arch/tile: bug fix: exec'ed task thought it was still single-stepping

To handle single-step, tile mmap's a page of memory in the process
space for each thread and uses it to construct a version of the
instruction that we want to single step. If the process exec's,
though, we lose that mapping, and the kernel needs to be aware that
it will need to recreate it if the exec'ed process than tries to
single-step as well.

Also correct some int32_t to s32 for better kernel style.

Signed-off-by: Chris Metcalf <[e-mail]>

arch/tile/include/asm/ptrace.h

···
 /* Single-step the instruction at regs->pc */
 extern void single_step_once(struct pt_regs *regs);
 
+/* Clean up after execve(). */
+extern void single_step_execve(void);
+
 struct task_struct;
 
 extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,

arch/tile/kernel/process.c

···
 		goto out;
 	error = do_execve(filename, argv, envp, regs);
 	putname(filename);
+	if (error == 0)
+		single_step_execve();
 out:
 	return error;
 }
···
 		goto out;
 	error = compat_do_execve(filename, argv, envp, regs);
 	putname(filename);
+	if (error == 0)
+		single_step_execve();
 out:
 	return error;
 }

arch/tile/kernel/single_step.c

···
 	MEMOP_STORE_POSTINCR
 };
 
-static inline tile_bundle_bits set_BrOff_X1(tile_bundle_bits n, int32_t offset)
+static inline tile_bundle_bits set_BrOff_X1(tile_bundle_bits n, s32 offset)
 {
 	tile_bundle_bits result;
 
···
 	return bundle;
 }
 
+/*
+ * Called after execve() has started the new image.  This allows us
+ * to reset the info state.  Note that the the mmap'ed memory, if there
+ * was any, has already been unmapped by the exec.
+ */
+void single_step_execve(void)
+{
+	struct thread_info *ti = current_thread_info();
+	kfree(ti->step_state);
+	ti->step_state = NULL;
+}
+
 /**
  * single_step_once() - entry point when single stepping has been triggered.
  * @regs: The machine register state
···
 		/* branches */
 		case BRANCH_OPCODE_X1:
 		{
-			int32_t offset = signExtend17(get_BrOff_X1(bundle));
+			s32 offset = signExtend17(get_BrOff_X1(bundle));
 
 			/*
 			 * For branches, we use a rewriting trick to let the
···
 	control |= SPR_SINGLE_STEP_CONTROL_1__INHIBIT_MASK;
 	__insn_mtspr(SPR_SINGLE_STEP_CONTROL_K, control);
 	__insn_mtspr(SPR_SINGLE_STEP_EN_K_K, 1 << USER_PL);
+}
+
+void single_step_execve(void)
+{
+	/* Nothing */
 }
 
 #endif /* !__tilegx__ */