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bsd-user: Implment madvise(2) to match the linux-user implementation.

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Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230925182709.4834-17-kariem.taha2.7@gmail.com>
This commit is contained in:
Karim Taha 2023-09-25 21:27:02 +03:00 • committed by Warner Losh
parent 0a49ef02a6
commit 0c1ced42c8
3 changed files with 59 additions and 0 deletions
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53
bsd-user/bsd-mem.h
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@ -129,6 +129,59 @@ static inline abi_long do_bsd_munlockall(void)
return get_errno(munlockall());
}
/* madvise(2) */
static inline abi_long do_bsd_madvise(abi_long arg1, abi_long arg2,
abi_long arg3)
{
abi_ulong len;
int ret = 0;
abi_long start = arg1;
abi_long len_in = arg2;
abi_long advice = arg3;
if (start & ~TARGET_PAGE_MASK) {
return -TARGET_EINVAL;
}
if (len_in == 0) {
return 0;
}
len = TARGET_PAGE_ALIGN(len_in);
if (len == 0 || !guest_range_valid_untagged(start, len)) {
return -TARGET_EINVAL;
}
/*
* Most advice values are hints, so ignoring and returning success is ok.
*
* However, some advice values such as MADV_DONTNEED, are not hints and
* need to be emulated.
*
* A straight passthrough for those may not be safe because qemu sometimes
* turns private file-backed mappings into anonymous mappings.
* If all guest pages have PAGE_PASSTHROUGH set, mappings have the
* same semantics for the host as for the guest.
*
* MADV_DONTNEED is passed through, if possible.
* If passthrough isn't possible, we nevertheless (wrongly!) return
* success, which is broken but some userspace programs fail to work
* otherwise. Completely implementing such emulation is quite complicated
* though.
*/
mmap_lock();
switch (advice) {
case MADV_DONTNEED:
if (page_check_range(start, len, PAGE_PASSTHROUGH)) {
ret = get_errno(madvise(g2h_untagged(start), len, advice));
if (ret == 0) {
page_reset_target_data(start, start + len - 1);
}
}
}
mmap_unlock();
return ret;
}
/* minherit(2) */
static inline abi_long do_bsd_minherit(abi_long addr, abi_long len,
abi_long inherit)