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Commit d9af12b7 authored by Steven Rostedt's avatar Steven Rostedt Committed by Ingo Molnar
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powerpc: ftrace, fix cast aliasing and add code verification 



Impact: clean up and robustness addition

This patch addresses the comments made by Paul Mackerras.
It removes the type casting between unsigned int and unsigned char
pointers, and replaces them with a use of all unsigned int.

Verification that the jump is indeed made to a trampoline has also
been added.

Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c7b0d173

arch/powerpc/kernel/ftrace.c

+65 −56
Original line number Diff line number Diff line
@@ -162,26 +162,25 @@ static int 
__ftrace_make_nop(struct module *mod,

		  struct dyn_ftrace *rec, unsigned long addr)

{

	unsigned char replaced[MCOUNT_INSN_SIZE * 2];

	unsigned int *op = (unsigned *)&replaced;

	unsigned char jmp[8];

	unsigned long *ptr = (unsigned long *)&jmp;

	unsigned int op;

	unsigned int jmp[5];

	unsigned long ptr;

	unsigned long ip = rec->ip;

	unsigned long tramp;

	int offset;



	/* read where this goes */

	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))

	if (probe_kernel_read(&op, (void *)ip, sizeof(int)))

		return -EFAULT;



	/* Make sure that that this is still a 24bit jump */

	if (!is_bl_op(*op)) {

		printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);

	if (!is_bl_op(op)) {

		printk(KERN_ERR "Not expected bl: opcode is %x\n", op);

		return -EINVAL;

	}



	/* lets find where the pointer goes */

	tramp = find_bl_target(ip, *op);

	tramp = find_bl_target(ip, op);



	/*

	 * On PPC64 the trampoline looks like:
@@ -200,19 +199,25 @@ __ftrace_make_nop(struct module *mod, 
	DEBUGP("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);



	/* Find where the trampoline jumps to */

	if (probe_kernel_read(jmp, (void *)tramp, 8)) {

	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {

		printk(KERN_ERR "Failed to read %lx\n", tramp);

		return -EFAULT;

	}



	DEBUGP(" %08x %08x",

	       (unsigned)(*ptr >> 32),

	       (unsigned)*ptr);

	DEBUGP(" %08x %08x", jmp[0], jmp[1]);



	/* verify that this is what we expect it to be */

	if (((jmp[0] & 0xffff0000) != 0x3d820000) ||

	    ((jmp[1] & 0xffff0000) != 0x398c0000) ||

	    (jmp[2] != 0xf8410028) ||

	    (jmp[3] != 0xe96c0020) ||

	    (jmp[4] != 0xe84c0028)) {

		printk(KERN_ERR "Not a trampoline\n");

		return -EINVAL;

	}



	offset = (unsigned)jmp[2] << 24 |

		(unsigned)jmp[3] << 16 |

		(unsigned)jmp[6] << 8 |

		(unsigned)jmp[7];

	offset = (unsigned)((unsigned short)jmp[0]) << 16 |

		(unsigned)((unsigned short)jmp[1]);



	DEBUGP(" %x ", offset);
@@ -225,13 +230,13 @@ __ftrace_make_nop(struct module *mod, 
		return -EFAULT;

	}



	DEBUGP(" %08x %08x\n",

	       (unsigned)(*ptr >> 32),

	       (unsigned)*ptr);

	DEBUGP(" %08x %08x\n", jmp[0], jmp[1]);



	ptr = ((unsigned long)jmp[0] << 32) + jmp[1];



	/* This should match what was called */

	if (*ptr != GET_ADDR(addr)) {

		printk(KERN_ERR "addr does not match %lx\n", *ptr);

	if (ptr != GET_ADDR(addr)) {

		printk(KERN_ERR "addr does not match %lx\n", ptr);

		return -EINVAL;

	}
@@ -240,11 +245,11 @@ __ftrace_make_nop(struct module *mod, 
	 *  0xe8, 0x41, 0x00, 0x28   ld r2,40(r1)

	 * This needs to be turned to a nop too.

	 */

	if (probe_kernel_read(replaced, (void *)(ip+4), MCOUNT_INSN_SIZE))

	if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))

		return -EFAULT;



	if (*op != 0xe8410028) {

		printk(KERN_ERR "Next line is not ld! (%08x)\n", *op);

	if (op != 0xe8410028) {

		printk(KERN_ERR "Next line is not ld! (%08x)\n", op);

		return -EINVAL;

	}
@@ -261,9 +266,9 @@ __ftrace_make_nop(struct module *mod, 
	 *   ld r2,40(r1)

	 *  1:

	 */

	op[0] = 0x48000008;	/* b +8 */

	op = 0x48000008;	/* b +8 */



	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))

	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))

		return -EPERM;



	return 0;
@@ -274,46 +279,52 @@ static int 
__ftrace_make_nop(struct module *mod,

		  struct dyn_ftrace *rec, unsigned long addr)

{

	unsigned char replaced[MCOUNT_INSN_SIZE];

	unsigned int *op = (unsigned *)&replaced;

	unsigned char jmp[8];

	unsigned int *ptr = (unsigned int *)&jmp;

	unsigned int op;

	unsigned int jmp[4];

	unsigned long ip = rec->ip;

	unsigned long tramp;

	int offset;



	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))

	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))

		return -EFAULT;



	/* Make sure that that this is still a 24bit jump */

	if (!is_bl_op(*op)) {

		printk(KERN_ERR "Not expected bl: opcode is %x\n", *op);

	if (!is_bl_op(op)) {

		printk(KERN_ERR "Not expected bl: opcode is %x\n", op);

		return -EINVAL;

	}



	/* lets find where the pointer goes */

	tramp = find_bl_target(ip, *op);

	tramp = find_bl_target(ip, op);



	/*

	 * On PPC32 the trampoline looks like:

	 * lis r11,sym@ha

	 * addi r11,r11,sym@l

	 * mtctr r11

	 * bctr

	 *  0x3d, 0x60, 0x00, 0x00  lis r11,sym@ha

	 *  0x39, 0x6b, 0x00, 0x00  addi r11,r11,sym@l

	 *  0x7d, 0x69, 0x03, 0xa6  mtctr r11

	 *  0x4e, 0x80, 0x04, 0x20  bctr

	 */



	DEBUGP("ip:%lx jumps to %lx", ip, tramp);



	/* Find where the trampoline jumps to */

	if (probe_kernel_read(jmp, (void *)tramp, 8)) {

	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {

		printk(KERN_ERR "Failed to read %lx\n", tramp);

		return -EFAULT;

	}



	DEBUGP(" %08x %08x ", ptr[0], ptr[1]);

	DEBUGP(" %08x %08x ", jmp[0], jmp[1]);



	/* verify that this is what we expect it to be */

	if (((jmp[0] & 0xffff0000) != 0x3d600000) ||

	    ((jmp[1] & 0xffff0000) != 0x396b0000) ||

	    (jmp[2] != 0x7d6903a6) ||

	    (jmp[3] != 0x4e800420)) {

		printk(KERN_ERR "Not a trampoline\n");

		return -EINVAL;

	}



	tramp = (ptr[1] & 0xffff) |

		((ptr[0] & 0xffff) << 16);

	tramp = (jmp[1] & 0xffff) |

		((jmp[0] & 0xffff) << 16);

	if (tramp & 0x8000)

		tramp -= 0x10000;
@@ -326,9 +337,9 @@ __ftrace_make_nop(struct module *mod, 
		return -EINVAL;

	}



	op[0] = PPC_NOP_INSTR;

	op = PPC_NOP_INSTR;



	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))

	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))

		return -EPERM;



	return 0;
@@ -384,13 +395,12 @@ int ftrace_make_nop(struct module *mod, 
static int

__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)

{

	unsigned char replaced[MCOUNT_INSN_SIZE * 2];

	unsigned int *op = (unsigned *)&replaced;

	unsigned int op[2];

	unsigned long ip = rec->ip;

	unsigned long offset;



	/* read where this goes */

	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE * 2))

	if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))

		return -EFAULT;



	/*
@@ -425,7 +435,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 


	DEBUGP("write to %lx\n", rec->ip);



	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE * 2))

	if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))

		return -EPERM;



	return 0;
@@ -434,18 +444,17 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
static int

__ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)

{

	unsigned char replaced[MCOUNT_INSN_SIZE];

	unsigned int *op = (unsigned *)&replaced;

	unsigned int op;

	unsigned long ip = rec->ip;

	unsigned long offset;



	/* read where this goes */

	if (probe_kernel_read(replaced, (void *)ip, MCOUNT_INSN_SIZE))

	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))

		return -EFAULT;



	/* It should be pointing to a nop */

	if (op[0] != PPC_NOP_INSTR) {

		printk(KERN_ERR "Expected NOP but have %x\n", op[0]);

	if (op != PPC_NOP_INSTR) {

		printk(KERN_ERR "Expected NOP but have %x\n", op);

		return -EINVAL;

	}
@@ -465,11 +474,11 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) 
	}



	/* Set to "bl addr" */

	op[0] = branch_offset(offset);

	op = branch_offset(offset);



	DEBUGP("write to %lx\n", rec->ip);



	if (probe_kernel_write((void *)ip, replaced, MCOUNT_INSN_SIZE))

	if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))

		return -EPERM;



	return 0;