[PULL,1/1] linux-user: fix preadv/pwritev offsets

Commit Message

Max Filippov April 10, 2018, 2:17 a.m. UTC

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.

Reviewed-by: Laurent Vivier <[e-mail]>
Reviewed-by: Richard Henderson <[e-mail]>
Signed-off-by: Max Filippov <[e-mail]>
---
 linux-user/syscall.c | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

Comments

Richard Henderson April 10, 2018, 3:20 a.m. UTC | #1

On 04/10/2018 12:17 PM, Max Filippov wrote:
> +    uint64_t off = tlow |
> +        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<

There's a second instance of long long here; needs uint64_t.


r~

Max Filippov April 10, 2018, 3:29 a.m. UTC | #2

On Mon, Apr 9, 2018 at 8:20 PM, Richard Henderson
<[e-mail]> wrote:
> On 04/10/2018 12:17 PM, Max Filippov wrote:
>> +    uint64_t off = tlow |
>> +        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<
>
> There's a second instance of long long here; needs uint64_t.

Ehh, will fix.
BTW, why is uint64_t here better than unsigned long long? Just
shorter?

Richard Henderson April 10, 2018, 4:05 a.m. UTC | #3

On 04/10/2018 01:29 PM, Max Filippov wrote:
> On Mon, Apr 9, 2018 at 8:20 PM, Richard Henderson
> <[e-mail]> wrote:
>> On 04/10/2018 12:17 PM, Max Filippov wrote:
>>> +    uint64_t off = tlow |
>>> +        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<
>>
>> There's a second instance of long long here; needs uint64_t.
> 
> Ehh, will fix.
> BTW, why is uint64_t here better than unsigned long long? Just
> shorter?

Because it's more explicit about the number of bits we're talking about.


r~

Patch

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5ef517613577..0eab5cc6ade1 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3386,6 +3386,23 @@  static abi_long do_getsockopt(int sockfd, int level, int optname,
     return ret;
 }
 
+/* Convert target low/high pair representing file offset into the host
+ * low/high pair. This function doesn't handle offsets bigger than 64 bits
+ * as the kernel doesn't handle them either.
+ */
+static void target_to_host_low_high(abi_ulong tlow,
+                                    abi_ulong thigh,
+                                    unsigned long *hlow,
+                                    unsigned long *hhigh)
+{
+    uint64_t off = tlow |
+        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<
+        TARGET_LONG_BITS / 2;
+
+    *hlow = off;
+    *hhigh = (off >> HOST_LONG_BITS / 2) >> HOST_LONG_BITS / 2;
+}
+
 static struct iovec *lock_iovec(int type, abi_ulong target_addr,
                                 abi_ulong count, int copy)
 {
@@ -10449,7 +10466,10 @@  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 +10482,10 @@  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);