From 8ed5372874377af4a84a330eeaff1d9d663ca930 Mon Sep 17 00:00:00 2001 From: "Daniel P. Berrange" Date: Tue, 4 Oct 2016 14:35:51 +0100 Subject: trace: don't abort qemu if ftrace can't be initialized If the ftrace backend is compiled into QEMU, any attempt to start QEMU while non-root will fail due to the inability to open /sys/kernel/debug/tracing/tracing_on. Add a fallback into the code so that it connects up the trace_marker_fd variable to /dev/null when getting EACCES on the 'trace_on' file. This allows QEMU to run, with ftrace turned into a no-op. [Fixed s/setting/getting/ and s/EACCESS/EACCES/ errors pointed out by Eric Blake . --Stefan] Signed-off-by: Daniel P. Berrange Message-id: 1475588159-30598-13-git-send-email-berrange@redhat.com Signed-off-by: Stefan Hajnoczi --- trace/ftrace.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'trace') diff --git a/trace/ftrace.c b/trace/ftrace.c index e953922f5b..3588bb0eb4 100644 --- a/trace/ftrace.c +++ b/trace/ftrace.c @@ -51,6 +51,12 @@ bool ftrace_init(void) snprintf(path, PATH_MAX, "%s/tracing/tracing_on", debugfs); trace_fd = open(path, O_WRONLY); if (trace_fd < 0) { + if (errno == EACCES) { + trace_marker_fd = open("/dev/null", O_WRONLY); + if (trace_marker_fd != -1) { + return true; + } + } perror("Could not open ftrace 'tracing_on' file"); return false; } else { -- cgit v1.2.3