I never understood why PTE entries waste 4 bits (WIMG)
for effectively very few valid combinations.
The only invalid combinations are WI=11 -- if you know of
a way to fit 12 combinations in fewer than 4 bits, let us
know :-)
Not all of those 12 are very useful, of course.
Segher
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On 8/16/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
Gabriel Paubert writes:
> BTW, there is one way to make pages non executable: mark
> them as guarded, but it will have a significant cost in
> terms of performance.
Indeed. I guess we could do that as a config option for machines that
rea
Gabriel Paubert writes:
> I agree, but I don't know why you believe it would cause
> a machine check (0x200): from my docs, it is an ISI (0x400).
I don't believe it would cause a machine check either, but that is
what Matt Sealey was saying. I don't know where he got that idea.
> BTW, there i
On Tue, Aug 15, 2006 at 01:59:05PM +1000, Paul Mackerras wrote:
> Matt Sealey writes:
>
> > Book I compatible PowerPC's have had a "no-executable" bit in
> > the page protection flags since the dark ages.. see page 7-38
> > and 7-39 of the 'Programming Environments Manual for 32-Bit
> > Microproce
Matt Sealey writes:
> Book I compatible PowerPC's have had a "no-executable" bit in
> the page protection flags since the dark ages.. see page 7-38
> and 7-39 of the 'Programming Environments Manual for 32-Bit
> Microprocessors'.. this document predates even the G3.
What are you referring to? I
On Aug 14, 2006, at 7:17 AM, Matt Sealey wrote:
That looks like a 64-bit system, which doesn't have the
granularity problem anyway. 32-bit powerpc seems to be
decent. The heap shares with the executable itself, and of
course there is the yucky 2 GB limit.
One thing I'm curious about, has a
> That looks like a 64-bit system, which doesn't have the
> granularity problem anyway. 32-bit powerpc seems to be
> decent. The heap shares with the executable itself, and of
> course there is the yucky 2 GB limit.
One thing I'm curious about, has anyone EVER made a system which
actually use
> Of course, that won't make all that much difference on your
> Cube, because the G4 CPU doesn't have hardware support for
> non-executable pages (any readable page is executable)
I don't think this is true?
Book I compatible PowerPC's have had a "no-executable" bit in
the page protection fla
On 8/13/06, Hollis Blanchard <[EMAIL PROTECTED]> wrote:
On Sun, 2006-08-13 at 00:11 -0400, Albert Cahalan wrote:
>
> On 8/12/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
> > Albert Cahalan writes:
> >
> > > VM_STACK_DEFAULT_FLAGS32 is wrong. A fail-safe
> > > default is important for security. I
On 8/12/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
Of course, that won't make all that much difference on your Cube,
because the G4 CPU doesn't have hardware support for non-executable
pages (any readable page is executable).
I now have an evil grin, and a kernel that prevents
execution from
On Sun, 2006-08-13 at 00:11 -0400, Albert Cahalan wrote:
>
> On 8/12/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
> > Albert Cahalan writes:
> >
> > > VM_STACK_DEFAULT_FLAGS32 is wrong. A fail-safe
> > > default is important for security. If gcc on PowerPC ever
> > > does generate code which puts
On 8/12/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
Albert Cahalan writes:
> VM_STACK_DEFAULT_FLAGS32 is wrong. A fail-safe
> default is important for security. If gcc on PowerPC ever
> does generate code which puts trampolines on the stack,
> then that can be fixed by converting to legal C co
On Sun, Aug 13, 2006 at 09:54:14AM +1000, Paul Mackerras wrote:
> To get the full benefit of -msecure-plt, every object file in your
> executable has to be compiled with it
Yes. In particular, glibc startup files need to be compiled with
-msecure-plt. If ld links any object file that uses the ol
Albert Cahalan writes:
> VM_STACK_DEFAULT_FLAGS32 is wrong. A fail-safe
> default is important for security. If gcc on PowerPC ever
> does generate code which puts trampolines on the stack,
> then that can be fixed by converting to legal C code or
> by adding the fragile marking to the defective e
On 8/12/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
Albert Cahalan writes:
> gcc version 4.1.2 20060613 (prerelease) (Debian 4.1.1-5)
OK, so I think that version should have the new -msecure-plt flag,
The flag matters not, even with the very latest binutils
that Debian offers, version 2.17-
Albert Cahalan writes:
> gcc version 4.1.2 20060613 (prerelease) (Debian 4.1.1-5)
OK, so I think that version should have the new -msecure-plt flag,
which changes the ppc32 ABI so that the PLT no longer has to be
writable and executable. Previously the dynamic linker would rewrite
each PLT entry
On 8/12/06, Paul Mackerras <[EMAIL PROTECTED]> wrote:
Albert Cahalan writes:
> I just ran paxtest on a Mac G4 Cube. Ouch. The results are shameful.
What gcc version, what binutils version, what kernel version?
My gcc claims to be:
Using built-in specs.
Target: powerpc-linux-gnu
Configured wi
Albert Cahalan writes:
> I just ran paxtest on a Mac G4 Cube. Ouch. The results are shameful.
What gcc version, what binutils version, what kernel version?
Paul.
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