From 753eb9378b5def16ed200173c249763d79f030dd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=B8ren=20Sandmann?= <sandmann@redhat.com>
Date: Sat, 23 Apr 2005 21:53:16 +0000
Subject: [PATCH] New function to check if the page is readable before reading.
 Noop on
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Sat Apr 23 17:49:33 2005  Søren Sandmann  <sandmann@redhat.com>

	* sysprof-module.c (page_readable): New function to check if the
	page is readable before reading. Noop on kernel <= 2.6.11

	* sysprof-module.c (get_mm, put_mm): New functions to confine
	#ifdefs.
---
 ChangeLog        | 13 +++++++++
 Makefile         |  2 +-
 sysprof-module.c | 75 ++++++++++++++++++++++++++++++++++++------------
 3 files changed, 71 insertions(+), 19 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 02720a6d..63577bf5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+Sat Apr 23 17:49:33 2005  Søren Sandmann  <sandmann@redhat.com>
+
+	* sysprof-module.c (page_readable): New function to check if the
+	page is readable before reading. Noop on kernel <= 2.6.11
+
+	* sysprof-module.c (get_mm, put_mm): New functions to confine
+	#ifdefs. 
+
+Sat Apr 23 17:48:22 2005  Søren Sandmann  <sandmann@redhat.com>
+
+	* Makefile (MODCFLAGS): Disable optimization as I suspect
+	the oops is related to miscompilation.
+
 Fri Apr 22 00:09:16 2005  Soeren Sandmann  <sandmann@redhat.com>
 
 	* sysprof-module.c (read_user_space): On >= 2.6.11 check that the
diff --git a/Makefile b/Makefile
index 5f7fc2df..d87da903 100644
--- a/Makefile
+++ b/Makefile
@@ -14,7 +14,7 @@ BINARY    := sysprof
 MODULE    := sysprof-module
 KDIR      := /lib/modules/$(shell uname -r)/build
 INCLUDE   := -isystem $(KDIR)/include
-MODCFLAGS := -O2 -DMODULE -D__KERNEL__ -Wall ${INCLUDE}
+MODCFLAGS := -DMODULE -D__KERNEL__ -Wall ${INCLUDE}
 MODULE    := sysprof-module
 
 all: check $(BINARY) $(MODULE).o
diff --git a/sysprof-module.c b/sysprof-module.c
index bef47f40..e899fb38 100644
--- a/sysprof-module.c
+++ b/sysprof-module.c
@@ -72,29 +72,50 @@ struct userspace_reader
  * Source/target buffer must be kernel space, 
  * Do not walk the page table directly, use get_user_pages
  */
- 
+
+static struct mm_struct *
+get_mm (struct task_struct *tsk)
+{
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,9)
+	struct mm_struct *mm;
+	
+	task_lock (tsk);
+	mm = tsk->mm;
+	task_unlock (tsk);
+
+	return mm;
+#else
+	return get_task_mm (tsk);
+#endif
+}
+
+static void
+put_mm (struct mm_struct *mm)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,9)
+	mmput(mm);
+#endif
+}
+
 static int
-x_access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write)
+x_access_process_vm (struct task_struct *tsk,
+		     unsigned long addr,
+		     void *buf, int len, int write)
 {
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	struct page *page;
 	void *old_buf = buf;
 
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,9)
-	task_lock (tsk);
-	mm = tsk->mm;
-	task_unlock (tsk);
-#else
-	mm = get_task_mm (tsk);
-#endif
+	mm = get_mm (tsk);
 	
 	if (!mm)
 		return 0;
 
 	down_read(&mm->mmap_sem);
 	/* ignore errors, just check how much was sucessfully transfered */
-	while (len) {
+	while (len)
+	{
 		int bytes, ret, offset;
 		void *maddr;
 
@@ -131,9 +152,7 @@ x_access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int
 	}
 	up_read(&mm->mmap_sem);
 
-#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,9)
-	mmput(mm);
-#endif
+	put_mm (mm);
 	
 	return buf - old_buf;
 }
@@ -150,6 +169,27 @@ init_userspace_reader (userspace_reader *reader,
 	return 1;
 }
 
+static int
+page_readable (userspace_reader *reader, unsigned long address)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION (2,6,11)
+		struct mm_struct *mm;
+		int result = 1;
+
+		mm = get_mm (reader->task);
+
+		if (!mm)
+			return 0;
+		
+		if (!check_user_page_readable (reader->task->mm, address))
+			result = 0;
+
+		put_mm (mm);
+
+		return result;
+#endif
+}
+
 static int
 read_user_space (userspace_reader *reader,
 		 unsigned long address,
@@ -158,11 +198,10 @@ read_user_space (userspace_reader *reader,
 	unsigned long cache_address = reader->cache_address;
 	int index, r;
 
-	if (!cache_address || cache_address != (address & PAGE_MASK)) {
-#if LINUX_VERSION_CODE >= KERNEL_VERSION (2,6,11)
-		if (!check_user_page_readable (reader->task->mm, address))
+	if (!cache_address || cache_address != (address & PAGE_MASK))
+	{
+		if (!page_readable (reader, address))
 			return 0;
-#endif
 		
 		cache_address = address & PAGE_MASK;
 
@@ -240,7 +279,7 @@ generate_stack_trace(struct task_struct *task,
 	if (init_userspace_reader (&reader, task))
 	{
 		while (i < SYSPROF_MAX_ADDRESSES &&
-		       read_frame (&reader, addr, &frame)  &&
+		       read_frame (&reader, addr, &frame) &&
 		       addr < START_OF_STACK && addr >= regs->esp)
 		{
 			trace->addresses[i++] = (void *)frame.return_address;