jump label: Make dynamic no-op selection available outside of ftrace (f49aa448) · Commits · 戴 / test

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

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