From: Alexandre Ghiti <alex@ghiti.fr>
To: Arnd Bergmann <arnd@arndb.de>, "H. Peter Anvin" <hpa@zytor.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Heiko Carstens <hca@linux.ibm.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Alexandre Ghiti <alexghiti@rivosinc.com>,
Jonathan Corbet <corbet@lwn.net>,
Richard Henderson <richard.henderson@linaro.org>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Vineet Gupta <vgupta@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
WANG Xuerui <kernel@xen0n.name>, Michal Simek <monstr@monstr.eu>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
"James E . J . Bottomley" <James.Bottomley@hansenpartnership.com>,
Helge Deller <deller@gmx.de>,
Michael Ellerman <mpe@ellerman.id.au>,
Nicholas Piggin <npiggin@gmail.com>,
Christophe Leroy <christophe.leroy>
Subject: Re: [PATCH v3 00/24] Remove COMMAND_LINE_SIZE from uapi
Date: Mon, 6 Mar 2023 10:35:17 +0100 [thread overview]
Message-ID: <caaed678-4a5a-70e5-2ee7-cb2c8042afc0@ghiti.fr> (raw)
In-Reply-To: <c500840b-b57d-47f2-a3d9-41465b10ffae@app.fastmail.com>
On 3/3/23 17:40, Arnd Bergmann wrote:
> On Fri, Mar 3, 2023, at 12:59, Alexandre Ghiti wrote:
>> On 3/2/23 20:50, H. Peter Anvin wrote:
>>> On March 1, 2023 7:17:18 PM PST, Palmer Dabbelt <palmer@dabbelt.com> wrote:
>>>>>> Commit 622021cd6c560ce7 ("s390: make command line configurable"),
>>>>>> I assume?
>>>>> Yes, sorry for that. I got distracted while writing and used the wrong
>>>>> branch to look this up.
>>>> Alex: Probably worth adding that to the list in the cover letter as it looks like you were planning on a v4 anyway (which I guess you now have to do, given that I just added the issue to RISC-V).
>>> The only use that is uapi is the *default* length of the command line if the kernel header doesn't include it (in the case of x86, it is in the bzImage header, but that is atchitecture- or even boot format-specific.)
>> Is COMMAND_LINE_SIZE what you call the default length? Does that mean
>> that to you the patchset is wrong?
> On x86, the COMMAND_LINE_SIZE value is already not part of a uapi header,
> but instead (since bzImage format version 2.06) is communicated from
> the kernel to the boot loader, which then knows how much data the
> kernel will read (at most) from the command line.
>
> Most x86 kernels these days are booted using UEFI, which I think has
> no such interface, the firmware just passes the command line and a
> length, but has no way of knowing if the kernel will truncate this.
> I think that is the same as with any other architecture that passes
> the command line through UEFI, DT or ATAGS, all of which use
> length/value pairs.
>
> Russell argued on IRC that this can be considered an ABI since a
> boot loader may use its knowledge of the kernel's command line size
> limit to reject long command lines. On the other hand, I don't
> think that any boot loader actually does, they just trust that it
> fits and don't have a good way of rejecting invalid configuration
> other than truncating and/or warning.
>
> One notable exception I found while looking through is the old
> (pre-ATAGS) parameter structure on Arm, which uses COMMAND_LINE_SIZE
> as part of the structure definition. Apparently this was deprecated
> 22 years ago, so hopefully the remaining riscpc and footbridge
> users have all upgraded their bootloaders.
>
> The only other case I could find that might go wrong is
> m68knommu with a few files copying a COMMAND_LINE_SIZE sized
> buffer from flash into a kernel buffer:
>
> arch/m68k/coldfire/m5206.c:void __init config_BSP(char *commandp, int size)
> arch/m68k/coldfire/m5206.c-{
> arch/m68k/coldfire/m5206.c-#if defined(CONFIG_NETtel)
> arch/m68k/coldfire/m5206.c- /* Copy command line from FLASH to local buffer... */
> arch/m68k/coldfire/m5206.c- memcpy(commandp, (char *) 0xf0004000, size);
> arch/m68k/coldfire/m5206.c- commandp[size-1] = 0;
> arch/m68k/coldfire/m5206.c-#endif /* CONFIG_NETtel */
I see, thanks your thorough explanation: I don't see this m64k issue as
a blocker (unless Geert disagrees but he already reviewed the m64k
patches), so I'll send the v5 now.
Thanks again,
Alex
>
> Arnd
next prev parent reply other threads:[~2023-03-06 9:35 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20230214074925.228106-1-alexghiti@rivosinc.com>
2023-02-14 7:49 ` [PATCH v3 01/24] alpha: Remove COMMAND_LINE_SIZE from uapi Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 02/24] arm64: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 03/24] arm: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 04/24] ia64: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 05/24] m68k: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 06/24] microblaze: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 07/24] mips: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 08/24] parisc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 09/24] powerpc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 10/24] sparc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 11/24] xtensa: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 12/24] asm-generic: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 13/24] alpha: Remove empty <uapi/asm/setup.h> Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 14/24] arc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 15/24] m68k: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 16/24] arm64: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 17/24] microblaze: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 18/24] sparc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 19/24] parisc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 20/24] x86: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 21/24] xtensa: " Alexandre Ghiti
2023-02-14 13:10 ` Max Filippov
2023-02-14 7:49 ` [PATCH v3 22/24] powerpc: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 23/24] mips: " Alexandre Ghiti
2023-02-14 7:49 ` [PATCH v3 24/24] s390: " Alexandre Ghiti
2023-02-14 8:38 ` [PATCH v3 00/24] Remove COMMAND_LINE_SIZE from uapi Heiko Carstens
2023-02-14 8:58 ` Geert Uytterhoeven
2023-02-14 9:19 ` Heiko Carstens
2023-03-02 3:17 ` Palmer Dabbelt
2023-03-02 7:57 ` Alexandre Ghiti
2023-03-02 19:50 ` H. Peter Anvin
2023-03-03 11:59 ` Alexandre Ghiti
2023-03-03 16:40 ` Arnd Bergmann
2023-03-06 9:35 ` Alexandre Ghiti [this message]
[not found] ` <20230214074925.228106-11-alexghiti@rivosinc.com>
2023-02-14 8:50 ` [PATCH v3 10/24] sparc: " Sergey Shtylyov
[not found] ` <017f0b40-8021-8b3b-24d2-c70661b6b292@omp.ru>
2023-02-14 8:59 ` WANG Xuerui
[not found] ` <f3db61bb-5c89-2724-769f-9d606f587f92@xen0n.name>
2023-02-14 9:11 ` Sergey Shtylyov
2023-02-14 10:38 ` John Paul Adrian Glaubitz
[not found] ` <20230214074925.228106-6-alexghiti@rivosinc.com>
2023-02-14 9:00 ` [PATCH v3 05/24] m68k: " Geert Uytterhoeven
[not found] ` <20230214074925.228106-16-alexghiti@rivosinc.com>
2023-02-14 9:01 ` [PATCH v3 15/24] m68k: Remove empty <uapi/asm/setup.h> Geert Uytterhoeven
[not found] ` <20230214074925.228106-21-alexghiti@rivosinc.com>
2023-02-14 9:04 ` [PATCH v3 20/24] x86: " Philippe Mathieu-Daudé
[not found] ` <20230214074925.228106-25-alexghiti@rivosinc.com>
2023-02-14 8:39 ` [PATCH v3 24/24] s390: " Heiko Carstens
2023-02-14 9:05 ` Philippe Mathieu-Daudé
[not found] ` <20230214074925.228106-15-alexghiti@rivosinc.com>
2023-02-14 9:05 ` [PATCH v3 14/24] arc: " Philippe Mathieu-Daudé
[not found] ` <20230214074925.228106-8-alexghiti@rivosinc.com>
2023-02-14 9:06 ` [PATCH v3 07/24] mips: Remove COMMAND_LINE_SIZE from uapi Philippe Mathieu-Daudé
[not found] ` <20230214074925.228106-2-alexghiti@rivosinc.com>
2023-02-14 9:07 ` [PATCH v3 01/24] alpha: " Philippe Mathieu-Daudé
[not found] ` <20230214074925.228106-9-alexghiti@rivosinc.com>
2023-02-14 9:08 ` [PATCH v3 08/24] parisc: " Philippe Mathieu-Daudé
[not found] ` <f327ff48-cd50-4caa-1bea-f9906994e998@linaro.org>
2023-02-14 9:43 ` Helge Deller
[not found] ` <20230214074925.228106-20-alexghiti@rivosinc.com>
2023-02-14 9:08 ` [PATCH v3 19/24] parisc: Remove empty <uapi/asm/setup.h> Philippe Mathieu-Daudé
[not found] ` <6f9c7a6b-4f6b-dead-2d9b-14b405f18397@linaro.org>
2023-02-14 9:44 ` Helge Deller
[not found] ` <20230214074925.228106-12-alexghiti@rivosinc.com>
2023-02-14 12:56 ` [PATCH v3 11/24] xtensa: Remove COMMAND_LINE_SIZE from uapi Max Filippov
[not found] ` <20230214074925.228106-3-alexghiti@rivosinc.com>
2023-02-14 14:14 ` [PATCH v3 02/24] arm64: " Catalin Marinas
[not found] ` <20230214074925.228106-10-alexghiti@rivosinc.com>
2023-02-15 7:04 ` [PATCH v3 09/24] powerpc: " Michael Ellerman
[not found] ` <20230214074925.228106-4-alexghiti@rivosinc.com>
2023-02-15 12:59 ` [PATCH v3 03/24] arm: " Russell King (Oracle)
2023-02-15 13:04 ` Arnd Bergmann
2023-02-23 9:54 ` Alexandre Ghiti
2023-02-23 13:09 ` Arnd Bergmann
2023-02-23 13:11 ` Alexandre Ghiti
2023-03-02 3:17 ` Palmer Dabbelt
2023-02-14 7:49 [PATCH v3 00/24] " Alexandre Ghiti
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