Messages in this thread | | | Date | Tue, 10 May 2016 19:30:45 +0300 | From | Cyrill Gorcunov <> | Subject | Re: Getting rid of dynamic TASK_SIZE (on x86, at least) |
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On Tue, May 10, 2016 at 09:07:49AM -0700, Andy Lutomirski wrote: > Hi all- > > I'm trying to get rid of x86's dynamic TASK_SIZE and just redefine it > to TASK_SIZE_MAX. So far, these are the TASK_SIZE users that actually > seem to care about the task in question: > > get_unmapped_area. This is used by mmap, mremap, exec, uprobe XOL, > and maybe some other things. > > - mmap, mremap, etc: IMO this should check in_compat_syscall, not > TIF_ADDR32. If a 64-bit task does an explicit 32-bit mmap (using int > $0x80, for example), it should get a 32-bit address back. > > - xol_add_vma: This one is weird: uprobes really is doing something > behind the task's back, and the addresses need to be consistent with > the address width. I'm not quite sure what to do here. > > - exec. This wants to set up mappings that are appropriate for the new task. > > My inclination would be add a new 'limit' parameter to all the > get_unmapped_area variants and possible to vm_brk and friends and to > thus push the decision into the callers. For the syscalls, we could > add: > > static inline unsigned long this_syscall_addr_limit(void) { return TASK_SIZE; } > > and override it on x86. > > I'm not super excited to write that patch, though...
Andy, could you please highlight what's wrong with TASK_SIZE helper in first place? The idea behind is to clean up the code or there some real problem?
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