diff options
| author | Ilya Leoshkevich <iii@linux.ibm.com> | 2022-06-21 16:42:05 +0200 |
|---|---|---|
| committer | Laurent Vivier <laurent@vivier.eu> | 2022-06-24 10:00:00 +0200 |
| commit | 892a4f6a750abceeda4c1ee8324f58f82fd6bd89 (patch) | |
| tree | e0653c18cff17f077638a38762d310072d649c7e /linux-user/user-mmap.h | |
| parent | 9263ba847352c2ec2fc37ad7f7d0558332bd077f (diff) | |
linux-user: Add partial support for MADV_DONTNEED
Currently QEMU ignores madvise(MADV_DONTNEED), which break apps that
rely on this for zeroing out memory [1]. Improve the situation by doing
a passthrough when the range in question is a host-page-aligned
anonymous mapping.
This is based on the patches from Simon Hausmann [2] and Chris Fallin
[3]. The structure is taken from Simon's patch. The PAGE_MAP_ANONYMOUS
bits are superseded by commit 26bab757d41b ("linux-user: Introduce
PAGE_ANON"). In the end the patch acts like the one from Chris: we
either pass-through the entire syscall, or do nothing, since doing this
only partially would not help the affected applications much. Finally,
add some extra checks to match the behavior of the Linux kernel [4].
[1] https://gitlab.com/qemu-project/qemu/-/issues/326
[2] https://patchew.org/QEMU/20180827084037.25316-1-simon.hausmann@qt.io/
[3] https://github.com/bytecodealliance/wasmtime/blob/v0.37.0/ci/qemu-madvise.patch
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/madvise.c?h=v5.19-rc3#n1368
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220621144205.158452-1-iii@linux.ibm.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Diffstat (limited to 'linux-user/user-mmap.h')
| -rw-r--r-- | linux-user/user-mmap.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/linux-user/user-mmap.h b/linux-user/user-mmap.h index d1dec99c02..480ce1c114 100644 --- a/linux-user/user-mmap.h +++ b/linux-user/user-mmap.h @@ -25,6 +25,7 @@ int target_munmap(abi_ulong start, abi_ulong len); abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, abi_ulong new_size, unsigned long flags, abi_ulong new_addr); +abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice); extern unsigned long last_brk; extern abi_ulong mmap_next_start; abi_ulong mmap_find_vma(abi_ulong, abi_ulong, abi_ulong); |