linux-kernel - [PATCH v2 0/2] Rewrite ret_from

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Message-ID: <20230623225529.34590-1-brgerst@gmail.com>
Date:   Fri, 23 Jun 2023 18:55:27 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        alyssa.milburn@...ux.intel.com, keescook@...omium.org,
        jpoimboe@...nel.org, joao@...rdrivepizza.com,
        tim.c.chen@...ux.intel.com, Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2 0/2] Rewrite ret_from_fork() in C

When kCFI is enabled, special handling is needed for the indirect call
to the kernel thread function.  Handling this in pure assembly is not
simple, so moving it to C is more appropriate.  Instead of moving just
the indirect call to C as Peter Zijlstra has proposed, this patchset
rewrites the whole ret_from_fork() function in C (other than some
necessary asm glue remaning).

V2:
- Fixed wrong address of pt_regs being passed
- Simplified 64-bit asm stub to not use a tail-call

Brian Gerst (2):
  x86/32: Remove schedule_tail_wrapper()
  x86: Rewrite ret_from_fork() in C

 arch/x86/entry/entry_32.S        | 53 ++++++++------------------------
 arch/x86/entry/entry_64.S        | 33 +++++---------------
 arch/x86/include/asm/switch_to.h |  4 ++-
 arch/x86/kernel/process.c        | 22 ++++++++++++-
 4 files changed, 45 insertions(+), 67 deletions(-)

-- 
2.41.0