From: "hch@infradead.org" <hch@infradead.org>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "hch@infradead.org" <hch@infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"daniel@iogearbox.net" <daniel@iogearbox.net>,
"peterz@infradead.org" <peterz@infradead.org>,
"jeyu@kernel.org" <jeyu@kernel.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"rppt@kernel.org" <rppt@kernel.org>,
"ast@kernel.org" <ast@kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"Weiny, Ira" <ira.weiny@intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"Reshetova, Elena" <elena.reshetova@intel.com>,
"Williams, Dan J" <dan.j.williams@intel.com>,
"luto@kernel.org" <luto@kernel.org>
Subject: Re: [PATCH RFC 01/10] vmalloc: Add basic perm alloc implementation
Date: Tue, 24 Nov 2020 10:19:01 +0000 [thread overview]
Message-ID: <20201124101901.GB9682@infradead.org> (raw)
In-Reply-To: <eccaa448f82e90c924d51d52525f766340026dfe.camel@intel.com>
On Mon, Nov 23, 2020 at 08:44:12PM +0000, Edgecombe, Rick P wrote:
> Well, there were two reasons:
> 1. Non-standard naming for the PAGE_FOO flags. For example,
> PAGE_KERNEL_ROX vs PAGE_KERNEL_READ_EXEC. This could be unified. I
> think it's just riscv that breaks the conventions. Others are just
> missing some.
We need to standardize those anyway. I've done that for a few
PAGE_* constants already but as you see there is more work to do.
> But I thought that using those pgprot flags was still sort overloading
> the meaning of pgprot. My understanding was that it is supposed to hold
> the actual bits set in the PTE. For example large pages or TLB hints
> (like PAGE_KERNEL_EXEC_CONT) could set or unset extra bits, so asking
> for PAGE_KERNEL_EXEC wouldn't necessarily mean "set these bits in all
> of the PTEs", it could mean something more like "infer what I want from
> these bits and do that".
>
> x86's cpa will also avoid changing NX if it is not supported, so if the
> caller asked for PAGE_KERNEL->PAGE_KERNEL_EXEC in perm_change() it
> should not necessarily bother setting all of the PAGE_KERNEL_EXEC bits
> in the actual PTEs. Asking for PERM_RW->PERM_RWX on the other hand,
> would let the implementation do whatever it needs to set the memory
> executable, like set_memory_x() does. It should work either way but
> seems like the expectations would be a little clearer with the PERM_
> flags.
Ok, maybe that is an argument, and we should use the new flags more
broadly.
> Could easily wrap this one, but just to clarify, do you mean lines over
> 80 chars? There were already some over 80 in vmalloc before the move to
> 100 chars, so figured it was ok to stretch out now.
CodingStyle still says 80 characters unless you have an exception where
a longer line improves the readability. The quoted code absolutely
does not fit the definition of an exception or improves readability.
next prev parent reply other threads:[~2020-11-24 10:19 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 20:24 [PATCH RFC 00/10] New permission vmalloc interface Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 01/10] vmalloc: Add basic perm alloc implementation Rick Edgecombe
2020-11-22 4:10 ` Andy Lutomirski
2020-11-23 0:01 ` Edgecombe, Rick P
2020-11-24 10:16 ` Christoph Hellwig
2020-11-24 20:00 ` Edgecombe, Rick P
2020-11-23 9:00 ` Christoph Hellwig
2020-11-23 20:44 ` Edgecombe, Rick P
2020-11-24 10:19 ` hch [this message]
2020-11-24 19:59 ` Edgecombe, Rick P
2020-12-04 23:24 ` Sean Christopherson
2020-12-07 23:55 ` Edgecombe, Rick P
2020-11-20 20:24 ` [PATCH RFC 02/10] bpf: Use perm_alloc() for BPF JIT filters Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 03/10] module: Use perm_alloc() for modules Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 04/10] module: Support separate writable allocation Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 05/10] x86/modules: Use real perm_allocations Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 06/10] x86/alternatives: Handle perm_allocs for modules Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 07/10] x86/unwind: Unwind orc at module writable address Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 08/10] jump_label: Handle " Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 09/10] ftrace: Use " Rick Edgecombe
2020-11-20 20:24 ` [PATCH RFC 10/10] vmalloc: Add perm_alloc x86 implementation Rick Edgecombe
2020-11-22 15:29 ` [vmalloc] 377647beed: WARNING:at_arch/x86/kernel/ftrace.c:#ftrace_verify_code kernel test robot
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