Re: [PATCH v2 8/9] bsd-user/mmap.c: Implement MAP_EXCL, required by jemalloc in head

[Richard Henderson]

On 9/21/21 9:56 PM, Warner Losh wrote:
> +        /* Reject the mapping if any page within the range is mapped */
> +        if (flags & MAP_EXCL) {
> +            for (addr = start; addr < end; addr++) {
> +                if (page_get_flags(addr) != 0)
> +                    goto fail;
> +            }
> +        }

How about

    if ((flags & MAP_EXCL) &&
        page_check_range(start, len, 0) < 0) {
       goto fail;
    }

Hmm.  This (and your page_get_flags check) could assert due to out-of-range guest address. 
 You're currently attempting that,

        /*
         * Test if requested memory area fits target address space
         * It can fail only on 64-bit host with 32-bit target.
         * On any other target/host host mmap() handles this error correctly.
         */
#if TARGET_ABI_BITS == 32 && HOST_LONG_BITS == 64
        if ((unsigned long)start + len - 1 > (abi_ulong) -1) {
            errno = EINVAL;
            goto fail;
        }
#endif

but the test isn't correct.  Note that reserved_va may be applied to 64-bit guests, and 
certainly may be smaller than (abi_ulong)-1.

You want guest_range_valid_untagged here.


r~