[Qemu-devel] [PATCH v3] linux-user: fix preadv/pwritev offsets

[Max Filippov]

preadv/pwritev accept low and high parts of file offset in two separate
parameters. When host bitness doesn't match guest bitness these parts
must be appropriately recombined.
Introduce target_to_host_low_high that does this recombination and use
it in preadv/pwritev syscalls.

This fixes glibc testsuite test misc/tst-preadvwritev64.

Signed-off-by: Max Filippov <address@hidden>
---
Changes v2->v3:
- rename helper to target_to_host_low_high;
- handle cases TARGET_LONG_BITS * 2 > HOST_LONG_BITS and
  TARGET_LONG_BITS < 2 * HOST_LONG_BITS correctly.

Changes v1->v2:
- fix host high computation in TARGET_LONG_BITS > HOST_LONG_BITS case

 linux-user/syscall.c | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5ef517613577..13ad572e0d3b 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3386,6 +3386,30 @@ static abi_long do_getsockopt(int sockfd, int level, int 
optname,
     return ret;
 }
 
+static void target_to_host_low_high(abi_ulong tlow,
+                                    abi_ulong thigh,
+                                    unsigned long *hlow,
+                                    unsigned long *hhigh)
+{
+#if TARGET_LONG_BITS == HOST_LONG_BITS
+        *hlow = tlow;
+        *hhigh = thigh;
+#elif TARGET_LONG_BITS < HOST_LONG_BITS
+        *hlow = tlow | (unsigned long)thigh << TARGET_LONG_BITS;
+#if TARGET_LONG_BITS * 2 <= HOST_LONG_BITS
+        *hhigh = 0;
+#else
+        *hhigh = (unsigned long)thigh >> (HOST_LONG_BITS - TARGET_LONG_BITS);
+#endif
+#else
+        *hlow = (unsigned long)tlow;
+        *hhigh = (unsigned long)(tlow >> HOST_LONG_BITS);
+#if TARGET_LONG_BITS < 2 * HOST_LONG_BITS
+        *hhigh |= (unsigned long)thigh << (TARGET_LONG_BITS - HOST_LONG_BITS);
+#endif
+#endif
+}
+
 static struct iovec *lock_iovec(int type, abi_ulong target_addr,
                                 abi_ulong count, int copy)
 {
@@ -10449,7 +10473,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
         {
             struct iovec *vec = lock_iovec(VERIFY_WRITE, arg2, arg3, 0);
             if (vec != NULL) {
-                ret = get_errno(safe_preadv(arg1, vec, arg3, arg4, arg5));
+                unsigned long low, high;
+
+                target_to_host_low_high(arg4, arg5, &low, &high);
+                ret = get_errno(safe_preadv(arg1, vec, arg3, low, high));
                 unlock_iovec(vec, arg2, arg3, 1);
             } else {
                 ret = -host_to_target_errno(errno);
@@ -10462,7 +10489,10 @@ abi_long do_syscall(void *cpu_env, int num, abi_long 
arg1,
         {
             struct iovec *vec = lock_iovec(VERIFY_READ, arg2, arg3, 1);
             if (vec != NULL) {
-                ret = get_errno(safe_pwritev(arg1, vec, arg3, arg4, arg5));
+                unsigned long low, high;
+
+                target_to_host_low_high(arg4, arg5, &low, &high);
+                ret = get_errno(safe_pwritev(arg1, vec, arg3, low, high));
                 unlock_iovec(vec, arg2, arg3, 0);
             } else {
                 ret = -host_to_target_errno(errno);
-- 
2.11.0