arm: Update _dl_tlsdesc_dynamic to preserve caller-saved registers (BZ 31372)

ARM _dl_tlsdesc_dynamic slow path has two issues:

  * The ip/r12 is defined by AAPCS as a scratch register, and gcc is
    used to save the stack pointer before on some function calls.  So it
    should also be saved/restored as well.  It fixes the tst-gnu2-tls2.

  * None of the possible VFP registers are saved/restored.  ARM has the
    additional complexity to have different VFP bank sizes (depending of
    VFP support by the chip).

The tst-gnu2-tls2 test is extended to check for VFP registers, although
only for hardfp builds.  Different than setcontext, _dl_tlsdesc_dynamic
does not have  HWCAP_ARM_IWMMXT (I don't have a way to properly test
it and it is almost a decade since newer hardware was released).

With this patch there is no need to mark tst-gnu2-tls2 as XFAIL.

Checked on arm-linux-gnueabihf.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/sysdeps/arm/configure b/sysdeps/arm/configure
index 35e2918..4ef4d46 100644
--- a/sysdeps/arm/configure
+++ b/sysdeps/arm/configure
@@ -187,6 +187,38 @@ else
 default-abi = soft"
 fi
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether VFP supports 32 registers" >&5
+printf %s "checking whether VFP supports 32 registers... " >&6; }
+if test ${libc_cv_arm_pcs_vfp_d32+y}
+then :
+  printf %s "(cached) " >&6
+else $as_nop
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+void foo (void)
+{
+  asm volatile ("vldr d16,=17" : : : "d16");
+}
+
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+  libc_cv_arm_pcs_vfp_d32=yes
+else $as_nop
+  libc_cv_arm_pcs_vfp_d32=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $libc_cv_arm_pcs_vfp_d32" >&5
+printf "%s\n" "$libc_cv_arm_pcs_vfp_d32" >&6; }
+if test "$libc_cv_arm_pcs_vfp_d32" = yes ;
+then
+  printf "%s\n" "#define HAVE_ARM_PCS_VFP_D32 1" >>confdefs.h
+
+fi
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether PC-relative relocs in movw/movt work properly" >&5
 printf %s "checking whether PC-relative relocs in movw/movt work properly... " >&6; }
 if test ${libc_cv_arm_pcrel_movw+y}