external/trace: Fall back to read()

Not all kernels support mmap() on an OPAL exported memory range. Fall
back to allocating a buffer and using the normal file IO system calls
to read the contents of the trace buffer in those cases.

This does mean we can't use "follow" mode since we can't monitor the
raw trace data effectively, but otherwise it works fine.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>

1 files changed, 16 insertions, 2 deletions

diff --git a/external/trace/dump_trace.c b/external/trace/dump_trace.c
index aba684b..5a832c7 100644
--- a/external/trace/dump_trace.c
+++ b/external/trace/dump_trace.c
@@ -261,6 +261,7 @@ int main(int argc, char *argv[])
 {
 	struct trace_reader *trs;
 	struct trace_info *ti;
+	bool no_mmap = false;
 	struct stat sb;
 	int fd, opt, i;
 
@@ -296,13 +297,26 @@ int main(int argc, char *argv[])
 			err(1, "Stating %s", argv[1]);
 
 		ti = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
-		if (ti == MAP_FAILED)
-			err(1, "Mmaping %s", argv[i]);
+		if (ti == MAP_FAILED) {
+			no_mmap = true;
+
+			ti = ezalloc(sb.st_size);
+			if (!ti)
+				err(1, "allocating memory for %s", argv[i]);
+
+			if (read(fd, ti, sb.st_size) == -1)
+				err(1, "reading from %s", argv[i]);
+		}
 
 		trs[i].tb = &ti->tb;
 		list_head_init(&trs[i].traces);
 	}
 
+	if (no_mmap) {
+		fprintf(stderr, "disabling follow mode: can't mmap() OPAL export files\n");
+		follow = 0;
+	}
+
 	do {
 		load_traces(trs, argc);
 		display_traces(trs, argc);