[3.14] 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 eea8996ba68ca0868ab0dfda35ee7c2e7e037053..5bbbdaab8f42dcd0dad0a2c82be1840f9632cb69 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 46eb0665bf4795a53c3322c2f5acf9437a41b0a5..645628fecf2df75fd652a33b4214b444efe85a72 100755 (executable)
--- a/configure
+++ b/configure
@@ -26010,8 +26010,8 @@ 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 bd4446e9488f7ba5e09b518caf7b71c01916ad54..d81c76fc12230f4ebc31b9ce74ef314e8a1dcf46 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -6099,8 +6099,8 @@ 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], [