I have been looking into testing the address_space() pointers in
the current Linux kernel and came up with a case where I am not
sure how this should work (the kernel's __user attribute).
We tested the following cases, In this case sparse correctly
identified the incorrect address space/no-dereference. The first
was not identified:
# define __user __attribute__((noderef, address_space(1)))
void test(char __user *ptr)
{
printk("%s\n", ptr);
printk("%c\n", ptr[0]);
}
I know that there is a gcc printf format attribute to allow
specifying the positions of the format and start of variadic
arguments.
I have had a quick look at the code but have not tried to make
any modifications yet, and would like some feedback or help
before making any:
- Should we automatically warn on possible de-ref (or address space)
on passing to a variadic function (I think the simplest)
- Is adding support for __attribute__((format(printf,a,b))) a
good idea (and if so is anyone looking into this already)
- If adding printf format a good idea, then should we extend it
to adding a kernel printk style one too (modern kernels seem
to love extending the printf formatting)
Any help would be appreciated.
--
Ben Dooks http://www.codethink.co.uk/
Senior Engineer Codethink - Providing Genius
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