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From: Linus Torvalds <>
To: Thomas Gleixner <>
Cc: Linux Kernel Mailing List <>,
	"the arch/x86 maintainers" <>
Subject: Re: [GIT pull] x86/urgent for v5.15-rc3
Date: Sun, 26 Sep 2021 10:21:18 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <163265189517.178609.6605494600326137493.tglx@xen13>

On Sun, Sep 26, 2021 at 3:30 AM Thomas Gleixner <> wrote:
>  - Prevent undefined behaviour to the potential unaligned accesss in the
>    instroction decoder library.

What a horrible fix that is.

This is why we have "get_unaligned()". It might use memcpy()
internally on some architectures (it doesn't really any more - Arnd
cleaned it all up and now it uses a pointer that is marked unaligned),
but more importantly it explains _why_ something is done the way it's
done, rather than be an odd memcpy().

Oh well. The memcpy works, and compilers will do the right thing for
it, but it's ugly.

In this case, it's actually *doubly* ugly, though, because we
literally have functions to "load unaligned data in little-endian

So instead of doing a "memcpy()", followed by a magic special macro
that does a "switch (sizeof(t))" and does a "le*_to_cpu()" on the
result, the code could  literally have used the functions that do this
all for them.

Ugh. Pulled. But it's ugly.


  reply	other threads:[~2021-09-26 17:21 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-26 10:30 [GIT pull] irq/urgent " Thomas Gleixner
2021-09-26 10:30 ` [GIT pull] timers/urgent " Thomas Gleixner
2021-09-26 17:27   ` pr-tracker-bot
2021-09-26 10:30 ` [GIT pull] x86/urgent " Thomas Gleixner
2021-09-26 17:21   ` Linus Torvalds [this message]
2021-09-26 18:15     ` Borislav Petkov
2021-09-26 19:10       ` Linus Torvalds
2021-09-28 17:56         ` Borislav Petkov
2021-09-28 20:13           ` Linus Torvalds
2021-09-28 20:41             ` Borislav Petkov
2021-09-28 22:44               ` Linus Torvalds
2021-09-29 18:10                 ` [PATCH] x86/insn: Use get_unaligned() instead of memcpy() Borislav Petkov
2021-09-30  0:00                   ` Masami Hiramatsu
2021-10-04  9:48                   ` [tip: x86/misc] " tip-bot2 for Borislav Petkov
2021-10-06 10:02                   ` tip-bot2 for Borislav Petkov
2021-09-26 17:27   ` [GIT pull] x86/urgent for v5.15-rc3 pr-tracker-bot
2021-09-26 17:27 ` [GIT pull] irq/urgent " pr-tracker-bot

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