arm64: ftrace: Add dynamic ftrace support (bd7d38db) · Commits · 戴 / test

arch/arm64/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -36,6 +36,7 @@ config ARM64
		select HAVE_DMA_API_DEBUG
		select HAVE_DMA_ATTRS
		select HAVE_DMA_CONTIGUOUS
		select HAVE_DYNAMIC_FTRACE
		select HAVE_EFFICIENT_UNALIGNED_ACCESS
		select HAVE_FTRACE_MCOUNT_RECORD
		select HAVE_FUNCTION_TRACER

arch/arm64/include/asm/ftrace.h

+15 −0

Original line number	Diff line number	Diff line
		@@ -18,6 +18,21 @@

		#ifndef __ASSEMBLY__
		extern void _mcount(unsigned long);

		struct dyn_arch_ftrace {
		/* No extra data needed for arm64 */
		};

		extern unsigned long ftrace_graph_call;

		static inline unsigned long ftrace_call_adjust(unsigned long addr)
		{
		/*
		* addr is the address of the mcount call instruction.
		* recordmcount does the necessary offset calculation.
		*/
		return addr;
		}
		#endif /* __ASSEMBLY__ */

		#endif /* __ASM_FTRACE_H */

arch/arm64/kernel/entry-ftrace.S

+43 −0

Original line number	Diff line number	Diff line
		@@ -86,6 +86,7 @@
		add \reg, \reg, #8
		.endm

		#ifndef CONFIG_DYNAMIC_FTRACE
		/*
		* void _mcount(unsigned long return_address)
		* @return_address: return address to instrumented function
		@@ -134,6 +135,48 @@ skip_ftrace_call:
		#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
		ENDPROC(_mcount)

		#else /* CONFIG_DYNAMIC_FTRACE */
		/*
		* _mcount() is used to build the kernel with -pg option, but all the branch
		* instructions to _mcount() are replaced to NOP initially at kernel start up,
		* and later on, NOP to branch to ftrace_caller() when enabled or branch to
		* NOP when disabled per-function base.
		*/
		ENTRY(_mcount)
		ret
		ENDPROC(_mcount)

		/*
		* void ftrace_caller(unsigned long return_address)
		* @return_address: return address to instrumented function
		*
		* This function is a counterpart of _mcount() in 'static' ftrace, and
		* makes calls to:
		* - tracer function to probe instrumented function's entry,
		* - ftrace_graph_caller to set up an exit hook
		*/
		ENTRY(ftrace_caller)
		mcount_enter

		mcount_get_pc0 x0 // function's pc
		mcount_get_lr x1 // function's lr

		.global ftrace_call
		ftrace_call: // tracer(pc, lr);
		nop // This will be replaced with "bl xxx"
		// where xxx can be any kind of tracer.

		#ifdef CONFIG_FUNCTION_GRAPH_TRACER
		.global ftrace_graph_call
		ftrace_graph_call: // ftrace_graph_caller();
		nop // If enabled, this will be replaced
		// "b ftrace_graph_caller"
		#endif

		mcount_exit
		ENDPROC(ftrace_caller)
		#endif /* CONFIG_DYNAMIC_FTRACE */

		ENTRY(ftrace_stub)
		ret
		ENDPROC(ftrace_stub)

arch/arm64/kernel/ftrace.c

+112 −0

Original line number	Diff line number	Diff line
		@@ -17,6 +17,87 @@
		#include <asm/ftrace.h>
		#include <asm/insn.h>

		#ifdef CONFIG_DYNAMIC_FTRACE
		/*
		* Replace a single instruction, which may be a branch or NOP.
		* If @validate == true, a replaced instruction is checked against 'old'.
		*/
		static int ftrace_modify_code(unsigned long pc, u32 old, u32 new,
		bool validate)
		{
		u32 replaced;

		/*
		* Note:
		* Due to modules and __init, code can disappear and change,
		* we need to protect against faulting as well as code changing.
		* We do this by aarch64_insn_() which use the probe_kernel_().
		*
		* No lock is held here because all the modifications are run
		* through stop_machine().
		*/
		if (validate) {
		if (aarch64_insn_read((void *)pc, &replaced))
		return -EFAULT;

		if (replaced != old)
		return -EINVAL;
		}
		if (aarch64_insn_patch_text_nosync((void *)pc, new))
		return -EPERM;

		return 0;
		}

		/*
		* Replace tracer function in ftrace_caller()
		*/
		int ftrace_update_ftrace_func(ftrace_func_t func)
		{
		unsigned long pc;
		u32 new;

		pc = (unsigned long)&ftrace_call;
		new = aarch64_insn_gen_branch_imm(pc, (unsigned long)func, true);

		return ftrace_modify_code(pc, 0, new, false);
		}

		/*
		* Turn on the call to ftrace_caller() in instrumented function
		*/
		int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
		{
		unsigned long pc = rec->ip;
		u32 old, new;

		old = aarch64_insn_gen_nop();
		new = aarch64_insn_gen_branch_imm(pc, addr, true);

		return ftrace_modify_code(pc, old, new, true);
		}

		/*
		* Turn off the call to ftrace_caller() in instrumented function
		*/
		int ftrace_make_nop(struct module mod, struct dyn_ftrace rec,
		unsigned long addr)
		{
		unsigned long pc = rec->ip;
		u32 old, new;

		old = aarch64_insn_gen_branch_imm(pc, addr, true);
		new = aarch64_insn_gen_nop();

		return ftrace_modify_code(pc, old, new, true);
		}

		int __init ftrace_dyn_arch_init(void)
		{
		return 0;
		}
		#endif /* CONFIG_DYNAMIC_FTRACE */

		#ifdef CONFIG_FUNCTION_GRAPH_TRACER
		/*
		* function_graph tracer expects ftrace_return_to_handler() to be called
		@@ -61,4 +142,35 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
		return;
		}
		}

		#ifdef CONFIG_DYNAMIC_FTRACE
		/*
		* Turn on/off the call to ftrace_graph_caller() in ftrace_caller()
		* depending on @enable.
		*/
		static int ftrace_modify_graph_caller(bool enable)
		{
		unsigned long pc = (unsigned long)&ftrace_graph_call;
		u32 branch, nop;

		branch = aarch64_insn_gen_branch_imm(pc,
		(unsigned long)ftrace_graph_caller, false);
		nop = aarch64_insn_gen_nop();

		if (enable)
		return ftrace_modify_code(pc, nop, branch, true);
		else
		return ftrace_modify_code(pc, branch, nop, true);
		}

		int ftrace_enable_ftrace_graph_caller(void)
		{
		return ftrace_modify_graph_caller(true);
		}

		int ftrace_disable_ftrace_graph_caller(void)
		{
		return ftrace_modify_graph_caller(false);
		}
		#endif /* CONFIG_DYNAMIC_FTRACE */
		#endif /* CONFIG_FUNCTION_GRAPH_TRACER */

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