kernel/amd64: Add backtrace support for panic()

Signed-off-by: Ian Moffett <ian@osmora.org>

3 files changed, 50 insertions, 0 deletions

diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 1c158da..809eb27 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -30,6 +30,7 @@
 #include <sys/machdep.h>
 #include <sys/cdefs.h>
 #include <sys/panic.h>
+#include <sys/ksyms.h>
 #include <machine/trap.h>
 #include <machine/idt.h>
 #include <machine/io.h>
@@ -161,6 +162,53 @@ intr_unmask(void)
     __ASMV("sti");
 }
 
+static const char*
+backtrace_addr_to_name(uintptr_t addr, off_t *off)
+{
+    uintptr_t prev_addr = 0;
+    const char *name = NULL;
+
+    for (size_t i = 0;;) {
+        if (g_ksym_table[i].addr > addr) {
+            *off = addr - prev_addr;
+            return name;
+        }
+
+        prev_addr = g_ksym_table[i].addr;
+        name = g_ksym_table[i].name;
+        if (g_ksym_table[i++].addr == (uint64_t)-1)
+            break;
+    }
+
+    return NULL;
+}
+
+void
+backtrace(void)
+{
+    uintptr_t *rbp;
+    uintptr_t rip;
+
+    off_t off;
+    const char *name;
+
+    kprintf("** Backtrace **\n");
+    __ASMV("mov %%rbp, %0" : "=r" (rbp) :: "memory");
+
+    while (1) {
+        rip = rbp[1];
+        rbp = (uintptr_t *)rbp[0];
+        name = backtrace_addr_to_name(rip, &off);
+
+        if (rbp == NULL)
+            break;
+        if (name == NULL)
+            name = "???";
+
+        kprintf("[0x%p] <%s+0x%x>\n", rip, name, off);
+    }
+}
+
 int
 processor_init_pcb(struct proc *proc)
 {
diff --git a/sys/include/sys/machdep.h b/sys/include/sys/machdep.h
index 0c06374..811f6be 100644
--- a/sys/include/sys/machdep.h
+++ b/sys/include/sys/machdep.h
@@ -48,6 +48,7 @@ void intr_unmask(void);
 __weak void chips_init(void);
 __weak void pre_init(void);
 __weak void serial_dbgch(char c);
+__weak void backtrace(void);
 
 #endif  /* defined(_KERNEL) */
 #endif  /* !_SYS_MACHDEP_H_ */
diff --git a/sys/kern/kern_panic.c b/sys/kern/kern_panic.c
index 9fe3fdd..d22f5b2 100644
--- a/sys/kern/kern_panic.c
+++ b/sys/kern/kern_panic.c
@@ -50,6 +50,7 @@ panic(const char *fmt, ...)
 
     kprintf("panic: ");
     vkprintf(fmt, &ap);
+    __TRY_CALL(backtrace);
 
     processor_halt();
     __builtin_unreachable();