diff options
Diffstat (limited to 'main/astmm.c')
| -rw-r--r-- | main/astmm.c | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/main/astmm.c b/main/astmm.c index eeeaf5bd8..bc2cd824a 100644 --- a/main/astmm.c +++ b/main/astmm.c @@ -31,6 +31,7 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$") #include <stdio.h> #include <string.h> +#include <stddef.h> #include <time.h> #include "asterisk/cli.h" @@ -66,14 +67,26 @@ enum func_type { static FILE *mmlog; +/* NOTE: Be EXTREMELY careful with modifying this structure; the total size of this structure + must result in 'automatic' alignment so that the 'fence' field lands exactly at the end of + the structure in memory (and thus immediately before the allocated region the fence is + supposed to be used to monitor). In other words, we cannot allow the compiler to insert + any padding between this structure and anything following it, so add up the sizes of all the + fields and compare to sizeof(struct ast_region)... if they don't match, then the compiler + is padding the structure and either the fields need to be rearranged to eliminate internal + padding, or a dummy field will need to be inserted before the 'fence' field to push it to + the end of the actual space it will consume. Note that this must be checked for both 32-bit + and 64-bit platforms, as the sizes of pointers and 'size_t' differ on these platforms. +*/ + static struct ast_region { struct ast_region *next; + size_t len; char file[40]; char func[40]; unsigned int lineno; enum func_type which; unsigned int cache; /* region was allocated as part of a cache pool */ - size_t len; unsigned int fence; unsigned char data[0]; } *regions[SOME_PRIME]; @@ -463,6 +476,11 @@ static struct ast_cli_entry cli_memory[] = { void __ast_mm_init(void) { char filename[PATH_MAX]; + int pad; + + if ((pad = (__alignof__(struct ast_region) - (offsetof(struct ast_region, data) % __alignof__(struct ast_region)))) != 0) { + ast_log(LOG_ERROR, "struct ast_region has %d bytes of padding! This must be eliminated for low-fence checking to work properly!\n", pad); + } ast_cli_register_multiple(cli_memory, sizeof(cli_memory) / sizeof(struct ast_cli_entry)); |