Smarter build of system error text database

We stored copies of the system error texts in a fixed line size array,
which is a huge waste.  Instead, use a static memory pool and pack all
the string in there.  The wasted space at the end, if any, gives us
some leeway for longer strings than we have measured so far.

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7681)

diff --git a/crypto/err/err.c b/crypto/err/err.c
index 03cbd738e19328e8e016e2392db51b1587a42d1d..ffdc140da296c6488686bad1852c096c46bb796e 100644 (file)
--- a/crypto/err/err.c
+++ b/crypto/err/err.c
@@ -181,8 +181,9 @@ static ERR_STRING_DATA *int_err_get_item(const ERR_STRING_DATA *d)
 }
 
 #ifndef OPENSSL_NO_ERR
+/* A measurement on Linux 2018-11-21 showed about 3.5kib */
+# define SPACE_SYS_STR_REASONS 4 * 1024
 # define NUM_SYS_STR_REASONS 127
-# define LEN_SYS_STR_REASON 32
 
 static ERR_STRING_DATA SYS_str_reasons[NUM_SYS_STR_REASONS + 1];
 /*
@@ -198,7 +199,9 @@ static ERR_STRING_DATA SYS_str_reasons[NUM_SYS_STR_REASONS + 1];
 static void build_SYS_str_reasons(void)
 {
     /* OPENSSL_malloc cannot be used here, use static storage instead */
-    static char strerror_tab[NUM_SYS_STR_REASONS][LEN_SYS_STR_REASON];
+    static char strerror_pool[SPACE_SYS_STR_REASONS];
+    char *cur = strerror_pool;
+    size_t cnt = 0;
     static int init = 1;
     int i;
 
@@ -213,9 +216,15 @@ static void build_SYS_str_reasons(void)
 
         str->error = ERR_PACK(ERR_LIB_SYS, 0, i);
         if (str->string == NULL) {
-            char (*dest)[LEN_SYS_STR_REASON] = &(strerror_tab[i - 1]);
-            if (openssl_strerror_r(i, *dest, sizeof(*dest)))
-                str->string = *dest;
+            if (openssl_strerror_r(i, cur, sizeof(strerror_pool) - cnt)) {
+                size_t l = strlen(cur) + 1;
+
+                str->string = cur;
+                cnt += l;
+                if (cnt > sizeof(strerror_pool))
+                    cnt = sizeof(strerror_pool);
+                cur += l;
+            }
         }
         if (str->string == NULL)
             str->string = "unknown";