From: Mark Rutland <mark.rutland@arm.com>
To: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, catalin.marinas@arm.com,
ard.biesheuvel@linaro.org, sboyd@codeaurora.org,
dave.hansen@linux.intel.com, keescook@chromium.org,
msalter@redhat.com, labbott@redhat.com, tglx@linutronix.de
Subject: Re: [PATCH v2 06/18] arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN
Date: Fri, 1 Dec 2017 11:48:13 +0000 [thread overview]
Message-ID: <20171201114813.lgqtdadjs6r3xiwg@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <1512059986-21325-7-git-send-email-will.deacon@arm.com>
On Thu, Nov 30, 2017 at 04:39:34PM +0000, Will Deacon wrote:
> With the ASID now installed in TTBR1, we can re-enable ARM64_SW_TTBR0_PAN
> by ensuring that we switch to a reserved ASID of zero when disabling
> user access and restore the active user ASID on the uaccess enable path.
>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
[...]
> diff --git a/arch/arm64/include/asm/asm-uaccess.h b/arch/arm64/include/asm/asm-uaccess.h
> index b3da6c886835..21b8cf304028 100644
> --- a/arch/arm64/include/asm/asm-uaccess.h
> +++ b/arch/arm64/include/asm/asm-uaccess.h
> @@ -16,11 +16,20 @@
> add \tmp1, \tmp1, #SWAPPER_DIR_SIZE // reserved_ttbr0 at the end of swapper_pg_dir
> msr ttbr0_el1, \tmp1 // set reserved TTBR0_EL1
> isb
> + sub \tmp1, \tmp1, #SWAPPER_DIR_SIZE
> + bic \tmp1, \tmp1, #(0xffff << 48)
> + msr ttbr1_el1, \tmp1 // set reserved ASID
> + isb
> .endm
>
> - .macro __uaccess_ttbr0_enable, tmp1
> + .macro __uaccess_ttbr0_enable, tmp1, tmp2
> get_thread_info \tmp1
> ldr \tmp1, [\tmp1, #TSK_TI_TTBR0] // load saved TTBR0_EL1
> + mrs \tmp2, ttbr1_el1
> + extr \tmp2, \tmp2, \tmp1, #48
> + ror \tmp2, \tmp2, #16
It took me a while to figure out what was going on here, as I confused
EXTR with BFX.
I also didn't realise that thread_info::ttbr0 still had the ASID
orred-in. I guess it doesn't matter if we write that into TTBR0_EL1, as
it should be ignored by HW.
> diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
> index fc0f9eb66039..750a3b76a01c 100644
> --- a/arch/arm64/include/asm/uaccess.h
> +++ b/arch/arm64/include/asm/uaccess.h
> @@ -107,15 +107,19 @@ static inline void __uaccess_ttbr0_disable(void)
> {
> unsigned long ttbr;
>
> + ttbr = read_sysreg(ttbr1_el1);
> /* reserved_ttbr0 placed at the end of swapper_pg_dir */
> - ttbr = read_sysreg(ttbr1_el1) + SWAPPER_DIR_SIZE;
> - write_sysreg(ttbr, ttbr0_el1);
> + write_sysreg(ttbr + SWAPPER_DIR_SIZE, ttbr0_el1);
> + isb();
> + /* Set reserved ASID */
> + ttbr &= ~(0xffffUL << 48);
Given we have this constant open-coded in a few places, maybe we should
have something like:
#define TTBR_ASID_MASK (UL(0xffff) << 48)
... in a header somewhere.
Otherwise, looks good to me.
Thanks,
Mark.
next prev parent reply other threads:[~2017-12-01 11:48 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 16:39 [PATCH v2 00/18] arm64: Unmap the kernel whilst running in userspace (KAISER) Will Deacon
2017-11-30 16:39 ` [PATCH v2 01/18] arm64: mm: Use non-global mappings for kernel space Will Deacon
2017-11-30 16:39 ` [PATCH v2 02/18] arm64: mm: Temporarily disable ARM64_SW_TTBR0_PAN Will Deacon
2017-11-30 16:39 ` [PATCH v2 03/18] arm64: mm: Move ASID from TTBR0 to TTBR1 Will Deacon
2017-11-30 17:36 ` Mark Rutland
2017-11-30 16:39 ` [PATCH v2 04/18] arm64: mm: Remove pre_ttbr0_update_workaround for Falkor erratum #E1003 Will Deacon
2017-11-30 16:39 ` [PATCH v2 05/18] arm64: mm: Rename post_ttbr0_update_workaround Will Deacon
2017-11-30 16:39 ` [PATCH v2 06/18] arm64: mm: Fix and re-enable ARM64_SW_TTBR0_PAN Will Deacon
2017-12-01 11:48 ` Mark Rutland [this message]
2017-11-30 16:39 ` [PATCH v2 07/18] arm64: mm: Allocate ASIDs in pairs Will Deacon
2017-11-30 16:39 ` [PATCH v2 08/18] arm64: mm: Add arm64_kernel_unmapped_at_el0 helper Will Deacon
2017-11-30 16:39 ` [PATCH v2 09/18] arm64: mm: Invalidate both kernel and user ASIDs when performing TLBI Will Deacon
2017-11-30 16:39 ` [PATCH v2 10/18] arm64: entry: Add exception trampoline page for exceptions from EL0 Will Deacon
2017-12-01 13:31 ` Mark Rutland
2017-12-06 10:25 ` Ard Biesheuvel
2017-11-30 16:39 ` [PATCH v2 11/18] arm64: mm: Map entry trampoline into trampoline and kernel page tables Will Deacon
2017-11-30 18:29 ` Mark Rutland
2017-11-30 16:39 ` [PATCH v2 12/18] arm64: entry: Explicitly pass exception level to kernel_ventry macro Will Deacon
2017-12-01 11:58 ` Mark Rutland
2017-12-01 17:51 ` Will Deacon
2017-12-01 18:00 ` Mark Rutland
2017-11-30 16:39 ` [PATCH v2 13/18] arm64: entry: Hook up entry trampoline to exception vectors Will Deacon
2017-12-01 13:53 ` Mark Rutland
2017-12-01 17:40 ` Will Deacon
2017-11-30 16:39 ` [PATCH v2 14/18] arm64: erratum: Work around Falkor erratum #E1003 in trampoline code Will Deacon
2017-11-30 17:06 ` Robin Murphy
2017-11-30 17:19 ` Will Deacon
2017-11-30 16:39 ` [PATCH v2 15/18] arm64: tls: Avoid unconditional zeroing of tpidrro_el0 for native tasks Will Deacon
2017-11-30 16:39 ` [PATCH v2 16/18] arm64: entry: Add fake CPU feature for unmapping the kernel at EL0 Will Deacon
2017-12-01 13:55 ` Mark Rutland
2017-11-30 16:39 ` [PATCH v2 17/18] arm64: Kconfig: Add CONFIG_UNMAP_KERNEL_AT_EL0 Will Deacon
2017-12-12 8:44 ` Geert Uytterhoeven
2017-12-12 10:28 ` Will Deacon
2017-11-30 16:39 ` [PATCH v2 18/18] perf: arm_spe: Disallow userspace profiling when arm_kernel_unmapped_at_el0() Will Deacon
2017-12-01 12:15 ` Mark Rutland
2017-12-01 16:49 ` Will Deacon
2017-12-01 16:26 ` Stephen Boyd
2017-12-01 14:04 ` [PATCH v2 00/18] arm64: Unmap the kernel whilst running in userspace (KAISER) Mark Rutland
2017-12-01 17:50 ` Will Deacon
2017-12-01 17:58 ` Mark Rutland
2017-12-01 18:02 ` Dave Hansen
2017-12-01 18:14 ` Will Deacon
2017-12-11 2:24 ` Shanker Donthineni
2017-12-04 23:47 ` Laura Abbott
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