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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
/*
* 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.
*/
/* skip is set if the stack was already partially adjusted */
.macro save_mcount_regs skip=0
/*
* We add enough stack to save all regs.
*/
subq $(SS+8-\skip), %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)
/* Move RIP to its proper location */
movq SS+8(%rsp), %rdi
movq %rdi, RIP(%rsp)
.endm
.macro restore_mcount_regs skip=0
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
addq $(SS+8-\skip), %rsp
.endm
/* skip is set if stack has been adjusted */
.macro ftrace_caller_setup trace_label skip=0
save_mcount_regs \skip
/* Save this location */
GLOBAL(\trace_label)
/* Load the ftrace_ops into the 3rd parameter */
movq function_trace_op(%rip), %rdx
/* %rdi already has %rip from the save_mcount_regs macro */
subq $MCOUNT_INSN_SIZE, %rdi
/* Load the parent_ip into the second parameter */
#ifdef CC_USING_FENTRY
movq SS+16(%rsp), %rsi
#else
movq 8(%rbp), %rsi
#endif
.endm
#ifdef CONFIG_DYNAMIC_FTRACE
ENTRY(function_hook)
retq
END(function_hook)
#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.
*/
.macro create_frame parent rip
#ifdef CC_USING_FENTRY
pushq \parent
pushq %rbp
movq %rsp, %rbp
#endif
pushq \rip
pushq %rbp
movq %rsp, %rbp
.endm
.macro restore_frame
#ifdef CC_USING_FENTRY
addq $16, %rsp
#endif
popq %rbp
addq $8, %rsp
.endm
#else
.macro create_frame parent rip
.endm
.macro restore_frame
.endm
#endif /* CONFIG_FRAME_POINTER */
ENTRY(ftrace_caller)
ftrace_caller_setup ftrace_caller_op_ptr
/* regs go into 4th parameter (but make it NULL) */
movq $0, %rcx
create_frame %rsi, %rdi
GLOBAL(ftrace_call)
call ftrace_stub
restore_frame
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 compare (in SS location)*/
pushfq
/* skip=8 to skip flags saved in SS */
ftrace_caller_setup ftrace_regs_caller_op_ptr 8
/* 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 %rbp, RBP(%rsp)
movq %rbx, RBX(%rsp)
/* Copy saved flags */
movq SS(%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 */
leaq SS+16(%rsp), %rcx
movq %rcx, RSP(%rsp)
/* regs go into 4th parameter */
leaq (%rsp), %rcx
create_frame %rsi, %rdi
GLOBAL(ftrace_regs_call)
call ftrace_stub
restore_frame
/* Copy flags back to SS, to restore them */
movq EFLAGS(%rsp), %rax
movq %rax, SS(%rsp)
/* Handlers can change the RIP */
movq RIP(%rsp), %rax
movq %rax, SS+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 RBP(%rsp), %rbp
movq RBX(%rsp), %rbx
/* skip=8 to skip flags saved in SS */
restore_mcount_regs 8
/* 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
popfq
jmp ftrace_stub
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:
ftrace_caller_setup ftrace_caller_op_ptr
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)
save_mcount_regs
#ifdef CC_USING_FENTRY
leaq SS+16(%rsp), %rdi
movq $0, %rdx /* No framepointers needed */
#else
leaq 8(%rbp), %rdi
movq (%rbp), %rdx
#endif
movq RIP(%rsp), %rsi
subq $MCOUNT_INSN_SIZE, %rsi
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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