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bsd-user: Implment madvise(2) to match the linux-user implementation.
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>
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@ -129,6 +129,59 @@ static inline abi_long do_bsd_munlockall(void)
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return get_errno(munlockall());
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}
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/* madvise(2) */
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static inline abi_long do_bsd_madvise(abi_long arg1, abi_long arg2,
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abi_long arg3)
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{
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abi_ulong len;
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int ret = 0;
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abi_long start = arg1;
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abi_long len_in = arg2;
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abi_long advice = arg3;
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if (start & ~TARGET_PAGE_MASK) {
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return -TARGET_EINVAL;
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}
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if (len_in == 0) {
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return 0;
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}
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len = TARGET_PAGE_ALIGN(len_in);
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if (len == 0 || !guest_range_valid_untagged(start, len)) {
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return -TARGET_EINVAL;
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}
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/*
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* Most advice values are hints, so ignoring and returning success is ok.
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*
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* However, some advice values such as MADV_DONTNEED, are not hints and
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* need to be emulated.
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*
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* A straight passthrough for those may not be safe because qemu sometimes
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* turns private file-backed mappings into anonymous mappings.
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* If all guest pages have PAGE_PASSTHROUGH set, mappings have the
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* same semantics for the host as for the guest.
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*
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* MADV_DONTNEED is passed through, if possible.
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* If passthrough isn't possible, we nevertheless (wrongly!) return
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* success, which is broken but some userspace programs fail to work
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* otherwise. Completely implementing such emulation is quite complicated
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* though.
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*/
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mmap_lock();
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switch (advice) {
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case MADV_DONTNEED:
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if (page_check_range(start, len, PAGE_PASSTHROUGH)) {
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ret = get_errno(madvise(g2h_untagged(start), len, advice));
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if (ret == 0) {
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page_reset_target_data(start, start + len - 1);
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}
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}
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}
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mmap_unlock();
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return ret;
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}
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/* minherit(2) */
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static inline abi_long do_bsd_minherit(abi_long addr, abi_long len,
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abi_long inherit)
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@ -831,6 +831,10 @@ static abi_long freebsd_syscall(void *cpu_env, int num, abi_long arg1,
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ret = do_bsd_munlockall();
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break;
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case TARGET_FREEBSD_NR_madvise: /* madvise(2) */
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ret = do_bsd_madvise(arg1, arg2, arg3);
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break;
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case TARGET_FREEBSD_NR_minherit: /* minherit(2) */
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ret = do_bsd_minherit(arg1, arg2, arg3);
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break;
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@ -95,6 +95,8 @@ struct bsd_shm_regions {
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/*
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* sys/mman.h
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*/
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#define TARGET_MADV_DONTNEED 4 /* dont need these pages */
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#define TARGET_FREEBSD_MAP_RESERVED0080 0x0080 /* previously misimplemented */
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/* MAP_INHERIT */
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#define TARGET_FREEBSD_MAP_RESERVED0100 0x0100 /* previously unimplemented */
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