From ddc58847e2bcff65a7950f0a866da041e73d3e76 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sat, 5 Jul 2025 01:09:24 +0000
Subject: kernel/amd64: conf: Add CPU_SMEP option

Allow the user to configure if SMEP would be enabled for their build of
the Hyra AMD64 port

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/amd64/machdep.c | 15 +++++++++++++++
 sys/arch/amd64/conf/GENERIC    |  1 +
 2 files changed, 16 insertions(+)

diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 5acacb4..9b65d6e 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -61,6 +61,12 @@
 #define SPECTRE_IBRS 0
 #endif
 
+#if defined(__CPU_SMEP)
+#define CPU_SMEP __CPU_SMEP
+#else
+#define CPU_SMEP 0
+#endif
+
 int ibrs_enable(void);
 int simd_init(void);
 void syscall_isr(void);
@@ -319,6 +325,11 @@ cpu_enable_smep(void)
     struct cpu_info *ci;
     uint64_t cr4;
 
+    /* Don't bother if not enabled */
+    if (!CPU_SMEP) {
+        return;
+    }
+
     ci = this_cpu();
     if (!ISSET(ci->feat, CPU_FEAT_SMEP)) {
         pr_trace_bsp("SMEP not supported\n");
@@ -336,6 +347,10 @@ cpu_disable_smep(void)
     struct cpu_info *ci;
     uint64_t cr4;
 
+    if (!CPU_SMEP) {
+        return;
+    }
+
     ci = this_cpu();
     if (!ISSET(ci->feat, CPU_FEAT_SMEP)) {
         return;
diff --git a/sys/arch/amd64/conf/GENERIC b/sys/arch/amd64/conf/GENERIC
index 69e071a..44ab8b5 100644
--- a/sys/arch/amd64/conf/GENERIC
+++ b/sys/arch/amd64/conf/GENERIC
@@ -8,6 +8,7 @@
 option SPECTRE_IBRS no   // Enable the IBRS CPU feature
 option SERIAL_DEBUG yes  // Enable kmsg serial logging
 option USER_KMSG    no   // Show kmsg in user consoles
+option CPU_SMEP     yes  // Supervisor Memory Exec Protection
 
 // Kernel constants
 setval SCHED_NQUEUE 4    // Number of scheduler queues (for MLFQ)
-- 
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