tools/add-cfi.x86_64.awk

   1 # Insert GAS CFI directives ("control frame information") into x86-64 asm input
   2
   3 BEGIN {
   4   # don't put CFI data in the .eh_frame ELF section (which we don't keep)
   5   print ".cfi_sections .debug_frame"
   6
   7   # only emit CFI directives inside a function
   8   in_function = 0
   9
  10   # emit .loc directives with line numbers from original source
  11   printf ".file 1 \"%s\"\n", ARGV[1]
  12   line_number = 0
  13
  14   # used to detect "call label; label:" trick
  15   called = ""
  16 }
  17
  18 function get_const1() {
  19   # for instructions with 2 operands, get 1st operand (assuming it is constant)
  20   match($0, /-?(0x[0-9a-fA-F]+|[0-9]+),/)
  21   return parse_const(substr($0, RSTART, RLENGTH-1))
  22 }
  23
  24 function canonicalize_reg(register) {
  25   if (match(register, /^r/))
  26     return register
  27   else if (match(register, /^e/))
  28     return "r" substr(register, 2, length(register)-1)
  29   else if (match(register, /[hl]$/)) # AH, AL, BH, BL, etc
  30     return "r" substr(register, 1, 1) "x"
  31   else # AX, BX, CX, etc
  32     return "r" register
  33 }
  34 function get_reg() {
  35   # only use if you already know there is 1 and only 1 register
  36   match($0, /%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/)
  37   return canonicalize_reg(substr($0, RSTART+1, RLENGTH-1))
  38 }
  39 function get_reg1() {
  40   # for instructions with 2 operands, get 1st operand (assuming it is register)
  41   match($0, /%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15),/)
  42   return canonicalize_reg(substr($0, RSTART+1, RLENGTH-2))
  43 }
  44 function get_reg2() {
  45   # for instructions with 2 operands, get 2nd operand (assuming it is register)
  46   match($0, /,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/)
  47   return canonicalize_reg(substr($0, RSTART+2, RLENGTH-2))
  48 }
  49
  50 function adjust_sp_offset(delta) {
  51   if (in_function)
  52     printf ".cfi_adjust_cfa_offset %d\n", delta
  53 }
  54
  55 {
  56   line_number = line_number + 1
  57
  58   # clean the input up before doing anything else
  59   # delete comments
  60   gsub(/(#|\/\/).*/, "")
  61
  62   # canonicalize whitespace
  63   gsub(/[ \t]+/, " ") # mawk doesn't understand \s
  64   gsub(/ *, */, ",")
  65   gsub(/ *: */, ": ")
  66   gsub(/ $/, "")
  67   gsub(/^ /, "")
  68 }
  69
  70 # check for assembler directives which we care about
  71 /^\.(section|data|text)/ {
  72   # a .cfi_startproc/.cfi_endproc pair should be within the same section
  73   # otherwise, clang will choke when generating ELF output
  74   if (in_function) {
  75     print ".cfi_endproc"
  76     in_function = 0
  77   }
  78 }
  79 /^\.type [a-zA-Z0-9_]+,\@function/ {
  80   functions[substr($2, 1, length($2)-10)] = 1
  81 }
  82 # not interested in assembler directives beyond this, just pass them through
  83 /^\./ {
  84   print
  85   next
  86 }
  87
  88 /^[a-zA-Z0-9_]+:/ {
  89   label = substr($1, 1, length($1)-1) # drop trailing :
  90
  91   if (called == label) {
  92     # note adjustment of stack pointer from "call label; label:"
  93     adjust_sp_offset(8)
  94   }
  95
  96   if (functions[label]) {
  97     if (in_function)
  98       print ".cfi_endproc"
  99
 100     in_function = 1
 101     print ".cfi_startproc"
 102
 103     for (register in saved)
 104       delete saved[register]
 105     for (register in dirty)
 106       delete dirty[register]
 107   }
 108
 109   # an instruction may follow on the same line, so continue processing
 110 }
 111
 112 /^$/ { next }
 113
 114 {
 115   called = ""
 116   printf ".loc 1 %d\n", line_number
 117   print
 118 }
 119
 120 # KEEPING UP WITH THE STACK POINTER
 121 # %rsp should only be adjusted by pushing/popping or adding/subtracting constants
 122 #
 123 /pushl?/ {
 124   adjust_sp_offset(8)
 125 }
 126 /popl?/ {
 127   adjust_sp_offset(-8)
 128 }
 129 /addl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%rsp/ { adjust_sp_offset(-get_const1()) }
 130 /subl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%rsp/ { adjust_sp_offset(get_const1()) }
 131
 132 /call/ {
 133   if (match($0, /call [0-9]+f/)) # "forward" label
 134     called = substr($0, RSTART+5, RLENGTH-6)
 135   else if (match($0, /call [0-9a-zA-Z_]+/))
 136     called = substr($0, RSTART+5, RLENGTH-5)
 137 }
 138
 139 # TRACKING REGISTER VALUES FROM THE PREVIOUS STACK FRAME
 140 #
 141 /pushl? %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15)/ { # don't match "push (%reg)"
 142   # if a register is being pushed, and its value has not changed since the
 143   #   beginning of this function, the pushed value can be used when printing
 144   #   local variables at the next level up the stack
 145   # emit '.cfi_rel_offset' for that
 146
 147   if (in_function) {
 148     register = get_reg()
 149     if (!saved[register] && !dirty[register]) {
 150       printf ".cfi_rel_offset %s,0\n", register
 151       saved[register] = 1
 152     }
 153   }
 154 }
 155
 156 /movl? %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15),-?(0x[0-9a-fA-F]+|[0-9]+)?\(%rsp\)/ {
 157   if (in_function) {
 158     register = get_reg()
 159     if (match($0, /-?(0x[0-9a-fA-F]+|[0-9]+)\(%rsp\)/)) {
 160       offset = parse_const(substr($0, RSTART, RLENGTH-6))
 161     } else {
 162       offset = 0
 163     }
 164     if (!saved[register] && !dirty[register]) {
 165       printf ".cfi_rel_offset %s,%d\n", register, offset
 166       saved[register] = 1
 167     }
 168   }
 169 }
 170
 171 # IF REGISTER VALUES ARE UNCEREMONIOUSLY TRASHED
 172 # ...then we want to know about it.
 173 #
 174 function trashed(register) {
 175   if (in_function && !saved[register] && !dirty[register]) {
 176     printf ".cfi_undefined %s\n", register
 177   }
 178   dirty[register] = 1
 179 }
 180 # this does NOT exhaustively check for all possible instructions which could
 181 # overwrite a register value inherited from the caller (just the common ones)
 182 /mov.*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ { trashed(get_reg2()) }
 183 /(add|addl|sub|subl|and|or|xor|lea|sal|sar|shl|shr).*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ {
 184   trashed(get_reg2())
 185 }
 186 /^i?mul [^,]*$/ { trashed("rax"); trashed("rdx") }
 187 /^i?mul.*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ { trashed(get_reg2()) }
 188 /^i?div/ { trashed("rax"); trashed("rdx") }
 189
 190 /(dec|inc|not|neg|pop) %[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/  { trashed(get_reg()) }
 191 /cpuid/ { trashed("rax"); trashed("rbx"); trashed("rcx"); trashed("rdx") }
 192
 193 END {
 194   if (in_function)
 195     print ".cfi_endproc"
 196 }