1 /* SPDX-License-Identifier: GPL-2.0 */
3 * Copyright (C) 2014 Steven Rostedt, Red Hat Inc
6 #include <linux/linkage.h>
7 #include <asm/ptrace.h>
8 #include <asm/ftrace.h>
9 #include <asm/export.h>
10 #include <asm/nospec-branch.h>
11 #include <asm/unwind_hints.h>
12 #include <asm/frame.h>
15 .section .entry.text, "ax"
17 #ifdef CC_USING_FENTRY
18 # define function_hook __fentry__
19 EXPORT_SYMBOL(__fentry__)
21 # define function_hook mcount
25 #ifdef CONFIG_FRAME_POINTER
26 # ifdef CC_USING_FENTRY
27 /* Save parent and function stack frames (rip and rbp) */
28 # define MCOUNT_FRAME_SIZE (8+16*2)
30 /* Save just function stack frame (rip and rbp) */
31 # define MCOUNT_FRAME_SIZE (8+16)
34 /* No need to save a stack frame */
35 # define MCOUNT_FRAME_SIZE 0
36 #endif /* CONFIG_FRAME_POINTER */
38 /* Size of stack used to save mcount regs in save_mcount_regs */
39 #define MCOUNT_REG_SIZE (SS+8 + MCOUNT_FRAME_SIZE)
42 * gcc -pg option adds a call to 'mcount' in most functions.
43 * When -mfentry is used, the call is to 'fentry' and not 'mcount'
44 * and is done before the function's stack frame is set up.
45 * They both require a set of regs to be saved before calling
46 * any C code and restored before returning back to the function.
48 * On boot up, all these calls are converted into nops. When tracing
49 * is enabled, the call can jump to either ftrace_caller or
50 * ftrace_regs_caller. Callbacks (tracing functions) that require
51 * ftrace_regs_caller (like kprobes) need to have pt_regs passed to
52 * it. For this reason, the size of the pt_regs structure will be
53 * allocated on the stack and the required mcount registers will
54 * be saved in the locations that pt_regs has them in.
58 * @added: the amount of stack added before calling this
60 * After this is called, the following registers contain:
62 * %rdi - holds the address that called the trampoline
63 * %rsi - holds the parent function (traced function's return address)
64 * %rdx - holds the original %rbp
66 .macro save_mcount_regs added=0
68 #ifdef CONFIG_FRAME_POINTER
69 /* Save the original rbp */
73 * Stack traces will stop at the ftrace trampoline if the frame pointer
74 * is not set up properly. If fentry is used, we need to save a frame
75 * pointer for the parent as well as the function traced, because the
76 * fentry is called before the stack frame is set up, where as mcount
77 * is called afterward.
79 #ifdef CC_USING_FENTRY
80 /* Save the parent pointer (skip orig rbp and our return address) */
81 pushq \added+8*2(%rsp)
84 /* Save the return address (now skip orig rbp, rbp and parent) */
85 pushq \added+8*3(%rsp)
87 /* Can't assume that rip is before this (unless added was zero) */
92 #endif /* CONFIG_FRAME_POINTER */
95 * We add enough stack to save all regs.
97 subq $(MCOUNT_REG_SIZE - MCOUNT_FRAME_SIZE), %rsp
106 * Save the original RBP. Even though the mcount ABI does not
107 * require this, it helps out callers.
109 #ifdef CONFIG_FRAME_POINTER
110 movq MCOUNT_REG_SIZE-8(%rsp), %rdx
116 /* Copy the parent address into %rsi (second parameter) */
117 #ifdef CC_USING_FENTRY
118 movq MCOUNT_REG_SIZE+8+\added(%rsp), %rsi
120 /* %rdx contains original %rbp */
124 /* Move RIP to its proper location */
125 movq MCOUNT_REG_SIZE+\added(%rsp), %rdi
129 * Now %rdi (the first parameter) has the return address of
130 * where ftrace_call returns. But the callbacks expect the
131 * address of the call itself.
133 subq $MCOUNT_INSN_SIZE, %rdi
136 .macro restore_mcount_regs
145 /* ftrace_regs_caller can modify %rbp */
148 addq $MCOUNT_REG_SIZE, %rsp
152 #ifdef CONFIG_DYNAMIC_FTRACE
156 ENDPROC(function_hook)
159 /* save_mcount_regs fills in first two parameters */
162 GLOBAL(ftrace_caller_op_ptr)
163 /* Load the ftrace_ops into the 3rd parameter */
164 movq function_trace_op(%rip), %rdx
166 /* regs go into 4th parameter (but make it NULL) */
175 * The code up to this label is copied into trampolines so
176 * think twice before adding any new code or changing the
179 GLOBAL(ftrace_epilogue)
181 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
182 GLOBAL(ftrace_graph_call)
187 * This is weak to keep gas from relaxing the jumps.
188 * It is also used to copy the retq for trampolines.
192 ENDPROC(ftrace_caller)
194 ENTRY(ftrace_regs_caller)
195 /* Save the current flags before any operations that can change them */
198 /* added 8 bytes to save flags */
200 /* save_mcount_regs fills in first two parameters */
202 GLOBAL(ftrace_regs_caller_op_ptr)
203 /* Load the ftrace_ops into the 3rd parameter */
204 movq function_trace_op(%rip), %rdx
206 /* Save the rest of pt_regs */
214 /* Copy saved flags */
215 movq MCOUNT_REG_SIZE(%rsp), %rcx
216 movq %rcx, EFLAGS(%rsp)
217 /* Kernel segments */
218 movq $__KERNEL_DS, %rcx
220 movq $__KERNEL_CS, %rcx
222 /* Stack - skipping return address and flags */
223 leaq MCOUNT_REG_SIZE+8*2(%rsp), %rcx
228 /* regs go into 4th parameter */
231 GLOBAL(ftrace_regs_call)
234 /* Copy flags back to SS, to restore them */
235 movq EFLAGS(%rsp), %rax
236 movq %rax, MCOUNT_REG_SIZE(%rsp)
238 /* Handlers can change the RIP */
240 movq %rax, MCOUNT_REG_SIZE+8(%rsp)
242 /* restore the rest of pt_regs */
256 * As this jmp to ftrace_epilogue can be a short jump
257 * it must not be copied into the trampoline.
258 * The trampoline will add the code to jump
261 GLOBAL(ftrace_regs_caller_end)
265 ENDPROC(ftrace_regs_caller)
268 #else /* ! CONFIG_DYNAMIC_FTRACE */
271 cmpq $ftrace_stub, ftrace_trace_function
275 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
276 cmpq $ftrace_stub, ftrace_graph_return
277 jnz ftrace_graph_caller
279 cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
280 jnz ftrace_graph_caller
287 /* save_mcount_regs fills in first two parameters */
291 * When DYNAMIC_FTRACE is not defined, ARCH_SUPPORTS_FTRACE_OPS is not
292 * set (see include/asm/ftrace.h and include/linux/ftrace.h). Only the
293 * ip and parent ip are used and the list function is called when
294 * function tracing is enabled.
296 movq ftrace_trace_function, %r8
301 ENDPROC(function_hook)
302 #endif /* CONFIG_DYNAMIC_FTRACE */
304 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
305 ENTRY(ftrace_graph_caller)
306 /* Saves rbp into %rdx and fills first parameter */
309 #ifdef CC_USING_FENTRY
310 leaq MCOUNT_REG_SIZE+8(%rsp), %rsi
311 movq $0, %rdx /* No framepointers needed */
313 /* Save address of the return address of traced function */
315 /* ftrace does sanity checks against frame pointers */
318 call prepare_ftrace_return
323 ENDPROC(ftrace_graph_caller)
325 ENTRY(return_to_handler)
329 /* Save the return values */
334 call ftrace_return_to_handler
341 END(return_to_handler)