From 892a4f6a750abceeda4c1ee8324f58f82fd6bd89 Mon Sep 17 00:00:00 2001 From: Ilya Leoshkevich Date: Tue, 21 Jun 2022 16:42:05 +0200 Subject: 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 The PAGE_MAP_ANONYMOUS bits are superseded by commit 26bab757d41b ("linux-user: Introduce PAGE_ANON").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 Reviewed-by: Laurent Vivier Message-Id: <20220621144205.158452-1-iii@linux.ibm.com> Signed-off-by: Laurent Vivier --- linux-user/syscall.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'linux-user/syscall.c') diff --git a/linux-user/syscall.c b/linux-user/syscall.c index f55cdebee5..8f68f255c0 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: -- cgit 1.4.1 From 9a7f682c26acae5bc8bfd1f7c774070da54f1625 Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Sat, 28 May 2022 12:52:10 +0200 Subject: linux-user: Adjust child_tidptr on set_tid_address() syscall Keep track of the new child tidptr given by a set_tid_address() syscall. Do not call the host set_tid_address() syscall because we are emulating the behaviour of writing to child_tidptr in the exit() path. Signed-off-by: Helge Deller Reviewed-by: Richard Henderson Reviewed-by: Laurent Vivier Message-Id: Signed-off-by: Laurent Vivier --- linux-user/syscall.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) (limited to 'linux-user/syscall.c') diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 8f68f255c0..669add74c1 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -320,9 +320,6 @@ _syscall3(int,sys_syslog,int,type,char*,bufp,int,len) #ifdef __NR_exit_group _syscall1(int,exit_group,int,error_code) #endif -#if defined(TARGET_NR_set_tid_address) && defined(__NR_set_tid_address) -_syscall1(int,set_tid_address,int *,tidptr) -#endif #if defined(__NR_futex) _syscall6(int,sys_futex,int *,uaddr,int,op,int,val, const struct timespec *,timeout,int *,uaddr2,int,val3) @@ -12196,9 +12193,14 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1, } #endif -#if defined(TARGET_NR_set_tid_address) && defined(__NR_set_tid_address) +#if defined(TARGET_NR_set_tid_address) case TARGET_NR_set_tid_address: - return get_errno(set_tid_address((int *)g2h(cpu, arg1))); + { + TaskState *ts = cpu->opaque; + ts->child_tidptr = arg1; + /* do not call host set_tid_address() syscall, instead return tid() */ + return get_errno(sys_gettid()); + } #endif case TARGET_NR_tkill: -- cgit 1.4.1