diff options
| -rw-r--r-- | bsd-user/bsd-mem.h | 53 | ||||
| -rw-r--r-- | bsd-user/freebsd/os-syscall.c | 4 | ||||
| -rw-r--r-- | bsd-user/syscall_defs.h | 2 |
3 files changed, 59 insertions, 0 deletions
diff --git a/bsd-user/bsd-mem.h b/bsd-user/bsd-mem.h index 16c22593bf..b00ab3aed8 100644 --- a/bsd-user/bsd-mem.h +++ b/bsd-user/bsd-mem.h @@ -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) diff --git a/bsd-user/freebsd/os-syscall.c b/bsd-user/freebsd/os-syscall.c index 7a7ae26793..b8c44cea0f 100644 --- a/bsd-user/freebsd/os-syscall.c +++ b/bsd-user/freebsd/os-syscall.c @@ -831,6 +831,10 @@ static abi_long freebsd_syscall(void *cpu_env, int num, abi_long arg1, ret = do_bsd_munlockall(); break; + case TARGET_FREEBSD_NR_madvise: /* madvise(2) */ + ret = do_bsd_madvise(arg1, arg2, arg3); + break; + case TARGET_FREEBSD_NR_minherit: /* minherit(2) */ ret = do_bsd_minherit(arg1, arg2, arg3); break; diff --git a/bsd-user/syscall_defs.h b/bsd-user/syscall_defs.h index ff69281433..52f84d5dd1 100644 --- a/bsd-user/syscall_defs.h +++ b/bsd-user/syscall_defs.h @@ -95,6 +95,8 @@ struct bsd_shm_regions { /* * sys/mman.h */ +#define TARGET_MADV_DONTNEED 4 /* dont need these pages */ + #define TARGET_FREEBSD_MAP_RESERVED0080 0x0080 /* previously misimplemented */ /* MAP_INHERIT */ #define TARGET_FREEBSD_MAP_RESERVED0100 0x0100 /* previously unimplemented */ |