[PATCH v3 2/3] sched: Add helper for task stack page overrun checking

From: Aaron Tomlin
Date: Thu Sep 11 2014 - 11:44:14 EST


This facility is used in a few places so let's introduce
a helper function to improve code readability.

Signed-off-by: Aaron Tomlin <atomlin@xxxxxxxxxx>
---
arch/powerpc/mm/fault.c | 4 +---
arch/x86/mm/fault.c | 4 +---
include/linux/sched.h | 2 ++
kernel/trace/trace_stack.c | 2 +-
4 files changed, 5 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 35d0760c..99b2f27 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -507,7 +507,6 @@ bail:
void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
{
const struct exception_table_entry *entry;
- unsigned long *stackend;

/* Are we prepared to handle this fault? */
if ((entry = search_exception_tables(regs->nip)) != NULL) {
@@ -536,8 +535,7 @@ void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
regs->nip);

- stackend = end_of_stack(current);
- if (*stackend != STACK_END_MAGIC)
+ if (task_stack_end_corrupted(current))
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");

die("Kernel access of bad area", regs, sig);
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index bc23a70..6240bc7 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -648,7 +648,6 @@ no_context(struct pt_regs *regs, unsigned long error_code,
unsigned long address, int signal, int si_code)
{
struct task_struct *tsk = current;
- unsigned long *stackend;
unsigned long flags;
int sig;

@@ -708,8 +707,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,

show_fault_oops(regs, error_code, address);

- stackend = end_of_stack(tsk);
- if (*stackend != STACK_END_MAGIC)
+ if (task_stack_end_corrupted(tsk))
printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");

tsk->thread.cr2 = address;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 7ef34b7..a80e35d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2615,6 +2615,8 @@ static inline unsigned long *end_of_stack(struct task_struct *p)
}

#endif
+#define task_stack_end_corrupted(task) \
+ (*(end_of_stack(task)) != STACK_END_MAGIC)

static inline int object_is_on_stack(void *obj)
{
diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 1636e41..16eddb3 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -170,7 +170,7 @@ check_stack(unsigned long ip, unsigned long *stack)
i++;
}

- if (*end_of_stack(current) != STACK_END_MAGIC) {
+ if (task_stack_end_corrupted(current)) {
print_max_stack();
BUG();
}
--
1.9.3

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