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/*
* 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
/* This is weak to keep gas from relaxing the jumps */
WEAK(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
/*
* When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not
* set (see include/asm/ftrace.h and include/linux/ftrace.h). Only the
* ip and parent ip are used and the list function is called when
* function tracing is enabled.
*/
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
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