Re: [Qemu-devel] [PULL 1/1] linux-user: fix preadv/pwritev offsets

[Richard Henderson]

On 04/10/2018 01:29 PM, Max Filippov wrote:
> On Mon, Apr 9, 2018 at 8:20 PM, Richard Henderson
>  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~

Re: [Qemu-devel] [PULL 1/1] linux-user: fix preadv/pwritev offsets

[Max Filippov]

On Mon, Apr 9, 2018 at 8:20 PM, Richard Henderson
 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?

-- 
Thanks.
-- Max

Re: [Qemu-devel] [PULL 1/1] linux-user: fix preadv/pwritev offsets

[Richard Henderson]

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~

[Qemu-devel] [PULL 1/1] 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.

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

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, , );
+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, , );
+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