Greetings.
I am keep working, and now I would like to discuss my second memory-related issue. In contrast with first one, the second issue happens only in SCHED004 test, in malloc function:
helper_thread_t **threads = (helper_thread_t **) malloc(sizeof(helper_thread_t*) * NUM_PRIOS);
malloc dies because there is no record inside TLB. someone tries to write something to an address, for example, 0x54f1c8. This address is important because it is located outside of the virtual memory allocated for the test. Previous, elf_loader allocates a region and the region ends exactly on 0x54efff. I have experimented with different setups, added some debug functions, and each time I saw the same picture: malloc dies because tries to write to next page outside the allocated region.
I know what is the function tries to write. It is a pretrim, part of libmuslc:
static int pretrim(struct chunk *self, size_t n, int i, int j)
{
size_t n1;
struct chunk *next, *split;
/* We cannot pretrim if it would require re-binning. */
if (j < 40) return 0;
if (j < i+3) {
if (j != 63) return 0;
n1 = CHUNK_SIZE(self);
if (n1-n <= MMAP_THRESHOLD) return 0;
} else {
n1 = CHUNK_SIZE(self);
}
if (bin_index(n1-n) != j) return 0;
next = NEXT_CHUNK(self);
printf("next - %x, n1 = %x\n", next, n1);
split = (void *)((char *)self + n); <————— the split points outside the allocated region
split->prev = self->prev; <————— here we die
split->next = self->next;
split->prev->next = split;
split->next->prev = split;
split->psize = n | C_INUSE;
split->csize = n1-n;
next->psize = n1-n;
self->csize = n | C_INUSE;
return 1;
}
As a previous, I would like to ask, should I keep in mind something platform specific? maybe you have modified, like a_and asm functions or something else in libmuslc?
Also, malloc itself raises questions:
void *malloc(size_t n)
{
struct chunk *c;
int i, j;
if (adjust_size(&n) < 0) return 0;
<….>
i = bin_index_up(n);
for (;;) {
uint64_t mask = mal.binmap & -(1ULL<<i);
mal.binmap is used uninitialised. also, when we set up bits inside it? Moreover, I have different values on ARM (0x80000000000) and MIPS (0x8000000000000000), I am not sure that it is ok
Thank you!
--
Vasily A. Sartakov
sartakov(a)ksyslabs.org
