diff options
| -rw-r--r-- | linux-user/mmap.c | 64 | ||||
| -rw-r--r-- | linux-user/syscall.c | 8 | ||||
| -rw-r--r-- | linux-user/user-internals.h | 1 | ||||
| -rw-r--r-- | linux-user/user-mmap.h | 1 |
4 files changed, 68 insertions, 6 deletions
diff --git a/linux-user/mmap.c b/linux-user/mmap.c index 48e1373..4e7a6be 100644 --- a/linux-user/mmap.c +++ b/linux-user/mmap.c @@ -835,3 +835,67 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size, mmap_unlock(); return new_addr; } + +static bool can_passthrough_madv_dontneed(abi_ulong start, abi_ulong end) +{ + ulong addr; + + if ((start | end) & ~qemu_host_page_mask) { + return false; + } + + for (addr = start; addr < end; addr += TARGET_PAGE_SIZE) { + if (!(page_get_flags(addr) & PAGE_ANON)) { + return false; + } + } + + return true; +} + +abi_long target_madvise(abi_ulong start, abi_ulong len_in, int advice) +{ + abi_ulong len, end; + int ret = 0; + + if (start & ~TARGET_PAGE_MASK) { + return -TARGET_EINVAL; + } + len = TARGET_PAGE_ALIGN(len_in); + + if (len_in && !len) { + return -TARGET_EINVAL; + } + + end = start + len; + if (end < start) { + return -TARGET_EINVAL; + } + + if (end == start) { + return 0; + } + + if (!guest_range_valid_untagged(start, len)) { + return -TARGET_EINVAL; + } + + /* + * A straight passthrough may not be safe because qemu sometimes turns + * private file-backed mappings into anonymous mappings. + * + * This is a hint, so ignoring and returning success is ok. + * + * This breaks MADV_DONTNEED, completely implementing which is quite + * complicated. However, there is one low-hanging fruit: host-page-aligned + * anonymous mappings. In this case passthrough is safe, so do it. + */ + mmap_lock(); + if ((advice & MADV_DONTNEED) && + can_passthrough_madv_dontneed(start, end)) { + ret = get_errno(madvise(g2h_untagged(start), len, MADV_DONTNEED)); + } + mmap_unlock(); + + return ret; +} diff --git a/linux-user/syscall.c b/linux-user/syscall.c index f55cdeb..8f68f25 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -538,7 +538,7 @@ static inline int target_to_host_errno(int target_errno) } } -static inline abi_long get_errno(abi_long ret) +abi_long get_errno(abi_long ret) { if (ret == -1) return -host_to_target_errno(errno); @@ -11807,11 +11807,7 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1, #ifdef TARGET_NR_madvise case TARGET_NR_madvise: - /* A straight passthrough may not be safe because qemu sometimes - turns private file-backed mappings into anonymous mappings. - This will break MADV_DONTNEED. - This is a hint, so ignoring and returning success is ok. */ - return 0; + return target_madvise(arg1, arg2, arg3); #endif #ifdef TARGET_NR_fcntl64 case TARGET_NR_fcntl64: diff --git a/linux-user/user-internals.h b/linux-user/user-internals.h index 6175ce5..0280e76 100644 --- a/linux-user/user-internals.h +++ b/linux-user/user-internals.h @@ -65,6 +65,7 @@ abi_long do_syscall(CPUArchState *cpu_env, int num, abi_long arg1, abi_long arg8); extern __thread CPUState *thread_cpu; G_NORETURN void cpu_loop(CPUArchState *env); +abi_long get_errno(abi_long ret); const char *target_strerror(int err); int get_osversion(void); void init_qemu_uname_release(void); diff --git a/linux-user/user-mmap.h b/linux-user/user-mmap.h index d1dec99..480ce1c 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); |