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Message-ID: <1399921766.3068.3.camel@localhost>
Date: Mon, 12 May 2014 15:09:26 -0400
From: Eric Paris <eparis@...hat.com>
To: Paul Moore <pmoore@...hat.com>
Cc: Markos Chandras <markos.chandras@...tec.com>,
linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
Andy Lutomirski <luto@...capital.net>,
Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: [PATCH 3.15] MIPS: Add new AUDIT_ARCH token for the N32 ABI on
MIPS64
On Mon, 2014-05-12 at 14:53 -0400, Paul Moore wrote:
> On Tuesday, April 22, 2014 03:40:36 PM Markos Chandras wrote:
> > A MIPS64 kernel may support ELF files for all 3 MIPS ABIs
> > (O32, N32, N64). Furthermore, the AUDIT_ARCH_MIPS{,EL}64 token
> > does not provide enough information about the ABI for the 64-bit
> > process. As a result of which, userland needs to use complex
> > seccomp filters to decide whether a syscall belongs to the o32 or n32
> > or n64 ABI. Therefore, a new arch token for MIPS64/n32 is added so it
> > can be used by seccomp to explicitely set syscall filters for this ABI.
> >
> > Link: http://sourceforge.net/p/libseccomp/mailman/message/32239040/
> > Cc: Andy Lutomirski <luto@...capital.net>
> > Cc: Eric Paris <eparis@...hat.com>
> > Cc: Paul Moore <pmoore@...hat.com>
> > Cc: Ralf Baechle <ralf@...ux-mips.org>
> > Signed-off-by: Markos Chandras <markos.chandras@...tec.com>
> > ---
> > Ralf, can we please have this in 3.15 (Assuming it's ACK'd)?
> >
> > Thanks a lot!
> > ---
> > arch/mips/include/asm/syscall.h | 2 ++
> > include/uapi/linux/audit.h | 12 ++++++++++++
> > 2 files changed, 14 insertions(+)
>
> [NOTE: Adding lkml to the To line to hopefully spur discussion/acceptance as
> this *really* should be in 3.15]
>
> I'm re-replying to this patch and adding lkml to the To line because I believe
> it is very important we get this patch into 3.15. For those who don't follow
> the MIPS architecture very closely, the upcoming 3.15 is the first release to
> include support for seccomp filters, the latest generation of syscall
> filtering which used a BPF based filter language. For reason that are easy to
> understand, the syscall filters are ABI specific (e.g. syscall tables, word
> length, endianness) and those generating syscall filters in userspace (e.g.
> libseccomp) need to take great care to ensure that the generated filters take
> the ABI into account and fail safely in the case where a different ABI is used
> (e.g. x86, x86_64, x32).
>
> The patch below corrects, what is IMHO, an omission in the original MIPS
> seccomp filter patch, allowing userspace to easily separate MIPS and MIPS64.
> Without this patch we will be forced to handle MIPS/MIPS64 like we handle
> x86_64/x32 which is a royal pain and not something I want to have deal with
> again.
>
> Further, while I don't want to speak for the audit folks, it is my
> understanding that they want this patch for similar reasons.
Audit would also like to see this patch. We can survive without it, but
having this patch lets us write a better/easier userspace.
Acked-by: Eric Paris <eparis@...hat.com>
>
> Please merge this patch for 3.15 or at least provide some feedback as to why
> this isn't a viable solution for upstream. Once 3.15 ships, fixing this will
> require breaking the MIPS ABI which isn't something any of us want.
>
> Thanks,
> -Paul
>
> > diff --git a/arch/mips/include/asm/syscall.h
> > b/arch/mips/include/asm/syscall.h index c6e9cd2..17960fe 100644
> > --- a/arch/mips/include/asm/syscall.h
> > +++ b/arch/mips/include/asm/syscall.h
> > @@ -133,6 +133,8 @@ static inline int syscall_get_arch(void)
> > #ifdef CONFIG_64BIT
> > if (!test_thread_flag(TIF_32BIT_REGS))
> > arch |= __AUDIT_ARCH_64BIT;
> > + if (test_thread_flag(TIF_32BIT_ADDR))
> > + arch |= __AUDIT_ARCH_CONVENTION_MIPS64_N32;
> > #endif
> > #if defined(__LITTLE_ENDIAN)
> > arch |= __AUDIT_ARCH_LE;
> > diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> > index 11917f7..1b1efdd 100644
> > --- a/include/uapi/linux/audit.h
> > +++ b/include/uapi/linux/audit.h
> > @@ -331,9 +331,17 @@ enum {
> > #define AUDIT_FAIL_PRINTK 1
> > #define AUDIT_FAIL_PANIC 2
> >
> > +/*
> > + * These bits disambiguate different calling conventions that share an
> > + * ELF machine type, bitness, and endianness
> > + */
> > +#define __AUDIT_ARCH_CONVENTION_MASK 0x30000000
> > +#define __AUDIT_ARCH_CONVENTION_MIPS64_N32 0x20000000
> > +
> > /* distinguish syscall tables */
> > #define __AUDIT_ARCH_64BIT 0x80000000
> > #define __AUDIT_ARCH_LE 0x40000000
> > +
> > #define AUDIT_ARCH_ALPHA (EM_ALPHA|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
> > #define AUDIT_ARCH_ARM (EM_ARM|__AUDIT_ARCH_LE)
> > #define AUDIT_ARCH_ARMEB (EM_ARM)
> > @@ -346,7 +354,11 @@ enum {
> > #define AUDIT_ARCH_MIPS (EM_MIPS)
> > #define AUDIT_ARCH_MIPSEL (EM_MIPS|__AUDIT_ARCH_LE)
> > #define AUDIT_ARCH_MIPS64 (EM_MIPS|__AUDIT_ARCH_64BIT)
> > +#define AUDIT_ARCH_MIPS64N32 (EM_MIPS|__AUDIT_ARCH_64BIT|\
> > + __AUDIT_ARCH_CONVENTION_MIPS64_N32)
> > #define AUDIT_ARCH_MIPSEL64 (EM_MIPS|__AUDIT_ARCH_64BIT|__AUDIT_ARCH_LE)
> > +#define AUDIT_ARCH_MIPSEL64N32 (EM_MIPS|__AUDIT_ARCH_64BIT|
> __AUDIT_ARCH_LE\
> > + __AUDIT_ARCH_CONVENTION_MIPS64_N32)
> > #define AUDIT_ARCH_OPENRISC (EM_OPENRISC)
> > #define AUDIT_ARCH_PARISC (EM_PARISC)
> > #define AUDIT_ARCH_PARISC64 (EM_PARISC|__AUDIT_ARCH_64BIT)
>
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