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On Tue, 30 Nov 2010 about 20:01:29 -0000, Oleg Nesterov wrote:
> Teach get_arg_ptr() to handle compat = T case correctly.
> #include <asm/uaccess.h>
> #include <asm/mmu_context.h>
> @@ -395,6 +396,18 @@ get_arg_ptr(const char __user * const __
> {
> const char __user *ptr;
>
> +#ifdef CONFIG_COMPAT
> + if (unlikely(compat)) {

This should not be marked unlikely. Unlikely tells gcc the path
with over 99% confidence and disables branch predictors on some
architectures. If called from a compat processes this will result
in a mispredicted branch every iteration. Just use if (compat)
and let the hardware branch predictors do their job.
> + compat_uptr_t __user *a = (void __user*)argv;
> + compat_uptr_t p;
> +
> + if (get_user(p, a + argc))
> + return ERR_PTR(-EFAULT);
> +
> + return compat_ptr(p);
> + }
> +#endif
> +
> if (get_user(ptr, argv + argc))
> return ERR_PTR(-EFAULT);
>
> @@ -1501,6 +1514,18 @@ int do_execve(const char *filename,
> return do_execve_common(filename, argv, envp, regs, false);
> }
>
> +#ifdef CONFIG_COMPAT
> +int compat_do_execve(char * filename,
> + compat_uptr_t __user *argv,
> + compat_uptr_t __user *envp,
> + struct pt_regs * regs)
> +{
> + return do_execve_common(filename,
> + (void __user*)argv, (void __user*)envp,

Shouldn't these be compat_ptr(argv)? (makes a difference on s390)

> + regs, true);
> +}
> +#endif
> +
> void set_binfmt(struct linux_binfmt *new)
> {
> struct mm_struct *mm = current->mm;

Thanks,
milton


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