Richard Henderson <richard.henderson@linaro.org> writes:
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> linux-user/mmap.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> index cb5369d2d1..41c2f09fd5 100644
> --- a/linux-user/mmap.c
> +++ b/linux-user/mmap.c
> @@ -502,7 +502,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
> * If the user is asking for the kernel to find a location, do that
> * before we truncate the length for mapping files below.
> */
> - if (!(flags & MAP_FIXED)) {
> + if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
> host_len = len + offset - host_offset;
> host_len = HOST_PAGE_ALIGN(host_len);
> start = mmap_find_vma(real_start, host_len, TARGET_PAGE_SIZE);
> @@ -544,7 +544,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
> }
> }
>
> - if (!(flags & MAP_FIXED)) {
> + if (!(flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))) {
> unsigned long host_start;
> void *p;
>
> @@ -593,6 +593,13 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
> goto fail;
> }
>
> + /* Validate that the chosen range is empty. */
> + if ((flags & MAP_FIXED_NOREPLACE)
> + && !page_check_range_empty(start, end - 1)) {
> + errno = EEXIST;
> + goto fail;
> + }
> +
> /*
> * worst case: we cannot map the file because the offset is not
> * aligned, so we read it
> @@ -608,7 +615,8 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int target_prot,
> goto fail;
> }
> retaddr = target_mmap(start, len, target_prot | PROT_WRITE,
> - MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS,
> + (flags & (MAP_FIXED | MAP_FIXED_NOREPLACE))
> + | MAP_PRIVATE | MAP_ANONYMOUS,
I thought we always MAP_FIXED because we've already jumped the hoops to
work out where in the memory space this allocation is going. Now if the
guest doesn't specify MAP_FIXED the kernel might decide to put the
memory somewhere else, potentially out of reach of the guest addressing?
IOW I thought the MAP_FIXED here was an internal QEMU implementation
details rather than reflecting the guests wishes.
> -1, 0);
> if (retaddr == -1) {
> goto fail;
--
Alex Bennée
Virtualisation Tech Lead @ Linaro