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Message-Id: <1443780123-6493-3-git-send-email-alexinbeijing@gmail.com>
Date: Fri, 2 Oct 2015 12:02:03 +0200
From: Alex Dowad <alexinbeijing@...il.com>
To: musl@...ts.openwall.com
Subject: [PATCH 3/3] Add script to add CFI directives to asm files in debug builds of x86_64
This makes debugging more pleasant for the odd times when you have to dig into
files implemented in x86_64 assembly.
It turns out that the parts we care about are almost exactly like i386, except
for the register names!
---
tools/add-cfi.x86_64.awk | 185 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 185 insertions(+)
create mode 100644 tools/add-cfi.x86_64.awk
diff --git a/tools/add-cfi.x86_64.awk b/tools/add-cfi.x86_64.awk
new file mode 100644
index 0000000..ed53fa5
--- /dev/null
+++ b/tools/add-cfi.x86_64.awk
@@ -0,0 +1,185 @@
+# 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 get_reg() {
+ # only use if you already know there is 1 and only 1 register
+ match($0, /%r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15)/)
+ return substr($0, RSTART+1, RLENGTH-1)
+}
+function get_reg1() {
+ # for instructions with 2 operands, get 1st operand (assuming it is register)
+ match($0, /%r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15),/)
+ return substr($0, RSTART+1, RLENGTH-2)
+}
+function get_reg2() {
+ # for instructions with 2 operands, get 2nd operand (assuming it is register)
+ match($0, /,%r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15)/)
+ return 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($0, RSTART, RLENGTH-6))
+ } else {
+ offset = 0
+ }
+ if (!saved[register] && !dirty[register]) {
+ printf ".cfi_rel_offset %s,%d\n", register, offset
+ saved[register] = 1
+ }
+ }
+}
+
+# IF REGISTER VALUES ARE UNCEREMONIOUSLY TRASHED
+# ...then we want to know about it.
+#
+function trashed(register) {
+ if (in_function && !saved[register] && !dirty[register]) {
+ printf ".cfi_undefined %s\n", register
+ }
+ dirty[register] = 1
+}
+# this does NOT exhaustively check for all possible instructions which could
+# overwrite a register value inherited from the caller (just the common ones)
+/mov.*,%r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15)/ { trashed(get_reg2()) }
+/(add|addl|sub|subl|and|or|xor|lea|sal|sar|shl|shr) %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15),/ {
+ trashed(get_reg1())
+}
+/i?mul [^,]*$/ { trashed("rax"); trashed("rdx") }
+/i?mul %r(ax|bx|cx|dx|si|di|bp|8|9|10|11|12|13|14|15),/ { trashed(get_reg1()) }
+/^i?div/ { trashed("rax"); trashed("rdx") }
+
+/(dec|inc|not|neg|pop) %r(ax|bx|cx|dx|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"
+}
--
2.0.0.GIT
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