[Qemu-devel] [PATCH v4] linux-user: fix preadv/pwritev offsets

[Qemu-devel] [PATCH v4] 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 <jcmvbkbc@gmail.com>
---
Changes v3->v4:
- recombine offset into unsigned long long and split it into two longs.

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 | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 5ef517613577..eb9a31f1e092 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3386,6 +3386,20 @@ 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)
+{
+    unsigned long long off = tlow |
+        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<
+        TARGET_LONG_BITS / 2;
+
+    *hlow = (unsigned long)off;
+    *hhigh = (unsigned long)((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 +10463,10 @@ 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 +10479,10 @@ 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

Re: [Qemu-devel] [PATCH v4] linux-user: fix preadv/pwritev offsets

[Laurent Vivier]

Le 06/04/2018 à 03:36, Max Filippov a écrit :
> 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 <jcmvbkbc@gmail.com>
> ---
> Changes v3->v4:
> - recombine offset into unsigned long long and split it into two longs.
> 
> 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 | 24 ++++++++++++++++++++++--
>  1 file changed, 22 insertions(+), 2 deletions(-)
> 

Reviewed-by: Laurent Vivier <laurent@vivier.eu>

Re: [Qemu-devel] [PATCH v4] linux-user: fix preadv/pwritev offsets

[Richard Henderson]

On 04/06/2018 11:36 AM, Max Filippov wrote:
> +static void target_to_host_low_high(abi_ulong tlow,
> +                                    abi_ulong thigh,
> +                                    unsigned long *hlow,
> +                                    unsigned long *hhigh)
> +{
> +    unsigned long long off = tlow |
> +        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<
> +        TARGET_LONG_BITS / 2;

Use uint64_t instead of unsigned long long.

> +
> +    *hlow = (unsigned long)off;
> +    *hhigh = (unsigned long)((off >> HOST_LONG_BITS / 2) >>
> +                             HOST_LONG_BITS / 2);

The casts here are unnecessary and are implied by the assignment.

Otherwise,
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

Re: [Qemu-devel] [PATCH v4] linux-user: fix preadv/pwritev offsets

[Max Filippov]

On Mon, Apr 9, 2018 at 5:23 PM, Richard Henderson
<richard.henderson@linaro.org> wrote:
> On 04/06/2018 11:36 AM, Max Filippov wrote:
>> +static void target_to_host_low_high(abi_ulong tlow,
>> +                                    abi_ulong thigh,
>> +                                    unsigned long *hlow,
>> +                                    unsigned long *hhigh)
>> +{
>> +    unsigned long long off = tlow |
>> +        ((unsigned long long)thigh << TARGET_LONG_BITS / 2) <<
>> +        TARGET_LONG_BITS / 2;
>
> Use uint64_t instead of unsigned long long.

Ok.

>> +
>> +    *hlow = (unsigned long)off;
>> +    *hhigh = (unsigned long)((off >> HOST_LONG_BITS / 2) >>
>> +                             HOST_LONG_BITS / 2);
>
> The casts here are unnecessary and are implied by the assignment.

Did that to avoid value truncation warning. Will drop.

> Otherwise,
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

-- 
Thanks.
-- Max