On 7/7/23 21:47, Richard Henderson wrote:
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<del...@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.hender...@linaro.org/20230630132159.376995-12-richard.hender...@linaro.org/
Wherein I use the host off_t (which must be 64-bits).
I like your patch.
But wouldn't it be better to use off64_t instead of off_t just to make
clear that this is a 64bit int?
And this part:
- arg5, arg6 << MMAP_SHIFT);
+ arg5, (off_t)(abi_ulong)arg6 << MMAP_SHIFT);
maybe should become (with brackets): ?
+ arg5, ((off64_t)(abi_ulong)arg6) << MMAP_SHIFT);
In any case I'm fine if your or my patch could be appled.
Helge
