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libbpf: Explicitly call write to append content to file

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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 <patteliu@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230320030720.650-1-patteliu@gmail.com
This commit is contained in:
Liu Pan 2023-03-20 11:07:20 +08:00 committed by Andrii Nakryiko
parent bb4a6a9237
commit 01dc26c980
1 changed files with 9 additions and 5 deletions
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14
tools/lib/bpf/libbpf.c
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@ -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);