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bh=Bp86L5fucSA+9Bwlt84/eQbHaJRbEE/iIVDIU2TrYmM=; b=RjDy/IqN7FwcMpeyxrwUV1BbnX2iMgbcZP/L4Fa2BAEIYx43g15adVO7RvPu5UkKoc uaL2zDkMyPfmi94FTT8NSkovxCTj02gqy/ytUU82jXRTY9haIkCx1Pr1YU9EUOuRC6Gw iXtrvQ2CvKBmHkr9T0PD3o98OE3ycmdSSwqLB4kW6ZcqTIm+0GhrTNVXh7pHL4MRevBy p0BmwwTsfJPKpFmdjCc7R0nyevgVxjHLcEoZ1xc3LIzVZ9h0AaBe7svz+28q9GYLXo2/ Ax0pA+k1WmIznGhEyw5e5f0uq16U+1OBcrp9SQakoDuij+D+YsJL0HZIcLgKbi2giTDN tczg== X-Gm-Message-State: APjAAAX8hpH6vJJz/aWhDVIj3k/w4aUCjN8jyQfHWwU3VjqsdM+RpJ9B Yt/MFzvsXlJclB56BEsi4PNpwAzPSCJX8yBpYy3EdA== X-Google-Smtp-Source: APXvYqzpFAhempBHWwl6LQCKUCJ19FjjZGAWA1oF9chpT593c5XiKJbvgs2xxIRCQukRs4o+FH4Rat+2Sk/7ytURtoo= X-Received: by 2002:aa7:8e56:: with SMTP id d22mr5854475pfr.3.1573072766085; Wed, 06 Nov 2019 12:39:26 -0800 (PST) MIME-Version: 1.0 References: <20191018161033.261971-1-samitolvanen@google.com> <20191105235608.107702-1-samitolvanen@google.com> <20191105235608.107702-11-samitolvanen@google.com> In-Reply-To: <20191105235608.107702-11-samitolvanen@google.com> From: Nick Desaulniers Date: Wed, 6 Nov 2019 12:39:14 -0800 Message-ID: Subject: Re: [PATCH v5 10/14] arm64: preserve x18 when CPU is suspended To: Sami Tolvanen Cc: Will Deacon , Catalin Marinas , Steven Rostedt , Masami Hiramatsu , Ard Biesheuvel , Dave Martin , Kees Cook , Laura Abbott , Mark Rutland , Marc Zyngier , Jann Horn , Miguel Ojeda , Masahiro Yamada , clang-built-linux , Kernel Hardening , Linux ARM , LKML Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 5, 2019 at 3:56 PM Sami Tolvanen wrote: > > Don't lose the current task's shadow stack when the CPU is suspended. > > Signed-off-by: Sami Tolvanen > Reviewed-by: Nick Desaulniers Re-LGTM > Reviewed-by: Kees Cook > --- > arch/arm64/include/asm/suspend.h | 2 +- > arch/arm64/mm/proc.S | 14 ++++++++++++++ > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h > index 8939c87c4dce..0cde2f473971 100644 > --- a/arch/arm64/include/asm/suspend.h > +++ b/arch/arm64/include/asm/suspend.h > @@ -2,7 +2,7 @@ > #ifndef __ASM_SUSPEND_H > #define __ASM_SUSPEND_H > > -#define NR_CTX_REGS 12 > +#define NR_CTX_REGS 13 > #define NR_CALLEE_SAVED_REGS 12 > > /* > diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S > index fdabf40a83c8..5c8219c55948 100644 > --- a/arch/arm64/mm/proc.S > +++ b/arch/arm64/mm/proc.S > @@ -49,6 +49,8 @@ > * cpu_do_suspend - save CPU registers context > * > * x0: virtual address of context pointer > + * > + * This must be kept in sync with struct cpu_suspend_ctx in . > */ > ENTRY(cpu_do_suspend) > mrs x2, tpidr_el0 > @@ -73,6 +75,11 @@ alternative_endif > stp x8, x9, [x0, #48] > stp x10, x11, [x0, #64] > stp x12, x13, [x0, #80] > + /* > + * Save x18 as it may be used as a platform register, e.g. by shadow > + * call stack. > + */ > + str x18, [x0, #96] > ret > ENDPROC(cpu_do_suspend) > > @@ -89,6 +96,13 @@ ENTRY(cpu_do_resume) > ldp x9, x10, [x0, #48] > ldp x11, x12, [x0, #64] > ldp x13, x14, [x0, #80] > + /* > + * Restore x18, as it may be used as a platform register, and clear > + * the buffer to minimize the risk of exposure when used for shadow > + * call stack. > + */ > + ldr x18, [x0, #96] > + str xzr, [x0, #96] > msr tpidr_el0, x2 > msr tpidrro_el0, x3 > msr contextidr_el1, x4 > -- > 2.24.0.rc1.363.gb1bccd3e3d-goog > -- Thanks, ~Nick Desaulniers