Re: [PATCH 01/10] jump label v11: make dynamic no-op selection available outside of ftrace

[Steven Rostedt <rostedt@goodmis.org>]

On Fri, 2010-09-17 at 11:08 -0400, Jason Baron wrote:
> Move Steve's code for finding the best 5-byte no-op from ftrace.c to alternative.c.
> The idea is that other consumers (in this case jump label) want to make use of
> that code.
> 
> Signed-off-by: Jason Baron <jbaron@redhat.com>

Acked-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve

> ---
>  arch/x86/include/asm/alternative.h |    8 ++++
>  arch/x86/kernel/alternative.c      |   64 ++++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/ftrace.c           |   63 +----------------------------------
>  arch/x86/kernel/setup.c            |    6 +++
>  4 files changed, 79 insertions(+), 62 deletions(-)
> 
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index bc6abb7..27a35b6 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -180,4 +180,12 @@ static inline void apply_paravirt(struct paravirt_patch_site *start,
>  extern void *text_poke(void *addr, const void *opcode, size_t len);
>  extern void *text_poke_smp(void *addr, const void *opcode, size_t len);
>  
> +#if defined(CONFIG_DYNAMIC_FTRACE)
> +#define IDEAL_NOP_SIZE_5 5
> +extern unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
> +extern void arch_init_ideal_nop5(void);
> +#else
> +static inline void arch_init_ideal_nop5(void) {}
> +#endif
> +
>  #endif /* _ASM_X86_ALTERNATIVE_H */
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index f65ab8b..1849d80 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -641,3 +641,67 @@ void *__kprobes text_poke_smp(void *addr, const void *opcode, size_t len)
>  	return addr;
>  }
>  
> +#if defined(CONFIG_DYNAMIC_FTRACE)
> +
> +unsigned char ideal_nop5[IDEAL_NOP_SIZE_5];
> +
> +void __init arch_init_ideal_nop5(void)
> +{
> +	extern const unsigned char ftrace_test_p6nop[];
> +	extern const unsigned char ftrace_test_nop5[];
> +	extern const unsigned char ftrace_test_jmp[];
> +	int faulted = 0;
> +
> +	/*
> +	 * There is no good nop for all x86 archs.
> +	 * We will default to using the P6_NOP5, but first we
> +	 * will test to make sure that the nop will actually
> +	 * work on this CPU. If it faults, we will then
> +	 * go to a lesser efficient 5 byte nop. If that fails
> +	 * we then just use a jmp as our nop. This isn't the most
> +	 * efficient nop, but we can not use a multi part nop
> +	 * since we would then risk being preempted in the middle
> +	 * of that nop, and if we enabled tracing then, it might
> +	 * cause a system crash.
> +	 *
> +	 * TODO: check the cpuid to determine the best nop.
> +	 */
> +	asm volatile (
> +		"ftrace_test_jmp:"
> +		"jmp ftrace_test_p6nop\n"
> +		"nop\n"
> +		"nop\n"
> +		"nop\n"  /* 2 byte jmp + 3 bytes */
> +		"ftrace_test_p6nop:"
> +		P6_NOP5
> +		"jmp 1f\n"
> +		"ftrace_test_nop5:"
> +		".byte 0x66,0x66,0x66,0x66,0x90\n"
> +		"1:"
> +		".section .fixup, \"ax\"\n"
> +		"2:	movl $1, %0\n"
> +		"	jmp ftrace_test_nop5\n"
> +		"3:	movl $2, %0\n"
> +		"	jmp 1b\n"
> +		".previous\n"
> +		_ASM_EXTABLE(ftrace_test_p6nop, 2b)
> +		_ASM_EXTABLE(ftrace_test_nop5, 3b)
> +		: "=r"(faulted) : "0" (faulted));
> +
> +	switch (faulted) {
> +	case 0:
> +		pr_info("converting mcount calls to 0f 1f 44 00 00\n");
> +		memcpy(ideal_nop5, ftrace_test_p6nop, IDEAL_NOP_SIZE_5);
> +		break;
> +	case 1:
> +		pr_info("converting mcount calls to 66 66 66 66 90\n");
> +		memcpy(ideal_nop5, ftrace_test_nop5, IDEAL_NOP_SIZE_5);
> +		break;
> +	case 2:
> +		pr_info("converting mcount calls to jmp . + 5\n");
> +		memcpy(ideal_nop5, ftrace_test_jmp, IDEAL_NOP_SIZE_5);
> +		break;
> +	}
> +
> +}
> +#endif
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index cd37469..3afb33f 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -257,14 +257,9 @@ do_ftrace_mod_code(unsigned long ip, void *new_code)
>  	return mod_code_status;
>  }
>  
> -
> -
> -
> -static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
> -
>  static unsigned char *ftrace_nop_replace(void)
>  {
> -	return ftrace_nop;
> +	return ideal_nop5;
>  }
>  
>  static int
> @@ -338,62 +333,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
>  
>  int __init ftrace_dyn_arch_init(void *data)
>  {
> -	extern const unsigned char ftrace_test_p6nop[];
> -	extern const unsigned char ftrace_test_nop5[];
> -	extern const unsigned char ftrace_test_jmp[];
> -	int faulted = 0;
> -
> -	/*
> -	 * There is no good nop for all x86 archs.
> -	 * We will default to using the P6_NOP5, but first we
> -	 * will test to make sure that the nop will actually
> -	 * work on this CPU. If it faults, we will then
> -	 * go to a lesser efficient 5 byte nop. If that fails
> -	 * we then just use a jmp as our nop. This isn't the most
> -	 * efficient nop, but we can not use a multi part nop
> -	 * since we would then risk being preempted in the middle
> -	 * of that nop, and if we enabled tracing then, it might
> -	 * cause a system crash.
> -	 *
> -	 * TODO: check the cpuid to determine the best nop.
> -	 */
> -	asm volatile (
> -		"ftrace_test_jmp:"
> -		"jmp ftrace_test_p6nop\n"
> -		"nop\n"
> -		"nop\n"
> -		"nop\n"  /* 2 byte jmp + 3 bytes */
> -		"ftrace_test_p6nop:"
> -		P6_NOP5
> -		"jmp 1f\n"
> -		"ftrace_test_nop5:"
> -		".byte 0x66,0x66,0x66,0x66,0x90\n"
> -		"1:"
> -		".section .fixup, \"ax\"\n"
> -		"2:	movl $1, %0\n"
> -		"	jmp ftrace_test_nop5\n"
> -		"3:	movl $2, %0\n"
> -		"	jmp 1b\n"
> -		".previous\n"
> -		_ASM_EXTABLE(ftrace_test_p6nop, 2b)
> -		_ASM_EXTABLE(ftrace_test_nop5, 3b)
> -		: "=r"(faulted) : "0" (faulted));
> -
> -	switch (faulted) {
> -	case 0:
> -		pr_info("converting mcount calls to 0f 1f 44 00 00\n");
> -		memcpy(ftrace_nop, ftrace_test_p6nop, MCOUNT_INSN_SIZE);
> -		break;
> -	case 1:
> -		pr_info("converting mcount calls to 66 66 66 66 90\n");
> -		memcpy(ftrace_nop, ftrace_test_nop5, MCOUNT_INSN_SIZE);
> -		break;
> -	case 2:
> -		pr_info("converting mcount calls to jmp . + 5\n");
> -		memcpy(ftrace_nop, ftrace_test_jmp, MCOUNT_INSN_SIZE);
> -		break;
> -	}
> -
>  	/* The return code is retured via data */
>  	*(unsigned long *)data = 0;
>  
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 1427c36..fb37842 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -112,6 +112,7 @@
>  #include <asm/numa_64.h>
>  #endif
>  #include <asm/mce.h>
> +#include <asm/alternative.h>
>  
>  /*
>   * end_pfn only includes RAM, while max_pfn_mapped includes all e820 entries.
> @@ -689,6 +690,7 @@ void __init setup_arch(char **cmdline_p)
>  {
>  	int acpi = 0;
>  	int k8 = 0;
> +	unsigned long flags;
>  
>  #ifdef CONFIG_X86_32
>  	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
> @@ -1036,6 +1038,10 @@ void __init setup_arch(char **cmdline_p)
>  	x86_init.oem.banner();
>  
>  	mcheck_init();
> +
> +	local_irq_save(flags);
> +	arch_init_ideal_nop5();
> +	local_irq_restore(flags);
>  }
>  
>  #ifdef CONFIG_X86_32