Ticket #2135: ramconsole-1.patch

kernel/printk.c

@@ -37 +37 @@
 
 #include <asm/uaccess.h>
 #include <asm/plat-s3c24xx/neo1973.h>
+#include <asm/io.h>
 
 /*
  * Architectures can override it:
@@ -145 +146 @@
 static int log_buf_len = __LOG_BUF_LEN;
 static unsigned logged_chars; /* Number of chars produced since last read+clear operation */
 
+struct ramconsole_header {
+        __u32 magic;
+        unsigned start;
+        unsigned end;
+        unsigned len;
+        char data[1];
+};
+static struct ramconsole_header *ramconsole;
+
 static int __init log_buf_len_setup(char *str)
 {
         unsigned size = memparse(str, &str);
@@ -500 +510 @@
                 con_start = log_end - log_buf_len;
         if (logged_chars < log_buf_len)
                 logged_chars++;
+        if (ramconsole) {
+                ramconsole->data[ramconsole->end % ramconsole->len] = c;
+                ramconsole->end++;
+                if (ramconsole->end - ramconsole->start > ramconsole->len)
+                        ramconsole->start = ramconsole->end - ramconsole->len;
+        }
 }
 
 /*
@@ -1341 +1357 @@
         return false;
 }
 EXPORT_SYMBOL(printk_timed_ratelimit);
+
+static int __init ramconsole_start(void)
+{
+        unsigned i;
+        struct ramconsole_header *log;
+
+        log = ioremap(0x30000000 + (127<<20), 1024*1024);
+        if (!log) {
+                printk(KERN_WARNING "ramconsole: ioremap failed\n");
+                return 1;
+        }
+
+        if (log->magic == 0xffffffff) {
+                printk(KERN_NOTICE "ramconsole: found uninitialized memory, initializing ramconsole\n");
+                log->magic = 0x12345678;
+                log->start = 0;
+                log->end = 0;
+                log->len = 1024*512;
+        } else if (log->magic == 0x12345678) {
+                log->len = 1024*512;
+                printk(KERN_NOTICE "ramconsole: found existing ramconsole. Dumping %d bytes of data:\n", log->len);
+                if (log->end - log->start > log->len) {
+                        printk(KERN_WARNING "ramconsole: end - start > len\n");
+                        log->start = log->end - log->len;
+                }
+                for (i = log->start; i != log->end; i++) {
+                        emit_log_char(log->data[i % log->len]);
+                }
+                printk(KERN_NOTICE "ramconsole: old data ends here\n");
+        } else {
+                printk(KERN_WARNING "ramconsole: invalid magic %08x\n", log->magic);
+                return 1;
+        }
+
+        ramconsole = log;
+        return 1;
+}
+late_initcall(ramconsole_start);
 #endif