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bpo-46968: Fix faulthandler for Sapphire Rapids Xeon (pythonGH-31789) (pythonGH-31831)
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. (cherry picked from commit 3b128c0) Co-authored-by: Oleksandr Pavlyk <oleksandr.pavlyk@intel.com>
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‎Misc/NEWS.d/next/Library/2022-03-10-14-51-11.bpo-46968.ym2QxL.rst‎

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:mod:`faulthandler`: On Linux 5.14 and newer, dynamically determine size of
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signal handler stack size CPython allocates using ``getauxval(AT_MINSIGSTKSZ)``.
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This changes allows for Python extension's request to Linux kernel to use
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AMX_TILE instruction set on Sapphire Rapids Xeon processor to succeed,
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unblocking use of the ISA in frameworks.

‎Modules/faulthandler.c‎

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

‎configure‎

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@@ -8042,7 +8042,7 @@ sys/stat.h sys/syscall.h sys/sys_domain.h sys/termio.h sys/time.h \
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sys/times.h sys/types.h sys/uio.h sys/un.h sys/utsname.h sys/wait.h pty.h \
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libutil.h sys/resource.h netpacket/packet.h sysexits.h bluetooth.h \
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linux/tipc.h linux/random.h spawn.h util.h alloca.h endian.h \
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sys/endian.h sys/sysmacros.h linux/memfd.h linux/wait.h sys/memfd.h sys/mman.h
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sys/endian.h sys/sysmacros.h linux/auxvec.h linux/memfd.h linux/wait.h sys/memfd.h sys/mman.h
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do :
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as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
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ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header" "$ac_includes_default"

‎configure.ac‎

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@@ -2228,7 +2228,7 @@ sys/stat.h sys/syscall.h sys/sys_domain.h sys/termio.h sys/time.h \
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sys/times.h sys/types.h sys/uio.h sys/un.h sys/utsname.h sys/wait.h pty.h \
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libutil.h sys/resource.h netpacket/packet.h sysexits.h bluetooth.h \
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linux/tipc.h linux/random.h spawn.h util.h alloca.h endian.h \
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sys/endian.h sys/sysmacros.h linux/memfd.h linux/wait.h sys/memfd.h sys/mman.h)
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sys/endian.h sys/sysmacros.h linux/auxvec.h linux/memfd.h linux/wait.h sys/memfd.h sys/mman.h)
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AC_HEADER_DIRENT
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AC_HEADER_MAJOR
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‎pyconfig.h.in‎

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/* Define to 1 if you have the `linkat' function. */
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#undef HAVE_LINKAT
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/* Define to 1 if you have the <linux/auxvec.h> header file. */
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#undef HAVE_LINUX_AUXVEC_H
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/* Define to 1 if you have the <linux/can/bcm.h> header file. */
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#undef HAVE_LINUX_CAN_BCM_H
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