Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Tue, 18 Jul 2017 22:49:15 -0400
From: Brian Gerst <brgerst@...il.com>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, "David S . Miller" <davem@...emloft.net>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>, 
	Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...hat.com>, 
	Arnd Bergmann <arnd@...db.de>, Matthias Kaehlcke <mka@...omium.org>, 
	Boris Ostrovsky <boris.ostrovsky@...cle.com>, Juergen Gross <jgross@...e.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, 
	Joerg Roedel <joro@...tes.org>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...en8.de>, 
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, Borislav Petkov <bp@...e.de>, 
	Christian Borntraeger <borntraeger@...ibm.com>, "Rafael J . Wysocki" <rjw@...ysocki.net>, 
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Tejun Heo <tj@...nel.org>, 
	Christoph Lameter <cl@...ux.com>, Kees Cook <keescook@...omium.org>, 
	Paul Gortmaker <paul.gortmaker@...driver.com>, Chris Metcalf <cmetcalf@...lanox.com>, 
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Christopher Li <sparse@...isli.org>, Dou Liyang <douly.fnst@...fujitsu.com>, 
	Masahiro Yamada <yamada.masahiro@...ionext.com>, Daniel Borkmann <daniel@...earbox.net>, 
	Markus Trippelsdorf <markus@...ppelsdorf.de>, Peter Foley <pefoley2@...oley.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Tim Chen <tim.c.chen@...ux.intel.com>, 
	Ard Biesheuvel <ard.biesheuvel@...aro.org>, Catalin Marinas <catalin.marinas@....com>, 
	Matthew Wilcox <mawilcox@...rosoft.com>, Michal Hocko <mhocko@...e.com>, Rob Landley <rob@...dley.net>, 
	Jiri Kosina <jkosina@...e.cz>, "H . J . Lu" <hjl.tools@...il.com>, Paul Bolle <pebolle@...cali.nl>, 
	Baoquan He <bhe@...hat.com>, Daniel Micay <danielmicay@...il.com>, 
	"the arch/x86 maintainers" <x86@...nel.org>, 
	"linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, xen-devel@...ts.xenproject.org, 
	kvm@...r.kernel.org, linux-pm <linux-pm@...r.kernel.org>, 
	linux-arch <linux-arch@...r.kernel.org>, linux-sparse@...r.kernel.org, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [RFC 06/22] kvm: Adapt assembly for PIE support

On Tue, Jul 18, 2017 at 6:33 PM, Thomas Garnier <thgarnie@...gle.com> wrote:
> Change the assembly code to use only relative references of symbols for the
> kernel to be PIE compatible. The new __ASM_GET_PTR_PRE macro is used to
> get the address of a symbol on both 32 and 64-bit with PIE support.
>
> Position Independent Executable (PIE) support will allow to extended the
> KASLR randomization range below the -2G memory limit.
>
> Signed-off-by: Thomas Garnier <thgarnie@...gle.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 6 ++++--
>  arch/x86/kernel/kvm.c           | 6 ++++--
>  arch/x86/kvm/svm.c              | 4 ++--
>  3 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 87ac4fba6d8e..3041201a3aeb 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1352,9 +1352,11 @@ asmlinkage void kvm_spurious_fault(void);
>         ".pushsection .fixup, \"ax\" \n" \
>         "667: \n\t" \
>         cleanup_insn "\n\t"                   \
> -       "cmpb $0, kvm_rebooting \n\t"         \
> +       "cmpb $0, kvm_rebooting" __ASM_SEL(,(%%rip)) " \n\t" \
>         "jne 668b \n\t"                       \
> -       __ASM_SIZE(push) " $666b \n\t"        \
> +       __ASM_SIZE(push) "%%" _ASM_AX " \n\t"           \
> +       __ASM_GET_PTR_PRE(666b) "%%" _ASM_AX "\n\t"     \
> +       "xchg %%" _ASM_AX ", (%%" _ASM_SP ") \n\t"      \
>         "call kvm_spurious_fault \n\t"        \
>         ".popsection \n\t" \
>         _ASM_EXTABLE(666b, 667b)
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 71c17a5be983..53b8ad162589 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -618,8 +618,10 @@ asm(
>  ".global __raw_callee_save___kvm_vcpu_is_preempted;"
>  ".type __raw_callee_save___kvm_vcpu_is_preempted, @function;"
>  "__raw_callee_save___kvm_vcpu_is_preempted:"
> -"movq  __per_cpu_offset(,%rdi,8), %rax;"
> -"cmpb  $0, " __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rax);"
> +"leaq  __per_cpu_offset(%rip), %rax;"
> +"movq  (%rax,%rdi,8), %rax;"
> +"addq  " __stringify(KVM_STEAL_TIME_preempted) "+steal_time(%rip), %rax;"

This doesn't look right.  It's accessing a per-cpu variable.  The
per-cpu section is an absolute, zero-based section and not subject to
relocation.

> +"cmpb  $0, (%rax);
>  "setne %al;"
>  "ret;"
>  ".popsection");

--
Brian Gerst

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.