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From: "Arnd Bergmann" <arnd@arndb.de>
To: "Samuel Holland" <samuel.holland@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	linux-riscv@lists.infradead.org
Cc: "Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Charlie Jenkins" <charlie@rivosinc.com>,
	guoren <guoren@kernel.org>, "Jisheng Zhang" <jszhang@kernel.org>,
	"Kemeng Shi" <shikemeng@huaweicloud.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Mike Rapoport" <rppt@kernel.org>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Xiao W Wang" <xiao.w.wang@intel.com>,
	"Yangyu Chen" <cyy@cyyself.name>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: Define TASK_SIZE_MAX for __access_ok()
Date: Mon, 25 Mar 2024 21:40:41 +0100	[thread overview]
Message-ID: <3ac65601-7102-4ad1-ad89-157f7d9cef87@app.fastmail.com> (raw)
In-Reply-To: <20240313180010.295747-1-samuel.holland@sifive.com>

On Wed, Mar 13, 2024, at 18:59, Samuel Holland wrote:
> TASK_SIZE_MAX should be set to the largest userspace address under any
> runtime configuration. This optimizes the check in __access_ok(), which
> no longer needs to compute the current value of TASK_SIZE. It is still
> safe because addresses between TASK_SIZE and TASK_SIZE_MAX are invalid
> at the hardware level.
>
> This removes about half of the references to pgtable_l[45]_enabled.
>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

>  #ifdef CONFIG_64BIT
>  #define TASK_SIZE_64	(PGDIR_SIZE * PTRS_PER_PGD / 2)
>  #define TASK_SIZE_MIN	(PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
> +#define TASK_SIZE_MAX	(PGDIR_SIZE_L5 * PTRS_PER_PGD / 2)

I see that TASK_SIZE_MIN is unused since 085e2ff9aeb0 ("efi:
libstub: Drop randomization of runtime memory map") and could
be dropped now, but it doesn't really hurt either.

     Arnd

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WARNING: multiple messages have this Message-ID (diff)
From: "Arnd Bergmann" <arnd@arndb.de>
To: "Samuel Holland" <samuel.holland@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	linux-riscv@lists.infradead.org
Cc: "Albert Ou" <aou@eecs.berkeley.edu>,
	"Alexandre Ghiti" <alexghiti@rivosinc.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Charlie Jenkins" <charlie@rivosinc.com>,
	guoren <guoren@kernel.org>, "Jisheng Zhang" <jszhang@kernel.org>,
	"Kemeng Shi" <shikemeng@huaweicloud.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Mike Rapoport" <rppt@kernel.org>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Xiao W Wang" <xiao.w.wang@intel.com>,
	"Yangyu Chen" <cyy@cyyself.name>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: Define TASK_SIZE_MAX for __access_ok()
Date: Mon, 25 Mar 2024 21:40:41 +0100	[thread overview]
Message-ID: <3ac65601-7102-4ad1-ad89-157f7d9cef87@app.fastmail.com> (raw)
In-Reply-To: <20240313180010.295747-1-samuel.holland@sifive.com>

On Wed, Mar 13, 2024, at 18:59, Samuel Holland wrote:
> TASK_SIZE_MAX should be set to the largest userspace address under any
> runtime configuration. This optimizes the check in __access_ok(), which
> no longer needs to compute the current value of TASK_SIZE. It is still
> safe because addresses between TASK_SIZE and TASK_SIZE_MAX are invalid
> at the hardware level.
>
> This removes about half of the references to pgtable_l[45]_enabled.
>
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>

Reviewed-by: Arnd Bergmann <arnd@arndb.de>

>  #ifdef CONFIG_64BIT
>  #define TASK_SIZE_64	(PGDIR_SIZE * PTRS_PER_PGD / 2)
>  #define TASK_SIZE_MIN	(PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
> +#define TASK_SIZE_MAX	(PGDIR_SIZE_L5 * PTRS_PER_PGD / 2)

I see that TASK_SIZE_MIN is unused since 085e2ff9aeb0 ("efi:
libstub: Drop randomization of runtime memory map") and could
be dropped now, but it doesn't really hurt either.

     Arnd

  parent reply	other threads:[~2024-03-25 20:41 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-13 17:59 [PATCH] riscv: Define TASK_SIZE_MAX for __access_ok() Samuel Holland
2024-03-13 17:59 ` Samuel Holland
2024-03-18 20:50 ` Alexandre Ghiti
2024-03-18 20:50   ` Alexandre Ghiti
2024-03-18 21:29   ` Samuel Holland
2024-03-18 21:29     ` Samuel Holland
2024-03-19 16:51     ` Alexandre Ghiti
2024-03-19 16:51       ` Alexandre Ghiti
2024-03-24 19:42       ` David Laight
2024-03-24 19:42         ` David Laight
2024-03-25  7:30         ` Alexandre Ghiti
2024-03-25  7:30           ` Alexandre Ghiti
2024-03-25  9:30           ` David Laight
2024-03-25  9:30             ` David Laight
2024-03-25 16:39           ` Mark Rutland
2024-03-25 16:39             ` Mark Rutland
2024-03-25 18:02             ` Arnd Bergmann
2024-03-25 18:02               ` Arnd Bergmann
2024-03-25 18:30               ` Mark Rutland
2024-03-25 18:30                 ` Mark Rutland
2024-03-25 19:20                 ` Samuel Holland
2024-03-25 19:20                   ` Samuel Holland
2024-03-25 20:38                 ` Arnd Bergmann
2024-03-25 20:38                   ` Arnd Bergmann
2024-03-26 10:19                   ` David Laight
2024-03-26 10:19                     ` David Laight
2024-03-26 14:49                     ` Mark Rutland
2024-03-26 14:49                       ` Mark Rutland
2024-03-25 20:12             ` Alexandre Ghiti
2024-03-25 20:12               ` Alexandre Ghiti
2024-03-24 22:05       ` Arnd Bergmann
2024-03-24 22:05         ` Arnd Bergmann
2024-03-25  7:25         ` Alexandre Ghiti
2024-03-25  7:25           ` Alexandre Ghiti
2024-03-25 11:15           ` Arnd Bergmann
2024-03-25 11:15             ` Arnd Bergmann
2024-03-25 20:40 ` Arnd Bergmann [this message]
2024-03-25 20:40   ` Arnd Bergmann

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