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ptrace: arch_has_single_step

From:  Roland McGrath <roland@redhat.com>
To:  Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>
Subject:  [PATCH 01/27] ptrace: arch_has_single_step
Date:  Sun, 25 Nov 2007 13:55:07 -0800 (PST)
Message-ID:  <20071125215507.4B89226F8C5@magilla.localdomain>
Cc:  linux-kernel@vger.kernel.org
Archive-link:  Article

This defines the new macro arch_has_single_step() in linux/ptrace.h, a
default for when asm/ptrace.h does not define it.  It declares the new
user_enable_single_step and user_disable_single_step functions.
This is not used yet, but paves the way to harmonize on this interface
for the arch-specific calls on all machines.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
 include/linux/ptrace.h |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index ae8146a..a6effc8 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -128,6 +128,52 @@ int generic_ptrace_pokedata(struct task_struct *tsk, long addr, long data);
 #define force_successful_syscall_return() do { } while (0)
 #endif
 
+/*
+ * <asm/ptrace.h> should define the following things inside #ifdef __KERNEL__.
+ *
+ * These do-nothing inlines are used when the arch does not
+ * implement single-step.  The kerneldoc comments are here
+ * to document the interface for all arch definitions.
+ */
+
+#ifndef arch_has_single_step
+/**
+ * arch_has_single_step - does this CPU support user-mode single-step?
+ *
+ * If this is defined, then there must be function declarations or
+ * inlines for user_enable_single_step() and user_disable_single_step().
+ * arch_has_single_step() should evaluate to nonzero iff the machine
+ * supports instruction single-step for user mode.
+ * It can be a constant or it can test a CPU feature bit.
+ */
+#define arch_has_single_step()		(0)
+
+/**
+ * user_enable_single_step - single-step in user-mode task
+ * @task: either current or a task stopped in %TASK_TRACED
+ *
+ * This can only be called when arch_has_single_step() has returned nonzero.
+ * Set @task so that when it returns to user mode, it will trap after the
+ * next single instruction executes.
+ */
+static inline void user_enable_single_step(struct task_struct *task)
+{
+	BUG();			/* This can never be called.  */
+}
+
+/**
+ * user_disable_single_step - cancel user-mode single-step
+ * @task: either current or a task stopped in %TASK_TRACED
+ *
+ * Clear @task of the effects of user_enable_single_step().  This can
+ * be called whether or not user_enable_single_step() was ever called
+ * on @task, and even if arch_has_single_step() returned zero.
+ */
+static inline void user_disable_single_step(struct task_struct *task)
+{
+}
+#endif	/* arch_has_single_step */
+
 #endif
 
 #endif
-- 
1.5.3.4



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