bpo-46968: Fix faulthandler for Sapphire Rapids Xeon (GH-31789)

In Linux kernel 5.14 one can dynamically request size of altstacksize
based on hardware capabilities with getauxval(AT_MINSIGSTKSZ).

This changes allows for Python extension's request to Linux kernel
to use AMX_TILE instruction set on Sapphire Rapids Xeon processor
to succeed, unblocking use of the ISA in frameworks.

Introduced HAVE_LINUX_AUXVEC_H in configure.ac and pyconfig.h.in
Used cpython_autoconf:269 docker container to generate configure.

diff --git a/Misc/NEWS.d/next/Library/2022-03-10-14-51-11.bpo-46968.ym2QxL.rst b/Misc/NEWS.d/next/Library/2022-03-10-14-51-11.bpo-46968.ym2QxL.rst
new file mode 100644 (file)
index 0000000..0da5ae7
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-03-10-14-51-11.bpo-46968.ym2QxL.rst
@@ -0,0 +1,5 @@
+:mod:`faulthandler`: On Linux 5.14 and newer, dynamically determine size of
+signal handler stack size CPython allocates using ``getauxval(AT_MINSIGSTKSZ)``.
+This changes allows for Python extension's request to Linux kernel to use
+AMX_TILE instruction set on Sapphire Rapids Xeon processor to succeed,
+unblocking use of the ISA in frameworks.

diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index db3f4fbe5c616b2fd045f136883d9cc9a3e65afc..744698cd7aba2521635d6bea9d98db27320f7d0b 100644 (file)
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -20,6 +20,17 @@
 #  include <sys/resource.h>
 #endif
 
+/* Using an alternative stack requires sigaltstack()
+   and sigaction() SA_ONSTACK */
+#if defined(HAVE_SIGALTSTACK) && defined(HAVE_SIGACTION)
+#  define FAULTHANDLER_USE_ALT_STACK
+#endif
+
+#if defined(FAULTHANDLER_USE_ALT_STACK) && defined(HAVE_LINUX_AUXVEC_H)
+#  include <linux/auxvec.h>
+#  include <sys/auxv.h>
+#endif
+
 /* Allocate at maximum 100 MiB of the stack to raise the stack overflow */
 #define STACK_OVERFLOW_MAX_SIZE (100 * 1024 * 1024)
 
@@ -137,12 +148,6 @@ static fault_handler_t faulthandler_handlers[] = {
 static const size_t faulthandler_nsignals = \
     Py_ARRAY_LENGTH(faulthandler_handlers);
 
-/* Using an alternative stack requires sigaltstack()
-   and sigaction() SA_ONSTACK */
-#if defined(HAVE_SIGALTSTACK) && defined(HAVE_SIGACTION)
-#  define FAULTHANDLER_USE_ALT_STACK
-#endif
-
 #ifdef FAULTHANDLER_USE_ALT_STACK
 static stack_t stack;
 static stack_t old_stack;
@@ -1373,6 +1378,15 @@ _PyFaulthandler_Init(int enable)
        signal handler uses more than SIGSTKSZ bytes of stack memory on some
        platforms. */
     stack.ss_size = SIGSTKSZ * 2;
+#ifdef AT_MINSIGSTKSZ
+    /* bpo-46968: Query Linux for minimal stack size to ensure signal delivery
+       for the hardware running CPython. This OS feature is available in
+       Linux kernel version >= 5.14 */
+    unsigned long at_minstack_size = getauxval(AT_MINSIGSTKSZ);
+    if (at_minstack_size != 0) {
+        stack.ss_size = SIGSTKSZ + at_minstack_size;
+    }
+#endif
 #endif
 
     memset(&thread, 0, sizeof(thread));

diff --git a/configure b/configure
index a8e78ce73e708be69f5c7b452ddd956501172442..4d585eba626a60c7f84ce7327538c4f1e46a8eb1 100755 (executable)
--- a/configure
+++ b/configure
@@ -8652,7 +8652,7 @@ $as_echo "#define STDC_HEADERS 1" >>confdefs.h
 # checks for header files
 for ac_header in  \
   alloca.h asm/types.h bluetooth.h conio.h crypt.h direct.h dlfcn.h endian.h errno.h fcntl.h grp.h \
-  ieeefp.h io.h langinfo.h libintl.h libutil.h linux/memfd.h linux/random.h linux/soundcard.h \
+  ieeefp.h io.h langinfo.h libintl.h libutil.h linux/auxvec.h linux/memfd.h linux/random.h linux/soundcard.h \
   linux/tipc.h linux/wait.h netinet/in.h netpacket/packet.h poll.h process.h pthread.h pty.h \
   sched.h setjmp.h shadow.h signal.h spawn.h stropts.h sys/audioio.h sys/bsdtty.h sys/devpoll.h \
   sys/endian.h sys/epoll.h sys/event.h sys/eventfd.h sys/file.h sys/ioctl.h sys/kern_control.h \

diff --git a/configure.ac b/configure.ac
index 3e7d04b8eae62030b611d873dc2be732144ecc5f..81262ae38e5344ef1b9b6d14002343f5bf68892a 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -2375,7 +2375,7 @@ AC_DEFINE(STDC_HEADERS, 1, [Define to 1 if you have the ANSI C header files.])
 # checks for header files
 AC_CHECK_HEADERS([ \
   alloca.h asm/types.h bluetooth.h conio.h crypt.h direct.h dlfcn.h endian.h errno.h fcntl.h grp.h \
-  ieeefp.h io.h langinfo.h libintl.h libutil.h linux/memfd.h linux/random.h linux/soundcard.h \
+  ieeefp.h io.h langinfo.h libintl.h libutil.h linux/auxvec.h linux/memfd.h linux/random.h linux/soundcard.h \
   linux/tipc.h linux/wait.h netinet/in.h netpacket/packet.h poll.h process.h pthread.h pty.h \
   sched.h setjmp.h shadow.h signal.h spawn.h stropts.h sys/audioio.h sys/bsdtty.h sys/devpoll.h \
   sys/endian.h sys/epoll.h sys/event.h sys/eventfd.h sys/file.h sys/ioctl.h sys/kern_control.h \

diff --git a/pyconfig.h.in b/pyconfig.h.in
index 40057e0ff87d954dea7d99692788961c398afbc6..1b84ee108fbfc8cfc9717118e5d45590da5b14c8 100644 (file)
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -661,6 +661,9 @@
 /* Define to 1 if you have the `linkat' function. */
 #undef HAVE_LINKAT
 
+/* Define to 1 if you have the <linux/auxvec.h> header file. */
+#undef HAVE_LINUX_AUXVEC_H
+
 /* Define to 1 if you have the <linux/can/bcm.h> header file. */
 #undef HAVE_LINUX_CAN_BCM_H