Bug#422421: gcc-4.1: generates wrong code on hppa when TLS variables are used

[Aurelien Jarno <aurel32@debian.org>]

Package: gcc-4.1
Version: 4.1.2-5
Severity: grave
Tags: patch
Justification: breaks the glibc

Hi,

You are already aware of the problem, but I think it is better to
summarize it here to get an history of the problem.

GCC generates wrong code on hppa when TLS registers are used. This is
due to a bug in __attribute__ ((tls_model ())) which doesn't express
that it uses r19 or r27.

Here is a small test case for the problem:

extern __thread int __libc_errno __attribute__ ((tls_model ("initial-exec")));
extern void free (void *__ptr) __attribute__ ((__nothrow__));

void test(int *p)
{
  free (p);
  __libc_errno = 25;
}

And the corresponding assembly code:

00000000 <test>:
test():
   0:   6b c2 3f d9     stw rp,-14(sp)
   4:   6f c4 00 80     stw,ma r4,40(sp)
   8:   e8 40 00 00     b,l 10 <test+0x10>,rp
                        8: R_PARISC_PCREL17F    free
   c:   6b d3 3f c1     stw r19,-20(sp)
  10:   2a 60 00 00     addil L%0,r19,r1
                        10: R_PARISC_LTOFF_TP21L        __libc_errno
  14:   48 3c 00 00     ldw 0(r1),ret0
                        14: R_PARISC_LTOFF_TP14R        __libc_errno
  18:   34 15 00 32     ldi 19,r21
  1c:   03 60 08 b4     mfctl tr3,r20
  20:   0b 94 0a 14     add,l r20,ret0,r20
  24:   0e 95 12 80     stw r21,0(r20)
  28:   4b c2 3f 59     ldw -54(sp),rp
  2c:   e8 40 c0 00     bv r0(rp)
  30:   4f c4 3f 81     ldw,mb -40(sp),r4

There is a missing a save/restore of the PIC register around the call to
free. 

The attached patch fixes the problem, it has been submitted upstream and 
almost accepted (just a typo in the Changelog to fix).

I have rebuilt gcc with it, and then rebuilt the glibc with the rebuilt
gcc. The bug is fixed, and there is no regression in the testsuite.

Bye,
Aurelien

PS: Thanks to Carlos O'Donell for his help in the debugging process.

-- System Information:
Debian Release: lenny/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.18-4-xen-amd64 (SMP w/2 CPU cores)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gcc-4.1 depends on:
ii  binutils               2.17cvs20070426-4 The GNU assembler, linker and bina
ii  cpp-4.1                4.1.2-5           The GNU C preprocessor
ii  gcc-4.1-base           4.1.2-5           The GNU Compiler Collection (base 
ii  libc6                  2.5-5             GNU C Library: Shared libraries
ii  libgcc1                1:4.1.2-5         GCC support library

Versions of packages gcc-4.1 recommends:
ii  libc6-dev                     2.5-5      GNU C Library: Development Librari
ii  libmudflap0-dev               4.1.2-5    GCC mudflap support libraries (dev

-- no debconf information

Attachment: hppa-caller-save-pic-tls.dpatch
Description: application/shellscript