Subject: [PATCHv3 5/5] arm64: Trace emulation of AArch32 legacy instructions

From: [email-masked] (Will Deacon)
Date: Mon, 10 Nov 2014 18:27:14 +0000

On Mon, Oct 27, 2014 at 06:40:07PM +0000, Punit Agrawal wrote:
> Introduce an event to trace the usage of emulated instructions. The
> trace event is intended to help identify and encourage the migration
> of legacy software using the emulation features.
> 
> Use this event to trace usage of swp and CP15 barrier emulation.
> 
> Cc: Steven Rostedt <[email-masked]>
> Signed-off-by: Punit Agrawal <[email-masked]>
> ---
>  arch/arm64/kernel/Makefile                 |  1 +
>  arch/arm64/kernel/armv8_deprecated.c       | 19 ++++++++++++--
>  arch/arm64/kernel/trace-events-emulation.h | 40 ++++++++++++++++++++++++++++++
>  3 files changed, 58 insertions(+), 2 deletions(-)
>  create mode 100644 arch/arm64/kernel/trace-events-emulation.h
> 
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 5362578..1fc7abd 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -5,6 +5,7 @@
>  CPPFLAGS_vmlinux.lds	:= -DTEXT_OFFSET=$(TEXT_OFFSET)
>  AFLAGS_head.o		:= -DTEXT_OFFSET=$(TEXT_OFFSET)
>  CFLAGS_efi-stub.o 	:= -DTEXT_OFFSET=$(TEXT_OFFSET)
> +CFLAGS_armv8_deprecated.o := -I$(src)
>  
>  CFLAGS_REMOVE_ftrace.o = -pg
>  CFLAGS_REMOVE_insn.o = -pg
> diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c
> index fded15f..d376fe2 100644
> --- a/arch/arm64/kernel/armv8_deprecated.c
> +++ b/arch/arm64/kernel/armv8_deprecated.c
> @@ -15,6 +15,9 @@
>  #include <linux/slab.h>
>  #include <linux/sysctl.h>
>  
> +#define CREATE_TRACE_POINTS
> +#include "trace-events-emulation.h"
> +
>  #include <asm/insn.h>
>  #include <asm/opcodes.h>
>  #include <asm/system_misc.h>
> @@ -203,6 +206,11 @@ static int swp_handler(struct pt_regs *regs, u32 instr)
>  		regs->user_regs.regs[destreg] = data;
>  
>  ret:
> +	if (type == TYPE_SWPB)
> +		trace_instruction_emulation("swpb", regs->pc);
> +	else
> +		trace_instruction_emulation("swp", regs->pc);
> +
>  	pr_warn_ratelimited("\"%s\" (%ld) uses obsolete SWP{B} instruction at 0x%llx\n",
>  			current->comm, (unsigned long)current->pid, regs->pc);
>  
> @@ -260,16 +268,23 @@ static int cp15barrier_handler(struct pt_regs *regs, u32 instr)
>  		 * dmb - mcr p15, 0, Rt, c7, c10, 5
>  		 * dsb - mcr p15, 0, Rt, c7, c10, 4
>  		 */
> -		if (aarch32_insn_mcr_extract_opc2(instr) == 5)
> +		if (aarch32_insn_mcr_extract_opc2(instr) == 5) {
>  			dmb(sy);
> -		else
> +			trace_instruction_emulation(
> +				"mcr p15, 0, Rt, c7, c10, 5", regs->pc);
> +		} else {
>  			dsb(sy);
> +			trace_instruction_emulation(
> +				"mcr p15, 0, Rt, c7, c10, 4", regs->pc);
> +		}
>  		break;
>  	case 5:
>  		/*
>  		 * isb - mcr p15, 0, Rt, c7, c5, 4
>  		 */
>  		isb();
> +		trace_instruction_emulation(
> +			"mcr p15, 0, Rt, c7, c5, 4", regs->pc);

Any chance you can put the barrier name in here too please? Maybe as an asm
comment, e.g.:

  "mcr p15, 0, Rt, c7, c5, 4 ; isb"

Will