[Qemu-devel] [PATCH] linux-user: Fix definition of target_sigevent for 32-bit guests

[Qemu-devel] [PATCH] linux-user: Fix definition of target_sigevent for 32-bit guests

[Peter Maydell]

The sigevent structure includes a union with some fields which
are pointers. For the QEMU target_sigevent structure we must
represent these as abi_ulongs, not host function pointers.

This error was causing the compiler to believe it should 8-align
the _sigev_un union on a 64-bit host, which meant that the
code in target_to_host_sigevent() was looking at the wrong
offset to find the _tid field, and timer_create() would
spuriously fail with EINVAL.

This fixes the final loose end noted in LP:1042388.

While we're editing the structure, switch the 'int32_t' fields
to 'abi_int'; this will only matter for guests with non-standard
integer alignment like m68k.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 linux-user/syscall_defs.h | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
index dbf6a38..f4417ee 100644
--- a/linux-user/syscall_defs.h
+++ b/linux-user/syscall_defs.h
@@ -2618,15 +2618,19 @@ typedef int32_t target_timer_t;
 
 struct target_sigevent {
     target_sigval_t sigev_value;
-    int32_t sigev_signo;
-    int32_t sigev_notify;
+    abi_int sigev_signo;
+    abi_int sigev_notify;
     union {
-        int32_t _pad[TARGET_SIGEV_PAD_SIZE];
-        int32_t _tid;
+        abi_int _pad[TARGET_SIGEV_PAD_SIZE];
+        abi_int _tid;
 
+        /* The kernel (and thus QEMU) never looks at these;
+         * they're only used as part of the ABI between a
+         * userspace program and libc.
+         */
         struct {
-            void (*_function)(sigval_t);
-            void *_attribute;
+            abi_ulong _function;
+            abi_ulong _attribute;
         } _sigev_thread;
     } _sigev_un;
 };
-- 
2.7.4

Re: [Qemu-devel] [PATCH] linux-user: Fix definition of target_sigevent for 32-bit guests

[Peter Maydell]

Ping ?

thanks
-- PMM

On 2 September 2016 at 18:40, Peter Maydell <peter.maydell@linaro.org> wrote:
> The sigevent structure includes a union with some fields which
> are pointers. For the QEMU target_sigevent structure we must
> represent these as abi_ulongs, not host function pointers.
>
> This error was causing the compiler to believe it should 8-align
> the _sigev_un union on a 64-bit host, which meant that the
> code in target_to_host_sigevent() was looking at the wrong
> offset to find the _tid field, and timer_create() would
> spuriously fail with EINVAL.
>
> This fixes the final loose end noted in LP:1042388.
>
> While we're editing the structure, switch the 'int32_t' fields
> to 'abi_int'; this will only matter for guests with non-standard
> integer alignment like m68k.
>
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  linux-user/syscall_defs.h | 16 ++++++++++------
>  1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index dbf6a38..f4417ee 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -2618,15 +2618,19 @@ typedef int32_t target_timer_t;
>
>  struct target_sigevent {
>      target_sigval_t sigev_value;
> -    int32_t sigev_signo;
> -    int32_t sigev_notify;
> +    abi_int sigev_signo;
> +    abi_int sigev_notify;
>      union {
> -        int32_t _pad[TARGET_SIGEV_PAD_SIZE];
> -        int32_t _tid;
> +        abi_int _pad[TARGET_SIGEV_PAD_SIZE];
> +        abi_int _tid;
>
> +        /* The kernel (and thus QEMU) never looks at these;
> +         * they're only used as part of the ABI between a
> +         * userspace program and libc.
> +         */
>          struct {
> -            void (*_function)(sigval_t);
> -            void *_attribute;
> +            abi_ulong _function;
> +            abi_ulong _attribute;
>          } _sigev_thread;
>      } _sigev_un;
>  };
> --
> 2.7.4

Re: [Qemu-devel] [PATCH] linux-user: Fix definition of target_sigevent for 32-bit guests

[Riku Voipio]

On Tue, Oct 04, 2016 at 02:08:24PM +0100, Peter Maydell wrote:
> Ping ?

Applied, thanks.
 
> thanks
> -- PMM
> 
> On 2 September 2016 at 18:40, Peter Maydell <peter.maydell@linaro.org> wrote:
> > The sigevent structure includes a union with some fields which
> > are pointers. For the QEMU target_sigevent structure we must
> > represent these as abi_ulongs, not host function pointers.
> >
> > This error was causing the compiler to believe it should 8-align
> > the _sigev_un union on a 64-bit host, which meant that the
> > code in target_to_host_sigevent() was looking at the wrong
> > offset to find the _tid field, and timer_create() would
> > spuriously fail with EINVAL.
> >
> > This fixes the final loose end noted in LP:1042388.
> >
> > While we're editing the structure, switch the 'int32_t' fields
> > to 'abi_int'; this will only matter for guests with non-standard
> > integer alignment like m68k.
> >
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > ---
> >  linux-user/syscall_defs.h | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> > index dbf6a38..f4417ee 100644
> > --- a/linux-user/syscall_defs.h
> > +++ b/linux-user/syscall_defs.h
> > @@ -2618,15 +2618,19 @@ typedef int32_t target_timer_t;
> >
> >  struct target_sigevent {
> >      target_sigval_t sigev_value;
> > -    int32_t sigev_signo;
> > -    int32_t sigev_notify;
> > +    abi_int sigev_signo;
> > +    abi_int sigev_notify;
> >      union {
> > -        int32_t _pad[TARGET_SIGEV_PAD_SIZE];
> > -        int32_t _tid;
> > +        abi_int _pad[TARGET_SIGEV_PAD_SIZE];
> > +        abi_int _tid;
> >
> > +        /* The kernel (and thus QEMU) never looks at these;
> > +         * they're only used as part of the ABI between a
> > +         * userspace program and libc.
> > +         */
> >          struct {
> > -            void (*_function)(sigval_t);
> > -            void *_attribute;
> > +            abi_ulong _function;
> > +            abi_ulong _attribute;
> >          } _sigev_thread;
> >      } _sigev_un;
> >  };
> > --
> > 2.7.4
>