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, 4 insertions, 0 deletions

diff --git a/elf/tst-gnu2-tls2.h b/elf/tst-gnu2-tls2.h
index 77964a57a3..1ade8151e2 100644
--- a/elf/tst-gnu2-tls2.h
+++ b/elf/tst-gnu2-tls2.h
@@ -27,6 +27,10 @@ extern struct tls *apply_tls (struct tls *);
 
 /* An architecture can define them to verify that clobber caller-saved
    registers aren't changed by the implicit TLSDESC call.  */
+#ifndef INIT_TLSDESC_CALL
+# define INIT_TLSDESC_CALL()
+#endif
+
 #ifndef BEFORE_TLSDESC_CALL
 # define BEFORE_TLSDESC_CALL()
 #endif