将加载的目标地址保存在寄存器中，直到指令退出

Question

我想使用基于事件的精确采样 (PEBS) 来记录 XeonE5 Sandy Bridge 上特定事件的所有地址（例如缓存未命中）。

但是，Core^TM i7 处理器和 Intel® XeonTM 5500 处理器的性能分析指南，第 24 页包含以下警告：

由于 PEBS 机制在以下位置捕获寄存器的值 指令完成后，取消引用的地址为 以下类型的加载指令（英特尔 asm 约定）不能 重构。
MOV RAX, [RAX+const]
这种 指令主要与指针追逐有关
mystruc = mystruc->next;
这是本方案的一个重大缺点 捕获内存指令地址的方法。

根据 objdump，我的程序中有许多这种形式的加载指令。 有什么办法可以避免这些吗？

由于这是一个特定于英特尔的问题，因此解决方案不必以任何方式可移植，它只需要工作即可。我的代码是用 C 编写的，理想情况下我正在寻找编译器级别的解决方案（gcc 或 icc），但欢迎提出任何建议。

---

一些例子：

mov    0x18(%rdi),%rdi

mov    (%rcx,%rax,8),%rax

在这两种情况下，在指令退出后（因此当我查看寄存器值以确定我加载到/从何处加载时）地址的值（在这些示例中分别为 %rdi + 18 和 %rcx + 8 * %rax）被覆盖mov 的结果。

---

我现在能想到的唯一方法是使用 &（与号）汇编程序约束。这意味着无论出现这样的指令，我都必须检查我的代码，并将每个取消引用 mystruc = mystruc->next; 的指针替换为：
asm volatile("mov (%1),%0" : "=&r" (mystruc) : "r" (&(mystruc->next)))

然而，这是一种非常简单的方法，并且可能存在比结构内的指针更复杂的情况。我知道这基本上会增加寄存器压力，所以编译器正在积极尝试避免。有没有其他方法可以做到这一点？

Answer 1

你想做的是转换表单的所有指令：

mov    (%rcx,%rax,8),%rax

进入：

mov    (%rcx,%rax,8),%r11
mov    %r11,%rax

---

这可以通过修改编译器生成的汇编源来更容易地完成。下面是一个perl 脚本，它将通过读取和修改.s 文件来完成所有必要的转换。

只需将构建更改为生成.s 文件而不是.o 文件，应用脚本，然后使用as 或gcc 生成.o

---

这是实际的脚本。按照下面 cmets 中的构建过程，我已经在我自己的一些资源上对其进行了测试。

该脚本具有以下特点：

1. 扫描并定位所有函数定义
2. 标识给定函数中使用的所有寄存器
3. 定位函数的所有返回点
4. 根据函数的寄存器使用情况选择要使用的临时寄存器（即，它将使用函数未已被函数使用的临时寄存器）
5. 用两个指令序列替换所有“麻烦的”指令
6. 在尝试使用被调用者保存的寄存器之前尝试使用未使用的临时寄存器（例如%r11 或未使用的参数寄存器）
7. 如果选择的寄存器被被调用者保存，将push添加到函数序言和pop到函数[多个]ret语句
8. 维护所有分析和转换的日志，并将其作为 cmets 附加到输出 .s 文件中

---

#!/usr/bin/perl
# pebsfix/pebsfixup -- fix assembler source for PEBS usage
#
# command line options:
#   "-a" -- use only full 64 bit targets
#   "-l" -- do _not_ use lea
#   "-D[diff-file]" -- show differences (default output: "./DIFF")
#   "-n10" -- do _not_ use register %r10 for temporary (default is use it)
#   "-o" -- overwrite input files (can be multiple)
#   "-O<outfile>" -- output file (only one .s input allowed)
#   "-q" -- suppress warnings
#   "-T[lvl]" -- debug trace
#
# "-o" and "-O" are mutually exclusive
#
# command line script test options:
#   "-N[TPA]" -- disable temp register types [for testing]
#   "-P" -- force push/pop on all functions
#
# command line arguments:
#   1-- list of .s files to process [or directory to search]
#       for a given file "foo.s", output is to "foo.TMP"
#       if (-o is given, "foo.TMP" is renamed to "foo.s")
#
# suggested usage:
#   change build to produce .s files
#   FROM:
#     cc [options] -c foo.c
#   TO:
#     cc [options] -c -S foo.c
#     pebsfixup -o foo.s
#     cc -c foo.s
#
# suggested compiler options:
# [probably only really needed if push/pop required. use -NP to verify]
#   (1) use either of
#       -O2 -fno-optimize-sibling-calls
#       -O1
#   (2) use -mno-omit-leaf-frame-pointer
#   (3) use -mno-red-zone [probably not required in any case]
#
# NOTES:
#   (1) red zones are only really useful for leaf functions (i.e. if fncA calls
#       fncB, fncA's red zone would be clobbered)
#   (2) pushing onto the stack isn't a problem if there is a formal stack frame
#   (3) the push is okay if the function has no more than six arguments (i.e.
#       does _not_ use positive offsets from %rsp to access them)

#pragma pgmlns
use strict qw(vars subs);

our $pgmtail;

our $opt_a;
our $opt_T;
our $opt_D;
our $opt_l;
our $opt_n10;
our $opt_N;
our $opt_P;
our $opt_q;
our $opt_o;
our $opt_O;
our $opt_s;

our @reguse;
our %reguse_tobase;
our %reguse_isbase;
our $regusergx;

our @regtmplist;
our %regtmp_type;

our $diff;

our $sepflg;
our $fatal;
our @cmtprt;

master(@ARGV);
exit(0);

# master -- master control
sub master
{
    my(@argv) = @_;
    my($xfsrc);
    my($file,@files);
    my($bf);

    $pgmtail = "pebsfixup";

    optget(\@argv);

    # define all known/usable registers
    regusejoin();

    # define all registers that we may use as a temporary
    regtmpall();

    if (defined($opt_D)) {
        unlink($opt_D);
    }

    # show usage
    if (@argv <= 0) {
        $file = $0;
        open($xfsrc,"<$file") ||
            sysfault("$pgmtail: unable to open '%s' -- $!\n",$file);

        while ($bf = <$xfsrc>) {
            chomp($bf);
            next if ($bf =~ /^#!/);
            last unless ($bf =~ s/^#//);
            $bf =~ s/^# ?//;
            print($bf,"\n");
        }

        close($xfsrc);
        exit(1);
    }

    foreach $file (@argv) {
        if (-d $file) {
            dodir(\@files,$file);
        }
        else {
            push(@files,$file);
        }
    }

    if (defined($opt_O)) {
        sysfault("$pgmtail: -O may have only one input file\n")
            if (@files != 1);
        sysfault("$pgmtail: -O and -o are mutually exclusive\n")
            if ($opt_o);
    }

    foreach $file (@files) {
        dofile($file);
    }

    if (defined($opt_D)) {
        exec("less",$opt_D);
    }
}

# dodir -- process directory
sub dodir
{
    my($files,$dir) = @_;
    my($file,@files);

    @files = (`find $dir -type f -name '*.s'`);
    foreach $file (@files) {
        chomp($file);
        push(@$files,$file);
    }
}

# dofile -- process file
sub dofile
{
    my($file) = @_;
    my($ofile);
    my($xfsrc);
    my($xfdst);
    my($bf,$lno,$outoff);
    my($fixoff);
    my($lhs,$rhs);
    my($xop,$arg);
    my($ix);
    my($sym,$val,$typ);
    my(%sym_type);
    my($fnc,$fnx,%fnx_lookup,@fnxlist);
    my($retlist);
    my($uselook,@uselist,%avail);
    my($fixreg,$fixrtyp);
    my($sixlist);
    my($fix,$fixlist);
    my($fixtot);
    my(@fix);
    my(@outlist);
    my($relaxflg);
    my($cmtchr);

    undef($fatal);
    undef(@cmtprt);

    msgprt("\n")
        if ($sepflg);
    $sepflg = 1;
    msgprt("$pgmtail: processing %s ...\n",$file);

    $cmtchr = "#";

    cmtprt("%s\n","-" x 78);
    cmtprt("FILE: %s\n",$file);

    # get the output file
    $ofile = $file;
    sysfault("$pgmtail: bad suffix -- file='%s'\n",$file)
        unless ($ofile =~ s/[.]s$//);
    $ofile .= ".TMP";

    # use explicit output file
    if (defined($opt_O)) {
        $ofile = $opt_O;
        sysfault("$pgmtail: output file may not be input file -- use -o instead\n")
            if ($ofile eq $file);
    }

    open($xfsrc,"<$file") ||
        sysfault("$pgmtail: unable to open '%s' -- $!\n",$file);

    $lno = 0;
    while ($bf = <$xfsrc>) {
        chomp($bf);
        $bf =~ s/\s+$//;

        $outoff = $lno;
        ++$lno;

        push(@outlist,$bf);

        # clang adds comments
        $ix = index($bf,"#");
        if ($ix >= 0) {
            $bf = substr($bf,0,$ix);
            $bf =~ s/\s+$//;
        }

        # look for ".type blah, @function"
        # NOTE: this always comes before the actual label line [we hope ;-)]
        if ($bf =~ /^\s+[.]type\s+([^,]+),\s*(\S+)/) {
            ($sym,$val) = ($1,$2);
            $val =~ s/^\@//;
            $sym_type{$sym} = $val;
            cmtprt("\n");
            cmtprt("TYPE: %s --> %s\n",$sym,$val);
            next;
        }

        # look for "label:"
        if ($bf =~ /^([a-z_A-Z][a-z_A-Z0-9]*):$/) {
            $sym = $1;
            next if ($sym_type{$sym} ne "function");

            $fnc = $sym;
            cmtprt("FUNCTION: %s\n",$fnc);

            $fnx = {};
            $fnx_lookup{$sym} = $fnx;
            push(@fnxlist,$fnx);

            $fnx->{fnx_fnc} = $fnc;
            $fnx->{fnx_outoff} = $outoff;

            $uselook = {};
            $fnx->{fnx_used} = $uselook;

            $retlist = [];
            $fnx->{fnx_retlist} = $retlist;

            $fixlist = [];
            $fnx->{fnx_fixlist} = $fixlist;

            $sixlist = [];
            $fnx->{fnx_sixlist} = $sixlist;
            next;
        }

        # remember all registers used by function:
        while ($bf =~ /($regusergx)/gpo) {
            $sym = ${^MATCH};
            $val = $reguse_tobase{$sym};
            dbgprt(3,"dofile: REGUSE sym='%s' val='%s'\n",$sym,$val);

            $uselook->{$sym} += 1;

            $uselook->{$val} += 1
                if ($val ne $sym);
        }

        # handle returns
        if ($bf =~ /^\s+ret/) {
            push(@$retlist,$outoff);
            next;
        }
        if ($bf =~ /^\s+rep[a-z]*\s+ret/) {
            push(@$retlist,$outoff);
            next;
        }

        # split up "movq 16(%rax),%rax" ...
        $ix = rindex($bf,",");
        next if ($ix < 0);

        # ... into "movq 16(%rax)"
        $lhs = substr($bf,0,$ix);
        $lhs =~ s/\s+$//;

        # check for "movq 16(%rsp)" -- this means that the function has/uses
        # more than six arguments (i.e. we may _not_ push/pop because it
        # wreaks havoc with positive offsets)
        # FIXME/CAE -- we'd have to adjust them by 8 which we don't do
        (undef,$rhs) = split(" ",$lhs);
        if ($rhs =~ /^(\d+)[(]%rsp[)]$/) {
            push(@$sixlist,$outoff);
            cmtprt("SIXARG: %s (line %d)\n",$rhs,$lno);
        }

        # ... and "%rax"
        $rhs = substr($bf,$ix + 1);
        $rhs =~ s/^\s+//;

        # target must be a [simple] register [or source scan will blow up]
        # (e.g. we actually had "cmp %ebp,(%rax,%r14)")
        next if ($rhs =~ /[)]/);

        # ensure we have the "%" prefix
        next unless ($rhs =~ /^%/);

        # we only want the full 64 bit reg as target
        # (e.g. "mov (%rbx),%al" doesn't count)
        $val = $reguse_tobase{$rhs};
        if ($opt_a) {
            next if ($val ne $rhs);
        }
        else {
            next unless (defined($val));
        }

        # source operand must contain target [base] register
        next unless ($lhs =~ /$val/);
        ###cmtprt("1: %s,%s\n",$lhs,$rhs);

        # source operand must be of the "right" type
        # FIXME/CAE -- we may need to revise this
        next unless ($lhs =~ /[(]/);
        cmtprt("NEEDFIX: %s,%s (line %d)\n",$lhs,$rhs,$lno);

        # remember the place we need to fix for later
        $fix = {};
        push(@$fixlist,$fix);
        $fix->{fix_outoff} = $outoff;
        $fix->{fix_lhs} = $lhs;
        $fix->{fix_rhs} = $rhs;
    }

    close($xfsrc);

    # get total number of fixups
    foreach $fnx (@fnxlist) {
        $fixlist = $fnx->{fnx_fixlist};
        $fixtot += @$fixlist;
    }
    msgprt("$pgmtail: needs %d fixups\n",$fixtot)
        if ($fixtot > 0);

    # fix each function
    foreach $fnx (@fnxlist) {
        cmtprt("\n");
        cmtprt("FNC: %s\n",$fnx->{fnx_fnc});

        $fixlist = $fnx->{fnx_fixlist};

        # get the fixup register
        ($fixreg,$fixrtyp) = regtmploc($fnx,$fixlist);

        # show number of return points
        {
            $retlist = $fnx->{fnx_retlist};
            cmtprt("  RET: %d\n",scalar(@$retlist));
            last if (@$retlist >= 1);

            # NOTE: we display this warning because we may not be able to
            # handle all situations

            $relaxflg = (@$fixlist <= 0) || ($fixrtyp ne "P");
            last if ($relaxflg && $opt_q);

            errprt("$pgmtail: in file '%s'\n",$file);
            errprt("$pgmtail: function '%s' has no return points\n",
                $fnx->{fnx_fnc});
            errprt("$pgmtail: suggest recompile with correct options\n");

            if (@$fixlist <= 0) {
                errprt("$pgmtail: working around because function needs no fixups\n");
                last;
            }

            if ($fixrtyp ne "P") {
                errprt("$pgmtail: working around because fixup reg does not need to be saved\n");
                last;
            }
        }

        # show stats on register usage in function
        $uselook = $fnx->{fnx_used};
        @uselist = sort(keys(%$uselook));
        cmtprt("  USED:\n");
        %avail = %reguse_isbase;
        foreach $sym (@uselist) {
            $val = $uselook->{$sym};

            $typ = $regtmp_type{$sym};
            $typ = sprintf(" (TYPE: %s)",$typ)
                if (defined($typ));

            cmtprt("    %s used %d%s\n",$sym,$val,$typ);
            $val = $reguse_tobase{$sym};
            delete($avail{$val});
        }

        # show function's available [unused] registers
        @uselist = keys(%avail);
        @uselist = sort(regusesort @uselist);
        if (@uselist > 0) {
            cmtprt("  AVAIL:\n");
            foreach $sym (@uselist) {
                $typ = $regtmp_type{$sym};
                $typ = sprintf(" (TYPE: %s)",$typ)
                    if (defined($typ));
                cmtprt("    %s%s\n",$sym,$typ);
            }
        }

        # skip over any functions that don't need fixing _and_ have a temp
        # register
        if (@$fixlist <= 0 && (! $opt_P)) {
            next if (defined($fixreg));
        }

        msgprt("$pgmtail: function %s\n",$fnx->{fnx_fnc});

        # skip function because we don't have a fixup register but report it
        # here
        unless (defined($fixreg)) {
            $bf = (@$fixlist > 0) ? "FATAL" : "can be ignored -- no fixups needed";
            msgprt("$pgmtail: FIXNOREG (%s)\n",$bf);
            cmtprt("  FIXNOREG (%s)\n",$bf);
            next;
        }

        msgprt("$pgmtail: FIXREG --> %s (TYPE: %s)\n",$fixreg,$fixrtyp);
        cmtprt("  FIXREG --> %s (TYPE: %s)\n",$fixreg,$fixrtyp);

        foreach $fix (@$fixlist) {
            $outoff = $fix->{fix_outoff};

            undef(@fix);
            cmtprt("  FIXOLD %s\n",$outlist[$outoff]);

            # original
            if ($opt_l) {
                $bf = sprintf("%s,%s",$fix->{fix_lhs},$fixreg);
                push(@fix,$bf);
                $bf = sprintf("\tmov\t%s,%s",$fixreg,$fix->{fix_rhs});
                push(@fix,$bf);
            }

            # use lea
            else {
                ($xop,$arg) = split(" ",$fix->{fix_lhs});
                $bf = sprintf("\tlea\t\t%s,%s",$arg,$fixreg);
                push(@fix,$bf);
                $bf = sprintf("\t%s\t(%s),%s",$xop,$fixreg,$fix->{fix_rhs});
                push(@fix,$bf);
            }

            foreach $bf (@fix) {
                cmtprt("  FIXNEW %s\n",$bf);
            }

            $outlist[$outoff] = [@fix];
        }

        unless ($opt_P) {
            next if ($fixrtyp ne "P");
        }

        # fix the function prolog
        $outoff = $fnx->{fnx_outoff};
        $lhs = $outlist[$outoff];
        $rhs = sprintf("\tpush\t%s",$fixreg);
        $bf = [$lhs,$rhs,""];
        $outlist[$outoff] = $bf;

        # fix the function return points
        $retlist = $fnx->{fnx_retlist};
        foreach $outoff (@$retlist) {
            $rhs = $outlist[$outoff];
            $lhs = sprintf("\tpop\t%s",$fixreg);
            $bf = ["",$lhs,$rhs];
            $outlist[$outoff] = $bf;
        }
    }

    open($xfdst,">$ofile") ||
        sysfault("$pgmtail: unable to open '%s' -- $!\n",$ofile);

    # output all the assembler text
    foreach $bf (@outlist) {
        # ordinary line
        unless (ref($bf)) {
            print($xfdst $bf,"\n");
            next;
        }

        # apply a fixup
        foreach $rhs (@$bf) {
            print($xfdst $rhs,"\n");
        }
    }

    # output all our reasoning as comments at the bottom
    foreach $bf (@cmtprt) {
        if ($bf eq "") {
            print($xfdst $cmtchr,$bf,"\n");
        }
        else {
            print($xfdst $cmtchr," ",$bf,"\n");
        }
    }

    close($xfdst);

    # get difference
    if (defined($opt_D)) {
        system("diff -u $file $ofile >> $opt_D");
    }

    # install fixed/modified file
    {
        last unless ($opt_o || defined($opt_O));
        last if ($fatal);
        msgprt("$pgmtail: installing ...\n");
        rename($ofile,$file);
    }
}

# regtmpall -- define all temporary register candidates
sub regtmpall
{

    dbgprt(1,"regtmpall: ENTER\n");

    regtmpdef("%r11","T");

    # NOTES:
    # (1) see notes on %r10 in ABI at bottom -- should we use it?
    # (2) a web search on "shared chain" and "x86" only produces 28 results
    # (3) some gcc code uses it as an ordinary register
    # (4) so, use it unless told not to
    regtmpdef("%r10","T")
        unless ($opt_n10);

    # argument registers (a6-a1)
    regtmpdef("%r9","A6");
    regtmpdef("%r8","A5");
    regtmpdef("%rcx","A4");
    regtmpdef("%rdx","A3");
    regtmpdef("%rsi","A2");
    regtmpdef("%rdi","A1");

    # callee preserved registers
    regtmpdef("%r15","P");
    regtmpdef("%r14","P");
    regtmpdef("%r13","P");
    regtmpdef("%r12","P");

    dbgprt(1,"regtmpall: EXIT\n");
}

# regtmpdef -- define usable temp registers
sub regtmpdef
{
    my($sym,$typ) = @_;

    dbgprt(1,"regtmpdef: SYM sym='%s' typ='%s'\n",$sym,$typ);

    push(@regtmplist,$sym);
    $regtmp_type{$sym} = $typ;
}

# regtmploc -- locate temp register to fix problem
sub regtmploc
{
    my($fnx,$fixlist) = @_;
    my($sixlist);
    my($uselook);
    my($regrhs);
    my($fixcnt);
    my($coretyp);
    my($reglhs,$regtyp);

    dbgprt(2,"regtmploc: ENTER fnx_fnc='%s'\n",$fnx->{fnx_fnc});

    $sixlist = $fnx->{fnx_sixlist};
    $fixcnt = @$fixlist;
    $fixcnt = 1
        if ($opt_P);

    $uselook = $fnx->{fnx_used};

    foreach $regrhs (@regtmplist) {
        dbgprt(2,"regtmploc: TRYREG regrhs='%s' uselook=%d\n",
            $regrhs,$uselook->{$regrhs});

        unless ($uselook->{$regrhs}) {
            $regtyp = $regtmp_type{$regrhs};
            $coretyp = $regtyp;
            $coretyp =~ s/\d+$//;

            # function uses stack arguments -- we can't push/pop
            if (($coretyp eq "P") && (@$sixlist > 0)) {
                dbgprt(2,"regtmploc: SIXREJ\n");
                next;
            }

            if (defined($opt_N)) {
                dbgprt(2,"regtmploc: TRYREJ opt_N='%s' regtyp='%s'\n",
                    $opt_N,$regtyp);
                next if ($opt_N =~ /$coretyp/);
            }

            $reglhs = $regrhs;
            last;
        }
    }

    {
        last if (defined($reglhs));

        errprt("regtmploc: unable to locate usable fixup register for function '%s'\n",
            $fnx->{fnx_fnc});

        last if ($fixcnt <= 0);

        $fatal = 1;
    }

    dbgprt(2,"regtmploc: EXIT reglhs='%s' regtyp='%s'\n",$reglhs,$regtyp);

    ($reglhs,$regtyp);
}

# regusejoin -- get regex for all registers
sub regusejoin
{
    my($reg);

    dbgprt(1,"regusejoin: ENTER\n");

    # rax
    foreach $reg (qw(a b c d))  {
        regusedef($reg,"r_x","e_x","_l","_h");
    }

    #   rdi/rsi
    foreach $reg (qw(d s)) {
        regusedef($reg,"r_i","e_i","_i","_il");
    }

    # rsp/rbp
    foreach $reg (qw(b s)) {
        regusedef($reg,"r_p","e_p");
    }

    foreach $reg (8,9,10,11,12,13,14,15) {
        regusedef($reg,"r_","r_d","r_w","r_b");
    }

    $regusergx = join("|",reverse(sort(@reguse)));

    dbgprt(1,"regusejoin: EXIT regusergx='%s'\n",$regusergx);
}

# regusedef -- define all registers
sub regusedef
{
    my(@argv) = @_;
    my($mid);
    my($pat);
    my($base);

    $mid = shift(@argv);

    dbgprt(1,"regusedef: ENTER mid='%s'\n",$mid);

    foreach $pat (@argv) {
        $pat = "%" . $pat;
        $pat =~ s/_/$mid/;
        $base //= $pat;
        dbgprt(1,"regusedef: PAT pat='%s' base='%s'\n",$pat,$base);

        push(@reguse,$pat);
        $reguse_tobase{$pat} = $base;
    }

    $reguse_isbase{$base} = 1;

    dbgprt(1,"regusedef: EXIT\n");
}

# regusesort -- sort base register names
sub regusesort
{
    my($symlhs,$numlhs);
    my($symrhs,$numrhs);
    my($cmpflg);

    {
        ($symlhs,$numlhs) = _regusesort($a);
        ($symrhs,$numrhs) = _regusesort($b);

        $cmpflg = $symlhs cmp $symrhs;
        last if ($cmpflg);

        $cmpflg = $numlhs <=> $numrhs;
    }

    $cmpflg;
}

# _regusesort -- split up base register name
sub _regusesort
{
    my($sym) = @_;
    my($num);

    if ($sym =~ s/(\d+)$//) {
        $num = $1;
        $num += 0;
        $sym =~ s/[^%]/z/g;
    }

    ($sym,$num);
}

# optget -- get options
sub optget
{
    my($argv) = @_;
    my($bf);
    my($sym,$val);
    my($dft,%dft);

    foreach $sym (qw(a l n10 P q o s T)) {
        $dft{$sym} = 1;
    }
    $dft{"N"} = "T";
    $dft{"D"} = "DIFF";

    while (1) {
        $bf = $argv->[0];
        $sym = $bf;

        last unless ($sym =~ s/^-//);
        last if ($sym eq "-");

        shift(@$argv);

        {
            if ($sym =~ /([^=]+)=(.+)$/) {
                ($sym,$val) = ($1,$2);
                last;
            }

            if ($sym =~ /^(.)(.+)$/) {
                ($sym,$val) = ($1,$2);
                last;
            }

            undef($val);
        }

        $dft = $dft{$sym};
        sysfault("$pgmtail: unknown option -- '%s'\n",$bf)
            unless (defined($dft));

        $val //= $dft;

        ${"opt_" . $sym} = $val;
    }
}

# cmtprt -- transformation comments
sub cmtprt
{

    $_ = shift(@_);
    $_ = sprintf($_,@_);
    chomp($_);
    push(@cmtprt,$_);
}

# msgprt -- progress output
sub msgprt
{

    printf(STDERR @_);
}

# errprt -- show errors
sub errprt
{

    cmtprt(@_);
    printf(STDERR @_);
}

# sysfault -- abort on error
sub sysfault
{

    printf(STDERR @_);
    exit(1);
}

# dbgprt -- debug print
sub dbgprt
{

    $_ = shift(@_);
    goto &_dbgprt
        if ($opt_T >= $_);
}

# _dbgprt -- debug print
sub _dbgprt
{

    printf(STDERR @_);
}

---

更新：

我已更新脚本以修复错误、添加更多检查和更多选项。 注意：我必须删除底部的 ABI 以适应 30,000 的限制。

否则奇怪的结果会出现在其他带括号的命令上，例如 cmpl %ebp, (%rax,%r14) 会拆分为 lhs='cmpl %ebp, (%rax' 和 rhs='%r14)'，这反过来会导致 /$rhs/ 失败。

是的，这是一个错误。固定。

您的$rhs =~ /%[er](.x|\d+)/ 与di 或ax 的字节或字负载不匹配。不过，这不太可能。哦，还有，我认为它无法匹配rdi / rsi。所以你不需要 r10d 中的尾随 d

已修复。查找所有变体。

哇，我认为这样的事情必须在编译时发生，而事后这样做太麻烦了。

无耻插件： 感谢您的“哇！”。 perl 非常适合这种凌乱的工作。我以前写过这样的汇编程序“注入”脚本。 （例如）回到 [在编译器支持之前] 添加分析调用。

您可以将 %r10 标记为另一个保留调用的寄存器。

在进行了几次网络搜索后，我只能在 "static chain" x86 上找到大约 84 个匹配项。唯一相关的是 x86 ABI。而且，除了将其作为脚注提及之外，它没有提供任何解释。此外，一些gcc 代码使用r10 没有 任何保存为被调用者 寄存器。所以，我现在默认程序使用r10（如果需要，可以使用命令行选项禁用它）。

如果函数已经使用了所有寄存器会怎样？

如果它是真的全部，那么我们就不走运了。如果找不到备用寄存器，该脚本将检测并报告此问题并禁止修复。

并且，它将通过注入push作为函数的第一个inst并在ret inst之前注入一个相应的pop来使用“被调用者必须保留”寄存器[可以有多个]。这可以通过一个选项禁用。

你不能只推/弹出，因为那会踩到红色区域

不，它确实不是。有几个原因：

(1) 几乎作为旁注：红色区域仅在叶函数中有用。否则，如果fncA 调用fncB，仅仅fncA 这样做就会踩到它自己的红色区域。请参阅脚本顶部注释块中的编译选项。

(2) 更重要的是，由于push/pop 的注入方式。 push 出现在之前任何其他 insts。 pop 出现在之后任何其他 insts [就在ret 之前]。

红色区域仍然存在——完好无损。它只是从原本的位置偏移了-8。所有红色区域活动都被保留，因为这些 insts 使用来自 %rsp

的 负 偏移量

这与内联 asm 块中的 push/pop 不同不同。通常的情况是红色区域代码执行（例如）mov $23,-4(%rsp)。之后会出现一个内联 asm 块，它会执行 push/pop 。

一些函数来展示这个：

# function_original -- original function before pebsfixup
# RETURNS: 23
function_original:
    mov     $23,-4(%rsp)                # red zone code generated by compiler
    ...
    mov     -4(%rsp),%rax               # will still have $23
    ret

# function_pebsfixup -- pebsfixup modified
# RETURNS: 23
function_pebsfixup:
    push    %r12                        # pebsfixup injected

    mov     $23,-4(%rsp)                # red zone code generated by compiler
    ...
    mov     -4(%rsp),%rax               # will still have $23

    pop     %r12                        # pebsfixup injected
    ret

# function_inline -- function with inline asm block and red zone
# RETURNS: unknown value
function_inline:
    mov     $23,-4(%rsp)                # red zone code generated by compiler

    # inline asm block -- steps on red zone
    push    %rdx
    push    %rcx
    ...
    pop     %rcx
    pop     %rdx

    ...

    mov     -4(%rsp),%rax               # now -4(%rsp) no longer has $23

    ret

push/pop 确实 让我们遇到麻烦的地方是函数使用的参数更多 多于六个参数（即 args 7+ 在堆栈上）。访问这些参数使用从%rsp 的正偏移：

mov     32(%rsp),%rax

使用我们的“技巧”push，偏移量将不正确。正确的偏移量现在会高出 8：

mov     40(%rsp),%rax

脚本会检测这个并抱怨。但是，它[尚未] 调整正偏移量，因为这种情况的概率很低。可能需要大约五行代码来解决这个问题。暂时下注……