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#!/usr/bin/env perl
# Transform assembly in order to clean each stack frame for X86_64.
use strict;
use warnings;
$SIG{__WARN__} = sub { die @_ };
# Whether we are still scanning the content of a function:
our $scanproc = 0;
# Save lines of the function:
our $lines = "";
# Size of the stack for this function:
our $size = 0;
# Counter for assigning unique ids to labels:
our $id=0;
sub emit_code {
my $qsize = $size / 8;
my $offset = - $size - 8;
if($size != 0) {
# This is a crude hack to disable the stack cleaning on the main
# stack. It relies on the fact that the main stack is high in
# the address space and the other stacks are in the heap (lower).
print("\tmovq \$0x7fff00000000, %r11\n");
print("\tcmpq %r11, %rsp\n");
print("\tjae .Lstack_cleaner_done$id\n");
# Loop over the stack frame quadwords and zero it:
print("\tmovabsq \$$qsize, %r11\n");
print(".Lstack_cleaner_loop$id:\n");
print("\tmovq \$0, $offset(%rsp,%r11,8)\n");
print("\tsubq \$1, %r11\n");
print("\tjne .Lstack_cleaner_loop$id\n");
print(".Lstack_cleaner_done$id:\n");
}
print $lines;
$id = $id + 1;
$size = 0;
$lines = "";
$scanproc = 0;
}
while (<>) {
if ($scanproc) {
$lines = $lines . $_;
if (m/^[ \t]*.cfi_endproc$/) {
emit_code();
} elsif (m/^[ \t]*pushq/) {
$size += 8;
} elsif (m/^[ \t]*subq[\t *]\$([0-9]*),[ \t]*%rsp$/) {
my $val = $1;
$val = oct($val) if $val =~ /^0/;
$size += $val;
emit_code();
}
} elsif (m/^[ \t]*.cfi_startproc$/) {
print $_;
$scanproc = 1;
} else {
print $_;
}
}
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