X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=liblttng-kconsumer%2Flttng-kconsumer.c;h=388cc5b20f8f4e67853a01b4ee7038f8a398cf1f;hp=778dd1631520d61c6c8eab2ae7a525d8c9a5660e;hb=7bd3904781fa78155c13952f5d5cb9ab42f44a08;hpb=f2fc6720dff91c4076318acff69aa3bb5e70060a

diff --git a/liblttng-kconsumer/lttng-kconsumer.c b/liblttng-kconsumer/lttng-kconsumer.c
index 778dd1631..388cc5b20 100644
--- a/liblttng-kconsumer/lttng-kconsumer.c
+++ b/liblttng-kconsumer/lttng-kconsumer.c
@@ -33,6 +33,7 @@
 #include <lttng-sessiond-comm.h>
 #include <lttng/lttng-kconsumer.h>
 #include <lttngerr.h>
+#include <runas.h>
 
 extern struct lttng_consumer_global_data consumer_data;
 extern int consumer_poll_timeout;
@@ -256,7 +257,9 @@ int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 				msg.u.stream.state,
 				msg.u.stream.mmap_len,
 				msg.u.stream.output,
-				msg.u.stream.path_name);
+				msg.u.stream.path_name,
+				msg.u.stream.uid,
+				msg.u.stream.gid);
 		if (new_stream == NULL) {
 			lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
 			goto end;
@@ -300,3 +303,143 @@ end:
 end_nosignal:
 	return 0;
 }
+
+/*
+ * Consume data on a file descriptor and write it on a trace file.
+ */
+int lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
+		struct lttng_consumer_local_data *ctx)
+{
+	unsigned long len;
+	int err;
+	long ret = 0;
+	int infd = stream->wait_fd;
+
+	DBG("In read_subbuffer (infd : %d)", infd);
+	/* Get the next subbuffer */
+	err = kernctl_get_next_subbuf(infd);
+	if (err != 0) {
+		ret = errno;
+		/*
+		 * This is a debug message even for single-threaded consumer,
+		 * because poll() have more relaxed criterions than get subbuf,
+		 * so get_subbuf may fail for short race windows where poll()
+		 * would issue wakeups.
+		 */
+		DBG("Reserving sub buffer failed (everything is normal, "
+				"it is due to concurrency)");
+		goto end;
+	}
+
+	switch (stream->output) {
+		case LTTNG_EVENT_SPLICE:
+			/* read the whole subbuffer */
+			err = kernctl_get_padded_subbuf_size(infd, &len);
+			if (err != 0) {
+				ret = errno;
+				perror("Getting sub-buffer len failed.");
+				goto end;
+			}
+
+			/* splice the subbuffer to the tracefile */
+			ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, len);
+			if (ret < 0) {
+				/*
+				 * display the error but continue processing to try
+				 * to release the subbuffer
+				 */
+				ERR("Error splicing to tracefile");
+			}
+			break;
+		case LTTNG_EVENT_MMAP:
+			/* read the used subbuffer size */
+			err = kernctl_get_padded_subbuf_size(infd, &len);
+			if (err != 0) {
+				ret = errno;
+				perror("Getting sub-buffer len failed.");
+				goto end;
+			}
+			/* write the subbuffer to the tracefile */
+			ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
+			if (ret < 0) {
+				/*
+				 * display the error but continue processing to try
+				 * to release the subbuffer
+				 */
+				ERR("Error writing to tracefile");
+			}
+			break;
+		default:
+			ERR("Unknown output method");
+			ret = -1;
+	}
+
+	err = kernctl_put_next_subbuf(infd);
+	if (err != 0) {
+		ret = errno;
+		if (errno == EFAULT) {
+			perror("Error in unreserving sub buffer\n");
+		} else if (errno == EIO) {
+			/* Should never happen with newer LTTng versions */
+			perror("Reader has been pushed by the writer, last sub-buffer corrupted.");
+		}
+		goto end;
+	}
+
+end:
+	return ret;
+}
+
+int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
+{
+	int ret;
+
+	/* Opening the tracefile in write mode */
+	if (stream->path_name != NULL) {
+		ret = open_run_as(stream->path_name,
+				O_WRONLY|O_CREAT|O_TRUNC,
+				S_IRWXU|S_IRWXG|S_IRWXO,
+				stream->uid, stream->gid);
+		if (ret < 0) {
+			ERR("Opening %s", stream->path_name);
+			perror("open");
+			goto error;
+		}
+		stream->out_fd = ret;
+	}
+
+	if (stream->output == LTTNG_EVENT_MMAP) {
+		/* get the len of the mmap region */
+		unsigned long mmap_len;
+
+		ret = kernctl_get_mmap_len(stream->wait_fd, &mmap_len);
+		if (ret != 0) {
+			ret = errno;
+			perror("kernctl_get_mmap_len");
+			goto error_close_fd;
+		}
+		stream->mmap_len = (size_t) mmap_len;
+
+		stream->mmap_base = mmap(NULL, stream->mmap_len,
+				PROT_READ, MAP_PRIVATE, stream->wait_fd, 0);
+		if (stream->mmap_base == MAP_FAILED) {
+			perror("Error mmaping");
+			ret = -1;
+			goto error_close_fd;
+		}
+	}
+
+	/* we return 0 to let the library handle the FD internally */
+	return 0;
+
+error_close_fd:
+	{
+		int err;
+
+		err = close(stream->out_fd);
+		assert(!err);
+	}
+error:
+	return ret;
+}
+