On Mon, Jun 22, 2015 at 10:05 AM, Brian Gerst <[email protected]> wrote: > On Mon, Jun 22, 2015 at 12:19 PM, Andy Lutomirski <[email protected]> wrote: >> On Mon, Jun 22, 2015 at 4:55 AM, Brian Gerst <[email protected]> wrote: >>> Change this to CONFIG_COMPAT so both 32-bit compat and x32 will do the >>> check. >>> >>> Signed-off-by: Brian Gerst <[email protected]> >>> --- >>> arch/x86/entry/vsyscall/vsyscall_64.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/arch/x86/entry/vsyscall/vsyscall_64.c >>> b/arch/x86/entry/vsyscall/vsyscall_64.c >>> index 2dcc6ff..26a46f4 100644 >>> --- a/arch/x86/entry/vsyscall/vsyscall_64.c >>> +++ b/arch/x86/entry/vsyscall/vsyscall_64.c >>> @@ -290,7 +290,7 @@ static struct vm_area_struct gate_vma = { >>> >>> struct vm_area_struct *get_gate_vma(struct mm_struct *mm) >>> { >>> -#ifdef CONFIG_IA32_EMULATION >>> +#ifdef CONFIG_COMPAT >>> if (!mm || mm->context.ia32_compat) >>> return NULL; >>> #endif >> >> >> This makes little sense to me. >> >> First, why is the !mm check guarded by any ifdef at all? If this said >> "if (mm && mm->...)", it would make no sense. >> >> Second, and more importantly, what does mm->context.ia32_compat mean >> in the new less-nonsensical regime? The flag itself is defined in a >> way that makes no sense (it's either 0, TIF_X32, or TIF_IA32 -- >> presumably it should be an enum). There aren't a whole lot of things >> that care -- it's just this check and some uprobe thing. At some >> point, mpx will start caring, too. There's also TIF_ADDR32, which is >> similarly ridiculous (why isn't it part of mm->context?, and why does >> it exist at all). >> >> I think that the questions we want to be able to answer are: >> >> 1. Is this mm intended to be addressable using 32 bits? If so, we >> should probably not show the vsyscall area in /proc/self/maps. >> >> 2. Is this mm's mpx context intended to be used by 32-bit userspace? >> (That's real 32 bit, not x32 -- x32 is certainly 64-bit as far as MPX >> is concerned.) >> >> 3. Is the current mmap call intended to return something in the low 32 >> bits? Presumably that should depend only on the mmap call's bitness >> (is_compat_task, etc, which we really need to rename to something like >> in_compat_syscall). >> >> I find myself wondering whether there is any legitimate reason that >> TASK_SIZE isn't the same thing as TASK_SIZE_MAX... >> >> Anyway, your patch is probably fine -- you're not actually making >> anything worse. >> >> --Andy > > I agree there are more cleanups needed here. But that's probably a > whole patch series in itself. This patch is intended to be no code > change when X32 doesn't depend on 32-bit compat anymore.
Fair enough. Acked-by: Andy Lutomirski <[email protected]> > > -- > Brian Gerst -- Andy Lutomirski AMA Capital Management, LLC -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in Please read the FAQ at http://www.tux.org/lkml/
