From d4b5c4803b778ab0ccccce8d13523067d85f8e06 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Wed, 21 Nov 2012 13:19:38 +0100
Subject: [PATCH] Fast memory test on Redis crash.

---
 src/debug.c   | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++
 src/memtest.c | 31 +++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+)

diff --git a/src/debug.c b/src/debug.c
index 9af6a6cc1fd5..003d2bd408f4 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -665,6 +665,49 @@ void logCurrentClient(void) {
     }
 }
 
+#if defined(HAVE_PROC_MAPS)
+int memtest_non_destructive(void *addr, size_t size); /* memtest.c */
+
+int memtest_test_linux_anonymous_maps(void) {
+    FILE *fp = fopen("/proc/self/maps","r");
+    char line[1024];
+    size_t start_addr, end_addr, size;
+
+    while(fgets(line,sizeof(line),fp) != NULL) {
+        char *start, *end, *p = line;
+        int j;
+
+        start = p;
+        p = strchr(p,'-');
+        if (!p) continue;
+        *p++ = '\0';
+        end = p;
+        p = strchr(p,' ');
+        if (!p) continue;
+        *p++ = '\0';
+        if (strstr(p,"stack") ||
+            strstr(p,"vdso") ||
+            strstr(p,"vsyscall")) continue;
+        if (!strstr(p,"00:00")) continue;
+        if (!strstr(p,"rw")) continue;
+
+        start_addr = strtoul(start,NULL,16);
+        end_addr = strtoul(end,NULL,16);
+        size = end_addr-start_addr;
+        redisLog(REDIS_WARNING,
+            "Testing memory at %lx (%lu bytes)", start_addr, size);
+        for (j = 0; j < 3; j++) {
+            if (memtest_non_destructive((void*)start_addr,size) != 0) {
+                fclose(fp);
+                return 1;
+            }
+        }
+    }
+    fclose(fp);
+    return 0;
+}
+#endif
+
 void sigsegvHandler(int sig, siginfo_t *info, void *secret) {
     ucontext_t *uc = (ucontext_t*) secret;
     sds infostring, clients;
@@ -700,6 +743,18 @@ void sigsegvHandler(int sig, siginfo_t *info, void *secret) {
     /* Log dump of processor registers */
     logRegisters(uc);
 
+#if defined(HAVE_PROC_MAPS)
+    /* Test memory */
+    redisLog(REDIS_WARNING, "--- FAST MEMORY TEST");
+    if (memtest_test_linux_anonymous_maps()) {
+        redisLog(REDIS_WARNING,
+            "!!! MEMORY ERROR DETECTED! Check your memory ASAP !!!");
+    } else {
+        redisLog(REDIS_WARNING,
+            "Fast memory test PASSED, however your memory can still be broken. Please run a memory test for several hours if possible.");
+    }
+#endif
+
     redisLog(REDIS_WARNING,
 "\n=== REDIS BUG REPORT END. Make sure to include from START to END. ===\n\n"
 "       Please report the crash opening an issue on github:\n\n"
diff --git a/src/memtest.c b/src/memtest.c
index 56162ff4fbcd..82da27c8bc7b 100644
--- a/src/memtest.c
+++ b/src/memtest.c
@@ -35,6 +35,7 @@
 #include <errno.h>
 #include <termios.h>
 #include <sys/ioctl.h>
+#include "config.h"
 
 #if (ULONG_MAX == 4294967295UL)
 #define MEMTEST_32BIT
@@ -240,6 +241,36 @@ void memtest_test(size_t megabytes, int passes) {
     }
 }
 
+/* This is a fast O(N) best effort memory test, only ZERO-ONE tests and
+ * checkerboard tests are performed, without pauses between setting and
+ * reading the value, so this can only detect a subclass of permanent errors.
+ *
+ * However the function does not destroy the content of the memory tested that
+ * is left unmodified.
+ *
+ * If a memory error is detected, 1 is returned. Otherwise 0 is returned. */
+int memtest_non_destructive(void *addr, size_t size) {
+    volatile unsigned long *p = addr;
+    unsigned long val;
+    size_t j;
+
+    size /= sizeof(unsigned long);
+    for (j = 0; j < size; j++) {
+        val = p[j];
+
+        p[j] = 0; if (p[j] != 0) goto err;
+        p[j] = (unsigned long)-1; if (p[j] != (unsigned long)-1) goto err;
+        p[j] = ULONG_ONEZERO; if (p[j] != ULONG_ONEZERO) goto err;
+        p[j] = ULONG_ZEROONE; if (p[j] != ULONG_ZEROONE) goto err;
+        p[j] = val; /* restore the original value. */
+    }
+    return 0;
+
+err: /* memory error detected. */
+    p[j] = val;
+    return 1;
+}
+
 void memtest(size_t megabytes, int passes) {
     if (ioctl(1, TIOCGWINSZ, &ws) == -1) {
         ws.ws_col = 80;