x86/sev-es: Compile early handler code into kernel image

Setup sev-es.c and include the code from the pre-decompression stage
to also build it into the image of the running kernel. Temporarily add
__maybe_unused annotations to avoid build warnings until the functions
get used.

 [ bp: Use the non-tracing rd/wrmsr variants because:
   vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0x11f: \
	   call to do_trace_write_msr() leaves .noinstr.text section
   as __sev_es_nmi_complete() is noinstr due to being called from the
   NMI handler exc_nmi(). ]
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-39-joro@8bytes.org

arch/x86/kernel/Makefile

@@ -145,6 +145,7 @@ obj-$(CONFIG_UNWINDER_ORC)		+= unwind_orc.o
 obj-$(CONFIG_UNWINDER_FRAME_POINTER)	+= unwind_frame.o
 obj-$(CONFIG_UNWINDER_GUESS)		+= unwind_guess.o
 
+obj-$(CONFIG_AMD_MEM_ENCRYPT)		+= sev-es.o
 ###
 # 64 bit specific files
 ifeq ($(CONFIG_X86_64),y)

arch/x86/kernel/sev-es-shared.c

@@ -9,7 +9,7 @@
  * and is included directly into both code-bases.
  */
 
-static void sev_es_terminate(unsigned int reason)
+static void __maybe_unused sev_es_terminate(unsigned int reason)
 {
 	u64 val = GHCB_SEV_TERMINATE;
 
@@ -27,7 +27,7 @@ static void sev_es_terminate(unsigned int reason)
 		asm volatile("hlt\n" : : : "memory");
 }
 
-static bool sev_es_negotiate_protocol(void)
+static bool __maybe_unused sev_es_negotiate_protocol(void)
 {
 	u64 val;
 
@@ -46,7 +46,7 @@ static bool sev_es_negotiate_protocol(void)
 	return true;
 }
 
-static void vc_ghcb_invalidate(struct ghcb *ghcb)
+static void __maybe_unused vc_ghcb_invalidate(struct ghcb *ghcb)
 {
 	memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
 }
@@ -58,9 +58,9 @@ static bool vc_decoding_needed(unsigned long exit_code)
 		 exit_code <= SVM_EXIT_LAST_EXCP);
 }
 
-static enum es_result vc_init_em_ctxt(struct es_em_ctxt *ctxt,
-				      struct pt_regs *regs,
-				      unsigned long exit_code)
+static enum es_result __maybe_unused vc_init_em_ctxt(struct es_em_ctxt *ctxt,
+						     struct pt_regs *regs,
+						     unsigned long exit_code)
 {
 	enum es_result ret = ES_OK;
 
@@ -73,7 +73,7 @@ static enum es_result vc_init_em_ctxt(struct es_em_ctxt *ctxt,
 	return ret;
 }
 
-static void vc_finish_insn(struct es_em_ctxt *ctxt)
+static void __maybe_unused vc_finish_insn(struct es_em_ctxt *ctxt)
 {
 	ctxt->regs->ip += ctxt->insn.length;
 }
@@ -325,7 +325,8 @@ static enum es_result vc_ioio_exitinfo(struct es_em_ctxt *ctxt, u64 *exitinfo)
 	return ES_OK;
 }
 
-static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
+static enum es_result __maybe_unused
+vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 {
 	struct pt_regs *regs = ctxt->regs;
 	u64 exit_info_1, exit_info_2;
@@ -433,8 +434,8 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 	return ret;
 }
 
-static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
-				      struct es_em_ctxt *ctxt)
+static enum es_result __maybe_unused vc_handle_cpuid(struct ghcb *ghcb,
+						     struct es_em_ctxt *ctxt)
 {
 	struct pt_regs *regs = ctxt->regs;
 	u32 cr4 = native_read_cr4();

arch/x86/kernel/sev-es.c

+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Memory Encryption Support
+ *
+ * Copyright (C) 2019 SUSE
+ *
+ * Author: Joerg Roedel <jroedel@suse.de>
+ */
+
+#include <linux/kernel.h>
+#include <linux/mm.h>
+
+#include <asm/sev-es.h>
+#include <asm/insn-eval.h>
+#include <asm/fpu/internal.h>
+#include <asm/processor.h>
+#include <asm/trap_pf.h>
+#include <asm/trapnr.h>
+#include <asm/svm.h>
+
+static inline u64 sev_es_rd_ghcb_msr(void)
+{
+	return __rdmsr(MSR_AMD64_SEV_ES_GHCB);
+}
+
+static inline void sev_es_wr_ghcb_msr(u64 val)
+{
+	u32 low, high;
+
+	low  = (u32)(val);
+	high = (u32)(val >> 32);
+
+	native_wrmsr(MSR_AMD64_SEV_ES_GHCB, low, high);
+}
+
+static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,
+				unsigned char *buffer)
+{
+	return copy_from_kernel_nofault(buffer, (unsigned char *)ctxt->regs->ip, MAX_INSN_SIZE);
+}
+
+static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
+{
+	char buffer[MAX_INSN_SIZE];
+	enum es_result ret;
+	int res;
+
+	res = vc_fetch_insn_kernel(ctxt, buffer);
+	if (unlikely(res == -EFAULT)) {
+		ctxt->fi.vector     = X86_TRAP_PF;
+		ctxt->fi.error_code = 0;
+		ctxt->fi.cr2        = ctxt->regs->ip;
+		return ES_EXCEPTION;
+	}
+
+	insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE - res, 1);
+	insn_get_length(&ctxt->insn);
+
+	ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
+
+	return ret;
+}
+
+static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
+				   char *dst, char *buf, size_t size)
+{
+	unsigned long error_code = X86_PF_PROT | X86_PF_WRITE;
+	char __user *target = (char __user *)dst;
+	u64 d8;
+	u32 d4;
+	u16 d2;
+	u8  d1;
+
+	switch (size) {
+	case 1:
+		memcpy(&d1, buf, 1);
+		if (put_user(d1, target))
+			goto fault;
+		break;
+	case 2:
+		memcpy(&d2, buf, 2);
+		if (put_user(d2, target))
+			goto fault;
+		break;
+	case 4:
+		memcpy(&d4, buf, 4);
+		if (put_user(d4, target))
+			goto fault;
+		break;
+	case 8:
+		memcpy(&d8, buf, 8);
+		if (put_user(d8, target))
+			goto fault;
+		break;
+	default:
+		WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
+		return ES_UNSUPPORTED;
+	}
+
+	return ES_OK;
+
+fault:
+	if (user_mode(ctxt->regs))
+		error_code |= X86_PF_USER;
+
+	ctxt->fi.vector = X86_TRAP_PF;
+	ctxt->fi.error_code = error_code;
+	ctxt->fi.cr2 = (unsigned long)dst;
+
+	return ES_EXCEPTION;
+}
+
+static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
+				  char *src, char *buf, size_t size)
+{
+	unsigned long error_code = X86_PF_PROT;
+	char __user *s = (char __user *)src;
+	u64 d8;
+	u32 d4;
+	u16 d2;
+	u8  d1;
+
+	switch (size) {
+	case 1:
+		if (get_user(d1, s))
+			goto fault;
+		memcpy(buf, &d1, 1);
+		break;
+	case 2:
+		if (get_user(d2, s))
+			goto fault;
+		memcpy(buf, &d2, 2);
+		break;
+	case 4:
+		if (get_user(d4, s))
+			goto fault;
+		memcpy(buf, &d4, 4);
+		break;
+	case 8:
+		if (get_user(d8, s))
+			goto fault;
+		memcpy(buf, &d8, 8);
+		break;
+	default:
+		WARN_ONCE(1, "%s: Invalid size: %zu\n", __func__, size);
+		return ES_UNSUPPORTED;
+	}
+
+	return ES_OK;
+
+fault:
+	if (user_mode(ctxt->regs))
+		error_code |= X86_PF_USER;
+
+	ctxt->fi.vector = X86_TRAP_PF;
+	ctxt->fi.error_code = error_code;
+	ctxt->fi.cr2 = (unsigned long)src;
+
+	return ES_EXCEPTION;
+}
+
+/* Include code shared with pre-decompression boot stage */
+#include "sev-es-shared.c"