diff options
| -rw-r--r-- | linux-user/elfload.c | 48 |
1 files changed, 48 insertions, 0 deletions
diff --git a/linux-user/elfload.c b/linux-user/elfload.c index ebc663ea0b..475d243f3b 100644 --- a/linux-user/elfload.c +++ b/linux-user/elfload.c @@ -2101,6 +2101,50 @@ static void pgb_have_guest_base(const char *image_name, abi_ulong guest_loaddr, } } +/** + * pgd_find_hole_fallback: potential mmap address + * @guest_size: size of available space + * @brk: location of break + * @align: memory alignment + * + * This is a fallback method for finding a hole in the host address + * space if we don't have the benefit of being able to access + * /proc/self/map. It can potentially take a very long time as we can + * only dumbly iterate up the host address space seeing if the + * allocation would work. + */ +static uintptr_t pgd_find_hole_fallback(uintptr_t guest_size, uintptr_t brk, long align) +{ + uintptr_t base; + + /* Start (aligned) at the bottom and work our way up */ + base = ROUND_UP(mmap_min_addr, align); + + while (true) { + uintptr_t align_start, end; + align_start = ROUND_UP(base, align); + end = align_start + guest_size; + + /* if brk is anywhere in the range give ourselves some room to grow. */ + if (align_start <= brk && brk < end) { + base = brk + (16 * MiB); + continue; + } else if (align_start + guest_size < align_start) { + /* we have run out of space */ + return -1; + } else { + int flags = MAP_ANONYMOUS | MAP_PRIVATE | MAP_NORESERVE | MAP_FIXED; + void * mmap_start = mmap((void *) align_start, guest_size, + PROT_NONE, flags, -1, 0); + if (mmap_start != MAP_FAILED) { + munmap((void *) align_start, guest_size); + return (uintptr_t) mmap_start; + } + base += qemu_host_page_size; + } + } +} + /* Return value for guest_base, or -1 if no hole found. */ static uintptr_t pgb_find_hole(uintptr_t guest_loaddr, uintptr_t guest_size, long align) @@ -2116,6 +2160,10 @@ static uintptr_t pgb_find_hole(uintptr_t guest_loaddr, uintptr_t guest_size, /* Read brk after we've read the maps, which will malloc. */ brk = (uintptr_t)sbrk(0); + if (!maps) { + return pgd_find_hole_fallback(guest_size, brk, align); + } + /* The first hole is before the first map entry. */ this_start = mmap_min_addr; |