Patrick Williams | c124f4f | 2015-09-15 14:41:29 -0500 | [diff] [blame] | 1 | From a0f53e1dbb3851bb0f0efcfdbd565b05e4be9cac 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 1/2] ARM: qemu related workarounds in cpu features detection |
| 5 | code |
| 6 | MIME-Version: 1.0 |
| 7 | Content-Type: text/plain; charset=UTF-8 |
| 8 | Content-Transfer-Encoding: 8bit |
| 9 | |
| 10 | This was ported from meta-oe's patch [1]. The original pixman patch is found |
| 11 | at [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 | |
| 16 | Upstream-Status: Inappropriate [other] qemu fix |
| 17 | |
| 18 | Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com> |
| 19 | --- |
| 20 | pixman/pixman-arm.c | 82 ++++++++++++++++++++++++++++++++++++++++---------- |
| 21 | 1 files changed, 65 insertions(+), 17 deletions(-) |
| 22 | |
| 23 | diff --git a/pixman/pixman-arm.c b/pixman/pixman-arm.c |
| 24 | index 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 | -- |
| 143 | 1.7.6.5 |
| 144 | |