From 753e4d07d1e9c149c03dbd5bfb70fcde92628ea2 Mon Sep 17 00:00:00 2001 From: Liu Pan Date: Mon, 20 Mar 2023 11:07:20 +0800 Subject: [PATCH] libbpf: Explicitly call write to append content to file Write data to fd by calling "vdprintf", in most implementations of the standard library, the data is finally written by the writev syscall. But "uprobe_events/kprobe_events" does not allow segmented writes, so switch the "append_to_file" function to explicit write() call. Signed-off-by: Liu Pan Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20230320030720.650-1-patteliu@gmail.com --- src/libbpf.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/src/libbpf.c b/src/libbpf.c index 4c34fbd..149864e 100644 --- a/src/libbpf.c +++ b/src/libbpf.c @@ -9918,16 +9918,20 @@ static int append_to_file(const char *file, const char *fmt, ...) { int fd, n, err = 0; va_list ap; + char buf[1024]; + + va_start(ap, fmt); + n = vsnprintf(buf, sizeof(buf), fmt, ap); + va_end(ap); + + if (n < 0 || n >= sizeof(buf)) + return -EINVAL; fd = open(file, O_WRONLY | O_APPEND | O_CLOEXEC, 0); if (fd < 0) return -errno; - va_start(ap, fmt); - n = vdprintf(fd, fmt, ap); - va_end(ap); - - if (n < 0) + if (write(fd, buf, n) < 0) err = -errno; close(fd);