x86: Make __get_user() generate an out-of-line call

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Instead of inlining the whole stac/lfence/mov/clac sequence (which also
requires individual exception table entries and several asm instruction
alternatives entries), just generate "call __get_user_nocheck_X" for the
__get_user() cases.

We can use all the same infrastructure that we already do for the
regular "get_user()", and the end result is simpler source code, and
much simpler code generation.

It also means that when I introduce asm goto with input for
"unsafe_get_user()", there are no nasty interactions with the
__get_user() code.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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Linus Torvalds 2020-04-08 12:50:01 -07:00

parent 53acd35050

commit ea6f043fc9

2 changed files with 114 additions and 74 deletions

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132

arch/x86/include/asm/uaccess.h

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60

arch/x86/lib/getuser.S

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