.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200113172245.27925-2-ardb@kernel.org
This commit is contained in:
Ard Biesheuvel 2020-01-13 18:22:33 +01:00 committed by Ingo Molnar
parent a786810cc8
commit 796eb8d26a
3 changed files with 10 additions and 13 deletions
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14
arch/x86/boot/compressed/eboot.c
View File

@ -21,16 +21,18 @@
#include "eboot.h"
static efi_system_table_t *sys_table;
static bool efi_is64 = IS_ENABLED(CONFIG_X86_64);
extern const bool efi_is64;
__pure efi_system_table_t *efi_system_table(void)
{
return sys_table;
}
__pure bool efi_is_64bit(void)
__attribute_const__ bool efi_is_64bit(void)
{
return efi_is64;
if (IS_ENABLED(CONFIG_EFI_MIXED))
return efi_is64;
return IS_ENABLED(CONFIG_X64_64);
}
static efi_status_t
@ -710,8 +712,7 @@ static efi_status_t exit_boot(struct boot_params *boot_params, void *handle)
*/
struct boot_params *efi_main(efi_handle_t handle,
efi_system_table_t *sys_table_arg,
struct boot_params *boot_params,
bool is64)
struct boot_params *boot_params)
{
struct desc_ptr *gdt = NULL;
struct setup_header *hdr = &boot_params->hdr;
@ -721,9 +722,6 @@ struct boot_params *efi_main(efi_handle_t handle,
sys_table = sys_table_arg;
if (IS_ENABLED(CONFIG_EFI_MIXED))
efi_is64 = is64;
/* Check if we were booted by the EFI firmware */
if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE)
goto fail;

7
arch/x86/boot/compressed/head_64.S
View File

@ -211,10 +211,9 @@ SYM_FUNC_START(startup_32)
movl efi32_boot_args(%ebp), %edi
cmp $0, %edi
jz 1f
leal handover_entry(%ebp), %eax
leal efi64_stub_entry(%ebp), %eax
movl %esi, %edx
movl efi32_boot_args+4(%ebp), %esi
movl $0x0, %ecx
1:
#endif
pushl %eax
@ -242,6 +241,7 @@ SYM_FUNC_START(efi32_stub_entry)
movl %ecx, efi32_boot_args(%ebp)
movl %edx, efi32_boot_args+4(%ebp)
sgdtl efi32_boot_gdt(%ebp)
movb $0, efi_is64(%ebp)
/* Disable paging */
movl %cr0, %eax
@ -452,8 +452,6 @@ SYM_CODE_END(startup_64)
.org 0x390
SYM_FUNC_START(efi64_stub_entry)
SYM_FUNC_START_ALIAS(efi_stub_entry)
movq $1, %rcx
SYM_INNER_LABEL(handover_entry, SYM_L_LOCAL)
and $~0xf, %rsp /* realign the stack */
call efi_main
movq %rax,%rsi
@ -632,6 +630,7 @@ 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(efi_is64, .byte 1)
#endif
/*

2
arch/x86/include/asm/efi.h
View File

@ -221,7 +221,7 @@ efi_status_t efi_set_virtual_address_map(unsigned long memory_map_size,
/* arch specific definitions used by the stub code */
__pure bool efi_is_64bit(void);
__attribute_const__ bool efi_is_64bit(void);
static inline bool efi_is_native(void)
{