efi/libstub: use EFI provided memcpy/memset routines

The stub is used in different execution environments, but on arm64,
RISC-V and LoongArch, we still use the core kernel's implementation of
memcpy and memset, as they are just a branch instruction away, and can
generally be reused even from code such as the EFI stub that runs in a
completely different address space.

KAsan complicates this slightly, resulting in the need for some hacks to
expose the uninstrumented, __ prefixed versions as the normal ones, as
the latter are instrumented to include the KAsan checks, which only work
in the core kernel.

Unfortunately, #define'ing memcpy to __memcpy when building C code does
not guarantee that no explicit memcpy() calls will be emitted. And with
the upcoming zboot support, which consists of a separate binary which
therefore needs its own implementation of memcpy/memset anyway, it's
better to provide one explicitly instead of linking to the existing one.

Given that EFI exposes implementations of memmove() and memset() via the
boot services table, let's wire those up in the appropriate way, and
drop the references to the core kernel ones.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

arch/arm64/kernel/image-vars.h

@@ -24,9 +24,6 @@ PROVIDE(__efistub_primary_entry_offset	= primary_entry - _text);
  */
 PROVIDE(__efistub_memcmp		= __pi_memcmp);
 PROVIDE(__efistub_memchr		= __pi_memchr);
-PROVIDE(__efistub_memcpy		= __pi_memcpy);
-PROVIDE(__efistub_memmove		= __pi_memmove);
-PROVIDE(__efistub_memset		= __pi_memset);
 PROVIDE(__efistub_strlen		= __pi_strlen);
 PROVIDE(__efistub_strnlen		= __pi_strnlen);
 PROVIDE(__efistub_strcmp		= __pi_strcmp);
@@ -40,16 +37,6 @@ PROVIDE(__efistub__edata		= _edata);
 PROVIDE(__efistub_screen_info		= screen_info);
 PROVIDE(__efistub__ctype		= _ctype);
 
-/*
- * The __ prefixed memcpy/memset/memmove symbols are provided by KASAN, which
- * instruments the conventional ones. Therefore, any references from the EFI
- * stub or other position independent, low level C code should be redirected to
- * the non-instrumented versions as well.
- */
-PROVIDE(__efistub___memcpy		= __pi_memcpy);
-PROVIDE(__efistub___memmove		= __pi_memmove);
-PROVIDE(__efistub___memset		= __pi_memset);
-
 PROVIDE(__pi___memcpy			= __pi_memcpy);
 PROVIDE(__pi___memmove			= __pi_memmove);
 PROVIDE(__pi___memset			= __pi_memset);

arch/loongarch/kernel/image-vars.h

@@ -9,9 +9,6 @@
 
 __efistub_memcmp		= memcmp;
 __efistub_memchr		= memchr;
-__efistub_memcpy		= memcpy;
-__efistub_memmove		= memmove;
-__efistub_memset		= memset;
 __efistub_strcat		= strcat;
 __efistub_strcmp		= strcmp;
 __efistub_strlen		= strlen;

arch/riscv/kernel/image-vars.h

@@ -25,21 +25,12 @@
  */
 __efistub_memcmp		= memcmp;
 __efistub_memchr		= memchr;
-__efistub_memcpy		= memcpy;
-__efistub_memmove		= memmove;
-__efistub_memset		= memset;
 __efistub_strlen		= strlen;
 __efistub_strnlen		= strnlen;
 __efistub_strcmp		= strcmp;
 __efistub_strncmp		= strncmp;
 __efistub_strrchr		= strrchr;
 
-#ifdef CONFIG_KASAN
-__efistub___memcpy		= memcpy;
-__efistub___memmove		= memmove;
-__efistub___memset		= memset;
-#endif
-
 __efistub__start		= _start;
 __efistub__start_kernel		= _start_kernel;
 __efistub__end			= _end;

drivers/firmware/efi/libstub/Makefile

@@ -65,7 +65,7 @@ efi-deps-y := fdt_rw.c fdt_ro.c fdt_wip.c fdt.c fdt_empty_tree.c fdt_sw.c
 $(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
 	$(call if_changed_rule,cc_o_c)
 
-lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o fdt.o string.o \
+lib-$(CONFIG_EFI_GENERIC_STUB)	+= efi-stub.o fdt.o string.o intrinsics.o \
 				   $(patsubst %.c,lib-%.o,$(efi-deps-y))
 
 lib-$(CONFIG_ARM)		+= arm32-stub.o

drivers/firmware/efi/libstub/efistub.h

@@ -301,8 +301,8 @@ union efi_boot_services {
 		efi_status_t (__efiapi *install_multiple_protocol_interfaces)(efi_handle_t *, ...);
 		efi_status_t (__efiapi *uninstall_multiple_protocol_interfaces)(efi_handle_t, ...);
 		void *calculate_crc32;
-		void *copy_mem;
-		void *set_mem;
+		void (__efiapi *copy_mem)(void *, const void *, unsigned long);
+		void (__efiapi *set_mem)(void *, unsigned long, unsigned char);
 		void *create_event_ex;
 	};
 	struct {

drivers/firmware/efi/libstub/intrinsics.c

+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/efi.h>
+#include <asm/efi.h>
+#include <asm/string.h>
+
+#include "efistub.h"
+
+#ifdef CONFIG_KASAN
+#undef memcpy
+#undef memmove
+#undef memset
+void *__memcpy(void *__dest, const void *__src, size_t __n) __alias(memcpy);
+void *__memmove(void *__dest, const void *__src, size_t count) __alias(memmove);
+void *__memset(void *s, int c, size_t count) __alias(memset);
+#endif
+
+void *memcpy(void *dst, const void *src, size_t len)
+{
+	efi_bs_call(copy_mem, dst, src, len);
+	return dst;
+}
+
+extern void *memmove(void *dst, const void *src, size_t len) __alias(memcpy);
+
+void *memset(void *dst, int c, size_t len)
+{
+	efi_bs_call(set_mem, dst, len, c & U8_MAX);
+	return dst;
+}