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

Steven Rostedt
2010-09-17T15:28:49Z

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