From a0f53e1dbb3851bb0f0efcfdbd565b05e4be9cac Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Andreas=20M=C3=BCller?= <schnitzeltony@googlemail.com>
Date: Thu, 23 Aug 2012 18:10:57 +0200
Subject: [PATCH 1/2] ARM: qemu related workarounds in cpu features detection
code
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This was ported from meta-oe's patch [1]. The original pixman patch is found
at [2].
[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
[2] http://lists.freedesktop.org/archives/pixman/2011-January/000906.html
Upstream-Status: Inappropriate [other] qemu fix
Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com>
---
pixman/pixman-arm.c | 82 ++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 65 insertions(+), 17 deletions(-)
diff --git a/pixman/pixman-arm.c b/pixman/pixman-arm.c
index 23374e4..d98bda6 100644
--- a/pixman/pixman-arm.c
+++ b/pixman/pixman-arm.c
@@ -129,16 +129,35 @@ detect_cpu_features (void)
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
+#include <sys/utsname.h>
#include <fcntl.h>
#include <string.h>
#include <elf.h>
+/*
+ * The whole CPU capabilities detection is a bit ugly: when running in
+ * userspace qemu, we see /proc/self/auxv from the host system. To make
+ * everything even worse, the size of each value is 64-bit when running
+ * on a 64-bit host system. So the data is totally bogus because we expect
+ * 32-bit values. As AT_PLATFORM value is used as a pointer, it may cause
+ * segfault (null pointer dereference on x86-64 host). So in order to be
+ * on a safe side, we require that AT_PLATFORM value is found only once,
+ * and it has non-zero value (this is still not totally reliable for a big
+ * endian 64-bit host system running qemu and may theoretically fail).
+ */
+#define ARM_HWCAP_VFP 64
+#define ARM_HWCAP_IWMMXT 512
+#define ARM_HWCAP_NEON 4096
+
static arm_cpu_features_t
detect_cpu_features (void)
{
arm_cpu_features_t features = 0;
Elf32_auxv_t aux;
int fd;
+ uint32_t hwcap = 0;
+ const char *plat = NULL;
+ int plat_cnt = 0;
fd = open ("/proc/self/auxv", O_RDONLY);
if (fd >= 0)
@@ -147,32 +166,61 @@ detect_cpu_features (void)
{
if (aux.a_type == AT_HWCAP)
{
- uint32_t hwcap = aux.a_un.a_val;
-
- /* hardcode these values to avoid depending on specific
- * versions of the hwcap header, e.g. HWCAP_NEON
- */
- if ((hwcap & 64) != 0)
- features |= ARM_VFP;
- if ((hwcap & 512) != 0)
- features |= ARM_IWMMXT;
- /* this flag is only present on kernel 2.6.29 */
- if ((hwcap & 4096) != 0)
- features |= ARM_NEON;
+ hwcap = aux.a_un.a_val;
}
else if (aux.a_type == AT_PLATFORM)
{
- const char *plat = (const char*) aux.a_un.a_val;
-
- if (strncmp (plat, "v7l", 3) == 0)
+ plat = (const char*) aux.a_un.a_val;
+ plat_cnt++;
+ }
+ }
+ close (fd);
+ if (plat == NULL || plat_cnt != 1 || *plat != 'v')
+ {
+ /*
+ * Something seems to be really wrong, most likely we are
+ * running under qemu. Let's use machine type from "uname" for
+ * CPU capabilities detection:
+ * http://www.mail-archive.com/qemu-devel at nongnu.org/msg22212.html
+ */
+ struct utsname u;
+ hwcap = 0; /* clear hwcap, because it is bogus */
+ if (uname (&u) == 0)
+ {
+ if (strcmp (u.machine, "armv7l") == 0)
+ {
features |= (ARM_V7 | ARM_V6);
- else if (strncmp (plat, "v6l", 3) == 0)
+ hwcap |= ARM_HWCAP_VFP; /* qemu is supposed to emulate vfp */
+ hwcap |= ARM_HWCAP_NEON; /* qemu is supposed to emulate neon */
+ }
+ else if (strcmp (u.machine, "armv6l") == 0)
+ {
features |= ARM_V6;
+ hwcap |= ARM_HWCAP_VFP; /* qemu is supposed to emulate vfp */
+ }
}
}
- close (fd);
+ else if (strncmp (plat, "v7l", 3) == 0)
+ {
+ features |= (ARM_V7 | ARM_V6);
+ }
+ else if (strncmp (plat, "v6l", 3) == 0)
+ {
+ features |= ARM_V6;
+ }
}
+ /* hardcode these values to avoid depending on specific
+ * versions of the hwcap header, e.g. HWCAP_NEON
+ */
+ if ((hwcap & ARM_HWCAP_VFP) != 0)
+ features |= ARM_VFP;
+ if ((hwcap & ARM_HWCAP_IWMMXT) != 0)
+ features |= ARM_IWMMXT;
+ /* this flag is only present on kernel 2.6.29 */
+ if ((hwcap & ARM_HWCAP_NEON) != 0)
+ features |= ARM_NEON;
+
return features;
}
--
1.7.6.5