From: Josh Stone <jistone@redhat.com>
Date: Fri Oct 12 14:45:55 2012 -0700
Subject: PR14172: Fix for kernels without VM_EXECUTABLE
Git-commit: 529c7eaed7360776b596af31c86d4e4712a1a3db
    
    We were using VM_EXECUTABLE in two ways:
    
    1) In task_finder for locating the process executable among all the
    vmas.  Since around 2.6.26 there is also mm->exe_file, which will serve
    this purpose just fine.
    
    2) In uprobes to avoid relocation offset for semaphores in ET_EXEC
    files.  This is actually incorrect, but harmless, because the callback
    path for ET_EXEC targets already sets relocation=offset=0 anyway.  So we
    can just remove the special case for VM_EXECUTABLE altogether.
    
    * runtime/task_finder_vma.c (stap_find_exe_file): New, locate the
      process executable either by VM_EXECUTABLE or mm->exe_file.
    * runtime/linux/task_finder.c (__stp_get_mm_path): Use stap_find_exe_file.
    * runtime/linux/task_finder2.c (__stp_get_mm_path): Ditto.
    * runtime/linux/uprobes-common.c (stap_uprobe_change_plus): Don't
      special case for VM_EXECUTABLE (and add a comment why).
    * runtime/linux/uprobes-inode.c (stapiu_change_plus): Ditto.
      (stapiu_get_task_inode): Use stap_find_exe_file.

diff --git a/runtime/linux/runtime.h b/runtime/linux/runtime.h
index e167be6..783f199 100644
--- a/runtime/linux/runtime.h
+++ b/runtime/linux/runtime.h
@@ -163,13 +163,13 @@ void *kallsyms_task_work_cancel;
 #include "copy.c"
 #include "regs.c"
 #include "regs-ia64.c"
+#include "sym.c"
 
 #if (defined(CONFIG_UTRACE) || defined(STAPCONF_UTRACE_VIA_TRACEPOINTS))
 #define HAVE_TASK_FINDER
 #include "task_finder.c"
 #endif
 
-#include "sym.c"
 #ifdef STP_PERFMON
 #include "perf.c"
 #endif
diff --git a/runtime/linux/task_finder.c b/runtime/linux/task_finder.c
index 2b1e22f..d718e80 100644
--- a/runtime/linux/task_finder.c
+++ b/runtime/linux/task_finder.c
@@ -440,7 +440,7 @@ __stp_task_finder_cleanup(void)
 static char *
 __stp_get_mm_path(struct mm_struct *mm, char *buf, int buflen)
 {
-	struct vm_area_struct *vma;
+	struct file *vm_file;
 	char *rc = NULL;
 
 	// The down_read() function can sleep, so we'll call
@@ -451,17 +451,12 @@ __stp_get_mm_path(struct mm_struct *mm, char *buf, int buflen)
 		return ERR_PTR(-ENOENT);
 	}
 
-	vma = mm->mmap;
-	while (vma) {
-		if ((vma->vm_flags & VM_EXECUTABLE) && vma->vm_file)
-			break;
-		vma = vma->vm_next;
-	}
-	if (vma) {
+	vm_file = stap_find_exe_file(mm);
+	if (vm_file) {
 #ifdef STAPCONF_DPATH_PATH
-		rc = d_path(&(vma->vm_file->f_path), buf, buflen);
+		rc = d_path(&(vm_file->f_path), buf, buflen);
 #else
-		rc = d_path(vma->vm_file->f_dentry, vma->vm_file->f_vfsmnt,
+		rc = d_path(vm_file->f_dentry, vm_file->f_vfsmnt,
 			    buf, buflen);
 #endif
 	}
diff --git a/runtime/linux/task_finder2.c b/runtime/linux/task_finder2.c
index 680b428..5cee195 100644
--- a/runtime/linux/task_finder2.c
+++ b/runtime/linux/task_finder2.c
@@ -425,7 +425,7 @@ __stp_task_finder_cleanup(void)
 static char *
 __stp_get_mm_path(struct mm_struct *mm, char *buf, int buflen)
 {
-	struct vm_area_struct *vma;
+	struct file *vm_file;
 	char *rc = NULL;
 
 	// The down_read() function can sleep, so we'll call
@@ -436,17 +436,12 @@ __stp_get_mm_path(struct mm_struct *mm, char *buf, int buflen)
 		return ERR_PTR(-ENOENT);
 	}
 
-	vma = mm->mmap;
-	while (vma) {
-		if ((vma->vm_flags & VM_EXECUTABLE) && vma->vm_file)
-			break;
-		vma = vma->vm_next;
-	}
-	if (vma) {
+	vm_file = stap_find_exe_file(mm);
+	if (vm_file) {
 #ifdef STAPCONF_DPATH_PATH
-		rc = d_path(&(vma->vm_file->f_path), buf, buflen);
+		rc = d_path(&(vm_file->f_path), buf, buflen);
 #else
-		rc = d_path(vma->vm_file->f_dentry, vma->vm_file->f_vfsmnt,
+		rc = d_path(vm_file->f_dentry, vm_file->f_vfsmnt,
 			    buf, buflen);
 #endif
 	}
diff --git a/runtime/linux/uprobes-common.c b/runtime/linux/uprobes-common.c
index 64b62cc..cdfb5a6 100644
--- a/runtime/linux/uprobes-common.c
+++ b/runtime/linux/uprobes-common.c
@@ -77,13 +77,10 @@ static int stap_uprobe_change_plus (struct task_struct *tsk, unsigned long reloc
 
     sdt_sem_pid = (sups->return_p ? sup->urp.u.pid : sup->up.pid);
     if (sups->sdt_sem_offset && (sdt_sem_pid != tsk->tgid || sup->sdt_sem_address == 0)) {
-      /* If the probe is in the executable itself, the offset *is* the address. */
-      if (vm_flags & VM_EXECUTABLE) {
-        sup->sdt_sem_address = relocation + sups->sdt_sem_offset;
-      }
-      else {
-        sup->sdt_sem_address = (relocation - offset) + sups->sdt_sem_offset;
-      }
+      /* If the probe is in an ET_EXEC binary, then the sdt_sem_offset already
+       * is a real address.  But stap_uprobe_process_found calls us in this
+       * case with relocation=offset=0, so we don't have to worry about it.  */
+      sup->sdt_sem_address = (relocation - offset) + sups->sdt_sem_offset;
     } /* sdt_sem_offset */
     if (slotted_p) {
       struct stap_uprobe *sup = & stap_uprobes[i];
diff --git a/runtime/linux/uprobes-inode.c b/runtime/linux/uprobes-inode.c
index 578123c..9d4d867 100644
--- a/runtime/linux/uprobes-inode.c
+++ b/runtime/linux/uprobes-inode.c
@@ -406,9 +406,14 @@ stapiu_change_plus(struct stapiu_target* target, struct task_struct *task,
 		if (!p->tgid) {
 			p->tgid = task->tgid;
 			p->relocation = relocation;
-			p->base = relocation;
-			if (!(vm_flags & VM_EXECUTABLE))
-				p->base -= offset;
+
+                        /* The base is used for relocating semaphores.  If the
+                         * probe is in an ET_EXEC binary, then that offset
+                         * already is a real address.  But stapiu_process_found
+                         * calls us in this case with relocation=offset=0, so
+                         * we don't have to worry about it.  */
+			p->base = relocation - offset;
+
 			list_add(&p->target_process, &target->processes);
 			break;
 		}
@@ -491,7 +496,7 @@ static struct inode *
 stapiu_get_task_inode(struct task_struct *task)
 {
 	struct mm_struct *mm;
-	struct vm_area_struct *vma;
+	struct file* vm_file;
 	struct inode *inode = NULL;
 
 	// Grab the inode associated with the task.
@@ -507,15 +512,9 @@ stapiu_get_task_inode(struct task_struct *task)
 	}
 
 	down_read(&mm->mmap_sem);
-	vma = mm->mmap;
-	while (vma) {
-		if ((vma->vm_flags & VM_EXECUTABLE) && vma->vm_file
-		    && vma->vm_file->f_path.dentry != NULL) {
-			inode = vma->vm_file->f_path.dentry->d_inode;
-			break;
-		}
-		vma = vma->vm_next;
-	}
+	vm_file = stap_find_exe_file(mm);
+	if (vm_file && vm_file->f_path.dentry)
+		inode = vm_file->f_path.dentry->d_inode;
 
 	up_read(&mm->mmap_sem);
 	return inode;
diff --git a/runtime/task_finder_vma.c b/runtime/task_finder_vma.c
index 7c872ba..1c1bfbc 100644
--- a/runtime/task_finder_vma.c
+++ b/runtime/task_finder_vma.c
@@ -371,3 +371,21 @@ stap_drop_vma_maps(struct task_struct *tsk)
 	write_unlock_irqrestore(&__stp_tf_vma_lock, flags);
 	return 0;
 }
+
+/* Find the main executable for this mm.
+ * NB: mmap_sem should be held already. */
+static struct file*
+stap_find_exe_file(struct mm_struct* mm)
+{
+	/* VM_EXECUTABLE was killed in kernel commit e9714acf, but in kernels
+	 * that new we can just use mm->exe_file anyway.  (PR14172)  */
+#ifdef VM_EXECUTABLE
+	struct vm_area_struct *vma;
+	for (vma = mm->mmap; vma; vma = vma->vm_next)
+		if ((vma->vm_flags & VM_EXECUTABLE) && vma->vm_file)
+			return vma->vm_file;
+	return NULL;
+#else
+	return mm->exe_file;
+#endif
+}