From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Garnier <thgarnie@chromium.org>
Cc: kernel-hardening@lists.openwall.com, kristen@linux.intel.com,
keescook@chromium.org, Juergen Gross <jgross@suse.com>,
Thomas Hellstrom <thellstrom@vmware.com>,
"VMware, Inc." <pv-drivers@vmware.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 10/11] x86/paravirt: Adapt assembly for PIE support
Date: Wed, 31 Jul 2019 14:53:06 +0200 [thread overview]
Message-ID: <20190731125306.GU31381@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20190730191303.206365-11-thgarnie@chromium.org>
On Tue, Jul 30, 2019 at 12:12:54PM -0700, Thomas Garnier wrote:
> if PIE is enabled, switch the paravirt assembly constraints to be
> compatible. The %c/i constrains generate smaller code so is kept by
> default.
>
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range below 0xffffffff80000000.
>
> Signed-off-by: Thomas Garnier <thgarnie@chromium.org>
> Acked-by: Juergen Gross <jgross@suse.com>
> ---
> arch/x86/include/asm/paravirt_types.h | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
> index 70b654f3ffe5..fd7dc37d0010 100644
> --- a/arch/x86/include/asm/paravirt_types.h
> +++ b/arch/x86/include/asm/paravirt_types.h
> @@ -338,9 +338,25 @@ extern struct paravirt_patch_template pv_ops;
> #define PARAVIRT_PATCH(x) \
> (offsetof(struct paravirt_patch_template, x) / sizeof(void *))
>
> +#ifdef CONFIG_X86_PIE
> +#define paravirt_opptr_call "a"
> +#define paravirt_opptr_type "p"
> +
> +/*
> + * Alternative patching requires a maximum of 7 bytes but the relative call is
> + * only 6 bytes. If PIE is enabled, add an additional nop to the call
> + * instruction to ensure patching is possible.
> + */
> +#define PARAVIRT_CALL_POST "nop;"
I'm confused; where does the 7 come from? The relative call is 6 bytes,
a normal call is 5 bytes (which is what we normally replace them with),
and the longest 'native' sequence we seem to have is also 6 bytes
(.cpu_usergs_sysret64).
> +#else
> +#define paravirt_opptr_call "c"
> +#define paravirt_opptr_type "i"
> +#define PARAVIRT_CALL_POST ""
> +#endif
> +
> #define paravirt_type(op) \
> [paravirt_typenum] "i" (PARAVIRT_PATCH(op)), \
> - [paravirt_opptr] "i" (&(pv_ops.op))
> + [paravirt_opptr] paravirt_opptr_type (&(pv_ops.op))
> #define paravirt_clobber(clobber) \
> [paravirt_clobber] "i" (clobber)
>
> @@ -379,9 +395,10 @@ int paravirt_disable_iospace(void);
> * offset into the paravirt_patch_template structure, and can therefore be
> * freely converted back into a structure offset.
> */
> -#define PARAVIRT_CALL \
> - ANNOTATE_RETPOLINE_SAFE \
> - "call *%c[paravirt_opptr];"
> +#define PARAVIRT_CALL \
> + ANNOTATE_RETPOLINE_SAFE \
> + "call *%" paravirt_opptr_call "[paravirt_opptr];" \
> + PARAVIRT_CALL_POST
next prev parent reply other threads:[~2019-07-31 12:53 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 19:12 [PATCH v9 00/11] x86: PIE support to extend KASLR randomization Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 01/11] x86/crypto: Adapt assembly for PIE support Thomas Garnier
2019-08-05 16:32 ` Borislav Petkov
2019-08-05 16:54 ` Kees Cook
2019-08-05 17:27 ` Borislav Petkov
2019-08-05 17:53 ` Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 02/11] x86: Add macro to get symbol address " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 03/11] x86: relocate_kernel - Adapt assembly " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 04/11] x86/entry/64: " Thomas Garnier
2019-08-05 17:28 ` Borislav Petkov
2019-08-05 17:50 ` Thomas Garnier
2019-08-06 5:08 ` Borislav Petkov
2019-08-06 8:30 ` Peter Zijlstra
2019-08-06 12:35 ` Borislav Petkov
2019-08-06 13:59 ` Steven Rostedt
2019-08-06 15:35 ` Borislav Petkov
2019-07-30 19:12 ` [PATCH v9 05/11] x86: pm-trace - " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 06/11] x86/CPU: " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 07/11] x86/acpi: " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 08/11] x86/boot/64: " Thomas Garnier
2019-08-09 17:30 ` Borislav Petkov
2019-10-29 21:29 ` Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 09/11] x86/power/64: " Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 10/11] x86/paravirt: " Thomas Garnier
2019-07-31 12:53 ` Peter Zijlstra [this message]
2019-08-12 12:55 ` Borislav Petkov
2019-10-29 21:30 ` Thomas Garnier
2019-07-30 19:12 ` [PATCH v9 11/11] x86/alternatives: " Thomas Garnier
2019-08-12 13:57 ` Borislav Petkov
2019-10-29 21:31 ` Thomas Garnier
2019-08-06 15:43 ` [PATCH v9 00/11] x86: PIE support to extend KASLR randomization Borislav Petkov
2019-08-06 15:50 ` Peter Zijlstra
2019-08-29 19:55 ` Thomas Garnier
2019-09-06 23:22 ` Thomas Garnier
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