[tip: x86/boot] x86/sev: Move instruction decoder into separate source file

tip-bot2 for Ard Biesheuvel
2025-05-04T14:20:18Z

The following commit has been merged into the x86/boot branch of tip:

Commit-ID: ae862964cbc562582576da91b0b92742a574c437
Gitweb: https://git.kernel.org/tip/ae862964cbc562582576da91b0b92742a574c437
Author: Ard Biesheuvel <ardb@kernel.org>
AuthorDate: Sun, 04 May 2025 11:52:35 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sun, 04 May 2025 15:53:06 +02:00

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 <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Dionna Amalie Glaze <dionnaglaze@google.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kevin Loughlin <kevinloughlin@google.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: linux-efi@vger.kernel.org
Link: https://lore.kernel.org/r/20250504095230.2932860-30-ardb+git@google.com
---
arch/x86/boot/compressed/Makefile | 6 +--
arch/x86/boot/compressed/misc.h | 7 +++-
arch/x86/boot/compressed/sev-handle-vc.c | 51 +++++++++++++++++++++++-
arch/x86/boot/compressed/sev.c | 39 +------------------
4 files changed, 62 insertions(+), 41 deletions(-)
create mode 100644 arch/x86/boot/compressed/sev-handle-vc.c

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 0fcad7b..f4f7b22 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -44,10 +44,10 @@ KBUILD_CFLAGS += -D__DISABLE_EXPORTS
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__

@@ -96,7 +96,7 @@ ifdef CONFIG_X86_64
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
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index dd8d1a8..04de48c 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -136,6 +136,9 @@ static inline void console_init(void)
#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);
@@ -143,6 +146,10 @@ extern bool sev_es_check_ghcb_fault(unsigned long address);
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)
{
diff --git a/arch/x86/boot/compressed/sev-handle-vc.c b/arch/x86/boot/compressed/sev-handle-vc.c
new file mode 100644
index 0000000..b1aa073
--- /dev/null
+++ b/arch/x86/boot/compressed/sev-handle-vc.c
@@ -0,0 +1,51 @@
+// 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);
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index f4b7f17..6fe7e85 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -30,25 +30,6 @@ static struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
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.
*/
@@ -74,20 +55,6 @@ static inline void sev_es_wr_ghcb_msr(u64 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,
void *dst, char *buf, size_t size)
{
@@ -122,10 +89,6 @@ static bool fault_in_kernel_space(unsigned long address)

#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;

@@ -230,7 +193,7 @@ static bool early_setup_ghcb(void)
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())