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Subject[PATCH 13/25] efi/libstub/x86: avoid thunking for native firmware calls
Date
We use special wrapper routines to invoke firmware services in the
native case as well as the mixed mode case. For mixed mode, the need
is obvious, but for the native cases, we can simply rely on the
compiler to generate the indirect call, given that GCC now has
support for the MS calling convention (and has had it for quite some
time now). Note that on i386, the decompressor and the EFI stub are not
built with -mregparm=3 like the rest of the i386 kernel, so we can
safely allow the compiler to emit the indirect calls here as well.

So drop all the wrappers and indirection, and switch to either native
calls, or direct calls into the thunk routine for mixed mode.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/Makefile | 2 +-
arch/x86/boot/compressed/eboot.c | 3 +-
arch/x86/boot/compressed/efi_stub_32.S | 87 --------------------------
arch/x86/boot/compressed/efi_stub_64.S | 5 --
arch/x86/boot/compressed/head_32.S | 6 --
arch/x86/boot/compressed/head_64.S | 23 +------
arch/x86/include/asm/efi.h | 34 +++++-----
arch/x86/platform/efi/efi_64.c | 2 -
8 files changed, 24 insertions(+), 138 deletions(-)
delete mode 100644 arch/x86/boot/compressed/efi_stub_32.S
delete mode 100644 arch/x86/boot/compressed/efi_stub_64.S

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index aa976adb7094..a20f55c59753 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -89,7 +89,7 @@ vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o

$(obj)/eboot.o: KBUILD_CFLAGS += -fshort-wchar -mno-red-zone

-vmlinux-objs-$(CONFIG_EFI_STUB) += $(obj)/eboot.o $(obj)/efi_stub_$(BITS).o \
+vmlinux-objs-$(CONFIG_EFI_STUB) += $(obj)/eboot.o \
$(objtree)/drivers/firmware/efi/libstub/lib.a
vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 2733bc263c04..36a26d6e2af0 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -44,7 +44,8 @@ BOOT_SERVICES(64);
void efi_char16_printk(efi_system_table_t *table, efi_char16_t *str)
{
efi_call_proto(efi_simple_text_output_protocol, output_string,
- efi_early->text_output, str);
+ ((efi_simple_text_output_protocol_t *)(unsigned long)
+ efi_early->text_output), str);
}

static efi_status_t
diff --git a/arch/x86/boot/compressed/efi_stub_32.S b/arch/x86/boot/compressed/efi_stub_32.S
deleted file mode 100644
index ed6c351d34ed..000000000000
--- a/arch/x86/boot/compressed/efi_stub_32.S
+++ /dev/null
@@ -1,87 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * EFI call stub for IA32.
- *
- * This stub allows us to make EFI calls in physical mode with interrupts
- * turned off. Note that this implementation is different from the one in
- * arch/x86/platform/efi/efi_stub_32.S because we're _already_ in physical
- * mode at this point.
- */
-
-#include <linux/linkage.h>
-#include <asm/page_types.h>
-
-/*
- * efi_call_phys(void *, ...) is a function with variable parameters.
- * All the callers of this function assure that all the parameters are 4-bytes.
- */
-
-/*
- * In gcc calling convention, EBX, ESP, EBP, ESI and EDI are all callee save.
- * So we'd better save all of them at the beginning of this function and restore
- * at the end no matter how many we use, because we can not assure EFI runtime
- * service functions will comply with gcc calling convention, too.
- */
-
-.text
-SYM_FUNC_START(efi_call_phys)
- /*
- * 0. The function can only be called in Linux kernel. So CS has been
- * set to 0x0010, DS and SS have been set to 0x0018. In EFI, I found
- * the values of these registers are the same. And, the corresponding
- * GDT entries are identical. So I will do nothing about segment reg
- * and GDT, but change GDT base register in prelog and epilog.
- */
-
- /*
- * 1. Because we haven't been relocated by this point we need to
- * use relative addressing.
- */
- call 1f
-1: popl %edx
- subl $1b, %edx
-
- /*
- * 2. Now on the top of stack is the return
- * address in the caller of efi_call_phys(), then parameter 1,
- * parameter 2, ..., param n. To make things easy, we save the return
- * address of efi_call_phys in a global variable.
- */
- popl %ecx
- movl %ecx, saved_return_addr(%edx)
- /* get the function pointer into ECX*/
- popl %ecx
- movl %ecx, efi_rt_function_ptr(%edx)
-
- /*
- * 3. Call the physical function.
- */
- call *%ecx
-
- /*
- * 4. Balance the stack. And because EAX contain the return value,
- * we'd better not clobber it. We need to calculate our address
- * again because %ecx and %edx are not preserved across EFI function
- * calls.
- */
- call 1f
-1: popl %edx
- subl $1b, %edx
-
- movl efi_rt_function_ptr(%edx), %ecx
- pushl %ecx
-
- /*
- * 10. Push the saved return address onto the stack and return.
- */
- movl saved_return_addr(%edx), %ecx
- pushl %ecx
- ret
-SYM_FUNC_END(efi_call_phys)
-.previous
-
-.data
-saved_return_addr:
- .long 0
-efi_rt_function_ptr:
- .long 0
diff --git a/arch/x86/boot/compressed/efi_stub_64.S b/arch/x86/boot/compressed/efi_stub_64.S
deleted file mode 100644
index 99494dff2113..000000000000
--- a/arch/x86/boot/compressed/efi_stub_64.S
+++ /dev/null
@@ -1,5 +0,0 @@
-#include <asm/segment.h>
-#include <asm/msr.h>
-#include <asm/processor-flags.h>
-
-#include "../../platform/efi/efi_stub_64.S"
diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index f2dfd6d083ef..0b03dc7bba12 100644
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -161,9 +161,7 @@ SYM_FUNC_START(efi_pe_entry)
popl %ecx
movl %ecx, efi32_config+8(%esi) /* EFI System table pointer */

- /* Relocate efi_config->call() */
leal efi32_config(%esi), %eax
- add %esi, 40(%eax)
pushl %eax

call make_boot_params
@@ -188,9 +186,7 @@ SYM_FUNC_START(efi32_stub_entry)
movl %ecx, efi32_config(%esi) /* Handle */
movl %edx, efi32_config+8(%esi) /* EFI System table pointer */

- /* Relocate efi_config->call() */
leal efi32_config(%esi), %eax
- add %esi, 40(%eax)
pushl %eax
2:
call efi_main
@@ -266,8 +262,6 @@ SYM_FUNC_END(.Lrelocated)
.data
efi32_config:
.fill 5,8,0
- .long efi_call_phys
- .long 0
.byte 0
#endif

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index ee60b81944a7..ad57edeaeeb3 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -459,15 +459,6 @@ SYM_FUNC_START(efi_pe_entry)
leaq efi64_config(%rip), %rax
movq %rax, efi_config(%rip)

- call 1f
-1: popq %rbp
- subq $1b, %rbp
-
- /*
- * Relocate efi_config->call().
- */
- addq %rbp, efi64_config+40(%rip)
-
movq %rax, %rdi
call make_boot_params
cmpq $0,%rax
@@ -475,20 +466,10 @@ SYM_FUNC_START(efi_pe_entry)
mov %rax, %rsi
leaq startup_32(%rip), %rax
movl %eax, BP_code32_start(%rsi)
- jmp 2f /* Skip the relocation */

handover_entry:
- call 1f
-1: popq %rbp
- subq $1b, %rbp
-
- /*
- * Relocate efi_config->call().
- */
- movq efi_config(%rip), %rax
- addq %rbp, 40(%rax)
-2:
movq efi_config(%rip), %rdi
+ and $~0xf, %rsp /* realign the stack */
call efi_main
movq %rax,%rsi
cmpq $0,%rax
@@ -688,14 +669,12 @@ SYM_DATA_LOCAL(efi_config, .quad 0)
#ifdef CONFIG_EFI_MIXED
SYM_DATA_START(efi32_config)
.fill 5,8,0
- .quad efi64_thunk
.byte 0
SYM_DATA_END(efi32_config)
#endif

SYM_DATA_START(efi64_config)
.fill 5,8,0
- .quad efi_call
.byte 1
SYM_DATA_END(efi64_config)
#endif /* CONFIG_EFI_STUB */
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index c27323cb49e5..001905daa110 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -152,6 +152,7 @@ struct efi_setup_data {
extern u64 efi_setup;

#ifdef CONFIG_EFI
+extern efi_status_t efi64_thunk(u32, ...);

static inline bool efi_is_mixed(void)
{
@@ -205,7 +206,6 @@ struct efi_config {
u64 runtime_services;
u64 boot_services;
u64 text_output;
- efi_status_t (*call)(unsigned long, ...);
bool is64;
} __packed;

@@ -235,30 +235,36 @@ static inline bool efi_is_native(void)
(unsigned long)(attr), (attr))

#define efi_table_attr(table, attr, instance) ({ \
- __typeof__(((table##_t *)0)->attr) __ret; \
+ __typeof__(instance->attr) __ret; \
if (efi_is_native()) { \
- __ret = ((table##_t *)(unsigned long)instance)->attr; \
+ __ret = instance->attr; \
} else { \
- __ret = (__typeof__(__ret))efi_mixed_mode_cast( \
- ((table##_t *)(unsigned long)instance)->mixed_mode.attr);\
+ __ret = (__typeof__(__ret)) \
+ efi_mixed_mode_cast(instance->mixed_mode.attr); \
} \
__ret; \
})

#define efi_call_proto(protocol, f, instance, ...) \
- __efi_early()->call((unsigned long) \
- efi_table_attr(protocol, f, instance), \
- instance, ##__VA_ARGS__)
+ (efi_is_native() \
+ ? instance->f(instance, ##__VA_ARGS__) \
+ : efi64_thunk(instance->mixed_mode.f, instance, ##__VA_ARGS__))

#define efi_call_early(f, ...) \
- __efi_early()->call((unsigned long) \
- efi_table_attr(efi_boot_services, f, \
- __efi_early()->boot_services), __VA_ARGS__)
+ (efi_is_native() \
+ ? ((efi_boot_services_t *)(unsigned long) \
+ __efi_early()->boot_services)->f(__VA_ARGS__) \
+ : efi64_thunk(((efi_boot_services_t *)(unsigned long) \
+ __efi_early()->boot_services)->mixed_mode.f, \
+ __VA_ARGS__))

#define efi_call_runtime(f, ...) \
- __efi_early()->call((unsigned long) \
- efi_table_attr(efi_runtime_services, f, \
- __efi_early()->runtime_services), __VA_ARGS__)
+ (efi_is_native() \
+ ? ((efi_runtime_services_t *)(unsigned long) \
+ __efi_early()->runtime_services)->f(__VA_ARGS__)\
+ : efi64_thunk(((efi_runtime_services_t *)(unsigned long)\
+ __efi_early()->runtime_services)->mixed_mode.f, \
+ __VA_ARGS__))

extern bool efi_reboot_required(void);
extern bool efi_is_table_address(unsigned long phys_addr);
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 885e50a707a6..03c2ed3c645c 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -635,8 +635,6 @@ void efi_switch_mm(struct mm_struct *mm)
}

#ifdef CONFIG_EFI_MIXED
-extern efi_status_t efi64_thunk(u32, ...);
-
static DEFINE_SPINLOCK(efi_runtime_lock);

#define runtime_service32(func) \
--
2.20.1
\
 
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