--- /dev/null
+# 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 hex2int(str, i) {
+ str = tolower(str)
+
+ for (i = 1; i <= 16; i++) {
+ char = substr("0123456789abcdef", i, 1)
+ lookup[char] = i-1
+ }
+
+ result = 0
+ for (i = 1; i <= length(str); i++) {
+ result = result * 16
+ char = substr(str, i, 1)
+ result = result + lookup[char]
+ }
+ return result
+}
+
+function parse_const(str) {
+ sign = sub(/^-/, "", str)
+ hex = sub(/^0x/, "", str)
+ if (hex)
+ n = hex2int(str)
+ else
+ n = str+0
+ return sign ? -n : n
+}
+
+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 get_reg() {
+ # only use if you already know there is 1 and only 1 register
+ match($0, /%e(ax|bx|cx|dx|si|di|bp)/)
+ return substr($0, RSTART+1, 3)
+}
+function get_reg1() {
+ # for instructions with 2 operands, get 1st operand (assuming it is register)
+ match($0, /%e(ax|bx|cx|dx|si|di|bp),/)
+ return substr($0, RSTART+1, 3)
+}
+function get_reg2() {
+ # for instructions with 2 operands, get 2nd operand (assuming it is register)
+ match($0, /,%e(ax|bx|cx|dx|si|di|bp)/)
+ return substr($0, RSTART+RLENGTH-3, 3)
+}
+
+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($0, RSTART, RLENGTH-6))
+ } else {
+ offset = 0
+ }
+ if (!saved[register] && !dirty[register]) {
+ printf ".cfi_rel_offset %s,%d\n", register, offset
+ saved[register] = 1
+ }
+ }
+}
+
+# IF REGISTER VALUES ARE UNCEREMONIOUSLY TRASHED
+# ...then we want to know about it.
+#
+function trashed(register) {
+ if (in_function && !saved[register] && !dirty[register]) {
+ printf ".cfi_undefined %s\n", register
+ }
+ dirty[register] = 1
+}
+# this does NOT exhaustively check for all possible instructions which could
+# overwrite a register value inherited from the caller (just the common ones)
+/mov.*,%e(ax|bx|cx|dx|si|di|bp)/ { trashed(get_reg2()) }
+/(add|addl|sub|subl|and|or|xor|lea|sal|sar|shl|shr) %e(ax|bx|cx|dx|si|di|bp),/ {
+ trashed(get_reg1())
+}
+/i?mul [^,]*$/ { trashed("eax"); trashed("edx") }
+/i?mul %e(ax|bx|cx|dx|si|di|bp),/ { trashed(get_reg1()) }
+/i?div/ { trashed("eax"); trashed("edx") }
+/(dec|inc|not|neg|pop) %e(ax|bx|cx|dx|si|di|bp)/ { trashed(get_reg()) }
+/cpuid/ { trashed("eax"); trashed("ebx"); trashed("ecx"); trashed("edx") }
+
+END {
+ if (in_function)
+ print ".cfi_endproc"
+}
projects / oweals / musl.git / commitdiff