linux-kernel - [PATCH v3 12/21] x86/sev-es: Split vc_decode

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Date:   Thu,  4 Mar 2021 18:42:28 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 12/21] x86/sev-es: Split vc_decode_insn()

From: Borislav Petkov <bp@...e.de>

Split it into two helpers - a user- and a kernel-mode one for
readability. Yes, the original function body is not that convoluted but
splitting it makes following through that code trivial than having to
pay attention to each little difference when in user or in kernel mode.

No functional changes.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/sev-es.c | 59 ++++++++++++++++++++++++++--------------
 1 file changed, 38 insertions(+), 21 deletions(-)

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 557386ce6e3b..e60ab556f51c 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -241,41 +241,58 @@ static int vc_fetch_insn_kernel(struct es_em_ctxt *ctxt,
 	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)
+static enum es_result __vc_decode_user_insn(struct es_em_ctxt *ctxt)
 {
 	char buffer[MAX_INSN_SIZE];
 	enum es_result ret;
 	int res;
 
-	if (user_mode(ctxt->regs)) {
-		res = insn_fetch_from_user(ctxt->regs, buffer);
-		if (!res) {
-			ctxt->fi.vector     = X86_TRAP_PF;
-			ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
-			ctxt->fi.cr2        = ctxt->regs->ip;
-			return ES_EXCEPTION;
-		}
+	res = insn_fetch_from_user(ctxt->regs, buffer);
+	if (!res) {
+		ctxt->fi.vector     = X86_TRAP_PF;
+		ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
+		ctxt->fi.cr2        = ctxt->regs->ip;
+		return ES_EXCEPTION;
+	}
 
-		if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, res))
-			return ES_DECODE_FAILED;
-	} else {
-		res = vc_fetch_insn_kernel(ctxt, buffer);
-		if (res) {
-			ctxt->fi.vector     = X86_TRAP_PF;
-			ctxt->fi.error_code = X86_PF_INSTR;
-			ctxt->fi.cr2        = ctxt->regs->ip;
-			return ES_EXCEPTION;
-		}
+	if (!insn_decode_from_regs(&ctxt->insn, ctxt->regs, buffer, res))
+		return ES_DECODE_FAILED;
+
+	ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
+
+	return ret;
+}
 
-		insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE, 1);
-		insn_get_length(&ctxt->insn);
+static enum es_result __vc_decode_kern_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 (res) {
+		ctxt->fi.vector     = X86_TRAP_PF;
+		ctxt->fi.error_code = X86_PF_INSTR;
+		ctxt->fi.cr2        = ctxt->regs->ip;
+		return ES_EXCEPTION;
 	}
 
+	insn_init(&ctxt->insn, buffer, MAX_INSN_SIZE, 1);
+	insn_get_length(&ctxt->insn);
+
 	ret = ctxt->insn.immediate.got ? ES_OK : ES_DECODE_FAILED;
 
 	return ret;
 }
 
+static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
+{
+	if (user_mode(ctxt->regs))
+		return __vc_decode_user_insn(ctxt);
+	else
+		return __vc_decode_kern_insn(ctxt);
+}
+
 static enum es_result vc_write_mem(struct es_em_ctxt *ctxt,
 				   char *dst, char *buf, size_t size)
 {
-- 
2.29.2