linux-kernel - [PATCH 0/4] riscv: uaccess: optimizations

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Date: Tue, 25 Jun 2024 12:04:56 +0800
From: Jisheng Zhang <jszhang@...nel.org>
To: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/4] riscv: uaccess: optimizations

This series tries to optimize riscv uaccess in the following way:

patch1 implement the user_access_begin and families, I.E the unsafe
accessors. when a function like strncpy_from_user() is called,
the userspace access protection is disabled and enabled for every
word read. After patch1, the protection is disabled at the beginning
of the copy and enabled at the end.

patch2 is a simple clean up

patch3 uses 'asm goto' for put_user()
patch4 uses 'asm goto output' for get_user()

Both patch3 and patch4 are based on the fact -- 'asm goto' and
'asm goto output'generates noticeably better code since we don't need
to test the error etc, the exception just jumps to the error handling
directly.

Jisheng Zhang (4):
  riscv: implement user_access_begin and families
  riscv: uaccess: use input constraints for ptr of __put_user
  riscv: uaccess: use 'asm goto' for put_user()
  riscv: uaccess: use 'asm goto output' for get_user

 arch/riscv/include/asm/uaccess.h | 201 +++++++++++++++++++++++--------
 1 file changed, 149 insertions(+), 52 deletions(-)

-- 
2.43.0