x86/sev: Move instruction decoder into separate source file

As a first step towards disentangling the SEV #VC handling code -which
is shared between the decompressor and the core kernel- from the SEV
startup code, move the decompressor's copy of the instruction decoder
into a separate source file.

Code movement only - no functional change intended.

Signed-off-by: Ard Biesheuvel <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: David Woodhouse <[e-mail]>
Cc: Dionna Amalie Glaze <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Kees Cook <[e-mail]>
Cc: Kevin Loughlin <[e-mail]>
Cc: Len Brown <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Rafael J. Wysocki <[e-mail]>
Cc: Tom Lendacky <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]

arch/x86/boot/compressed/Makefile

···
 KBUILD_CFLAGS += $(call cc-option,-Wa$(comma)-mrelax-relocations=no)
 KBUILD_CFLAGS += -include $(srctree)/include/linux/hidden.h
 
-# sev.c indirectly includes inat-table.h which is generated during
+# sev-decode-insn.c indirectly includes inat-table.c which is generated during
 # compilation and stored in $(objtree). Add the directory to the includes so
 # that the compiler finds it even with out-of-tree builds (make O=/some/path).
-CFLAGS_sev.o += -I$(objtree)/arch/x86/lib/
+CFLAGS_sev-handle-vc.o += -I$(objtree)/arch/x86/lib/
 
 KBUILD_AFLAGS  := $(KBUILD_CFLAGS) -D__ASSEMBLY__
 
···
 	vmlinux-objs-y += $(obj)/idt_64.o $(obj)/idt_handlers_64.o
 	vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/mem_encrypt.o
 	vmlinux-objs-y += $(obj)/pgtable_64.o
-	vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/sev.o
+	vmlinux-objs-$(CONFIG_AMD_MEM_ENCRYPT) += $(obj)/sev.o $(obj)/sev-handle-vc.o
 endif
 
 vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o

arch/x86/boot/compressed/misc.h

···
 #endif
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
+struct es_em_ctxt;
+struct insn;
+
 void sev_enable(struct boot_params *bp);
 void snp_check_features(void);
 void sev_es_shutdown_ghcb(void);
···
 void snp_set_page_private(unsigned long paddr);
 void snp_set_page_shared(unsigned long paddr);
 void sev_prep_identity_maps(unsigned long top_level_pgt);
+
+enum es_result vc_decode_insn(struct es_em_ctxt *ctxt);
+bool insn_has_rep_prefix(struct insn *insn);
+void sev_insn_decode_init(void);
 #else
 static inline void sev_enable(struct boot_params *bp)
 {

arch/x86/boot/compressed/sev-handle-vc.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#include "misc.h"
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <asm/insn.h>
+#include <asm/pgtable_types.h>
+#include <asm/ptrace.h>
+#include <asm/sev.h>
+
+#define __BOOT_COMPRESSED
+
+/* Basic instruction decoding support needed */
+#include "../../lib/inat.c"
+#include "../../lib/insn.c"
+
+/*
+ * Copy a version of this function here - insn-eval.c can't be used in
+ * pre-decompression code.
+ */
+bool insn_has_rep_prefix(struct insn *insn)
+{
+	insn_byte_t p;
+	int i;
+
+	insn_get_prefixes(insn);
+
+	for_each_insn_prefix(insn, i, p) {
+		if (p == 0xf2 || p == 0xf3)
+			return true;
+	}
+
+	return false;
+}
+
+enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
+{
+	char buffer[MAX_INSN_SIZE];
+	int ret;
+
+	memcpy(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
+
+	ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
+	if (ret < 0)
+		return ES_DECODE_FAILED;
+
+	return ES_OK;
+}
+
+extern void sev_insn_decode_init(void) __alias(inat_init_tables);

arch/x86/boot/compressed/sev.c

···
 struct ghcb *boot_ghcb;
 
 /*
- * Copy a version of this function here - insn-eval.c can't be used in
- * pre-decompression code.
- */
-static bool insn_has_rep_prefix(struct insn *insn)
-{
-	insn_byte_t p;
-	int i;
-
-	insn_get_prefixes(insn);
-
-	for_each_insn_prefix(insn, i, p) {
-		if (p == 0xf2 || p == 0xf3)
-			return true;
-	}
-
-	return false;
-}
-
-/*
  * Only a dummy for insn_get_seg_base() - Early boot-code is 64bit only and
  * doesn't use segments.
  */
···
 
 	m.q = val;
 	boot_wrmsr(MSR_AMD64_SEV_ES_GHCB, &m);
-}
-
-static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
-{
-	char buffer[MAX_INSN_SIZE];
-	int ret;
-
-	memcpy(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
-
-	ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE, INSN_MODE_64);
-	if (ret < 0)
-		return ES_DECODE_FAILED;
-
-	return ES_OK;
 }
 
 static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
···
 #define __head
 
 #define __BOOT_COMPRESSED
-
-/* Basic instruction decoding support needed */
-#include "../../lib/inat.c"
-#include "../../lib/insn.c"
 
 extern struct svsm_ca *boot_svsm_caa;
 extern u64 boot_svsm_caa_pa;
···
 	boot_ghcb = &boot_ghcb_page;
 
 	/* Initialize lookup tables for the instruction decoder */
-	inat_init_tables();
+	sev_insn_decode_init();
 
 	/* SNP guest requires the GHCB GPA must be registered */
 	if (sev_snp_enabled())