From: Michael Ellerman <mpe@ellerman.id.au>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Andrew Donnellan <ajd@linux.ibm.com>,
linuxppc-dev@lists.ozlabs.org, linux-integrity@vger.kernel.org,
sudhakar@linux.ibm.com, bgray@linux.ibm.com,
erichte@linux.ibm.com, gregkh@linuxfoundation.org,
nayna@linux.ibm.com, linux-kernel@vger.kernel.org,
zohar@linux.ibm.com, gjoyce@linux.ibm.com, joel@jms.id.au,
ruscur@russell.cc, gcwilson@linux.ibm.com
Subject: Re: [PATCH v4 02/24] powerpc/pseries: Fix alignment of PLPKS structures and buffers
Date: Fri, 27 Jan 2023 21:52:31 +1100 [thread overview]
Message-ID: <871qngtfkg.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20230126171925.GN25951@gate.crashing.org>
Segher Boessenkool <segher@kernel.crashing.org> writes:
> On Thu, Jan 26, 2023 at 12:09:53AM +1100, Michael Ellerman wrote:
>> Andrew Donnellan <ajd@linux.ibm.com> writes:
>> > A number of structures and buffers passed to PKS hcalls have alignment
>> > requirements, which could on occasion cause problems:
>> >
>> > - Authorisation structures must be 16-byte aligned and must not cross a
>> > page boundary
>> >
>> > - Label structures must not cross page boundaries
>> >
>> > - Password output buffers must not cross page boundaries
>> >
>> > Round up the allocations of these structures/buffers to the next power of
>> > 2 to make sure this happens.
>>
>> It's not the *next* power of 2, it's the *nearest* power of 2, including
>> the initial value if it's already a power of 2.
>
> It's not the nearest either, the nearest power of two to 65 is 64. You
> could say "but, round up" to which I would say "round?" :-P
OK you got me there :)
The function name makes it pretty clear that it will round *up* to the
nearest power of 2 but you're right the comment should also make that
clear.
> "Adjust the allocation size to be the smallest power of two greater than
> or equal to the given size."
>
> "Pad to a power of two" in shorthand. "Padded to a power of two if
> necessary" if you want to emphasise it can be a no-op.
The initial wording implied that it would always over-allocate so yes I
think it's important to make it clear that it doesn't round up if it
doesn't need to.
cheers
WARNING: multiple messages have this Message-ID (diff)
From: Michael Ellerman <mpe@ellerman.id.au>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: gjoyce@linux.ibm.com, Andrew Donnellan <ajd@linux.ibm.com>,
erichte@linux.ibm.com, gregkh@linuxfoundation.org,
nayna@linux.ibm.com, linux-kernel@vger.kernel.org,
zohar@linux.ibm.com, sudhakar@linux.ibm.com, ruscur@russell.cc,
joel@jms.id.au, bgray@linux.ibm.com,
linux-integrity@vger.kernel.org, gcwilson@linux.ibm.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v4 02/24] powerpc/pseries: Fix alignment of PLPKS structures and buffers
Date: Fri, 27 Jan 2023 21:52:31 +1100 [thread overview]
Message-ID: <871qngtfkg.fsf@mpe.ellerman.id.au> (raw)
In-Reply-To: <20230126171925.GN25951@gate.crashing.org>
Segher Boessenkool <segher@kernel.crashing.org> writes:
> On Thu, Jan 26, 2023 at 12:09:53AM +1100, Michael Ellerman wrote:
>> Andrew Donnellan <ajd@linux.ibm.com> writes:
>> > A number of structures and buffers passed to PKS hcalls have alignment
>> > requirements, which could on occasion cause problems:
>> >
>> > - Authorisation structures must be 16-byte aligned and must not cross a
>> > page boundary
>> >
>> > - Label structures must not cross page boundaries
>> >
>> > - Password output buffers must not cross page boundaries
>> >
>> > Round up the allocations of these structures/buffers to the next power of
>> > 2 to make sure this happens.
>>
>> It's not the *next* power of 2, it's the *nearest* power of 2, including
>> the initial value if it's already a power of 2.
>
> It's not the nearest either, the nearest power of two to 65 is 64. You
> could say "but, round up" to which I would say "round?" :-P
OK you got me there :)
The function name makes it pretty clear that it will round *up* to the
nearest power of 2 but you're right the comment should also make that
clear.
> "Adjust the allocation size to be the smallest power of two greater than
> or equal to the given size."
>
> "Pad to a power of two" in shorthand. "Padded to a power of two if
> necessary" if you want to emphasise it can be a no-op.
The initial wording implied that it would always over-allocate so yes I
think it's important to make it clear that it doesn't round up if it
doesn't need to.
cheers
next prev parent reply other threads:[~2023-01-27 10:52 UTC|newest]
Thread overview: 104+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-20 7:42 [PATCH v4 00/24] pSeries dynamic secure boot secvar interface + platform keyring loading Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 01/24] powerpc/pseries: Fix handling of PLPKS object flushing timeout Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 02/24] powerpc/pseries: Fix alignment of PLPKS structures and buffers Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-25 13:09 ` Michael Ellerman
2023-01-25 13:09 ` Michael Ellerman
2023-01-26 17:19 ` Segher Boessenkool
2023-01-26 17:19 ` Segher Boessenkool
2023-01-26 17:31 ` David Laight
2023-01-26 17:31 ` David Laight
2023-01-27 3:20 ` Andrew Donnellan
2023-01-27 3:20 ` Andrew Donnellan
2023-01-27 9:05 ` David Laight
2023-01-27 9:05 ` David Laight
2023-01-27 11:08 ` Michael Ellerman
2023-01-27 11:08 ` Michael Ellerman
2023-01-27 10:52 ` Michael Ellerman [this message]
2023-01-27 10:52 ` Michael Ellerman
2023-01-20 7:42 ` [PATCH v4 03/24] powerpc/secvar: Use u64 in secvar_operations Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 04/24] powerpc/secvar: Warn and error if multiple secvar ops are set Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 05/24] powerpc/secvar: Use sysfs_emit() instead of sprintf() Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 06/24] powerpc/secvar: Handle format string in the consumer Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 07/24] powerpc/secvar: Handle max object size " Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 08/24] powerpc/secvar: Clean up init error messages Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 09/24] powerpc/secvar: Extend sysfs to include config vars Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 10/24] powerpc/secvar: Allow backend to populate static list of variable names Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 11/24] powerpc/secvar: Warn when PAGE_SIZE is smaller than max object size Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 12/24] powerpc/secvar: Don't print error on ENOENT when reading variables Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 13/24] powerpc/pseries: Move plpks.h to include directory Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 14/24] powerpc/pseries: Move PLPKS constants to header file Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 15/24] powerpc/pseries: Expose PLPKS config values, support additional fields Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:42 ` [PATCH v4 16/24] powerpc/pseries: Implement signed update for PLPKS objects Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-24 4:16 ` Nicholas Piggin
2023-01-24 4:16 ` Nicholas Piggin
2023-01-30 4:43 ` Andrew Donnellan
2023-01-30 4:43 ` Andrew Donnellan
2023-01-31 4:23 ` Russell Currey
2023-01-31 4:23 ` Russell Currey
2023-01-20 7:42 ` [PATCH v4 17/24] powerpc/pseries: Log hcall return codes for PLPKS debug Andrew Donnellan
2023-01-20 7:42 ` Andrew Donnellan
2023-01-20 7:43 ` [PATCH v4 18/24] powerpc/pseries: Make caller pass buffer to plpks_read_var() Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-20 7:43 ` [PATCH v4 19/24] powerpc/pseries: Turn PSERIES_PLPKS into a hidden option Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-24 4:26 ` Nicholas Piggin
2023-01-24 4:26 ` Nicholas Piggin
2023-01-20 7:43 ` [PATCH v4 20/24] powerpc/pseries: Add helpers to get PLPKS password Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-20 7:43 ` [PATCH v4 21/24] powerpc/pseries: Pass PLPKS password on kexec Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-24 4:36 ` Nicholas Piggin
2023-01-24 4:36 ` Nicholas Piggin
2023-01-24 4:40 ` Andrew Donnellan
2023-01-24 4:40 ` Andrew Donnellan
2023-01-25 3:59 ` Michael Ellerman
2023-01-25 3:59 ` Michael Ellerman
2023-01-31 2:43 ` Russell Currey
2023-01-31 2:43 ` Russell Currey
2023-01-20 7:43 ` [PATCH v4 22/24] powerpc/pseries: Implement secvars for dynamic secure boot Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-24 5:17 ` Nicholas Piggin
2023-01-24 5:17 ` Nicholas Piggin
2023-01-31 2:54 ` Andrew Donnellan
2023-01-31 2:54 ` Andrew Donnellan
2023-01-31 4:25 ` Andrew Donnellan
2023-01-31 4:25 ` Andrew Donnellan
2023-01-31 8:55 ` Nicholas Piggin
2023-01-31 8:55 ` Nicholas Piggin
2023-02-01 2:15 ` Andrew Donnellan
2023-02-01 2:15 ` Andrew Donnellan
2023-01-20 7:43 ` [PATCH v4 23/24] integrity/powerpc: Improve error handling & reporting when loading certs Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-24 15:42 ` Mimi Zohar
2023-01-24 15:42 ` Mimi Zohar
2023-01-20 7:43 ` [PATCH v4 24/24] integrity/powerpc: Support loading keys from pseries secvar Andrew Donnellan
2023-01-20 7:43 ` Andrew Donnellan
2023-01-24 5:24 ` Nicholas Piggin
2023-01-24 5:24 ` Nicholas Piggin
2023-01-24 15:14 ` Mimi Zohar
2023-01-24 15:14 ` Mimi Zohar
2023-01-25 0:45 ` Andrew Donnellan
2023-01-25 0:45 ` Andrew Donnellan
2023-01-25 2:23 ` Russell Currey
2023-01-25 2:23 ` Russell Currey
2023-01-25 2:47 ` Mimi Zohar
2023-01-25 2:47 ` Mimi Zohar
2023-01-31 1:03 ` Andrew Donnellan
2023-01-31 1:03 ` Andrew Donnellan
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