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From: Peter Zijlstra <peterz@infradead.org>
To: Lai Jiangshan <laijs@linux.alibaba.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>,
	linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	Joerg Roedel <jroedel@suse.de>,
	Youquan Song <youquan.song@intel.com>,
	Tony Luck <tony.luck@intel.com>
Subject: Re: [PATCH 22/24] x86/entry: Implement and use do_paranoid_entry() and paranoid_exit()
Date: Thu, 2 Sep 2021 14:02:38 +0200	[thread overview]
Message-ID: <YTC9Xv5K6npINezG@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <465e2f89-402d-6f05-ab36-46a6f005f2b3@linux.alibaba.com>

On Thu, Sep 02, 2021 at 06:42:16PM +0800, Lai Jiangshan wrote:
> On 2021/9/2 18:33, Peter Zijlstra wrote:
> > On Wed, Sep 01, 2021 at 01:50:23AM +0800, Lai Jiangshan wrote:
> > 
> > > +	call	do_paranoid_entry
> > >   	ret
> > 
> > That's normally spelled like:
> > 
> > 	jmp do_paranoid_entry
> > 
> > But the same comment as for error_entry but more; pretty much all that's
> > left in asm is things like:
> > 
> > 
> > 	call paranoid_entry;
> > 
> > 	# setup args
> > 	call \cfunc
> > 
> > 	call paranoid_exit
> > 
> > which seems like prime material to also pull into C to avoid the
> > back-and-forth thing. In fact, why can't you call paranoid_entry/exit
> > from \cfunc itself? The IDT macros should be able to help.
> > 
> 
> It sounds better.
> 
> I should have moved the code of pushing pt_regs out of paranoid_entry(),
> so that I could also have seen this.
> (and we don't need do_paranoid_entry(), paranoid_entry() itself can be in C)
> 
> The \cfunc would need to be marked as entry_text, right?

Yes I think so. The distinction between .entry.text and .noinstr.text is
that the former it mapped into the userspace mapping, while the latter
is not. Seeing how the PTI swizzling still has to happen when calling
cfunc, that had bettern be .entry.text.

If we care about a strict minimum of .entry.text the IDT macros can
generate a noinstr function to be called the moment we've done the PTI
munging I suppose.

  reply	other threads:[~2021-09-02 12:03 UTC|newest]

Thread overview: 72+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31 17:50 [PATCH 00/24] x86/entry/64: Convert a bunch of ASM entry code into C code Lai Jiangshan
2021-08-31 17:50 ` [PATCH 01/24] x86/traps: Remove stack-protector from traps.c Lai Jiangshan
2021-08-31 17:50 ` [PATCH 02/24] x86/traps: Move arch/x86/kernel/traps.c to arch/x86/entry/ Lai Jiangshan
2021-09-02  8:09   ` Joerg Roedel
2021-09-02  9:21     ` Lai Jiangshan
2021-09-02 10:50       ` Peter Zijlstra
2021-09-02 11:54         ` Lai Jiangshan
2021-09-02 12:05           ` Peter Zijlstra
2021-09-02 13:34             ` Peter Zijlstra
2021-09-02 17:05               ` Nick Desaulniers
2021-09-02 17:19                 ` Miguel Ojeda
2021-09-02 17:23                   ` Nick Desaulniers
2021-09-03  7:36                 ` Martin Liška
2021-09-07 21:12                   ` Nick Desaulniers
2021-09-08  7:33                     ` Martin Liška
2021-08-31 17:50 ` [PATCH 03/24] x86/traps: Move declaration of native_irq_return_iret up Lai Jiangshan
2021-08-31 17:50 ` [PATCH 04/24] x86/entry: Expose the address of .Lgs_change to traps.c Lai Jiangshan
2021-09-02  9:14   ` Peter Zijlstra
2021-09-02  9:20     ` Lai Jiangshan
2021-08-31 17:50 ` [PATCH 05/24] x86/entry: Introduce __entry_text for entry code written in C Lai Jiangshan
2021-08-31 19:34   ` Peter Zijlstra
2021-09-01  0:23     ` Lai Jiangshan
2021-08-31 17:50 ` [PATCH 06/24] x86/entry: Move PTI_USER_* to arch/x86/include/asm/processor-flags.h Lai Jiangshan
2021-08-31 17:50 ` [PATCH 07/24] x86: Mark __native_read_cr3() & native_write_cr3() as __always_inline Lai Jiangshan
2021-08-31 17:50 ` [PATCH 08/24] x86/traps: Add C verion of SWITCH_TO_KERNEL_CR3 as switch_to_kernel_cr3() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 09/24] x86/traps: Add fence_swapgs_{user,kernel}_entry() Lai Jiangshan
2021-09-02  9:25   ` Peter Zijlstra
2021-08-31 17:50 ` [PATCH 10/24] x86/traps: Move pt_regs only in fixup_bad_iret() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 11/24] x86/entry: Replace the most of asm code of error_entry to C code Lai Jiangshan
2021-09-02 10:16   ` Peter Zijlstra
2021-09-02 12:08     ` Lai Jiangshan
2021-08-31 17:50 ` [PATCH 12/24] x86/traps: Reconstruct pt_regs on task stack directly in fixup_bad_iret() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 13/24] x86/traps: Mark sync_regs() and fixup_bad_iret() as static __always_inline Lai Jiangshan
2021-08-31 17:50 ` [PATCH 14/24] x86/entry: Make paranoid_exit() callable Lai Jiangshan
2021-08-31 17:50 ` [PATCH 15/24] x86/entry: Call paranoid_exit() in asm_exc_nmi() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 16/24] x86/entry: Use skip_rdi instead of save_ret for PUSH_AND_CLEAR_REGS Lai Jiangshan
2021-08-31 17:50 ` [PATCH 17/24] x86/entry: Introduce struct ist_regs Lai Jiangshan
2021-09-10  0:18   ` Lai Jiangshan
2021-09-10  0:36     ` Lai Jiangshan
2021-09-10  4:31     ` H. Peter Anvin
2021-09-10  7:13       ` Lai Jiangshan
2021-09-10  7:14         ` H. Peter Anvin
2021-09-10  4:50     ` H. Peter Anvin
2021-09-10  4:51       ` H. Peter Anvin
2021-08-31 17:50 ` [PATCH 18/24] x86/entry: Add the C version ist_switch_to_kernel_cr3() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 19/24] x86/entry: Add the C version ist_restore_cr3() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 20/24] x86/entry: Add the C version get_percpu_base() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 21/24] x86/entry: Add the C version ist_switch_to_kernel_gsbase() Lai Jiangshan
2021-08-31 17:50 ` [PATCH 22/24] x86/entry: Implement and use do_paranoid_entry() and paranoid_exit() Lai Jiangshan
2021-09-02 10:33   ` Peter Zijlstra
2021-09-02 10:42     ` Lai Jiangshan
2021-09-02 12:02       ` Peter Zijlstra [this message]
2021-09-02 11:58     ` Lai Jiangshan
2021-09-02 12:29       ` Joerg Roedel
2021-08-31 17:50 ` [PATCH 23/24] x86/entry: Remove the unused ASM macros Lai Jiangshan
2021-08-31 17:50 ` [PATCH 24/24] x86/syscall/64: Move the checking for sysret to C code Lai Jiangshan
2021-09-10  7:20   ` Nikolay Borisov
2021-09-10  7:30     ` Lai Jiangshan
2021-08-31 20:44 ` [PATCH 00/24] x86/entry/64: Convert a bunch of ASM entry code into " Peter Zijlstra
2021-09-02  6:28   ` Lai Jiangshan
2021-09-02  7:44     ` Peter Zijlstra
2021-09-02 10:50 ` [PATCH 25/24] x86/traps: Rewrite native_load_gs_index in " Lai Jiangshan
2021-09-08  1:38   ` H. Peter Anvin
2021-09-08  4:42     ` H. Peter Anvin
2021-09-08  5:00       ` H. Peter Anvin
2021-09-08  7:12         ` Lai Jiangshan
2021-09-09 23:16           ` H. Peter Anvin
2021-09-13 20:01   ` Andy Lutomirski
2021-09-14  2:04     ` Lai Jiangshan
2021-09-14  8:14       ` Peter Zijlstra
2021-09-14  8:17         ` Borislav Petkov
2021-09-14  8:40         ` Lai Jiangshan

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