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Subject[PATCH 1/2] mm: Fix task_nommu build regression in linux-next
Date
Commit b7b2a0afacada237005068294cb0ccc49d32889e resulted in a build
failure for nommu builds:

fs/built-in.o: In function `nommu_vma_show':
task_nommu.c:(.text+0x564a0): undefined reference to `vm_is_stack'
make[1]: *** [.tmp_vmlinux1] Error 1

Fix is to provide definitions of vm_is_stack() and
vm_is_stack_for_task() for nommu as well. This patch also adds an
explicit include of sched.h based on observations and patch submission
by Paul Gortmaker <paul.gortmaker@windriver.com>:

https://lkml.org/lkml/2012/3/5/326

Signed-off-by: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
---
mm/memory.c | 1 +
mm/nommu.c | 40 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 2533d9f..0ca7fe6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -57,6 +57,7 @@
#include <linux/swapops.h>
#include <linux/elf.h>
#include <linux/gfp.h>
+#include <linux/sched.h>

#include <asm/io.h>
#include <asm/pgalloc.h>
diff --git a/mm/nommu.c b/mm/nommu.c
index b982290..5a5c3fc 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -29,6 +29,7 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
+#include <linux/sched.h>

#include <asm/uaccess.h>
#include <asm/tlb.h>
@@ -2089,3 +2090,42 @@ int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
up_write(&nommu_region_sem);
return 0;
}
+
+/* Check if the vma is being used as a stack by this task */
+static int vm_is_stack_for_task(struct task_struct *t,
+ struct vm_area_struct *vma)
+{
+ return (vma->vm_start <= KSTK_ESP(t) && vma->vm_end >= KSTK_ESP(t));
+}
+
+/*
+ * Check if the vma is being used as a stack.
+ * If is_group is non-zero, check in the entire thread group or else
+ * just check in the current task. Returns the pid of the task that
+ * the vma is stack for.
+ */
+pid_t vm_is_stack(struct task_struct *task,
+ struct vm_area_struct *vma, int in_group)
+{
+ pid_t ret = 0;
+
+ if (vm_is_stack_for_task(task, vma))
+ return task->pid;
+
+ if (in_group) {
+ struct task_struct *t;
+ rcu_read_lock();
+ t = list_first_entry_rcu(&task->thread_group,
+ struct task_struct, thread_group);
+ do {
+ if (vm_is_stack_for_task(t, vma)) {
+ ret = t->pid;
+ goto done;
+ }
+ } while_each_thread(task, t);
+done:
+ rcu_read_unlock();
+ }
+
+ return ret;
+}
--
1.7.7.4


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