github.com/afumu/libc@v0.0.6/musl/tools/add-cfi.x86_64.awk (about)

     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  }