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tracing: Fix user event write on buffer disabled 

The user events write currently returns the size of what was suppose to be
 written when tracing is disabled and nothing was written. Instead, behave like
 trace_marker and return -EBADF, as that is what is returned if a file is opened
 for read only, and a write is performed on it. Writing to the buffer
 that is disabled is like trying to write to a file opened for read
 only, as the buffer still can be read, but just not written to.
 
 This also includes test cases for this use case
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Merge tag 'trace-v6.4-rc7-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull tracing fix from Steven Rostedt:
 "Fix user event write on buffer disabled.

  The user events write currently returns the size of what was supposed
  to be written when tracing is disabled and nothing was written.

  Instead, behave like trace_marker and return -EBADF, as that is what
  is returned if a file is opened for read only, and a write is
  performed on it. Writing to the buffer that is disabled is like trying
  to write to a file opened for read only, as the buffer still can be
  read, but just not written to.

  This also includes test cases for this use case"

* tag 'trace-v6.4-rc7-v3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  selftests/user_events: Add test cases when event is disabled
  selftests/user_events: Enable the event before write_fault test in ftrace self-test
  tracing/user_events: Fix incorrect return value for writing operation when events are disabled
This commit is contained in:
Linus Torvalds 2023-06-29 17:36:00 -07:00
parent 2eb15b4248 d34a271acc
commit 3ad7b12c72
2 changed files with 10 additions and 1 deletions
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3
kernel/trace/trace_events_user.c
View File

@ -2096,7 +2096,8 @@ static ssize_t user_events_write_core(struct file *file, struct iov_iter *i)
if (unlikely(faulted))
return -EFAULT;
}
} else
return -EBADF;
return ret;
}

8
tools/testing/selftests/user_events/ftrace_test.c
View File

@ -324,6 +324,10 @@ TEST_F(user, write_events) {
io[0].iov_base = &reg.write_index;
io[0].iov_len = sizeof(reg.write_index);
/* Write should return -EBADF when event is not enabled */
ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));
ASSERT_EQ(EBADF, errno);
/* Enable event */
self->enable_fd = open(enable_file, O_RDWR);
ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
@ -400,6 +404,10 @@ TEST_F(user, write_fault) {
ASSERT_EQ(0, ioctl(self->data_fd, DIAG_IOCSREG, &reg));
ASSERT_EQ(0, reg.write_index);
/* Enable event */
self->enable_fd = open(enable_file, O_RDWR);
ASSERT_NE(-1, write(self->enable_fd, "1", sizeof("1")))
/* Write should work normally */
ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 2));