Am Donnerstag, den 30.01.2014, 10:17 -0800 schrieb Andy Lutomirski:
> > +struct vsyscall_gtod_data vvar_vsyscall_gtod_data
> > + __attribute__((visibility("hidden")));
> > +
> > +u32 hpet_counter
> > + __attribute__((visibility("hidden")));
> > +
> > +#define gtod (&vvar_vsyscall_gtod_data)
>
> Is it possible to keep the VVAR macro working for this? It'll keep
> this code more unified and make it easier for anyone who tries to add
> vgetcpu support.
>
Nope, since the access to the VVAR area differs in a 32 bit VDSO differ.
64 Bit VDSO always use FIXMAP Address, 32 bit VDSO depends on the sysctl
parameter vsyscall32 and the vdso32= kernel parameter.
In the origin code there is still gtod macro in the vclock_gettime.c,
but there is a mixed used of the gtod macro and
VVAR(vsyscall_gtod_data), so i cleaned it up only use the gtod Macro.
This has also nothing to do with vgetcpu, this is locate in a own file
called vgetcpu.c
> > if (compat_uses_vma || !compat) {
> > - /*
> > - * MAYWRITE to allow gdb to COW and set breakpoints
> > - */
> > - ret = install_special_mapping(mm, addr, PAGE_SIZE,
> > - VM_READ|VM_EXEC|
> > -
> > VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
> > - vdso32_pages);
> > +
> > + vma = _install_special_mapping(mm,
> > + addr,
> > + VDSO_OFFSET(VDSO_PAGES),
> > + VM_READ|VM_EXEC,
> > + vdso32_pages);
> > +
> > + if (IS_ERR(vma)) {
> > + ret = PTR_ERR(vma);
> > + goto up_fail;
> > + }
> > +
> > + ret = remap_pfn_range(vma,
> > + vma->vm_start + VDSO_OFFSET(VDSO_VVAR_PAGE),
> > + __pa_symbol(&__vvar_page) >> PAGE_SHIFT,
> > + PAGE_SIZE,
> > + PAGE_READONLY);
> >
> > if (ret)
> > goto up_fail;
> > +
> > +#ifdef CONFIG_HPET_TIMER
> > + if (hpet_address) {
> > + ret = io_remap_pfn_range(vma,
> > + vma->vm_start + VDSO_OFFSET(VDSO_HPET_PAGE),
> > + hpet_address >> PAGE_SHIFT,
> > + PAGE_SIZE,
> > + pgprot_noncached(PAGE_READONLY));
> > +
> > + if (ret)
> > + goto up_fail;
> > + }
> > +#endif
> > }
>
> Now I'm confused. What's the fixmap stuff for? Isn't this sufficient?
>
> Also, presumably remap_pfn_range is already smart enough to prevent
> mprotect and ptrace from doing evil things.
>
The fixmap code is for the original behaviour. It saves address space
and does not change the layout. Never break user space.
> >
> > @@ -19,11 +22,17 @@ ENTRY(__kernel_vsyscall);
> > */
> > VERSION
> > {
> > - LINUX_2.5 {
> > + LINUX_2.6 {
> > global:
> > __kernel_vsyscall;
> > __kernel_sigreturn;
> > __kernel_rt_sigreturn;
> > + clock_gettime;
> > + __vdso_clock_gettime;
> > + gettimeofday;
> > + __vdso_gettimeofday;
> > + time;
> > + __vdso_time;
> > local: *;
>
> Please remove the functions that don't start with __vdso -- I don't
> think they serve any purpose. They can be confusing, since they're
> not interchangeable with the glibc functions of the same name. (The
> 64-bit vdso needs them for historical reasons.)
I can do this...
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