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| author | Michael Holzheu <holzheu@linux.vnet.ibm.com> | 2009-09-11 10:28:59 +0200 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2009-09-11 10:29:53 +0200 |
| commit | f64d04c042193183c6dad98944ae2861b998e8b7 (patch) | |
| tree | d275472a5559e0333c8c55dfe418e3e30108b8bc /Documentation/s390 | |
| parent | 0c88ee5b7523e76e290d558c28cd0be48ffad597 (diff) | |
| download | lwn-f64d04c042193183c6dad98944ae2861b998e8b7.tar.gz lwn-f64d04c042193183c6dad98944ae2861b998e8b7.zip | |
[S390] s390dbf: Add description for usage of "%s" in sprintf events
Using "%s" in sprintf event functions is dangerous. This patch adds a short
description for this issue to the s390 debug feature documentation.
Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'Documentation/s390')
| -rw-r--r-- | Documentation/s390/s390dbf.txt | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/s390/s390dbf.txt b/Documentation/s390/s390dbf.txt index 2d10053dd97e..ae66f9b90a25 100644 --- a/Documentation/s390/s390dbf.txt +++ b/Documentation/s390/s390dbf.txt @@ -495,6 +495,13 @@ and for each vararg a long value. So e.g. for a debug entry with a format string plus two varargs one would need to allocate a (3 * sizeof(long)) byte data area in the debug_register() function. +IMPORTANT: Using "%s" in sprintf event functions is dangerous. You can only +use "%s" in the sprintf event functions, if the memory for the passed string is +available as long as the debug feature exists. The reason behind this is that +due to performance considerations only a pointer to the string is stored in +the debug feature. If you log a string that is freed afterwards, you will get +an OOPS when inspecting the debug feature, because then the debug feature will +access the already freed memory. NOTE: If using the sprintf view do NOT use other event/exception functions than the sprintf-event and -exception functions. |