root/arch/x86/kernel/ftrace_32.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  *  Copyright (C) 2017  Steven Rostedt, VMware Inc.
   4  */
   5 
   6 #include <linux/linkage.h>
   7 #include <asm/page_types.h>
   8 #include <asm/segment.h>
   9 #include <asm/export.h>
  10 #include <asm/ftrace.h>
  11 #include <asm/nospec-branch.h>
  12 #include <asm/frame.h>
  13 #include <asm/asm-offsets.h>
  14 
  15 # define function_hook  __fentry__
  16 EXPORT_SYMBOL(__fentry__)
  17 
  18 #ifdef CONFIG_FRAME_POINTER
  19 # define MCOUNT_FRAME                   1       /* using frame = true  */
  20 #else
  21 # define MCOUNT_FRAME                   0       /* using frame = false */
  22 #endif
  23 
  24 ENTRY(function_hook)
  25         ret
  26 END(function_hook)
  27 
  28 ENTRY(ftrace_caller)
  29 
  30 #ifdef CONFIG_FRAME_POINTER
  31         /*
  32          * Frame pointers are of ip followed by bp.
  33          * Since fentry is an immediate jump, we are left with
  34          * parent-ip, function-ip. We need to add a frame with
  35          * parent-ip followed by ebp.
  36          */
  37         pushl   4(%esp)                         /* parent ip */
  38         pushl   %ebp
  39         movl    %esp, %ebp
  40         pushl   2*4(%esp)                       /* function ip */
  41 
  42         /* For mcount, the function ip is directly above */
  43         pushl   %ebp
  44         movl    %esp, %ebp
  45 #endif
  46         pushl   %eax
  47         pushl   %ecx
  48         pushl   %edx
  49         pushl   $0                              /* Pass NULL as regs pointer */
  50 
  51 #ifdef CONFIG_FRAME_POINTER
  52         /* Load parent ebp into edx */
  53         movl    4*4(%esp), %edx
  54 #else
  55         /* There's no frame pointer, load the appropriate stack addr instead */
  56         lea     4*4(%esp), %edx
  57 #endif
  58 
  59         movl    (MCOUNT_FRAME+4)*4(%esp), %eax  /* load the rip */
  60         /* Get the parent ip */
  61         movl    4(%edx), %edx                   /* edx has ebp */
  62 
  63         movl    function_trace_op, %ecx
  64         subl    $MCOUNT_INSN_SIZE, %eax
  65 
  66 .globl ftrace_call
  67 ftrace_call:
  68         call    ftrace_stub
  69 
  70         addl    $4, %esp                        /* skip NULL pointer */
  71         popl    %edx
  72         popl    %ecx
  73         popl    %eax
  74 #ifdef CONFIG_FRAME_POINTER
  75         popl    %ebp
  76         addl    $4,%esp                         /* skip function ip */
  77         popl    %ebp                            /* this is the orig bp */
  78         addl    $4, %esp                        /* skip parent ip */
  79 #endif
  80 .Lftrace_ret:
  81 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  82 .globl ftrace_graph_call
  83 ftrace_graph_call:
  84         jmp     ftrace_stub
  85 #endif
  86 
  87 /* This is weak to keep gas from relaxing the jumps */
  88 WEAK(ftrace_stub)
  89         ret
  90 END(ftrace_caller)
  91 
  92 ENTRY(ftrace_regs_caller)
  93         /*
  94          * We're here from an mcount/fentry CALL, and the stack frame looks like:
  95          *
  96          *  <previous context>
  97          *  RET-IP
  98          *
  99          * The purpose of this function is to call out in an emulated INT3
 100          * environment with a stack frame like:
 101          *
 102          *  <previous context>
 103          *  gap / RET-IP
 104          *  gap
 105          *  gap
 106          *  gap
 107          *  pt_regs
 108          *
 109          * We do _NOT_ restore: ss, flags, cs, gs, fs, es, ds
 110          */
 111         subl    $3*4, %esp      # RET-IP + 3 gaps
 112         pushl   %ss             # ss
 113         pushl   %esp            # points at ss
 114         addl    $5*4, (%esp)    #   make it point at <previous context>
 115         pushfl                  # flags
 116         pushl   $__KERNEL_CS    # cs
 117         pushl   7*4(%esp)       # ip <- RET-IP
 118         pushl   $0              # orig_eax
 119 
 120         pushl   %gs
 121         pushl   %fs
 122         pushl   %es
 123         pushl   %ds
 124 
 125         pushl   %eax
 126         pushl   %ebp
 127         pushl   %edi
 128         pushl   %esi
 129         pushl   %edx
 130         pushl   %ecx
 131         pushl   %ebx
 132 
 133         ENCODE_FRAME_POINTER
 134 
 135         movl    PT_EIP(%esp), %eax      # 1st argument: IP
 136         subl    $MCOUNT_INSN_SIZE, %eax
 137         movl    21*4(%esp), %edx        # 2nd argument: parent ip
 138         movl    function_trace_op, %ecx # 3rd argument: ftrace_pos
 139         pushl   %esp                    # 4th argument: pt_regs
 140 
 141 GLOBAL(ftrace_regs_call)
 142         call    ftrace_stub
 143 
 144         addl    $4, %esp                # skip 4th argument
 145 
 146         /* place IP below the new SP */
 147         movl    PT_OLDESP(%esp), %eax
 148         movl    PT_EIP(%esp), %ecx
 149         movl    %ecx, -4(%eax)
 150 
 151         /* place EAX below that */
 152         movl    PT_EAX(%esp), %ecx
 153         movl    %ecx, -8(%eax)
 154 
 155         popl    %ebx
 156         popl    %ecx
 157         popl    %edx
 158         popl    %esi
 159         popl    %edi
 160         popl    %ebp
 161 
 162         lea     -8(%eax), %esp
 163         popl    %eax
 164 
 165         jmp     .Lftrace_ret
 166 
 167 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 168 ENTRY(ftrace_graph_caller)
 169         pushl   %eax
 170         pushl   %ecx
 171         pushl   %edx
 172         movl    3*4(%esp), %eax
 173         /* Even with frame pointers, fentry doesn't have one here */
 174         lea     4*4(%esp), %edx
 175         movl    $0, %ecx
 176         subl    $MCOUNT_INSN_SIZE, %eax
 177         call    prepare_ftrace_return
 178         popl    %edx
 179         popl    %ecx
 180         popl    %eax
 181         ret
 182 END(ftrace_graph_caller)
 183 
 184 .globl return_to_handler
 185 return_to_handler:
 186         pushl   %eax
 187         pushl   %edx
 188         movl    $0, %eax
 189         call    ftrace_return_to_handler
 190         movl    %eax, %ecx
 191         popl    %edx
 192         popl    %eax
 193         JMP_NOSPEC %ecx
 194 #endif