Re: [PATCH 3/4] linux-user: Fix mmap2() syscall on 32-bit targets to allow file mapping beyond 4GB

[Richard Henderson <richard.henderson@linaro.org>]

On 7/7/23 14:19, Helge Deller wrote:
> The mmap2() syscall allows 32-bit guests to specify the offset into a
> file in page units (instead of bytes, as done by mmap(2)).
> On physical machines this allows 32-bit applications to map such parts
> of large files which are stored beyond the 4GB limit.
> 
> Allow the same behaviour when emulating 32-bit guests with qemu.
> 
> For that switch the mmap2() function to always take an abi_ullong
> (64-bit) offset parameter for target_mmap() and mmap_frag() to avoid an
> arithmetical overflow when shifing a 32-bit offset parameter by
> 12 bits (=PAGE_SHIFT) and thus possibly overflow the abi_ulong (32-bit)
> type.
> 
> Signed-off-by: Helge Deller<deller@gmx.de>
> ---
>   linux-user/mmap.c      | 9 +++++----
>   linux-user/syscall.c   | 2 +-
>   linux-user/user-mmap.h | 2 +-
>   3 files changed, 7 insertions(+), 6 deletions(-)

https://patchew.org/QEMU/20230630132159.376995-1-richard.henderson@linaro.org/20230630132159.376995-12-richard.henderson@linaro.org/

Wherein I use the host off_t (which must be 64-bits).
(I'm pretty sure there's an older similar patch, but I couldn't find it.)


r~