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callstack.cr
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callstack.cr
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require "c/dlfcn"
require "c/stdio"
require "c/string"
require "callstack/lib_unwind"
{% if flag?(:darwin) %}
require "debug/mach_o"
require "debug/dwarf"
lib LibC
fun _dyld_image_count : UInt32
fun _dyld_get_image_name(image_index : UInt32) : Char*
fun _dyld_get_image_vmaddr_slide(image_index : UInt32) : Long
end
{% elsif flag?(:freebsd) || flag?(:linux) || flag?(:openbsd) %}
require "debug/elf"
require "debug/dwarf"
{% end %}
def caller
CallStack.new.printable_backtrace
end
# :nodoc:
struct CallStack
@@skip = [] of String
def self.skip(filename)
@@skip << filename
end
skip(__FILE__)
@callstack : Array(Void*)
@backtrace : Array(String)?
def initialize
@callstack = CallStack.unwind
end
def printable_backtrace
@backtrace ||= decode_backtrace
end
{% if flag?(:gnu) && flag?(:i686) %}
# This is only used for the workaround described in `Exception.unwind`
@@makecontext_range : Range(Void*, Void*)?
def self.makecontext_range
@@makecontext_range ||= begin
makecontext_start = makecontext_end = LibC.dlsym(LibC::RTLD_DEFAULT, "makecontext")
while true
ret = LibC.dladdr(makecontext_end, out info)
break if ret == 0 || info.dli_sname.null?
break unless LibC.strcmp(info.dli_sname, "makecontext") == 0
makecontext_end += 1
end
(makecontext_start...makecontext_end)
end
end
{% end %}
protected def self.unwind
callstack = [] of Void*
backtrace_fn = ->(context : LibUnwind::Context, data : Void*) do
bt = data.as(typeof(callstack))
ip = {% if flag?(:arm) %}
Pointer(Void).new(__crystal_unwind_get_ip(context))
{% else %}
Pointer(Void).new(LibUnwind.get_ip(context))
{% end %}
bt << ip
{% if flag?(:gnu) && flag?(:i686) %}
# This is a workaround for glibc bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18635
# The unwind info is corrupted when `makecontext` is used.
# Stop the backtrace here. There is nothing interest beyond this point anyway.
if CallStack.makecontext_range.includes?(ip)
return LibUnwind::ReasonCode::END_OF_STACK
end
{% end %}
LibUnwind::ReasonCode::NO_REASON
end
LibUnwind.backtrace(backtrace_fn, callstack.as(Void*))
callstack
end
struct RepeatedFrame
getter ip : Void*, count : Int32
def initialize(@ip : Void*)
@count = 0
end
def incr
@count += 1
end
end
def self.print_backtrace
backtrace_fn = ->(context : LibUnwind::Context, data : Void*) do
last_frame = data.as(RepeatedFrame*)
ip = {% if flag?(:arm) %}
Pointer(Void).new(__crystal_unwind_get_ip(context))
{% else %}
Pointer(Void).new(LibUnwind.get_ip(context))
{% end %}
if last_frame.value.ip == ip
last_frame.value.incr
else
print_frame(last_frame.value) unless last_frame.value.ip.address == 0
last_frame.value = RepeatedFrame.new ip
end
LibUnwind::ReasonCode::NO_REASON
end
rf = RepeatedFrame.new(Pointer(Void).null)
LibUnwind.backtrace(backtrace_fn, pointerof(rf).as(Void*))
print_frame(rf)
end
private def self.print_frame(repeated_frame)
frame = decode_frame(repeated_frame.ip)
if frame
offset, sname = frame
if repeated_frame.count == 0
LibC.dprintf 2, "[0x%lx] %s +%ld\n", repeated_frame.ip, sname, offset
else
LibC.dprintf 2, "[0x%lx] %s +%ld (%ld times)\n", repeated_frame.ip, sname, offset, repeated_frame.count + 1
end
else
if repeated_frame.count == 0
LibC.dprintf 2, "[0x%lx] ???\n", repeated_frame.ip
else
LibC.dprintf 2, "[0x%lx] ??? (%ld times)\n", repeated_frame.ip, repeated_frame.count + 1
end
end
end
private def decode_backtrace
@callstack.compact_map do |ip|
pc = CallStack.decode_address(ip)
file, line, column = CallStack.decode_line_number(pc)
if file == "??"
file_line_column = "??"
else
next if @@skip.includes?(file)
file_line_column = "#{file} #{line}:#{column}"
end
if name = CallStack.decode_function_name(pc)
function = name
elsif frame = CallStack.decode_frame(ip)
_, sname = frame
function = String.new(sname)
else
function = "???"
end
"0x#{ip.address.to_s(16)}: #{function} at #{file_line_column}"
end
end
{% if flag?(:darwin) || flag?(:freebsd) || flag?(:linux) || flag?(:openbsd) %}
@@dwarf_line_numbers : Debug::DWARF::LineNumbers?
@@dwarf_function_names : Array(Tuple(LibC::SizeT, LibC::SizeT, String))?
protected def self.decode_line_number(pc)
read_dwarf_sections unless @@dwarf_line_numbers
if ln = @@dwarf_line_numbers
if row = ln.find(pc)
path = ln.files[row.file]?
if dirname = ln.directories[row.directory]?
path = "#{dirname}/#{path}"
end
return {path, row.line, row.column}
end
end
{"??", 0, 0}
end
protected def self.decode_function_name(pc)
read_dwarf_sections unless @@dwarf_function_names
if fn = @@dwarf_function_names
fn.each do |(low_pc, high_pc, function_name)|
return function_name if low_pc <= pc <= high_pc
end
end
end
protected def self.parse_function_names_from_dwarf(info, strings)
info.each do |code, abbrev, attributes|
next unless abbrev && abbrev.tag.subprogram?
name = low_pc = high_pc = nil
attributes.each do |(at, form, value)|
case at
when Debug::DWARF::AT::DW_AT_name
value = strings.try(&.decode(value.as(UInt32 | UInt64))) if form.strp?
name = value.as(String)
when Debug::DWARF::AT::DW_AT_low_pc
low_pc = value.as(LibC::SizeT)
when Debug::DWARF::AT::DW_AT_high_pc
if form.addr?
high_pc = value.as(LibC::SizeT)
elsif value.responds_to?(:to_i)
high_pc = low_pc.as(LibC::SizeT) + value.to_i
end
end
end
if low_pc && high_pc && name
yield low_pc, high_pc, name
end
end
end
{% if flag?(:darwin) %}
@@image_slide : LibC::Long?
protected def self.read_dwarf_sections
locate_dsym_bundle do |mach_o|
mach_o.read_section?("__debug_line") do |sh, io|
@@dwarf_line_numbers = Debug::DWARF::LineNumbers.new(io, sh.size)
end
strings = mach_o.read_section?("__debug_str") do |sh, io|
Debug::DWARF::Strings.new(io, sh.offset)
end
mach_o.read_section?("__debug_info") do |sh, io|
names = [] of {LibC::SizeT, LibC::SizeT, String}
while io.tell - sh.offset < sh.size
offset = io.tell - sh.offset
info = Debug::DWARF::Info.new(io, offset)
mach_o.read_section?("__debug_abbrev") do |sh, io|
info.read_abbreviations(io)
end
parse_function_names_from_dwarf(info, strings) do |name, low_pc, high_pc|
names << {name, low_pc, high_pc}
end
end
@@dwarf_function_names = names
end
end
end
# DWARF uses fixed addresses but Darwin loads exectutables at a random
# address, so we must remove the load offset from the IP to match the
# addresses in DWARF sections.
#
# See https://en.wikipedia.org/wiki/Address_space_layout_randomization
protected def self.decode_address(ip)
ip.address - image_slide
end
# Searches the companion dSYM bundle with the DWARF sections for the
# current program as generated by `dsymutil`. It may be a `foo.dwarf` file
# or within a `foo.dSYM` bundle for a program named `foo`.
#
# See <http://wiki.dwarfstd.org/index.php?title=Apple%27s_%22Lazy%22_DWARF_Scheme> for details.
private def self.locate_dsym_bundle
program = Process.executable_path
return unless program
files = {
"#{program}.dSYM/Contents/Resources/DWARF/#{File.basename(program)}",
"#{program}.dwarf"
}
files.each do |dwarf|
next unless File.exists?(dwarf)
Debug::MachO.open(program) do |mach_o|
Debug::MachO.open(dwarf) do |dsym|
if dsym.uuid == mach_o.uuid
return yield dsym
end
end
end
end
nil
end
# The address offset at which the program was loaded at.
private def self.image_slide
@@image_slide ||= search_image_slide
end
private def self.search_image_slide
buffer = GC.malloc_atomic(LibC::PATH_MAX).as(UInt8*)
size = LibC::PATH_MAX.to_u32
if LibC._NSGetExecutablePath(buffer, pointerof(size)) == -1
buffer = GC.malloc_atomic(size).as(UInt8*)
if LibC._NSGetExecutablePath(buffer, pointerof(size)) == -1
return LibC::Long.new(0)
end
end
program = String.new(buffer)
LibC._dyld_image_count.times do |i|
if program == String.new(LibC._dyld_get_image_name(i))
return LibC._dyld_get_image_vmaddr_slide(i)
end
end
LibC::Long.new(0)
end
{% else %}
@@base_address : UInt64|UInt32|Nil
protected def self.read_dwarf_sections
Debug::ELF.open(PROGRAM_NAME) do |elf|
elf.read_section?(".text") do |sh, _|
@@base_address = sh.addr - sh.offset
end
elf.read_section?(".debug_line") do |sh, io|
@@dwarf_line_numbers = Debug::DWARF::LineNumbers.new(io, sh.size)
end
strings = elf.read_section?(".debug_str") do |sh, io|
Debug::DWARF::Strings.new(io, sh.offset)
end
elf.read_section?(".debug_info") do |sh, io|
names = [] of {LibC::SizeT, LibC::SizeT, String}
while io.tell - sh.offset < sh.size
offset = io.tell - sh.offset
info = Debug::DWARF::Info.new(io, offset)
elf.read_section?(".debug_abbrev") do |sh, io|
info.read_abbreviations(io)
end
parse_function_names_from_dwarf(info, strings) do |name, low_pc, high_pc|
names << {name, low_pc, high_pc}
end
end
@@dwarf_function_names = names
end
end
end
# DWARF uses fixed addresses but some platforms (e.g., OpenBSD or Linux
# with the [PaX patch](https://en.wikipedia.org/wiki/PaX)) load
# executables at a random address, so we must remove the load offset from
# the IP to match the addresses in DWARF sections.
#
# See https://en.wikipedia.org/wiki/Address_space_layout_randomization
protected def self.decode_address(ip)
if LibC.dladdr(ip, out info) != 0
unless info.dli_fbase.address == @@base_address
return ip.address - info.dli_fbase.address
end
end
ip.address
end
{% end %}
{% else %}
def self.decode_address(ip)
ip
end
def self.decode_line_number(pc)
{"??", 0, 0}
end
def self.decode_function_name(pc)
nil
end
{% end %}
protected def self.decode_frame(ip, original_ip = ip)
if LibC.dladdr(ip, out info) != 0
offset = original_ip - info.dli_saddr
if offset == 0
return decode_frame(ip - 1, original_ip)
end
unless info.dli_sname.null?
{offset, info.dli_sname}
end
end
end
end