x86: single_step: share code

This removes the single-step code from ptrace_32.c and uses the step.c code
shared with the 64-bit kernel.  The two versions of the code were nearly
identical already, so the shared code has only a couple of simple #ifdef's.
Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/Makefile_32

@@ -11,6 +11,7 @@ obj-y	:= process_32.o signal_32.o entry_32.o traps_32.o irq_32.o \
 		quirks.o i8237.o topology.o alternative.o i8253.o tsc_32.o io_delay.o rtc.o
 
 obj-y				+= tls.o
+obj-y				+= step.o
 obj-$(CONFIG_STACKTRACE)	+= stacktrace.o
 obj-y				+= cpu/
 obj-y				+= acpi/

arch/x86/kernel/ptrace_32.c

@@ -137,131 +137,6 @@ static unsigned long getreg(struct task_struct *child,
 	return retval;
 }
 
-#define LDT_SEGMENT 4
-
-static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_regs *regs)
-{
-	unsigned long addr, seg;
-
-	addr = regs->eip;
-	seg = regs->xcs & 0xffff;
-	if (regs->eflags & VM_MASK) {
-		addr = (addr & 0xffff) + (seg << 4);
-		return addr;
-	}
-
-	/*
-	 * We'll assume that the code segments in the GDT
-	 * are all zero-based. That is largely true: the
-	 * TLS segments are used for data, and the PNPBIOS
-	 * and APM bios ones we just ignore here.
-	 */
-	if (seg & LDT_SEGMENT) {
-		u32 *desc;
-		unsigned long base;
-
-		seg &= ~7UL;
-
-		mutex_lock(&child->mm->context.lock);
-		if (unlikely((seg >> 3) >= child->mm->context.size))
-			addr = -1L; /* bogus selector, access would fault */
-		else {
-			desc = child->mm->context.ldt + seg;
-			base = ((desc[0] >> 16) |
-				((desc[1] & 0xff) << 16) |
-				(desc[1] & 0xff000000));
-
-			/* 16-bit code segment? */
-			if (!((desc[1] >> 22) & 1))
-				addr &= 0xffff;
-			addr += base;
-		}
-		mutex_unlock(&child->mm->context.lock);
-	}
-	return addr;
-}
-
-static inline int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
-{
-	int i, copied;
-	unsigned char opcode[15];
-	unsigned long addr = convert_eip_to_linear(child, regs);
-
-	copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
-	for (i = 0; i < copied; i++) {
-		switch (opcode[i]) {
-		/* popf and iret */
-		case 0x9d: case 0xcf:
-			return 1;
-		/* opcode and address size prefixes */
-		case 0x66: case 0x67:
-			continue;
-		/* irrelevant prefixes (segment overrides and repeats) */
-		case 0x26: case 0x2e:
-		case 0x36: case 0x3e:
-		case 0x64: case 0x65:
-		case 0xf0: case 0xf2: case 0xf3:
-			continue;
-
-		/*
-		 * pushf: NOTE! We should probably not let
-		 * the user see the TF bit being set. But
-		 * it's more pain than it's worth to avoid
-		 * it, and a debugger could emulate this
-		 * all in user space if it _really_ cares.
-		 */
-		case 0x9c:
-		default:
-			return 0;
-		}
-	}
-	return 0;
-}
-
-void user_enable_single_step(struct task_struct *child)
-{
-	struct pt_regs *regs = get_child_regs(child);
-
-	/*
-	 * Always set TIF_SINGLESTEP - this guarantees that 
-	 * we single-step system calls etc..  This will also
-	 * cause us to set TF when returning to user mode.
-	 */
-	set_tsk_thread_flag(child, TIF_SINGLESTEP);
-
-	/*
-	 * If TF was already set, don't do anything else
-	 */
-	if (regs->eflags & X86_EFLAGS_TF)
-		return;
-
-	/* Set TF on the kernel stack.. */
-	regs->eflags |= X86_EFLAGS_TF;
-
-	/*
-	 * ..but if TF is changed by the instruction we will trace,
-	 * don't mark it as being "us" that set it, so that we
-	 * won't clear it by hand later.
-	 */
-	if (is_setting_trap_flag(child, regs))
-		return;
-	
-	child->ptrace |= PT_DTRACE;
-}
-
-void user_disable_single_step(struct task_struct *child)
-{
-	/* Always clear TIF_SINGLESTEP... */
-	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
-
-	/* But touch TF only if it was set by us.. */
-	if (child->ptrace & PT_DTRACE) {
-		struct pt_regs *regs = get_child_regs(child);
-		regs->eflags &= ~X86_EFLAGS_TF;
-		child->ptrace &= ~PT_DTRACE;
-	}
-}
-
 /*
  * Called by kernel/ptrace.c when detaching..
  *

arch/x86/kernel/step.c

@@ -5,12 +5,24 @@
 #include <linux/mm.h>
 #include <linux/ptrace.h>
 
+#ifdef CONFIG_X86_32
+static
+#endif
 unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs)
 {
 	unsigned long addr, seg;
 
+#ifdef CONFIG_X86_64
 	addr = regs->rip;
 	seg = regs->cs & 0xffff;
+#else
+	addr = regs->eip;
+	seg = regs->xcs & 0xffff;
+	if (regs->eflags & X86_EFLAGS_VM) {
+		addr = (addr & 0xffff) + (seg << 4);
+		return addr;
+	}
+#endif
 
 	/*
 	 * We'll assume that the code segments in the GDT
@@ -69,12 +81,14 @@ static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
 		case 0xf0: case 0xf2: case 0xf3:
 			continue;
 
+#ifdef CONFIG_X86_64
 		case 0x40 ... 0x4f:
 			if (regs->cs != __USER_CS)
 				/* 32-bit mode: register increment */
 				return 0;
 			/* 64-bit mode: REX prefix */
 			continue;
+#endif
 
 			/* CHECKME: f2, f3 */