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From: Will Deacon <will@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	rostedt@goodmis.org, mhiramat@kernel.org, bristot@redhat.com,
	jbaron@akamai.com, torvalds@linux-foundation.org,
	tglx@linutronix.de, mingo@kernel.org, namit@vmware.com,
	hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org,
	jpoimboe@redhat.com, jeyu@kernel.org, rabin@rab.in,
	Mark Rutland <mark.rutland@arm.com>,
	james.morse@arm.com
Subject: Re: [PATCH v4 13/16] arm/ftrace: Use __patch_text_real()
Date: Mon, 28 Oct 2019 16:25:26 +0000	[thread overview]
Message-ID: <20191028162525.GF5576@willie-the-truck> (raw)
In-Reply-To: <20191018074634.687479693@infradead.org>

Hi Peter,

On Fri, Oct 18, 2019 at 09:35:38AM +0200, Peter Zijlstra wrote:
> Instead of flipping text protection, use the patch_text infrastructure
> that uses a fixmap alias where required.
> 
> This removes the last user of set_all_modules_text_*().
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: ard.biesheuvel@linaro.org
> Cc: rabin@rab.in
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: james.morse@arm.com
> ---
>  arch/arm/kernel/ftrace.c |   16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> --- a/arch/arm/kernel/ftrace.c
> +++ b/arch/arm/kernel/ftrace.c
> @@ -22,6 +22,7 @@
>  #include <asm/ftrace.h>
>  #include <asm/insn.h>
>  #include <asm/set_memory.h>
> +#include <asm/patch.h>
>  
>  #ifdef CONFIG_THUMB2_KERNEL
>  #define	NOP		0xf85deb04	/* pop.w {lr} */
> @@ -31,13 +32,15 @@
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE
>  
> +static int patch_text_remap = 0;
> +
>  static int __ftrace_modify_code(void *data)
>  {
>  	int *command = data;
>  
> -	set_kernel_text_rw();
> +	patch_text_remap++;
>  	ftrace_modify_all_code(*command);
> -	set_kernel_text_ro();
> +	patch_text_remap--;
>  
>  	return 0;
>  }
> @@ -59,13 +62,13 @@ static unsigned long adjust_address(stru
>  
>  int ftrace_arch_code_modify_prepare(void)
>  {
> -	set_all_modules_text_rw();
> +	patch_text_remap++;
>  	return 0;
>  }
>  
>  int ftrace_arch_code_modify_post_process(void)
>  {
> -	set_all_modules_text_ro();
> +	patch_text_remap--;
>  	/* Make sure any TLB misses during machine stop are cleared. */
>  	flush_tlb_all();
>  	return 0;
> @@ -97,10 +100,7 @@ static int ftrace_modify_code(unsigned l
>  			return -EINVAL;
>  	}
>  
> -	if (probe_kernel_write((void *)pc, &new, MCOUNT_INSN_SIZE))
> -		return -EPERM;
> -
> -	flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
> +	__patch_text_real((void *)pc, new, patch_text_remap);

Why can't you just pass 'true' for patch_text_remap? AFAICT, the only
time you want to pass false is during early boot when the text is
assumedly still writable without the fixmap.

Will

  reply	other threads:[~2019-10-28 16:25 UTC|newest]

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  7:35 [PATCH v4 00/16] Rewrite x86/ftrace to use text_poke (and more) Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 01/16] x86/alternatives: Teach text_poke_bp() to emulate instructions Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 02/16] x86/alternatives: Update int3_emulate_push() comment Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 03/16] x86/alternatives,jump_label: Provide better text_poke() batching interface Peter Zijlstra
2019-10-21  8:48   ` Ingo Molnar
2019-10-21  9:21     ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 04/16] x86/alternatives: Add and use text_gen_insn() helper Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 05/16] x86/ftrace: Use text_poke() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 06/16] x86/mm: Remove set_kernel_text_r[ow]() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 07/16] x86/alternative: Add text_opcode_size() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 08/16] x86/ftrace: Use text_gen_insn() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 09/16] x86/alternative: Remove text_poke_loc::len Peter Zijlstra
2019-10-21  8:58   ` Ingo Molnar
2019-10-21  9:02     ` Ingo Molnar
2019-10-18  7:35 ` [PATCH v4 10/16] x86/alternative: Shrink text_poke_loc Peter Zijlstra
2019-10-21  9:01   ` Ingo Molnar
2019-10-21  9:25     ` Peter Zijlstra
2019-10-21  9:33       ` Ingo Molnar
2019-10-18  7:35 ` [PATCH v4 11/16] x86/kprobes: Convert to text-patching.h Peter Zijlstra
2019-10-21 14:57   ` Masami Hiramatsu
2019-10-18  7:35 ` [PATCH v4 12/16] x86/kprobes: Fix ordering Peter Zijlstra
2019-10-22  1:35   ` Masami Hiramatsu
2019-10-22 10:31     ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 13/16] arm/ftrace: Use __patch_text_real() Peter Zijlstra
2019-10-28 16:25   ` Will Deacon [this message]
2019-10-28 16:34     ` Peter Zijlstra
2019-10-28 16:35       ` Peter Zijlstra
2019-10-28 16:47       ` Will Deacon
2019-10-28 16:55         ` Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 14/16] module: Remove set_all_modules_text_*() Peter Zijlstra
2019-10-18  7:35 ` [PATCH v4 15/16] module: Move where we mark modules RO,X Peter Zijlstra
2019-10-21 13:53   ` Josh Poimboeuf
2019-10-21 14:14     ` Peter Zijlstra
2019-10-21 15:34       ` Peter Zijlstra
2019-10-21 15:44         ` Peter Zijlstra
2019-10-21 16:11         ` Peter Zijlstra
2019-10-22 11:31           ` Heiko Carstens
2019-10-22 12:31             ` Peter Zijlstra
2019-10-23 11:48       ` Peter Zijlstra
2019-10-23 15:16         ` Peter Zijlstra
2019-10-23 17:15           ` Josh Poimboeuf
2019-10-24 10:59             ` Peter Zijlstra
2019-10-24 18:31               ` Josh Poimboeuf
2019-10-24 20:33                 ` Peter Zijlstra
2019-10-23 17:00         ` Josh Poimboeuf
2019-10-24 13:16           ` Peter Zijlstra
2019-10-25  6:44             ` Petr Mladek
2019-10-25  8:43               ` Peter Zijlstra
2019-10-25 10:06                 ` Peter Zijlstra
2019-10-25 13:50                   ` Josh Poimboeuf
2019-10-26  1:17                   ` Josh Poimboeuf
2019-10-28 10:07                     ` Peter Zijlstra
2019-10-28 10:43                     ` Peter Zijlstra
2019-10-25  9:16               ` Peter Zijlstra
2019-10-22  2:21   ` Steven Rostedt
2019-10-22 20:24     ` Peter Zijlstra
2019-10-22 20:40       ` Steven Rostedt
2019-10-23  9:07         ` Peter Zijlstra
2019-10-23 18:52       ` Steven Rostedt
2019-10-24 10:16         ` Peter Zijlstra
2019-10-24 10:18           ` Peter Zijlstra
2019-10-24 15:00           ` Steven Rostedt
2019-10-24 16:43             ` Peter Zijlstra
2019-10-24 18:17               ` Steven Rostedt
2019-10-24 20:24                 ` Peter Zijlstra
2019-10-24 20:28                   ` Steven Rostedt
2019-10-18  7:35 ` [PATCH v4 16/16] ftrace: Merge ftrace_module_{init,enable}() Peter Zijlstra
2019-10-18  8:20   ` Peter Zijlstra
2019-10-21  9:09 ` [PATCH v4 00/16] Rewrite x86/ftrace to use text_poke (and more) Ingo Molnar
2019-10-21 13:38   ` Steven Rostedt

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