# Insert GAS CFI directives ("control frame information") into x86-64 asm input 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($0, RSTART, RLENGTH-1)) } function canonicalize_reg(register) { if (match(register, /^r/)) return register else if (match(register, /^e/)) return "r" substr(register, 2, length(register)-1) else if (match(register, /[hl]$/)) # AH, AL, BH, BL, etc return "r" substr(register, 1, 1) "x" else # AX, BX, CX, etc return "r" register } function get_reg() { # only use if you already know there is 1 and only 1 register match($0, /%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/) 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, /%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15),/) 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, /,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/) 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($1)-1) # drop trailing : if (called == label) { # note adjustment of stack pointer from "call label; label:" adjust_sp_offset(8) } if (functions[label]) { if (in_function) print ".cfi_endproc" in_function = 1 print ".cfi_startproc" for (register in saved) delete saved[register] for (register in dirty) delete dirty[register] } # an instruction may follow on the same line, so continue processing } /^$/ { next } { called = "" printf ".loc 1 %d\n", line_number print } # KEEPING UP WITH THE STACK POINTER # %rsp should only be adjusted by pushing/popping or adding/subtracting constants # /pushl?/ { adjust_sp_offset(8) } /popl?/ { adjust_sp_offset(-8) } /addl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%rsp/ { adjust_sp_offset(-get_const1()) } /subl? \$-?(0x[0-9a-fA-F]+|[0-9]+),%rsp/ { 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? %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15)/ { # 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? %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15),-?(0x[0-9a-fA-F]+|[0-9]+)?\(%rsp\)/ { if (in_function) { register = get_reg() if (match($0, /-?(0x[0-9a-fA-F]+|[0-9]+)\(%rsp\)/)) { offset = parse_const(substr($0, RSTART, RLENGTH-6)) } else { offset = 0 } if (!saved[register] && !dirty[register]) { printf ".cfi_rel_offset %s,%d\n", register, offset saved[register] = 1 } } } # IF REGISTER VALUES ARE UNCEREMONIOUSLY TRASHED # ...then we want to know about it. # function trashed(register) { if (in_function && !saved[register] && !dirty[register]) { printf ".cfi_undefined %s\n", register } dirty[register] = 1 } # this does NOT exhaustively check for all possible instructions which could # overwrite a register value inherited from the caller (just the common ones) /mov.*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ { trashed(get_reg2()) } /(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)$/ { trashed(get_reg2()) } /^i?mul [^,]*$/ { trashed("rax"); trashed("rdx") } /^i?mul.*,%[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)$/ { trashed(get_reg2()) } /^i?div/ { trashed("rax"); trashed("rdx") } /(dec|inc|not|neg|pop) %[er]?([abcd][xlh]|si|di|bp|8|9|10|11|12|13|14|15)/ { trashed(get_reg()) } /cpuid/ { trashed("rax"); trashed("rbx"); trashed("rcx"); trashed("rdx") } END { if (in_function) print ".cfi_endproc" }