On Wed, 14 Dec 2011, Josh Triplett wrote:
In the Linux kernel, "current" refers to the current task, of type
"struct task_struct *", by way of a stack of (sometimes arch-specific)
macros. For instance, arch/x86/include/asm/current.h defines current as
get_current(), an inline function returning "struct task_struct *".
Other architectures, as well as asm-generic, use variations on the same
theme with varying depths of macros.
However, coccinelle doesn't seem to manage to figure out the type of
current, because rules defined with @@struct task_struct *task;@@ don't
match current.
I can work around this by writing a duplicate set of rules with
@@identifier current;@@, but I'd rather not have to introduce that
identifier current; would not be right at all, because it would match any
identifier. The choices are only either to make an explicit rule for
current or to use strong enough include options so that coccinelle can
find the type itself. You can try -all_includes or for even more include
files -recursive_includes. But this will slow down a lot your processing
time. On the other hand, you probably need at least all_includes to get
the types of structure fields.
julia
duplication.
For a test case, try the following semantic patch:
@@ struct task_struct *task; @@
- (task)->pid == 0
+ is_idle_task(task)
@@ struct task_struct *task; @@
- (task)->pid != 0
+ !is_idle_task(task)
And the following test file:
#include <linux/sched.h>
extern struct task_struct *t;
void context(void)
{
if (t->pid)
do_something();
if (current->pid)
do_something();
}
Coccinelle successfully patches the first condition, but not the second.
- Josh Triplett
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