git.ipfire.org Git - thirdparty/openembedded/openembedded-core-contrib.git/blob

   1 From 0beed8c190b27a07e7f1145a46a7ca8a75864263 Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Andreas=20M=C3=BCller?= <schnitzeltony@googlemail.com>
   3 Date: Thu, 23 Aug 2012 18:10:57 +0200
   4 Subject: [PATCH] ARM: qemu related workarounds in cpu features detection code
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 This was ported from meta-oe's patch [1]. The original pixman patch is found
  10 at [2].
  11
  12 [1] http://cgit.openembedded.org/meta-openembedded/tree/meta-oe/recipes-graphics/xorg-lib/pixman-0.26.2/0001-ARM-qemu-related-workarounds-in-cpu-features-detecti.patch
  13 [2] http://lists.freedesktop.org/archives/pixman/2011-January/000906.html
  14
  15 Upstream-Status: Inappropriate [other] qemu fix
  16
  17 Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
  18 ---
  19  pixman/pixman-arm.c | 77 ++++++++++++++++++++++++++++++++++++---------
  20  1 file changed, 62 insertions(+), 15 deletions(-)
  21
  22 diff --git a/pixman/pixman-arm.c b/pixman/pixman-arm.c
  23 index d271e96..8f6e241 100644
  24 --- a/pixman/pixman-arm.c
  25 +++ b/pixman/pixman-arm.c
  26 @@ -128,16 +128,34 @@ detect_cpu_features (void)
  27  #include <sys/types.h>
  28  #include <sys/stat.h>
  29  #include <sys/mman.h>
  30 +#include <sys/utsname.h>
  31  #include <fcntl.h>
  32  #include <string.h>
  33  #include <elf.h>
  34
  35 +/*
  36 + * The whole CPU capabilities detection is a bit ugly: when running in
  37 + * userspace qemu, we see /proc/self/auxv from the host system. To make
  38 + * everything even worse, the size of each value is 64-bit when running
  39 + * on a 64-bit host system. So the data is totally bogus because we expect
  40 + * 32-bit values. As AT_PLATFORM value is used as a pointer, it may cause
  41 + * segfault (null pointer dereference on x86-64 host). So in order to be
  42 + * on a safe side, we require that AT_PLATFORM value is found only once,
  43 + * and it has non-zero value (this is still not totally reliable for a big
  44 + * endian 64-bit host system running qemu and may theoretically fail).
  45 + */
  46 +#define ARM_HWCAP_VFP 64
  47 +#define ARM_HWCAP_NEON 4096
  48 +
  49  static arm_cpu_features_t
  50  detect_cpu_features (void)
  51  {
  52      arm_cpu_features_t features = 0;
  53      Elf32_auxv_t aux;
  54      int fd;
  55 +    uint32_t hwcap = 0;
  56 +    const char *plat = NULL;
  57 +    int plat_cnt = 0;
  58
  59      fd = open ("/proc/self/auxv", O_RDONLY);
  60      if (fd >= 0)
  61 @@ -146,30 +164,59 @@ detect_cpu_features (void)
  62         {
  63             if (aux.a_type == AT_HWCAP)
  64             {
  65 -               uint32_t hwcap = aux.a_un.a_val;
  66 -
  67 -               /* hardcode these values to avoid depending on specific
  68 -                * versions of the hwcap header, e.g. HWCAP_NEON
  69 -                */
  70 -               if ((hwcap & 64) != 0)
  71 -                   features |= ARM_VFP;
  72 -               /* this flag is only present on kernel 2.6.29 */
  73 -               if ((hwcap & 4096) != 0)
  74 -                   features |= ARM_NEON;
  75 +               hwcap = aux.a_un.a_val;
  76             }
  77             else if (aux.a_type == AT_PLATFORM)
  78             {
  79 -               const char *plat = (const char*) aux.a_un.a_val;
  80 -
  81 -               if (strncmp (plat, "v7l", 3) == 0)
  82 +               plat = (const char*) aux.a_un.a_val;
  83 +               plat_cnt++;
  84 +           }
  85 +       }
  86 +       close (fd);
  87 +       if (plat == NULL || plat_cnt != 1 || *plat != 'v')
  88 +       {
  89 +           /*
  90 +            * Something seems to be really wrong, most likely we are
  91 +            * running under qemu. Let's use machine type from "uname" for
  92 +            * CPU capabilities detection:
  93 +            * http://www.mail-archive.com/qemu-devel at nongnu.org/msg22212.html
  94 +            */
  95 +           struct utsname u;
  96 +           hwcap = 0; /* clear hwcap, because it is bogus */
  97 +           if (uname (&u) == 0)
  98 +           {
  99 +               if (strcmp (u.machine, "armv7l") == 0)
 100 +               {
 101                     features |= (ARM_V7 | ARM_V6);
 102 -               else if (strncmp (plat, "v6l", 3) == 0)
 103 +                   hwcap |= ARM_HWCAP_VFP;  /* qemu is supposed to emulate vfp */
 104 +                   hwcap |= ARM_HWCAP_NEON; /* qemu is supposed to emulate neon */
 105 +               }
 106 +               else if (strcmp (u.machine, "armv6l") == 0)
 107 +               {
 108                     features |= ARM_V6;
 109 +                   hwcap |= ARM_HWCAP_VFP;  /* qemu is supposed to emulate vfp */
 110 +               }
 111             }
 112         }
 113 -       close (fd);
 114 +       else if (strncmp (plat, "v7l", 3) == 0)
 115 +       {
 116 +           features |= (ARM_V7 | ARM_V6);
 117 +       }
 118 +       else if (strncmp (plat, "v6l", 3) == 0)
 119 +       {
 120 +           features |= ARM_V6;
 121 +       }
 122      }
 123
 124 +    /* hardcode these values to avoid depending on specific
 125 +     * versions of the hwcap header, e.g. HWCAP_NEON
 126 +     */
 127 +    if ((hwcap & ARM_HWCAP_VFP) != 0)
 128 +        features |= ARM_VFP;
 129 +    /* this flag is only present on kernel 2.6.29 */
 130 +    if ((hwcap & ARM_HWCAP_NEON) != 0)
 131 +        features |= ARM_NEON;
 132 +
 133      return features;
 134  }
 135