如何从用gcc在libc内联函数?(How to inline a function from li

2019-10-18 20:37发布

我有以下问题:我的软件造成的僵局,我有关于它的起源唯一的线索是一个只有8我的芯片组,这样的情况下提供水平的原始堆栈跟踪。

然而,我的堆栈跟踪是这样的:

memset
memset
memset
memset
memset
memset
memset
memset

我想删除的memset我的方式,看看哪些功能是造成这个烂摊子。 如果我问的gcc内联memset的,它会抱怨,说明我没有函数体吧。

那么,有没有一种方法,内联memset的? 有没有人有调试这个问题的任何其他的想法?

编辑

我已经尝试过使用一哑巴实施更换memset的,但是这使我的软件运行异常等问题出现,防止我获得的僵局。

编辑

顺便说一句,我使用的是MIPS拱。 我不是一个MIPS汇编专家,所以我做了在获得反汇编代码的memset和在C函数体中插入一个愚蠢的尝试。 我从objdump的-d和gdb拆机不同的指令,所以我对他们俩的尝试。 下面是我创建的功能:

void * memset(void * str_a, int ch, size_t count) {
    asm("mov    #12,r0");
    asm("cmp/gt r6,r0");
    asm("mov    r4,r0");
    asm("bt.s   30 <.L_dup_bytes+0x18>");
    asm("add    r4,r6");
    asm("tst    #3,r0");
    asm("bt.s   18 <.L_dup_bytes>");
    asm("extu.b r5,r5");
    asm("mov.b  r5,@r0");
    asm("add    #1,r0");
    asm("tst    #3,r0");
    asm("bf 10 <_memset+0x10>");
}

void * memset(void * str_a, int ch, size_t count) {
    asm("mov    #12,r0");
    asm("cmp/gt r6,r0");
    asm("mov    r4,r0");
    asm("bt.s   0x8163682c <memset+48>");
    asm("add    r4,r6");
    asm("tst    #3,r0");
    asm("bt.s   0x81636814 <memset+24>");
    asm("extu.b r5,r5");
    asm("mov.b  r5,@r0");
    asm("add    #1,r0");
    asm("tst    #3,r0");
    asm("bf 0x8163680c <memset+16>");
    asm("swap.b r5,r2");
    asm("or r2,r5");
    asm("swap.w r5,r2");
    asm("or r2,r5");
    asm("add    #-16,r6");
    asm("nop    ");
    asm("mov.l  r5,@r0");
    asm("cmp/hs r6,r0");
    asm("mov.l  r5,@(4,r0)");
    asm("bf.s   0x81636820 <memset+36>");
    asm("add    #8,r0");
    asm("add    #16,r6");
    asm("cmp/eq r6,r0");
    asm("bt 0x81636838 <memset+60>");
    asm("mov.b  r5,@r0");
    asm("add    #1,r0");
    asm("cmp/eq r6,r0");
    asm("bf 0x81636830 <memset+52>");
    asm("rts    ");
    asm("mov    r4,r0");
}

这给了我以下错误:

首先memset的:

/tmp/ccAuFFap.s: Assembler messages:
/tmp/ccAuFFap.s:3457: Warning: missing operand; zero assumed
/tmp/ccAuFFap.s:3469: Warning: missing operand; zero assumed
/tmp/ccAuFFap.s:3489: Warning: missing operand; zero assumed
/tmp/ccAuFFap.s:3457: Error: displacement to defined symbol .L0 overflows 8-bit field
/tmp/ccAuFFap.s:3469: Error: displacement to undefined symbol .L0 overflows 8-bit field 
/tmp/ccAuFFap.s:3489: Error: displacement to defined symbol .L0 overflows 8-bit field

第二memset的:

/tmp/cctCDgi5.s: Assembler messages:
/tmp/cctCDgi5.s:3457: Warning: missing operand; zero assumed
/tmp/cctCDgi5.s:3469: Warning: missing operand; zero assumed
/tmp/cctCDgi5.s:3489: Warning: missing operand; zero assumed
/tmp/cctCDgi5.s:3529: Warning: missing operand; zero assumed
/tmp/cctCDgi5.s:3545: Warning: missing operand; zero assumed
/tmp/cctCDgi5.s:3561: Warning: missing operand; zero assumed
/tmp/cctCDgi5.s:3457: Error: displacement to defined symbol .L0 overflows 8-bit field
/tmp/cctCDgi5.s:3469: Error: displacement to defined symbol .L0 overflows 8-bit field
/tmp/cctCDgi5.s:3489: Error: displacement to defined symbol .L0 overflows 8-bit field
/tmp/cctCDgi5.s:3529: Error: displacement to defined symbol .L0 overflows 8-bit field
/tmp/cctCDgi5.s:3545: Error: displacement to defined symbol .L0 overflows 8-bit field
/tmp/cctCDgi5.s:3561: Error: displacement to defined symbol .L0 overflows 8-bit field

有人可以用这些错误帮助吗?

编辑

尝试另一个版本,从源代码:

void * memset(void * str_a, int ch, size_t count) {    
    asm("slti    t1, a2, 8               ");
    asm("bne     t1, zero, L(last8)");
    asm("move    v0, a0                  ");
    asm("beq     a1, zero, L(ueven)      ");
    asm("andi    a1, 0xff                ");
    asm("sll     t0, a1, 8");
    asm("or      a1, t0");
    asm("sll     t0, a1, 16");
    asm("or      a1, t0                  ");
    asm("L(ueven):       ");
    asm("subu    t0, zero, a0            ");
    asm("andi    t0, 0x3");
    asm("beq     t0, zero, L(chkw)");
    asm("subu    a2, t0");
    asm("SWHI    a1, 0(a0)               ");
    asm("addu    a0, t0                  ");
    asm("L(chkw):        ");
    asm("andi    t0, a2, 0x7             ");
    asm("beq     t0, a2, L(chkl)");
    asm("subu    a3, a2, t0");
    asm("addu    a3, a0                  ");
    asm("move    a2, t0                  ");
    asm("L(loopw):       ");
    asm("addiu   a0, 8                   ");
    asm("sw      a1, -8(a0)");
    asm("bne     a0, a3, L(loopw)");
    asm("sw      a1, -4(a0)");
    asm("L(chkl):        ");
    asm("andi    t0, a2, 0x4             ");
    asm("beq     t0, zero, L(last8)      ");
    asm("subu    a2, t0");
    asm("sw      a1, 0(a0)               ");
    asm("addiu   a0, 4");
    asm("L(last8):       ");
    asm("blez    a2, L(exit)             ");
    asm("addu    a3, a2, a0              ");
    asm("L(lst8l):       ");
    asm("addiu   a0, 1");
    asm("bne     a0, a3, L(lst8l)");
    asm("sb      a1, -1(a0)");
    asm("L(exit):        ");
    asm("j       ra                      ");
    asm("nop");
}

下面是错误的这个时候:

/tmp/ccuyfGW5.s: Assembler messages:
/tmp/ccuyfGW5.s:5131: Error: unknown opcode
/tmp/ccuyfGW5.s:5135: Error: unknown opcode
/tmp/ccuyfGW5.s:5139: Error: unknown opcode
/tmp/ccuyfGW5.s:5143: Error: unknown opcode
/tmp/ccuyfGW5.s:5147: Error: unknown opcode
/tmp/ccuyfGW5.s:5151: Error: unknown opcode
/tmp/ccuyfGW5.s:5155: Error: invalid operands for opcode
/tmp/ccuyfGW5.s:5159: Error: unknown opcode
/tmp/ccuyfGW5.s:5163: Error: invalid operands for opcode
/tmp/ccuyfGW5.s:5167: Error: unknown opcode
/tmp/ccuyfGW5.s:5171: Error: unknown opcode
/tmp/ccuyfGW5.s:5175: Error: unknown opcode
/tmp/ccuyfGW5.s:5179: Error: unknown opcode
/tmp/ccuyfGW5.s:5183: Error: unknown opcode
/tmp/ccuyfGW5.s:5187: Error: unknown opcode
/tmp/ccuyfGW5.s:5191: Error: unknown opcode
/tmp/ccuyfGW5.s:5195: Error: unknown opcode
/tmp/ccuyfGW5.s:5199: Error: unknown opcode
/tmp/ccuyfGW5.s:5203: Error: unknown opcode
/tmp/ccuyfGW5.s:5207: Error: unknown opcode
/tmp/ccuyfGW5.s:5211: Error: unknown opcode
/tmp/ccuyfGW5.s:5215: Error: unknown opcode
/tmp/ccuyfGW5.s:5219: Error: unknown opcode
/tmp/ccuyfGW5.s:5223: Error: unknown opcode
/tmp/ccuyfGW5.s:5227: Error: unknown opcode
/tmp/ccuyfGW5.s:5231: Error: unknown opcode
/tmp/ccuyfGW5.s:5235: Error: unknown opcode
/tmp/ccuyfGW5.s:5239: Error: unknown opcode
/tmp/ccuyfGW5.s:5243: Error: unknown opcode
/tmp/ccuyfGW5.s:5247: Error: unknown opcode
/tmp/ccuyfGW5.s:5251: Error: unknown opcode
/tmp/ccuyfGW5.s:5255: Error: unknown opcode
/tmp/ccuyfGW5.s:5259: Error: unknown opcode
/tmp/ccuyfGW5.s:5263: Error: unknown opcode
/tmp/ccuyfGW5.s:5267: Error: unknown opcode
/tmp/ccuyfGW5.s:5271: Error: unknown opcode
/tmp/ccuyfGW5.s:5275: Error: unknown opcode
/tmp/ccuyfGW5.s:5279: Error: unknown opcode
/tmp/ccuyfGW5.s:5283: Error: unknown opcode
/tmp/ccuyfGW5.s:5287: Error: unknown opcode
/tmp/ccuyfGW5.s:5291: Error: unknown opcode
/tmp/ccuyfGW5.s:5295: Error: unknown opcode

编辑

这个问题确实是关系到堆栈损坏,但我会在这里,让这个问题,看看是否有人知道如何从一个子程序的反汇编代码,并把它恢复成C函数体为内联的答案。

Answer 1:

无论是gdb也不objdump产品代码,在gcc内联汇编MIPS会接受。 我不知道自动修复的语法,将需要汇编语法所以手动校正任何工具。 您还需要告诉gcc哪些寄存器和/或存储将由联汇编代码得到改变。 所有的这不是一个简单的任务。

如果你有C源代码, -S的选项gcc产生几乎语法正确的MIPS汇编,但即使这需要一些手工编辑。



文章来源: How to inline a function from libc with gcc?
标签: gcc inline mips