Re: [PATCH 00 of 10] x86: unify asm/pgtable.h

Ingo Molnar
2008-01-09T00:43:54Z

* Ingo Molnar <mingo@elte.hu> wrote:

>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > > >>> #define __PAGE_KERNEL_EXEC \
> > > >>> - (_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_GLOBAL)
> > > >>> + (_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED)
> > > >>>
> > > >
> > > > This shouldn't be necessary. The old 64-bit code defined everything
> > > > without _PAGE_GLOBAL, but then used a MAKE_GLOBAL() macro to OR it
> > > > in later. This seemed a bit roundabout to me, so I just put it in
> > > > from the outset.
> >
> > actually, this is wrong.
> >
> > a couple of places use __PAGE_* values, which you've now changed to
> > include the _PAGE_GLOBAL flag.
>
> yep, fixing this resolves the crash.

but then it crashes init:

init[1]: segfault at ffffffffff600400 ip ffffffffff600400 sp
7fff81bedda8 error5printk: 7740690 messages suppressed.

because you changed __PAGE_KERNEL_VSYSCALL as well, from:

#define __PAGE_KERNEL_VSYSCALL \
(_PAGE_PRESENT | _PAGE_USER | _PAGE_ACCESSED)

to:

#define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RO | _PAGE_USER)

but __PAGE_KERNEL_RO is an NX one, so the vsyscall cannot execute
instructions.

so this wants to be:

#define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RX | _PAGE_USER)

this was the last bug and the resulting kernel boots fine. 3 nasty bugs
in one patch :-/

Ingo

---------------->
Subject: x86: move all asm/pgtable constants into one place, fix
From: Ingo Molnar <mingo@elte.hu>

fix.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
include/asm-x86/pgtable.h | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

Index: linux-x86.q/include/asm-x86/pgtable.h
===================================================================
--- linux-x86.q.orig/include/asm-x86/pgtable.h
+++ linux-x86.q/include/asm-x86/pgtable.h
@@ -68,27 +68,27 @@ extern unsigned long long __PAGE_KERNEL,
#endif /* __ASSEMBLER__ */
#else
#define __PAGE_KERNEL_EXEC \
- (_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_GLOBAL)
+ (_PAGE_PRESENT | _PAGE_RW | _PAGE_DIRTY | _PAGE_ACCESSED)
#define __PAGE_KERNEL (__PAGE_KERNEL_EXEC | _PAGE_NX)
#endif

#define __PAGE_KERNEL_RO (__PAGE_KERNEL & ~_PAGE_RW)
#define __PAGE_KERNEL_RX (__PAGE_KERNEL_EXEC & ~_PAGE_RW)
#define __PAGE_KERNEL_NOCACHE (__PAGE_KERNEL | _PAGE_PCD | _PAGE_PWT)
-#define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RO | _PAGE_USER)
+#define __PAGE_KERNEL_VSYSCALL (__PAGE_KERNEL_RX | _PAGE_USER)
#define __PAGE_KERNEL_VSYSCALL_NOCACHE (__PAGE_KERNEL_VSYSCALL | _PAGE_PCD | _PAGE_PWT)
#define __PAGE_KERNEL_LARGE (__PAGE_KERNEL | _PAGE_PSE)
#define __PAGE_KERNEL_LARGE_EXEC (__PAGE_KERNEL_EXEC | _PAGE_PSE)

-#define PAGE_KERNEL __pgprot(__PAGE_KERNEL)
-#define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO)
-#define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC)
-#define PAGE_KERNEL_RX __pgprot(__PAGE_KERNEL_RX)
-#define PAGE_KERNEL_NOCACHE __pgprot(__PAGE_KERNEL_NOCACHE)
-#define PAGE_KERNEL_LARGE __pgprot(__PAGE_KERNEL_LARGE)
-#define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC)
-#define PAGE_KERNEL_VSYSCALL __pgprot(__PAGE_KERNEL_VSYSCALL)
-#define PAGE_KERNEL_VSYSCALL_NOCACHE __pgprot(__PAGE_KERNEL_VSYSCALL_NOCACHE)
+#define PAGE_KERNEL __pgprot(__PAGE_KERNEL | _PAGE_GLOBAL)
+#define PAGE_KERNEL_RO __pgprot(__PAGE_KERNEL_RO | _PAGE_GLOBAL)
+#define PAGE_KERNEL_EXEC __pgprot(__PAGE_KERNEL_EXEC | _PAGE_GLOBAL)
+#define PAGE_KERNEL_RX __pgprot(__PAGE_KERNEL_RX | _PAGE_GLOBAL)
+#define PAGE_KERNEL_NOCACHE __pgprot(__PAGE_KERNEL_NOCACHE | _PAGE_GLOBAL)
+#define PAGE_KERNEL_LARGE __pgprot(__PAGE_KERNEL_LARGE | _PAGE_GLOBAL)
+#define PAGE_KERNEL_LARGE_EXEC __pgprot(__PAGE_KERNEL_LARGE_EXEC | _PAGE_GLOBAL)
+#define PAGE_KERNEL_VSYSCALL __pgprot(__PAGE_KERNEL_VSYSCALL | _PAGE_GLOBAL)
+#define PAGE_KERNEL_VSYSCALL_NOCACHE __pgprot(__PAGE_KERNEL_VSYSCALL_NOCACHE | _PAGE_GLOBAL)

/* xwr */
#define __P000 PAGE_NONE