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Commit d9771e8c authored by Roland McGrath's avatar Roland McGrath Committed by Ingo Molnar
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x86: x86-32 ptrace debugreg cleanup 



This cleans up the 32-bit ptrace code to separate the guts of the
debug register access from the implementation of PTRACE_PEEKUSR and
PTRACE_POKEUSR.  The new functions ptrace_[gs]et_debugreg match the
new 64-bit entry points for parity, but they don't need to be global.

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent d0f08175

arch/x86/kernel/ptrace_32.c

+69 −50
Original line number Diff line number Diff line
@@ -118,6 +118,72 @@ static unsigned long getreg(struct task_struct *child, unsigned long regno) 
	return retval;

}



/*

 * This function is trivial and will be inlined by the compiler.

 * Having it separates the implementation details of debug

 * registers from the interface details of ptrace.

 */

static unsigned long ptrace_get_debugreg(struct task_struct *child, int n)

{

	return child->thread.debugreg[n];

}



static int ptrace_set_debugreg(struct task_struct *child,

			       int n, unsigned long data)

{

	if (unlikely(n == 4 || n == 5))

		return -EIO;



	if (n < 4 && unlikely(data >= TASK_SIZE - 3))

		return -EIO;



	if (n == 7) {

		/*

		 * Sanity-check data. Take one half-byte at once with

		 * check = (val >> (16 + 4*i)) & 0xf. It contains the

		 * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits

		 * 2 and 3 are LENi. Given a list of invalid values,

		 * we do mask |= 1 << invalid_value, so that

		 * (mask >> check) & 1 is a correct test for invalid

		 * values.

		 *

		 * R/Wi contains the type of the breakpoint /

		 * watchpoint, LENi contains the length of the watched

		 * data in the watchpoint case.

		 *

		 * The invalid values are:

		 * - LENi == 0x10 (undefined), so mask |= 0x0f00.

		 * - R/Wi == 0x10 (break on I/O reads or writes), so

		 *   mask |= 0x4444.

		 * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=

		 *   0x1110.

		 *

		 * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.

		 *

		 * See the Intel Manual "System Programming Guide",

		 * 15.2.4

		 *

		 * Note that LENi == 0x10 is defined on x86_64 in long

		 * mode (i.e. even for 32-bit userspace software, but

		 * 64-bit kernel), so the x86_64 mask value is 0x5454.

		 * See the AMD manual no. 24593 (AMD64 System Programming)

		 */

		int i;

		data &= ~DR_CONTROL_RESERVED;

		for (i = 0; i < 4; i++)

			if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)

				return -EIO;

		if (data)

			set_tsk_thread_flag(child, TIF_DEBUG);

		else

			clear_tsk_thread_flag(child, TIF_DEBUG);

	}



	child->thread.debugreg[n] = data;



	return 0;

}



/*

 * Called by kernel/ptrace.c when detaching..

 *
@@ -158,7 +224,7 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) 
		   addr <= (long) &dummy->u_debugreg[7]){

			addr -= (long) &dummy->u_debugreg[0];

			addr = addr >> 2;

			tmp = child->thread.debugreg[addr];

			tmp = ptrace_get_debugreg(child, addr);

		}

		ret = put_user(tmp, datap);

		break;
@@ -188,56 +254,9 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) 
		  ret = -EIO;

		  if(addr >= (long) &dummy->u_debugreg[0] &&

		     addr <= (long) &dummy->u_debugreg[7]){



			  if(addr == (long) &dummy->u_debugreg[4]) break;

			  if(addr == (long) &dummy->u_debugreg[5]) break;

			  if(addr < (long) &dummy->u_debugreg[4] &&

			     ((unsigned long) data) >= TASK_SIZE-3) break;

			  

			  /* Sanity-check data. Take one half-byte at once with

			   * check = (val >> (16 + 4*i)) & 0xf. It contains the

			   * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits

			   * 2 and 3 are LENi. Given a list of invalid values,

			   * we do mask |= 1 << invalid_value, so that

			   * (mask >> check) & 1 is a correct test for invalid

			   * values.

			   *

			   * R/Wi contains the type of the breakpoint /

			   * watchpoint, LENi contains the length of the watched

			   * data in the watchpoint case.

			   *

			   * The invalid values are:

			   * - LENi == 0x10 (undefined), so mask |= 0x0f00.

			   * - R/Wi == 0x10 (break on I/O reads or writes), so

			   *   mask |= 0x4444.

			   * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=

			   *   0x1110.

			   *

			   * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.

			   *

			   * See the Intel Manual "System Programming Guide",

			   * 15.2.4

			   *

			   * Note that LENi == 0x10 is defined on x86_64 in long

			   * mode (i.e. even for 32-bit userspace software, but

			   * 64-bit kernel), so the x86_64 mask value is 0x5454.

			   * See the AMD manual no. 24593 (AMD64 System

			   * Programming)*/



			  if(addr == (long) &dummy->u_debugreg[7]) {

				  data &= ~DR_CONTROL_RESERVED;

				  for(i=0; i<4; i++)

					  if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)

						  goto out_tsk;

				  if (data)

					  set_tsk_thread_flag(child, TIF_DEBUG);

				  else

					  clear_tsk_thread_flag(child, TIF_DEBUG);

			  }

			  addr -= (long) &dummy->u_debugreg;

			  addr = addr >> 2;

			  child->thread.debugreg[addr] = data;

			  ret = 0;

			  ret = ptrace_set_debugreg(child, addr, data);

		  }

		  break;
@@ -335,7 +354,7 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data) 
		ret = ptrace_request(child, request, addr, data);

		break;

	}

 out_tsk:



	return ret;

}