1From a0f53e1dbb3851bb0f0efcfdbd565b05e4be9cac Mon Sep 17 00:00:00 2001 2From: =?UTF-8?q?Andreas=20M=C3=BCller?= <schnitzeltony@googlemail.com> 3Date: Thu, 23 Aug 2012 18:10:57 +0200 4Subject: [PATCH 1/2] ARM: qemu related workarounds in cpu features detection 5 code 6MIME-Version: 1.0 7Content-Type: text/plain; charset=UTF-8 8Content-Transfer-Encoding: 8bit 9 10This was ported from meta-oe's patch [1]. The original pixman patch is found 11at [2]. 12 13[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 14[2] http://lists.freedesktop.org/archives/pixman/2011-January/000906.html 15 16Upstream-Status: Inappropriate [other] qemu fix 17 18Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com> 19--- 20 pixman/pixman-arm.c | 82 ++++++++++++++++++++++++++++++++++++++++---------- 21 1 files changed, 65 insertions(+), 17 deletions(-) 22 23diff --git a/pixman/pixman-arm.c b/pixman/pixman-arm.c 24index 23374e4..d98bda6 100644 25--- a/pixman/pixman-arm.c 26+++ b/pixman/pixman-arm.c 27@@ -129,16 +129,35 @@ detect_cpu_features (void) 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/mman.h> 31+#include <sys/utsname.h> 32 #include <fcntl.h> 33 #include <string.h> 34 #include <elf.h> 35 36+/* 37+ * The whole CPU capabilities detection is a bit ugly: when running in 38+ * userspace qemu, we see /proc/self/auxv from the host system. To make 39+ * everything even worse, the size of each value is 64-bit when running 40+ * on a 64-bit host system. So the data is totally bogus because we expect 41+ * 32-bit values. As AT_PLATFORM value is used as a pointer, it may cause 42+ * segfault (null pointer dereference on x86-64 host). So in order to be 43+ * on a safe side, we require that AT_PLATFORM value is found only once, 44+ * and it has non-zero value (this is still not totally reliable for a big 45+ * endian 64-bit host system running qemu and may theoretically fail). 46+ */ 47+#define ARM_HWCAP_VFP 64 48+#define ARM_HWCAP_IWMMXT 512 49+#define ARM_HWCAP_NEON 4096 50+ 51 static arm_cpu_features_t 52 detect_cpu_features (void) 53 { 54 arm_cpu_features_t features = 0; 55 Elf32_auxv_t aux; 56 int fd; 57+ uint32_t hwcap = 0; 58+ const char *plat = NULL; 59+ int plat_cnt = 0; 60 61 fd = open ("/proc/self/auxv", O_RDONLY); 62 if (fd >= 0) 63@@ -147,32 +166,61 @@ detect_cpu_features (void) 64 { 65 if (aux.a_type == AT_HWCAP) 66 { 67- uint32_t hwcap = aux.a_un.a_val; 68- 69- /* hardcode these values to avoid depending on specific 70- * versions of the hwcap header, e.g. HWCAP_NEON 71- */ 72- if ((hwcap & 64) != 0) 73- features |= ARM_VFP; 74- if ((hwcap & 512) != 0) 75- features |= ARM_IWMMXT; 76- /* this flag is only present on kernel 2.6.29 */ 77- if ((hwcap & 4096) != 0) 78- features |= ARM_NEON; 79+ hwcap = aux.a_un.a_val; 80 } 81 else if (aux.a_type == AT_PLATFORM) 82 { 83- const char *plat = (const char*) aux.a_un.a_val; 84- 85- if (strncmp (plat, "v7l", 3) == 0) 86+ plat = (const char*) aux.a_un.a_val; 87+ plat_cnt++; 88+ } 89+ } 90+ close (fd); 91+ if (plat == NULL || plat_cnt != 1 || *plat != 'v') 92+ { 93+ /* 94+ * Something seems to be really wrong, most likely we are 95+ * running under qemu. Let's use machine type from "uname" for 96+ * CPU capabilities detection: 97+ * http://www.mail-archive.com/qemu-devel at nongnu.org/msg22212.html 98+ */ 99+ struct utsname u; 100+ hwcap = 0; /* clear hwcap, because it is bogus */ 101+ if (uname (&u) == 0) 102+ { 103+ if (strcmp (u.machine, "armv7l") == 0) 104+ { 105 features |= (ARM_V7 | ARM_V6); 106- else if (strncmp (plat, "v6l", 3) == 0) 107+ hwcap |= ARM_HWCAP_VFP; /* qemu is supposed to emulate vfp */ 108+ hwcap |= ARM_HWCAP_NEON; /* qemu is supposed to emulate neon */ 109+ } 110+ else if (strcmp (u.machine, "armv6l") == 0) 111+ { 112 features |= ARM_V6; 113+ hwcap |= ARM_HWCAP_VFP; /* qemu is supposed to emulate vfp */ 114+ } 115 } 116 } 117- close (fd); 118+ else if (strncmp (plat, "v7l", 3) == 0) 119+ { 120+ features |= (ARM_V7 | ARM_V6); 121+ } 122+ else if (strncmp (plat, "v6l", 3) == 0) 123+ { 124+ features |= ARM_V6; 125+ } 126 } 127 128+ /* hardcode these values to avoid depending on specific 129+ * versions of the hwcap header, e.g. HWCAP_NEON 130+ */ 131+ if ((hwcap & ARM_HWCAP_VFP) != 0) 132+ features |= ARM_VFP; 133+ if ((hwcap & ARM_HWCAP_IWMMXT) != 0) 134+ features |= ARM_IWMMXT; 135+ /* this flag is only present on kernel 2.6.29 */ 136+ if ((hwcap & ARM_HWCAP_NEON) != 0) 137+ features |= ARM_NEON; 138+ 139 return features; 140 } 141 142-- 1431.7.6.5 144 145