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Subject[PATCH] task_struct + kernel stack colouring ...

This patch implement task_struct plus kernel stack colouring for the x86
CPU family, and it can be easily adapted for other architectures.
The slab allocator for task_struct's ( Manfred ) is cacheline aligned and
gives us a free colouring w/out any other intervention.
The kernel stack frame jittering is done inside arch/??/kernel/process.c
and right now uses 8 colours ( STACK_COLOUR_BITS == 3 ).
The task_struct pointer is kept at the stack base for a fast seek.
The patch is briefly described here :

http://www.xmailserver.org/linux-patches/misc.html#TskStackCol



- Davide



[diffstat]
arch/i386/kernel/entry.S | 7 ++---
arch/i386/kernel/head.S | 2 -
arch/i386/kernel/init_task.c | 14 ++++++++--
arch/i386/kernel/irq.c | 2 -
arch/i386/kernel/process.c | 58 +++++++++++++++++++++++++++++++++++++++++--
arch/i386/kernel/smpboot.c | 2 -
arch/i386/kernel/traps.c | 2 -
arch/i386/lib/getuser.S | 3 ++
include/asm-i386/current.h | 6 ++--
include/asm-i386/hw_irq.h | 3 +-
include/asm-i386/processor.h | 21 ++++++++++-----
include/linux/sched.h | 16 ++++++++++-
init/main.c | 6 ++++
kernel/ksyms.c | 2 -
14 files changed, 118 insertions, 26 deletions



diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/entry.S linux-2.5.0.sstc/arch/i386/kernel/entry.S
--- linux-2.5.0.vanilla/arch/i386/kernel/entry.S Fri Nov 2 17:18:49 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/entry.S Sun Dec 2 16:34:15 2001
@@ -130,7 +130,8 @@

#define GET_CURRENT(reg) \
movl $-8192, reg; \
- andl %esp, reg
+ andl %esp, reg; \
+ movl (reg), reg;

ENTRY(lcall7)
pushfl # We get a different stack layout with call gates,
@@ -144,7 +145,7 @@
movl %ecx,CS(%esp) #
movl %esp,%ebx
pushl %ebx
- andl $-8192,%ebx # GET_CURRENT
+ GET_CURRENT(%ebx)
movl exec_domain(%ebx),%edx # Get the execution domain
movl 4(%edx),%edx # Get the lcall7 handler for the domain
pushl $0x7
@@ -165,7 +166,7 @@
movl %ecx,CS(%esp) #
movl %esp,%ebx
pushl %ebx
- andl $-8192,%ebx # GET_CURRENT
+ GET_CURRENT(%ebx)
movl exec_domain(%ebx),%edx # Get the execution domain
movl 4(%edx),%edx # Get the lcall7 handler for the domain
pushl $0x27
diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/head.S linux-2.5.0.sstc/arch/i386/kernel/head.S
--- linux-2.5.0.vanilla/arch/i386/kernel/head.S Wed Jun 20 11:00:53 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/head.S Sun Dec 2 18:17:15 2001
@@ -320,7 +320,7 @@
ret

ENTRY(stack_start)
- .long SYMBOL_NAME(init_task_union)+8192
+ .long SYMBOL_NAME(init_ts)+8192
.long __KERNEL_DS

/* This is the default interrupt "handler" :-) */
diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/init_task.c linux-2.5.0.sstc/arch/i386/kernel/init_task.c
--- linux-2.5.0.vanilla/arch/i386/kernel/init_task.c Mon Sep 17 15:29:09 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/init_task.c Sun Dec 2 21:49:14 2001
@@ -18,9 +18,17 @@
* way process stacks are handled. This is done by having a special
* "init_task" linker map entry..
*/
-union task_union init_task_union
- __attribute__((__section__(".data.init_task"))) =
- { INIT_TASK(init_task_union.task) };
+struct init_task_struct init_ts __attribute__((__section__(".data.init_task"))) =
+{
+ stack: {(unsigned long) &init_ts.ftsk.task, 0, },
+ ftsk: {
+ task: INIT_TASK(init_ts.ftsk.task),
+ count: ATOMIC_INIT(1),
+ stack: (unsigned long) init_ts.stack,
+ stack_top: (unsigned long) init_ts.stack + INIT_TASK_SIZE
+ }
+};
+

/*
* per-CPU TSS segments. Threads are completely 'soft' on Linux,
diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/irq.c linux-2.5.0.sstc/arch/i386/kernel/irq.c
--- linux-2.5.0.vanilla/arch/i386/kernel/irq.c Thu Oct 25 13:53:46 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/irq.c Sun Dec 2 17:50:26 2001
@@ -223,7 +223,7 @@
continue;
}
esp &= ~(THREAD_SIZE-1);
- esp += sizeof(struct task_struct);
+ esp += sizeof(long);
show_stack((void*)esp);
}
printk("\nCPU %d:",cpu);
diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/process.c linux-2.5.0.sstc/arch/i386/kernel/process.c
--- linux-2.5.0.vanilla/arch/i386/kernel/process.c Thu Oct 4 18:42:54 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/process.c Sun Dec 2 21:50:44 2001
@@ -575,18 +575,27 @@
#define savesegment(seg,value) \
asm volatile("movl %%" #seg ",%0":"=m" (*(int *)&(value)))

+#define STACK_COLOUR_BITS 3
+#define STACK_COLOUR_MASK ((1 << STACK_COLOUR_BITS) - 1)
+#define STACK_SHIFT_BITS (PAGE_SHIFT + 1)
+
+static inline unsigned long get_stack_jitter(struct task_struct *p)
+{
+ return ((TSK_TO_KSTACK(p) >> STACK_SHIFT_BITS) & STACK_COLOUR_MASK) << L1_CACHE_SHIFT;
+}
+
int copy_thread(int nr, unsigned long clone_flags, unsigned long esp,
unsigned long unused,
struct task_struct * p, struct pt_regs * regs)
{
struct pt_regs * childregs;

- childregs = ((struct pt_regs *) (THREAD_SIZE + (unsigned long) p)) - 1;
+ childregs = ((struct pt_regs *) (THREAD_SIZE + TSK_TO_KSTACK(p) - get_stack_jitter(p))) - 1;
struct_cpy(childregs, regs);
childregs->eax = 0;
childregs->esp = esp;

- p->thread.esp = (unsigned long) childregs;
+ p->thread.esp = TSK_KSTACK_TOP(p) = (unsigned long) childregs;
p->thread.esp0 = (unsigned long) (childregs+1);

p->thread.eip = (unsigned long) ret_from_fork;
@@ -821,3 +830,48 @@
}
#undef last_sched
#undef first_sched
+
+
+/*
+ * this part should be moved in a system independent section.
+ */
+static kmem_cache_t * tsk_cache;
+
+void __init init_tsk_allocator(void)
+{
+ tsk_cache = kmem_cache_create("task_struct_cache",
+ sizeof(struct full_task_struct),
+ 0,
+ SLAB_HWCACHE_ALIGN,
+ NULL, NULL);
+ if (!tsk_cache)
+ panic("Cannot create task struct cache");
+
+}
+
+struct task_struct *alloc_task_struct(void)
+{
+ struct full_task_struct *f = (struct full_task_struct *) kmem_cache_alloc(tsk_cache, GFP_KERNEL);
+
+ if (!f)
+ return NULL;
+ f->stack = __get_free_pages(GFP_KERNEL, 1);
+ if (!f->stack) {
+ kmem_cache_free(tsk_cache, f);
+ return NULL;
+ }
+ atomic_set(&f->count, 1);
+ *((struct task_struct **) f->stack) = (struct task_struct *) f;
+ return (struct task_struct *) f;
+}
+
+void free_task_struct(struct task_struct *p)
+{
+ struct full_task_struct *f = (struct full_task_struct *) p;
+
+ if (atomic_dec_and_test(&f->count)) {
+ free_pages(f->stack, 1);
+ kmem_cache_free(tsk_cache, f);
+ }
+}
+
diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/smpboot.c linux-2.5.0.sstc/arch/i386/kernel/smpboot.c
--- linux-2.5.0.vanilla/arch/i386/kernel/smpboot.c Wed Nov 21 10:35:48 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/smpboot.c Sun Dec 2 19:31:23 2001
@@ -815,7 +815,7 @@

/* So we see what's up */
printk("Booting processor %d/%d eip %lx\n", cpu, apicid, start_eip);
- stack_start.esp = (void *) (1024 + PAGE_SIZE + (char *)idle);
+ stack_start.esp = (void *) (THREAD_SIZE + (char *) TSK_TO_KSTACK(idle));

/*
* This grunge runs the startup process for
diff -Nru linux-2.5.0.vanilla/arch/i386/kernel/traps.c linux-2.5.0.sstc/arch/i386/kernel/traps.c
--- linux-2.5.0.vanilla/arch/i386/kernel/traps.c Sun Sep 30 12:26:08 2001
+++ linux-2.5.0.sstc/arch/i386/kernel/traps.c Sun Dec 2 19:37:15 2001
@@ -209,7 +209,7 @@
printk("ds: %04x es: %04x ss: %04x\n",
regs->xds & 0xffff, regs->xes & 0xffff, ss);
printk("Process %s (pid: %d, stackpage=%08lx)",
- current->comm, current->pid, 4096+(unsigned long)current);
+ current->comm, current->pid, TSK_TO_KSTACK(current));
/*
* When in-kernel, we also print out the stack and code at the
* time of the fault..
diff -Nru linux-2.5.0.vanilla/arch/i386/lib/getuser.S linux-2.5.0.sstc/arch/i386/lib/getuser.S
--- linux-2.5.0.vanilla/arch/i386/lib/getuser.S Mon Jan 12 13:42:52 1998
+++ linux-2.5.0.sstc/arch/i386/lib/getuser.S Sun Dec 2 16:34:15 2001
@@ -29,6 +29,7 @@
__get_user_1:
movl %esp,%edx
andl $0xffffe000,%edx
+ movl (%edx),%edx
cmpl addr_limit(%edx),%eax
jae bad_get_user
1: movzbl (%eax),%edx
@@ -42,6 +43,7 @@
movl %esp,%edx
jc bad_get_user
andl $0xffffe000,%edx
+ movl (%edx),%edx
cmpl addr_limit(%edx),%eax
jae bad_get_user
2: movzwl -1(%eax),%edx
@@ -55,6 +57,7 @@
movl %esp,%edx
jc bad_get_user
andl $0xffffe000,%edx
+ movl (%edx),%edx
cmpl addr_limit(%edx),%eax
jae bad_get_user
3: movl -3(%eax),%edx
diff -Nru linux-2.5.0.vanilla/include/asm-i386/current.h linux-2.5.0.sstc/include/asm-i386/current.h
--- linux-2.5.0.vanilla/include/asm-i386/current.h Fri Aug 14 16:35:22 1998
+++ linux-2.5.0.sstc/include/asm-i386/current.h Sun Dec 2 16:34:15 2001
@@ -5,9 +5,9 @@

static inline struct task_struct * get_current(void)
{
- struct task_struct *current;
- __asm__("andl %%esp,%0; ":"=r" (current) : "0" (~8191UL));
- return current;
+ unsigned long *tskptr;
+ __asm__("andl %%esp,%0; ":"=r" (tskptr) : "0" (~8191UL));
+ return (struct task_struct *) *tskptr;
}

#define current get_current()
diff -Nru linux-2.5.0.vanilla/include/asm-i386/hw_irq.h linux-2.5.0.sstc/include/asm-i386/hw_irq.h
--- linux-2.5.0.vanilla/include/asm-i386/hw_irq.h Thu Nov 22 11:46:18 2001
+++ linux-2.5.0.sstc/include/asm-i386/hw_irq.h Sun Dec 2 22:22:06 2001
@@ -115,7 +115,8 @@

#define GET_CURRENT \
"movl %esp, %ebx\n\t" \
- "andl $-8192, %ebx\n\t"
+ "andl $-8192, %ebx\n\t" \
+ "movl (%ebx), %ebx\n\t"

/*
* SMP has a few special interrupts for IPI messages
diff -Nru linux-2.5.0.vanilla/include/asm-i386/processor.h linux-2.5.0.sstc/include/asm-i386/processor.h
--- linux-2.5.0.vanilla/include/asm-i386/processor.h Thu Nov 22 11:46:19 2001
+++ linux-2.5.0.sstc/include/asm-i386/processor.h Sun Dec 2 22:22:06 2001
@@ -14,6 +14,8 @@
#include <asm/types.h>
#include <asm/sigcontext.h>
#include <asm/cpufeature.h>
+#include <asm/ptrace.h>
+#include <linux/kernel.h>
#include <linux/cache.h>
#include <linux/config.h>
#include <linux/threads.h>
@@ -444,16 +446,21 @@
}

unsigned long get_wchan(struct task_struct *p);
-#define KSTK_EIP(tsk) (((unsigned long *)(4096+(unsigned long)(tsk)))[1019])
-#define KSTK_ESP(tsk) (((unsigned long *)(4096+(unsigned long)(tsk)))[1022])
+#define KSTK_EIP(tsk) ((unsigned long *) TSK_KSTACK_TOP(tsk))[EIP]
+#define KSTK_ESP(tsk) ((unsigned long *) TSK_KSTACK_TOP(tsk))[UESP]
+

#define THREAD_SIZE (2*PAGE_SIZE)
-#define alloc_task_struct() ((struct task_struct *) __get_free_pages(GFP_KERNEL,1))
-#define free_task_struct(p) free_pages((unsigned long) (p), 1)
-#define get_task_struct(tsk) atomic_inc(&virt_to_page(tsk)->count)

-#define init_task (init_task_union.task)
-#define init_stack (init_task_union.stack)
+extern void init_tsk_allocator(void);
+extern struct task_struct *alloc_task_struct(void);
+extern void free_task_struct(struct task_struct *p);
+
+#define get_task_struct(tsk) atomic_inc(&TSK_COUNT(tsk))
+
+#define init_task (init_ts.ftsk.task)
+#define init_stack (init_ts.stack)
+

struct microcode {
unsigned int hdrver;
diff -Nru linux-2.5.0.vanilla/include/linux/sched.h linux-2.5.0.sstc/include/linux/sched.h
--- linux-2.5.0.vanilla/include/linux/sched.h Thu Nov 22 11:46:19 2001
+++ linux-2.5.0.sstc/include/linux/sched.h Sun Dec 2 22:22:06 2001
@@ -507,12 +507,24 @@
# define INIT_TASK_SIZE 2048*sizeof(long)
#endif

-union task_union {
+#define TSK_TO_KSTACK(p) (((struct full_task_struct *) (p))->stack)
+#define TSK_KSTACK_TOP(p) (((struct full_task_struct *) (p))->stack_top)
+#define TSK_COUNT(p) (((struct full_task_struct *) (p))->count)
+
+struct full_task_struct {
struct task_struct task;
+ atomic_t count;
+ unsigned long stack;
+ unsigned long stack_top;
+};
+
+struct init_task_struct {
unsigned long stack[INIT_TASK_SIZE/sizeof(long)];
+ struct full_task_struct ftsk;
};

-extern union task_union init_task_union;
+extern struct init_task_struct init_ts;
+

extern struct mm_struct init_mm;
extern struct task_struct *init_tasks[NR_CPUS];
diff -Nru linux-2.5.0.vanilla/init/main.c linux-2.5.0.sstc/init/main.c
--- linux-2.5.0.vanilla/init/main.c Fri Nov 9 14:15:00 2001
+++ linux-2.5.0.sstc/init/main.c Sun Dec 2 18:04:08 2001
@@ -594,6 +594,12 @@
mempages = num_physpages;

fork_init(mempages);
+ /*
+ * task_struct/stack colouring is implemented only for x86 right now.
+ */
+#ifdef __i386__
+ init_tsk_allocator();
+#endif
proc_caches_init();
vfs_caches_init(mempages);
buffer_init(mempages);
diff -Nru linux-2.5.0.vanilla/kernel/ksyms.c linux-2.5.0.sstc/kernel/ksyms.c
--- linux-2.5.0.vanilla/kernel/ksyms.c Wed Nov 21 14:07:25 2001
+++ linux-2.5.0.sstc/kernel/ksyms.c Sun Dec 2 18:11:17 2001
@@ -548,7 +548,7 @@

/* init task, for moving kthread roots - ought to export a function ?? */

-EXPORT_SYMBOL(init_task_union);
+EXPORT_SYMBOL(init_ts);

EXPORT_SYMBOL(tasklist_lock);
EXPORT_SYMBOL(pidhash);



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