[PATCH] linux-user: Use public sigev_notify_thread_id member if available

[PATCH] linux-user: Use public sigev_notify_thread_id member if available

[Michael Forney]

_sigev_un._tid is an internal glibc field and is not available on
musl libc. The sigevent(7) man page and Linux UAPI headers both use
sigev_notify_thread_id as a public way to access this field.

musl libc supports this field since 1.2.2[0], and glibc plans to
add support as well[1][2].

If sigev_notify_thread_id is not available, fall back to _sigev_un._tid
as before.

[0] http://git.musl-libc.org/cgit/musl/commit/?id=7c71792e87691451f2a6b76348e83ad1889f1dcb
[1] https://www.openwall.com/lists/musl/2019/08/01/5
[2] https://sourceware.org/bugzilla/show_bug.cgi?id=27417

Signed-off-by: Michael Forney <mforney@mforney.org>
---
 configure            | 16 ++++++++++++++++
 linux-user/syscall.c |  6 +++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 676239c697..fa39b0a727 100755
--- a/configure
+++ b/configure
@@ -4462,6 +4462,19 @@ if compile_prog "" "" ; then
     st_atim=yes
 fi
 
+##########################################
+# check if we have sigev_notify_thread_id
+
+sigev_notify_thread_id=no
+cat > $TMPC << EOF
+#include <stddef.h>
+#include <signal.h>
+int main(void) { return offsetof(struct sigevent, sigev_notify_thread_id); }
+EOF
+if compile_prog "" "" ; then
+    sigev_notify_thread_id=yes
+fi
+
 ##########################################
 # check if trace backend exists
 
@@ -5718,6 +5731,9 @@ fi
 if test "$st_atim" = "yes" ; then
   echo "HAVE_STRUCT_STAT_ST_ATIM=y" >> $config_host_mak
 fi
+if test "$sigev_notify_thread_id" = "yes" ; then
+  echo "HAVE_SIGEV_NOTIFY_THREAD_ID=y" >> $config_host_mak
+fi
 if test "$byteswap_h" = "yes" ; then
   echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
 fi
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index c9f812091c..63464f9a96 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7393,6 +7393,10 @@ static inline abi_long host_to_target_timex64(abi_long target_addr,
 }
 #endif
 
+#ifndef HAVE_SIGEV_NOTIFY_THREAD_ID
+#define sigev_notify_thread_id _sigev_un._tid
+#endif
+
 static inline abi_long target_to_host_sigevent(struct sigevent *host_sevp,
                                                abi_ulong target_addr)
 {
@@ -7413,7 +7417,7 @@ static inline abi_long target_to_host_sigevent(struct sigevent *host_sevp,
     host_sevp->sigev_signo =
         target_to_host_signal(tswap32(target_sevp->sigev_signo));
     host_sevp->sigev_notify = tswap32(target_sevp->sigev_notify);
-    host_sevp->_sigev_un._tid = tswap32(target_sevp->_sigev_un._tid);
+    host_sevp->sigev_notify_thread_id = tswap32(target_sevp->_sigev_un._tid);
 
     unlock_user_struct(target_sevp, target_addr, 1);
     return 0;
-- 
2.31.1

Re: [PATCH] linux-user: Use public sigev_notify_thread_id member if available

[Laurent Vivier]

Le 26/05/2021 à 05:55, Michael Forney a écrit :
> _sigev_un._tid is an internal glibc field and is not available on
> musl libc. The sigevent(7) man page and Linux UAPI headers both use
> sigev_notify_thread_id as a public way to access this field.
> 
> musl libc supports this field since 1.2.2[0], and glibc plans to
> add support as well[1][2].
> 
> If sigev_notify_thread_id is not available, fall back to _sigev_un._tid
> as before.
> 
> [0] http://git.musl-libc.org/cgit/musl/commit/?id=7c71792e87691451f2a6b76348e83ad1889f1dcb
> [1] https://www.openwall.com/lists/musl/2019/08/01/5
> [2] https://sourceware.org/bugzilla/show_bug.cgi?id=27417
> 
> Signed-off-by: Michael Forney <mforney@mforney.org>
> ---
>  configure            | 16 ++++++++++++++++
>  linux-user/syscall.c |  6 +++++-
>  2 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index 676239c697..fa39b0a727 100755
> --- a/configure
> +++ b/configure
> @@ -4462,6 +4462,19 @@ if compile_prog "" "" ; then
>      st_atim=yes
>  fi
>  
> +##########################################
> +# check if we have sigev_notify_thread_id
> +
> +sigev_notify_thread_id=no
> +cat > $TMPC << EOF
> +#include <stddef.h>
> +#include <signal.h>
> +int main(void) { return offsetof(struct sigevent, sigev_notify_thread_id); }
> +EOF
> +if compile_prog "" "" ; then
> +    sigev_notify_thread_id=yes
> +fi
> +
>  ##########################################
>  # check if trace backend exists
>  
> @@ -5718,6 +5731,9 @@ fi
>  if test "$st_atim" = "yes" ; then
>    echo "HAVE_STRUCT_STAT_ST_ATIM=y" >> $config_host_mak
>  fi
> +if test "$sigev_notify_thread_id" = "yes" ; then
> +  echo "HAVE_SIGEV_NOTIFY_THREAD_ID=y" >> $config_host_mak
> +fi
>  if test "$byteswap_h" = "yes" ; then
>    echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
>  fi
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index c9f812091c..63464f9a96 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -7393,6 +7393,10 @@ static inline abi_long host_to_target_timex64(abi_long target_addr,
>  }
>  #endif
>  
> +#ifndef HAVE_SIGEV_NOTIFY_THREAD_ID
> +#define sigev_notify_thread_id _sigev_un._tid
> +#endif
> +
>  static inline abi_long target_to_host_sigevent(struct sigevent *host_sevp,
>                                                 abi_ulong target_addr)
>  {
> @@ -7413,7 +7417,7 @@ static inline abi_long target_to_host_sigevent(struct sigevent *host_sevp,
>      host_sevp->sigev_signo =
>          target_to_host_signal(tswap32(target_sevp->sigev_signo));
>      host_sevp->sigev_notify = tswap32(target_sevp->sigev_notify);
> -    host_sevp->_sigev_un._tid = tswap32(target_sevp->_sigev_un._tid);
> +    host_sevp->sigev_notify_thread_id = tswap32(target_sevp->_sigev_un._tid);
>  
>      unlock_user_struct(target_sevp, target_addr, 1);
>      return 0;
> 

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