| # Insert GAS CFI directives ("control frame information") into x86-32 asm input |
| # |
| # CFI directives tell the assembler how to generate "stack frame" debug info |
| # This information can tell a debugger (like gdb) how to find the current stack |
| # frame at any point in the program code, and how to find the values which |
| # various registers had at higher points in the call stack |
| # With this information, the debugger can show a backtrace, and you can move up |
| # and down the call stack and examine the values of local variables |
| |
| BEGIN { |
| # don't put CFI data in the .eh_frame ELF section (which we don't keep) |
| print ".cfi_sections .debug_frame" |
| |
| # only emit CFI directives inside a function |
| in_function = 0 |
| |
| # emit .loc directives with line numbers from original source |
| printf ".file 1 \"%s\"\n", ARGV[1] |
| line_number = 0 |
| |
| # used to detect "call label; label:" trick |
| called = "" |
| } |
| |
| function get_const1() { |
| # for instructions with 2 operands, get 1st operand (assuming it is constant) |
| match($0, /-?(0x[0-9a-fA-F]+|[0-9]+),/) |
| return parse_const(substr($0, RSTART, RLENGTH-1)) |
| } |
| |
| function canonicalize_reg(register) { |
| if (match(register, /^e/)) |
| return register |
| else if (match(register, /[hl]$/)) # AH, AL, BH, BL, etc |
| return "e" substr(register, 1, 1) "x" |
| else # AX, BX, CX, etc |
| return "e" register |
| } |
| function get_reg() { |
| # only use if you already know there is 1 and only 1 register |
| match($0, /%e?([abcd][hlx]|si|di|bp)/) |
| return canonicalize_reg(substr($0, RSTART+1, RLENGTH-1)) |
| } |
| function get_reg1() { |
| # for instructions with 2 operands, get 1st operand (assuming it is register) |
| match($0, /%e?([abcd][hlx]|si|di|bp),/) |
| return canonicalize_reg(substr($0, RSTART+1, RLENGTH-2)) |
| } |
| function get_reg2() { |
| # for instructions with 2 operands, get 2nd operand (assuming it is register) |
| match($0, /,%e?([abcd][hlx]|si|di|bp)/) |
| return canonicalize_reg(substr($0, RSTART+2, RLENGTH-2)) |
| } |
| |
| function adjust_sp_offset(delta) { |
| if (in_function) |
| printf ".cfi_adjust_cfa_offset %d\n", delta |
| } |
| |
| { |
| line_number = line_number + 1 |
| |
| # clean the input up before doing anything else |
| # delete comments |
| gsub(/(#|\/\/).*/, "") |
| |
| # canonicalize whitespace |
| gsub(/[ \t]+/, " ") # mawk doesn't understand \s |
| gsub(/ *, */, ",") |
| gsub(/ *: */, ": ") |
| gsub(/ $/, "") |
| gsub(/^ /, "") |
| } |
| |
| # check for assembler directives which we care about |
| /^\.(section|data|text)/ { |
| # a .cfi_startproc/.cfi_endproc pair should be within the same section |
| # otherwise, clang will choke when generating ELF output |
| if (in_function) { |
| print ".cfi_endproc" |
| in_function = 0 |
| } |
| } |
| /^\.type [a-zA-Z0-9_]+,@function/ { |
| functions[substr($2, 1, length($2)-10)] = 1 |
| } |
| # not interested in assembler directives beyond this, just pass them through |
| /^\./ { |
| print |
| next |
| } |
| |
| /^[a-zA-Z0-9_]+:/ { |
| label = substr($1, 1, length($1)-1) # drop trailing : |
| |
| if (called == label) { |
| # note adjustment of stack pointer from "call label; label:" |
| adjust_sp_offset(4) |
| } |
| |
| if (functions[label]) { |
| if (in_function) |
| print ".cfi_endproc" |
| |
| in_function = 1 |
| print ".cfi_startproc" |
| |
| for (register in saved) |
| delete saved[register] |
| for (register in dirty) |
| delete dirty[register] |
| } |
| |
| # an instruction may follow on the same line, so continue processing |
| } |
| |
| /^$/ { next } |
| |
| { |
| called = "" |
| printf ".loc 1 %d\n", line_number |
| print |
| } |
| |
| # KEEPING UP WITH THE STACK POINTER |
| # We do NOT attempt to understand foolish and ridiculous tricks like stashing |
| # the stack pointer and then using %esp as a scratch register, or bitshifting |
| # it or taking its square root or anything stupid like that. |
| # %esp should only be adjusted by pushing/popping or adding/subtracting constants |
| # |
| /pushl?/ { |
| if (match($0, / %(ax|bx|cx|dx|di|si|bp|sp)/)) |
| adjust_sp_offset(2) |
| else |
| adjust_sp_offset(4) |
| } |
| /popl?/ { |
| if (match($0, / %(ax|bx|cx|dx|di|si|bp|sp)/)) |
| adjust_sp_offset(-2) |
| else |
| adjust_sp_offset(-4) |
| } |
| /addl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%esp/ { adjust_sp_offset(-get_const1()) } |
| /subl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%esp/ { adjust_sp_offset(get_const1()) } |
| |
| /call/ { |
| if (match($0, /call [0-9]+f/)) # "forward" label |
| called = substr($0, RSTART+5, RLENGTH-6) |
| else if (match($0, /call [0-9a-zA-Z_]+/)) |
| called = substr($0, RSTART+5, RLENGTH-5) |
| } |
| |
| # TRACKING REGISTER VALUES FROM THE PREVIOUS STACK FRAME |
| # |
| /pushl? %e(ax|bx|cx|dx|si|di|bp)/ { # don't match "push (%reg)" |
| # if a register is being pushed, and its value has not changed since the |
| # beginning of this function, the pushed value can be used when printing |
| # local variables at the next level up the stack |
| # emit '.cfi_rel_offset' for that |
| |
| if (in_function) { |
| register = get_reg() |
| if (!saved[register] && !dirty[register]) { |
| printf ".cfi_rel_offset %s,0\n", register |
| saved[register] = 1 |
| } |
| } |
| } |
| |
| /movl? %e(ax|bx|cx|dx|si|di|bp),-?(0x[0-9a-fA-F]+|[0-9]+)?\(%esp\)/ { |
| if (in_function) { |
| register = get_reg() |
| if (match($0, /-?(0x[0-9a-fA-F]+|[0-9]+)\(%esp\)/)) { |
| offset = parse_const(substr($0, RSTART, RLENGTH-6)) |
| } else { |
| offset = 0 |
| } |
| if (!saved[register] && !dirty[register]) { |
| printf ".cfi_rel_offset %s,%d\n", register, offset |
| saved[register] = 1 |
| } |
| } |
| } |
| |
| # IF REGISTER VALUES ARE UNCEREMONIOUSLY TRASHED |
| # ...then we want to know about it. |
| # |
| function trashed(register) { |
| if (in_function && !saved[register] && !dirty[register]) { |
| printf ".cfi_undefined %s\n", register |
| } |
| dirty[register] = 1 |
| } |
| # this does NOT exhaustively check for all possible instructions which could |
| # overwrite a register value inherited from the caller (just the common ones) |
| /mov.*,%e?([abcd][hlx]|si|di|bp)$/ { trashed(get_reg2()) } |
| /(add|addl|sub|subl|and|or|xor|lea|sal|sar|shl|shr).*,%e?([abcd][hlx]|si|di|bp)$/ { |
| trashed(get_reg2()) |
| } |
| /^i?mul [^,]*$/ { trashed("eax"); trashed("edx") } |
| /^i?mul.*,%e?([abcd][hlx]|si|di|bp)$/ { trashed(get_reg2()) } |
| /^i?div/ { trashed("eax"); trashed("edx") } |
| /(dec|inc|not|neg|pop) %e?([abcd][hlx]|si|di|bp)/ { trashed(get_reg()) } |
| /cpuid/ { trashed("eax"); trashed("ebx"); trashed("ecx"); trashed("edx") } |
| |
| END { |
| if (in_function) |
| print ".cfi_endproc" |
| } |