[3.13] gh-142342: Fix m68k assembler operand constraints for `%fpcr` access (gh-14234...

On m68k, an fmove instruction accessing %fpcr may only move from
or to a data register or a memory operand. The constraint "g" also
permits the use of address registers, which is invalid. The correct
constraint is "dm". Beginning with GCC 15, the register allocator
picks an address register in the code which causes SIGILL during
runtime.
(cherry picked from commit 02c085d48b59c00fb7f4454fb13933e1c2c0b01a)

Co-authored-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Co-authored-by: Michael Karcher <github@mkarcher.dialup.fu-berlin.de>

diff --git a/Include/internal/pycore_pymath.h b/Include/internal/pycore_pymath.h
index 7a4e1c1eb714f732a399baaecb81848b8d0f5527..12d3efc33c6f036392816f7ac4dfd33e3412d51a 100644 (file)
--- a/Include/internal/pycore_pymath.h
+++ b/Include/internal/pycore_pymath.h
@@ -146,17 +146,17 @@ extern void _Py_set_387controlword(unsigned short);
     unsigned int old_fpcr, new_fpcr
 #define _Py_SET_53BIT_PRECISION_START                                   \
     do {                                                                \
-        __asm__ ("fmove.l %%fpcr,%0" : "=g" (old_fpcr));                \
+        __asm__ ("fmove.l %%fpcr,%0" : "=dm" (old_fpcr));               \
         /* Set double precision / round to nearest.  */                 \
         new_fpcr = (old_fpcr & ~0xf0) | 0x80;                           \
         if (new_fpcr != old_fpcr) {                                     \
-              __asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (new_fpcr));\
+            __asm__ volatile ("fmove.l %0,%%fpcr" : : "dm" (new_fpcr)); \
         }                                                               \
     } while (0)
 #define _Py_SET_53BIT_PRECISION_END                                     \
     do {                                                                \
         if (new_fpcr != old_fpcr) {                                     \
-            __asm__ volatile ("fmove.l %0,%%fpcr" : : "g" (old_fpcr));  \
+            __asm__ volatile ("fmove.l %0,%%fpcr" : : "dm" (old_fpcr)); \
         }                                                               \
     } while (0)
 #endif

diff --git a/Misc/NEWS.d/next/Core and Builtins/2025-12-08-13-04-37.gh-issue-142343.BTAyML.rst b/Misc/NEWS.d/next/Core and Builtins/2025-12-08-13-04-37.gh-issue-142343.BTAyML.rst
new file mode 100644 (file)
index 0000000..9da936c
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2025-12-08-13-04-37.gh-issue-142343.BTAyML.rst
@@ -0,0 +1 @@
+Fix SIGILL crash on m68k due to incorrect assembly constraint.

diff --git a/configure b/configure
index 901a26c9602e922d6dd2b4b64699504022782ddb..9c5b8c717eb144be1732d6c9ed9fc0fb9beef208 100755 (executable)
--- a/configure
+++ b/configure
@@ -24105,8 +24105,8 @@ main (void)
 {
 
   unsigned int fpcr;
-  __asm__ __volatile__ ("fmove.l %%fpcr,%0" : "=g" (fpcr));
-  __asm__ __volatile__ ("fmove.l %0,%%fpcr" : : "g" (fpcr));
+  __asm__ __volatile__ ("fmove.l %%fpcr,%0" : "=dm" (fpcr));
+  __asm__ __volatile__ ("fmove.l %0,%%fpcr" : : "dm" (fpcr));
 
   ;
   return 0;

diff --git a/configure.ac b/configure.ac
index 597a44b331a02f69248fc0e1a17798efc3b501f3..5bd98df87f336b8dcfe893bee9be045c0ef41133 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -6040,8 +6040,8 @@ AS_VAR_IF([ac_cv_gcc_asm_for_x87], [yes], [
 AC_CACHE_CHECK([whether we can use gcc inline assembler to get and set mc68881 fpcr], [ac_cv_gcc_asm_for_mc68881], [
 AC_LINK_IFELSE(   [AC_LANG_PROGRAM([[]], [[
   unsigned int fpcr;
-  __asm__ __volatile__ ("fmove.l %%fpcr,%0" : "=g" (fpcr));
-  __asm__ __volatile__ ("fmove.l %0,%%fpcr" : : "g" (fpcr));
+  __asm__ __volatile__ ("fmove.l %%fpcr,%0" : "=dm" (fpcr));
+  __asm__ __volatile__ ("fmove.l %0,%%fpcr" : : "dm" (fpcr));
 ]])],[ac_cv_gcc_asm_for_mc68881=yes],[ac_cv_gcc_asm_for_mc68881=no])
 ])
 AS_VAR_IF([ac_cv_gcc_asm_for_mc68881], [yes], [