From 01dc26c980b0a92d9ba94c28652b2675968727b6 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 --- tools/lib/bpf/libbpf.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 4c34fbd7b5be..149864ea88d1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/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);