diff options
Diffstat (limited to 'lib/bcheck.c')
| -rw-r--r-- | lib/bcheck.c | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/lib/bcheck.c b/lib/bcheck.c index 5ea2d0b..ea5b233 100644 --- a/lib/bcheck.c +++ b/lib/bcheck.c @@ -25,6 +25,7 @@ && !defined(__DragonFly__) && !defined(__OpenBSD__) #include <malloc.h> #endif +#include <unistd.h> //#define BOUND_DEBUG @@ -94,9 +95,6 @@ static void *saved_realloc_hook; static void *saved_memalign_hook; #endif -/* linker definitions */ -extern char _end; - /* TCC definitions */ extern char __bounds_start; /* start of static bounds table */ /* error message, just for TCC */ @@ -379,9 +377,32 @@ void __bound_init(void) #if !defined(__TINYC__) && defined(CONFIG_TCC_MALLOC_HOOKS) /* malloc zone is also marked invalid. can only use that with - hooks because all libs should use the same malloc. The solution - would be to build a new malloc for tcc. */ - start = (unsigned long)&_end; + * hooks because all libs should use the same malloc. The solution + * would be to build a new malloc for tcc. + * + * usually heap (= malloc zone) comes right after bss, i.e. after _end, but + * not always - either if we are running from under `tcc -b -run`, or if + * address space randomization is turned on(a), heap start will be separated + * from bss end. + * + * So sbrk(0) will be a good approximation for start_brk: + * + * - if we are a separately compiled program, __bound_init() runs early, + * and sbrk(0) should be equal or very near to start_brk(b) (in case other + * constructors malloc something), or + * + * - if we are running from under `tcc -b -run`, sbrk(0) will return + * start of heap portion which is under this program control, and not + * mark as invalid earlier allocated memory. + * + * + * (a) /proc/sys/kernel/randomize_va_space = 2, on Linux; + * usually turned on by default. + * + * (b) on Linux >= v3.3, the alternative is to read + * start_brk from /proc/self/stat + */ + start = (unsigned long)sbrk(0); size = 128 * 0x100000; mark_invalid(start, size); #endif |