Commit 0a425405 authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Andi Kleen
Browse files

[PATCH] Add the canary field to the PDA area and the task struct

This patch adds the per thread cookie field to the task struct and the PDA.
Also it makes sure that the PDA value gets the new cookie value at context
switch, and that a new task gets a new cookie at task creation time.
Signed-off-by: default avatarArjan van Ven <>
Signed-off-by: default avatarIngo Molnar <>
Signed-off-by: default avatarAndi Kleen <>
CC: Andi Kleen <>
parent b62a5c74
......@@ -625,6 +625,14 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
task_stack_page(next_p) + THREAD_SIZE - PDA_STACKOFFSET);
write_pda(stack_canary, next_p->stack_canary);
* Build time only check to make sure the stack_canary is at
* offset 40 in the pda; this is a gcc ABI requirement
BUILD_BUG_ON(offsetof(struct x8664_pda, stack_canary) != 40);
* Now maybe reload the debug registers and handle I/O bitmaps
......@@ -16,7 +16,12 @@ struct x8664_pda {
unsigned long oldrsp; /* 24 user rsp for system call */
int irqcount; /* 32 Irq nesting counter. Starts with -1 */
int cpunumber; /* 36 Logical CPU number */
char *irqstackptr; /* 40 top of irqstack */
unsigned long stack_canary; /* 40 stack canary value */
/* gcc-ABI: this canary MUST be at
offset 40!!! */
char *irqstackptr;
int nodenumber; /* number of current node */
unsigned int __softirq_pending;
unsigned int __nmi_count; /* number of NMI on this CPUs */
......@@ -819,6 +819,11 @@ struct task_struct {
unsigned did_exec:1;
pid_t pid;
pid_t tgid;
/* Canary value for the -fstack-protector gcc feature */
unsigned long stack_canary;
* pointers to (original) parent process, youngest child, younger sibling,
* older sibling, respectively. (p->father can be replaced with
......@@ -45,6 +45,7 @@
#include <linux/cn_proc.h>
#include <linux/delayacct.h>
#include <linux/taskstats_kern.h>
#include <linux/random.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
......@@ -175,6 +176,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig)
tsk->thread_info = ti;
setup_thread_stack(tsk, orig);
tsk->stack_canary = get_random_int();
/* One for us, one for whoever does the "release_task()" (usually parent) */
atomic_set(&tsk->fs_excl, 0);
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