From: Catalin Marinas <catalin.marinas@arm.com>
To: Kevin Brodsky <kevin.brodsky@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Richard Earnshaw <Richard.Earnshaw@arm.com>,
Andrey Konovalov <andreyknvl@google.com>,
Peter Collingbourne <pcc@google.com>,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
Alan Hayward <Alan.Hayward@arm.com>,
Luis Machado <luis.machado@linaro.org>,
Omair Javaid <omair.javaid@linaro.org>
Subject: Re: [PATCH v3 19/23] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support
Date: Wed, 29 Apr 2020 16:24:44 +0100 [thread overview]
Message-ID: <20200429152443.GD10651@gaia> (raw)
In-Reply-To: <e568615c-7f13-5ad6-48cc-45f5211ed1df@arm.com>
On Wed, Apr 29, 2020 at 11:27:10AM +0100, Kevin Brodsky wrote:
> On 21/04/2020 15:25, Catalin Marinas wrote:
> > diff --git a/arch/arm64/lib/mte.S b/arch/arm64/lib/mte.S
> > index bd51ea7e2fcb..45be04a8c73c 100644
> > --- a/arch/arm64/lib/mte.S
> > +++ b/arch/arm64/lib/mte.S
> > @@ -5,6 +5,7 @@
> > #include <linux/linkage.h>
> > #include <asm/assembler.h>
> > +#include <asm/mte.h>
> > /*
> > * Compare tags of two pages
> > @@ -44,3 +45,52 @@ SYM_FUNC_START(mte_memcmp_pages)
> > ret
> > SYM_FUNC_END(mte_memcmp_pages)
> > +
> > +/*
> > + * Read tags from a user buffer (one tag per byte) and set the corresponding
> > + * tags at the given kernel address. Used by PTRACE_POKEMTETAGS.
> > + * x0 - kernel address (to)
> > + * x1 - user buffer (from)
> > + * x2 - number of tags/bytes (n)
> > + * Returns:
> > + * x0 - number of tags read/set
> > + */
> > +SYM_FUNC_START(mte_copy_tags_from_user)
> > + mov x3, x1
> > +1:
> > +USER(2f, ldtrb w4, [x1])
>
> Here we are making either of the following assumptions:
> 1. The __user pointer (here `from`) actually points to user memory, not
> kernel memory (and we have set_fs(USER_DS) in place).
> 2. CONFIG_ARM64_UAO is enabled and the hardware implements UAO.
>
> 1. is currently true because these functions are only used for the new
> ptrace requests, which indeed pass pointers to user memory. However, future
> users of these functions may not know about this requirement.
> 2. is not necessarily true because ARM64_MTE does not depend on ARM64_UAO.
>
> It is unlikely that future users of these functions actually need to pass
> __user pointers to kernel memory, so adding a comment spelling out the first
> assumption is probably fine.
I found it easier to add uao_user_alternative rather than writing a
comment ;).
Thanks.
--
Catalin
next prev parent reply other threads:[~2020-04-29 15:24 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 14:25 [PATCH v3 00/23] arm64: Memory Tagging Extension user-space support Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 01/23] arm64: alternative: Allow alternative_insn to always issue the first instruction Catalin Marinas
2020-04-27 16:57 ` Dave Martin
2020-04-28 11:43 ` Catalin Marinas
2020-04-29 10:26 ` Dave Martin
2020-04-29 14:04 ` Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 02/23] arm64: mte: system register definitions Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 03/23] arm64: mte: CPU feature detection and initial sysreg configuration Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 04/23] arm64: mte: Use Normal Tagged attributes for the linear map Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 05/23] arm64: mte: Assembler macros and default architecture for .S files Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 06/23] arm64: mte: Tags-aware clear_page() implementation Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 07/23] arm64: mte: Tags-aware copy_page() implementation Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 08/23] arm64: Tags-aware memcmp_pages() implementation Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 09/23] arm64: mte: Add specific SIGSEGV codes Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 10/23] arm64: mte: Handle synchronous and asynchronous tag check faults Catalin Marinas
2020-04-23 10:38 ` Catalin Marinas
2020-04-27 16:58 ` Dave Martin
2020-04-28 13:43 ` Catalin Marinas
2020-04-29 10:26 ` Dave Martin
2020-04-21 14:25 ` [PATCH v3 11/23] mm: Introduce arch_calc_vm_flag_bits() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 12/23] arm64: mte: Add PROT_MTE support to mmap() and mprotect() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 13/23] mm: Introduce arch_validate_flags() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 14/23] arm64: mte: Validate the PROT_MTE request via arch_validate_flags() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 15/23] mm: Allow arm64 mmap(PROT_MTE) on RAM-based files Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 16/23] arm64: mte: Allow user control of the tag check mode via prctl() Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 17/23] arm64: mte: Allow user control of the generated random tags " Catalin Marinas
2020-04-21 14:25 ` [PATCH v3 18/23] arm64: mte: Restore the GCR_EL1 register after a suspend Catalin Marinas
2020-04-23 15:23 ` Lorenzo Pieralisi
2020-04-21 14:25 ` [PATCH v3 19/23] arm64: mte: Add PTRACE_{PEEK,POKE}MTETAGS support Catalin Marinas
2020-04-24 23:28 ` Peter Collingbourne
2020-04-29 10:27 ` Kevin Brodsky
2020-04-29 15:24 ` Catalin Marinas [this message]
2020-04-29 16:46 ` Dave Martin
2020-04-30 10:21 ` Catalin Marinas
2020-05-04 16:40 ` Dave Martin
2020-05-05 18:03 ` Luis Machado
2020-05-12 19:05 ` Luis Machado
2020-05-13 10:48 ` Catalin Marinas
2020-05-13 12:52 ` Luis Machado
2020-05-13 14:11 ` Catalin Marinas
2020-05-13 15:09 ` Luis Machado
2020-05-13 16:45 ` Luis Machado
2020-05-13 17:11 ` Catalin Marinas
2020-05-18 16:47 ` Dave Martin
2020-05-18 17:12 ` Luis Machado
2020-05-19 16:10 ` Catalin Marinas
2020-04-21 14:26 ` [PATCH v3 20/23] fs: Allow copy_mount_options() to access user-space in a single pass Catalin Marinas
2020-04-21 15:29 ` Al Viro
2020-04-21 16:45 ` Catalin Marinas
2020-04-27 16:56 ` Dave Martin
2020-04-28 14:06 ` Catalin Marinas
2020-04-29 10:28 ` Dave Martin
2020-04-28 18:16 ` Kevin Brodsky
2020-04-28 19:40 ` Catalin Marinas
2020-04-29 11:58 ` Catalin Marinas
2020-04-28 19:36 ` Catalin Marinas
2020-04-29 10:26 ` Dave Martin
2020-04-29 13:52 ` Catalin Marinas
2020-05-04 16:40 ` Dave Martin
2020-04-21 14:26 ` [PATCH v3 21/23] arm64: mte: Check the DT memory nodes for MTE support Catalin Marinas
2020-04-24 13:57 ` Catalin Marinas
2020-04-24 16:17 ` Catalin Marinas
2020-04-27 11:14 ` Suzuki K Poulose
2020-04-21 14:26 ` [PATCH v3 22/23] arm64: mte: Kconfig entry Catalin Marinas
2020-04-21 14:26 ` [PATCH v3 23/23] arm64: mte: Add Memory Tagging Extension documentation Catalin Marinas
2020-04-29 16:47 ` Dave Martin
2020-04-30 16:23 ` Catalin Marinas
2020-05-04 16:46 ` Dave Martin
2020-05-11 16:40 ` Catalin Marinas
2020-05-13 15:48 ` Dave Martin
2020-05-14 11:37 ` Catalin Marinas
2020-05-15 10:38 ` Catalin Marinas
2020-05-15 11:14 ` Szabolcs Nagy
2020-05-15 11:27 ` Catalin Marinas
2020-05-15 12:04 ` Szabolcs Nagy
2020-05-15 12:13 ` Catalin Marinas
2020-05-15 12:53 ` Szabolcs Nagy
2020-05-18 16:52 ` Dave Martin
2020-05-18 17:13 ` Catalin Marinas
2020-05-05 10:32 ` Szabolcs Nagy
2020-05-05 17:30 ` Catalin Marinas
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