Commit f49aa448 authored by Jason Baron's avatar Jason Baron Committed by Steven Rostedt
Browse files

jump label: Make dynamic no-op selection available outside of ftrace 



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: default avatarJason Baron <jbaron@redhat.com>
LKML-Reference: <96259ae74172dcac99c0020c249743c523a92e18.1284733808.git.jbaron@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent e9d2b064

arch/x86/include/asm/alternative.h

+8 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/alternative.c

+64 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/ftrace.c

+1 −62
Original line number Diff line number Diff line
@@ -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;

arch/x86/kernel/setup.c

+6 −0
Original line number Diff line number Diff line
@@ -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.
@@ -726,6 +727,7 @@ 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));
@@ -1071,6 +1073,10 @@ 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