3 files changed, 29 insertions, 5 deletions
diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 9b65d6e..af00c5a 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -44,6 +44,8 @@
 #include <machine/intr.h>
 #include <machine/cdefs.h>
 #include <machine/isa/i8042var.h>
+#include <dev/cons/cons.h>
+#include <string.h>
 
 #define pr_trace(fmt, ...) kprintf("cpu: " fmt, ##__VA_ARGS__)
 #define pr_error(...) pr_trace(__VA_ARGS__)
@@ -224,6 +226,7 @@ md_backtrace(void)
     uintptr_t rip;
     off_t off;
     const char *name;
+    char line[256];
 
     __ASMV("mov %%rbp, %0" : "=r" (rbp) :: "memory");
     while (1) {
@@ -236,7 +239,8 @@ md_backtrace(void)
         if (name == NULL)
             name = "???";
 
-        kprintf(OMIT_TIMESTAMP "%p  @ <%s+0x%x>\n", rip, name, off);
+        snprintf(line, sizeof(line), "%p @ <%s+0x%x>\n", rip, name, off);
+        cons_putstr(&g_root_scr, line, strlen(line));
     }
 }
 
diff --git a/sys/arch/amd64/conf/GENERIC b/sys/arch/amd64/conf/GENERIC
index 44ab8b5..95fe2e0 100644
--- a/sys/arch/amd64/conf/GENERIC
+++ b/sys/arch/amd64/conf/GENERIC
@@ -9,6 +9,7 @@ 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
+option PANIC_SCR    no   // Clear screen on panic
 
 // Kernel constants
 setval SCHED_NQUEUE 4    // Number of scheduler queues (for MLFQ)
diff --git a/sys/kern/kern_panic.c b/sys/kern/kern_panic.c
index 099f620..13b4964 100644
--- a/sys/kern/kern_panic.c
+++ b/sys/kern/kern_panic.c
@@ -34,6 +34,22 @@
 #include <dev/cons/cons.h>
 #include <machine/cdefs.h>
 #include <machine/cpu.h>
+#include <string.h>
+
+#if defined(__PANIC_SCR)
+#define PANIC_SCR  __PANIC_SCR
+#else
+#define PANIC_SCR 0
+#endif
+
+static void
+panic_puts(const char *str)
+{
+    size_t len;
+
+    len = strlen(str);
+    cons_putstr(&g_root_scr, str, len);
+}
 
 /*
  * Burn and sizzle - the core logic that really ends
@@ -50,11 +66,11 @@ bas(bool do_trace, int reboot_type)
     spinlock_acquire(&lock);    /* Never released */
 
     if (do_trace) {
-        kprintf(OMIT_TIMESTAMP "** backtrace\n");
+        panic_puts(" ** backtrace\n");
         md_backtrace();
     }
 
-    kprintf(OMIT_TIMESTAMP "\n-- ALL CORES HAVE BEEN HALTED --\n");
+    panic_puts("\n-- ALL CORES HAVE BEEN HALTED --\n");
     cpu_reboot(reboot_type);
     __builtin_unreachable();
 }
@@ -76,7 +92,8 @@ static void
 do_panic(const char *fmt, va_list *ap)
 {
     syslog_silence(false);
-    kprintf(OMIT_TIMESTAMP "panic: ");
+    spinlock_release(&g_root_scr.lock);
+    panic_puts("panic: ");
     vkprintf(fmt, ap);
     bas(true, REBOOT_HALT);
 
@@ -101,7 +118,9 @@ panic(const char *fmt, ...)
     md_intoff();
     cpu_halt_others();
 
-    panic_screen();
+    if (PANIC_SCR) {
+        panic_screen();
+    }
     va_start(ap, fmt);
     do_panic(fmt, &ap);
     __builtin_unreachable();