--- /dev/null
+/*
+ * linux/arch/x86_64/mcount_64.S
+ *
+ * Copyright (C) 2014 Steven Rostedt, Red Hat Inc
+ */
+
+#include <linux/linkage.h>
+#include <asm/ptrace.h>
+#include <asm/ftrace.h>
+
+
+ .code64
+ .section .entry.text, "ax"
+
+
+#ifdef CONFIG_FUNCTION_TRACER
+
+#ifdef CC_USING_FENTRY
+# define function_hook __fentry__
+#else
+# define function_hook mcount
+#endif
+
+/* All cases save the original rbp (8 bytes) */
+#ifdef CONFIG_FRAME_POINTER
+# ifdef CC_USING_FENTRY
+/* Save parent and function stack frames (rip and rbp) */
+# define MCOUNT_FRAME_SIZE (8+16*2)
+# else
+/* Save just function stack frame (rip and rbp) */
+# define MCOUNT_FRAME_SIZE (8+16)
+# endif
+#else
+/* No need to save a stack frame */
+# define MCOUNT_FRAME_SIZE 8
+#endif /* CONFIG_FRAME_POINTER */
+
+/* Size of stack used to save mcount regs in save_mcount_regs */
+#define MCOUNT_REG_SIZE (SS+8 + MCOUNT_FRAME_SIZE)
+
+/*
+ * gcc -pg option adds a call to 'mcount' in most functions.
+ * When -mfentry is used, the call is to 'fentry' and not 'mcount'
+ * and is done before the function's stack frame is set up.
+ * They both require a set of regs to be saved before calling
+ * any C code and restored before returning back to the function.
+ *
+ * On boot up, all these calls are converted into nops. When tracing
+ * is enabled, the call can jump to either ftrace_caller or
+ * ftrace_regs_caller. Callbacks (tracing functions) that require
+ * ftrace_regs_caller (like kprobes) need to have pt_regs passed to
+ * it. For this reason, the size of the pt_regs structure will be
+ * allocated on the stack and the required mcount registers will
+ * be saved in the locations that pt_regs has them in.
+ */
+
+/*
+ * @added: the amount of stack added before calling this
+ *
+ * After this is called, the following registers contain:
+ *
+ * %rdi - holds the address that called the trampoline
+ * %rsi - holds the parent function (traced function's return address)
+ * %rdx - holds the original %rbp
+ */
+.macro save_mcount_regs added=0
+
+ /* Always save the original rbp */
+ pushq %rbp
+
+#ifdef CONFIG_FRAME_POINTER
+ /*
+ * Stack traces will stop at the ftrace trampoline if the frame pointer
+ * is not set up properly. If fentry is used, we need to save a frame
+ * pointer for the parent as well as the function traced, because the
+ * fentry is called before the stack frame is set up, where as mcount
+ * is called afterward.
+ */
+#ifdef CC_USING_FENTRY
+ /* Save the parent pointer (skip orig rbp and our return address) */
+ pushq \added+8*2(%rsp)
+ pushq %rbp
+ movq %rsp, %rbp
+ /* Save the return address (now skip orig rbp, rbp and parent) */
+ pushq \added+8*3(%rsp)
+#else
+ /* Can't assume that rip is before this (unless added was zero) */
+ pushq \added+8(%rsp)
+#endif
+ pushq %rbp
+ movq %rsp, %rbp
+#endif /* CONFIG_FRAME_POINTER */
+
+ /*
+ * We add enough stack to save all regs.
+ */
+ subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp
+ movq %rax, RAX(%rsp)
+ movq %rcx, RCX(%rsp)
+ movq %rdx, RDX(%rsp)
+ movq %rsi, RSI(%rsp)
+ movq %rdi, RDI(%rsp)
+ movq %r8, R8(%rsp)
+ movq %r9, R9(%rsp)
+ /*
+ * Save the original RBP. Even though the mcount ABI does not
+ * require this, it helps out callers.
+ */
+ movq MCOUNT_REG_SIZE-8(%rsp), %rdx
+ movq %rdx, RBP(%rsp)
+
+ /* Copy the parent address into %rsi (second parameter) */
+#ifdef CC_USING_FENTRY
+ movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi
+#else
+ /* %rdx contains original %rbp */
+ movq 8(%rdx), %rsi
+#endif
+
+ /* Move RIP to its proper location */
+ movq MCOUNT_REG_SIZE+\added(%rsp), %rdi
+ movq %rdi, RIP(%rsp)
+
+ /*
+ * Now %rdi (the first parameter) has the return address of
+ * where ftrace_call returns. But the callbacks expect the
+ * address of the call itself.
+ */
+ subq $MCOUNT_INSN_SIZE, %rdi
+ .endm
+
+.macro restore_mcount_regs
+ movq R9(%rsp), %r9
+ movq R8(%rsp), %r8
+ movq RDI(%rsp), %rdi
+ movq RSI(%rsp), %rsi
+ movq RDX(%rsp), %rdx
+ movq RCX(%rsp), %rcx
+ movq RAX(%rsp), %rax
+
+ /* ftrace_regs_caller can modify %rbp */
+ movq RBP(%rsp), %rbp
+
+ addq $MCOUNT_REG_SIZE, %rsp
+
+ .endm
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+ENTRY(function_hook)
+ retq
+END(function_hook)
+
+ENTRY(ftrace_caller)
+ /* save_mcount_regs fills in first two parameters */
+ save_mcount_regs
+
+GLOBAL(ftrace_caller_op_ptr)
+ /* Load the ftrace_ops into the 3rd parameter */
+ movq function_trace_op(%rip), %rdx
+
+ /* regs go into 4th parameter (but make it NULL) */
+ movq $0, %rcx
+
+GLOBAL(ftrace_call)
+ call ftrace_stub
+
+ restore_mcount_regs
+
+ /*
+ * The copied trampoline must call ftrace_return as it
+ * still may need to call the function graph tracer.
+ */
+GLOBAL(ftrace_caller_end)
+
+GLOBAL(ftrace_return)
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+GLOBAL(ftrace_graph_call)
+ jmp ftrace_stub
+#endif
+
+GLOBAL(ftrace_stub)
+ retq
+END(ftrace_caller)
+
+ENTRY(ftrace_regs_caller)
+ /* Save the current flags before any operations that can change them */
+ pushfq
+
+ /* added 8 bytes to save flags */
+ save_mcount_regs 8
+ /* save_mcount_regs fills in first two parameters */
+
+GLOBAL(ftrace_regs_caller_op_ptr)
+ /* Load the ftrace_ops into the 3rd parameter */
+ movq function_trace_op(%rip), %rdx
+
+ /* Save the rest of pt_regs */
+ movq %r15, R15(%rsp)
+ movq %r14, R14(%rsp)
+ movq %r13, R13(%rsp)
+ movq %r12, R12(%rsp)
+ movq %r11, R11(%rsp)
+ movq %r10, R10(%rsp)
+ movq %rbx, RBX(%rsp)
+ /* Copy saved flags */
+ movq MCOUNT_REG_SIZE(%rsp), %rcx
+ movq %rcx, EFLAGS(%rsp)
+ /* Kernel segments */
+ movq $__KERNEL_DS, %rcx
+ movq %rcx, SS(%rsp)
+ movq $__KERNEL_CS, %rcx
+ movq %rcx, CS(%rsp)
+ /* Stack - skipping return address and flags */
+ leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx
+ movq %rcx, RSP(%rsp)
+
+ /* regs go into 4th parameter */
+ leaq (%rsp), %rcx
+
+GLOBAL(ftrace_regs_call)
+ call ftrace_stub
+
+ /* Copy flags back to SS, to restore them */
+ movq EFLAGS(%rsp), %rax
+ movq %rax, MCOUNT_REG_SIZE(%rsp)
+
+ /* Handlers can change the RIP */
+ movq RIP(%rsp), %rax
+ movq %rax, MCOUNT_REG_SIZE+8(%rsp)
+
+ /* restore the rest of pt_regs */
+ movq R15(%rsp), %r15
+ movq R14(%rsp), %r14
+ movq R13(%rsp), %r13
+ movq R12(%rsp), %r12
+ movq R10(%rsp), %r10
+ movq RBX(%rsp), %rbx
+
+ restore_mcount_regs
+
+ /* Restore flags */
+ popfq
+
+ /*
+ * As this jmp to ftrace_return can be a short jump
+ * it must not be copied into the trampoline.
+ * The trampoline will add the code to jump
+ * to the return.
+ */
+GLOBAL(ftrace_regs_caller_end)
+
+ jmp ftrace_return
+
+END(ftrace_regs_caller)
+
+
+#else /* ! CONFIG_DYNAMIC_FTRACE */
+
+ENTRY(function_hook)
+ cmpq $ftrace_stub, ftrace_trace_function
+ jnz trace
+
+fgraph_trace:
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ cmpq $ftrace_stub, ftrace_graph_return
+ jnz ftrace_graph_caller
+
+ cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
+ jnz ftrace_graph_caller
+#endif
+
+GLOBAL(ftrace_stub)
+ retq
+
+trace:
+ /* save_mcount_regs fills in first two parameters */
+ save_mcount_regs
+
+ call *ftrace_trace_function
+
+ restore_mcount_regs
+
+ jmp fgraph_trace
+END(function_hook)
+#endif /* CONFIG_DYNAMIC_FTRACE */
+#endif /* CONFIG_FUNCTION_TRACER */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ENTRY(ftrace_graph_caller)
+ /* Saves rbp into %rdx and fills first parameter */
+ save_mcount_regs
+
+#ifdef CC_USING_FENTRY
+ leaq MCOUNT_REG_SIZE+8(%rsp), %rsi
+ movq $0, %rdx /* No framepointers needed */
+#else
+ /* Save address of the return address of traced function */
+ leaq 8(%rdx), %rsi
+ /* ftrace does sanity checks against frame pointers */
+ movq (%rdx), %rdx
+#endif
+ call prepare_ftrace_return
+
+ restore_mcount_regs
+
+ retq
+END(ftrace_graph_caller)
+
+GLOBAL(return_to_handler)
+ subq $24, %rsp
+
+ /* Save the return values */
+ movq %rax, (%rsp)
+ movq %rdx, 8(%rsp)
+ movq %rbp, %rdi
+
+ call ftrace_return_to_handler
+
+ movq %rax, %rdi
+ movq 8(%rsp), %rdx
+ movq (%rsp), %rax
+ addq $24, %rsp
+ jmp *%rdi
+#endif
Code Review / kvmfornfv.git / blobdiff