From: David Ahern Date: Tue, 18 Oct 2011 23:34:01 +0000 (-0600) Subject: perf tools: handle endianness of feature bitmap X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=d327fa435996c3e559b55e254bad6ed801a92f89;p=linux-beck.git perf tools: handle endianness of feature bitmap Feature bitmap is declared as an array of unsigned longs -- not good since its size can differ between the host that generated the data file and the host analyzing the file. We need to handle endianness, but we don't know the size of the unsigned long where the file was generated. Take a best guess at determining it: try 64-bit swap first (ie., file created on a 64-bit host), and check if the hostname feature bit is set (this feature bit is forced on as of fbe96f2). If the bit is not, undo the 64-bit swap and try a 32-bit swap. If the hostname bit is still not set (e.g., older data file), punt and fallback to the original behavior -- clearing all feature bits and setting buildid. Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Paul Mackerras Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1318980841-12616-1-git-send-email-dsahern@gmail.com Signed-off-by: David Ahern Signed-off-by: Arnaldo Carvalho de Melo --- diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c index 3724707425ea..6a9c041134bb 100644 --- a/tools/perf/util/header.c +++ b/tools/perf/util/header.c @@ -1703,21 +1703,41 @@ int perf_file_header__read(struct perf_file_header *header, bitmap_zero(header->adds_features, HEADER_FEAT_BITS); else return -1; + } else if (ph->needs_swap) { + unsigned int i; + /* + * feature bitmap is declared as an array of unsigned longs -- + * not good since its size can differ between the host that + * generated the data file and the host analyzing the file. + * + * We need to handle endianness, but we don't know the size of + * the unsigned long where the file was generated. Take a best + * guess at determining it: try 64-bit swap first (ie., file + * created on a 64-bit host), and check if the hostname feature + * bit is set (this feature bit is forced on as of fbe96f2). + * If the bit is not, undo the 64-bit swap and try a 32-bit + * swap. If the hostname bit is still not set (e.g., older data + * file), punt and fallback to the original behavior -- + * clearing all feature bits and setting buildid. + */ + for (i = 0; i < BITS_TO_LONGS(HEADER_FEAT_BITS); ++i) + header->adds_features[i] = bswap_64(header->adds_features[i]); + + if (!test_bit(HEADER_HOSTNAME, header->adds_features)) { + for (i = 0; i < BITS_TO_LONGS(HEADER_FEAT_BITS); ++i) { + header->adds_features[i] = bswap_64(header->adds_features[i]); + header->adds_features[i] = bswap_32(header->adds_features[i]); + } + } + + if (!test_bit(HEADER_HOSTNAME, header->adds_features)) { + bitmap_zero(header->adds_features, HEADER_FEAT_BITS); + set_bit(HEADER_BUILD_ID, header->adds_features); + } } memcpy(&ph->adds_features, &header->adds_features, sizeof(ph->adds_features)); - /* - * FIXME: hack that assumes that if we need swap the perf.data file - * may be coming from an arch with a different word-size, ergo different - * DEFINE_BITMAP format, investigate more later, but for now its mostly - * safe to assume that we have a build-id section. Trace files probably - * have several other issues in this realm anyway... - */ - if (ph->needs_swap) { - memset(&ph->adds_features, 0, sizeof(ph->adds_features)); - perf_header__set_feat(ph, HEADER_BUILD_ID); - } ph->event_offset = header->event_types.offset; ph->event_size = header->event_types.size;