i386 stack handling updates
cover i386 stack handling updates
This is a series of patches to improve i386 stack handling in several manners. The net result is to improve system stability via IRQ stacks while remaining memory efficient and to improve stack debugging.
[1/3] dynamically allocate irq stacks
This conserves memory while using IRQ stacks.
[2/3] make irqstacks unconditional, while retaining 4/8k stack selection
This makes IRQ stacks the standard for mainline.
[3/3] DEBUG_STACK option enabling vmalloc()'ed stacks and __pa checks
Stack debugging option using vmalloc() to establish guard pages.
-- wli
PATCH 1/3 dynamically allocate IRQ stacks
Dynamically allocate IRQ stacks in order to conserve memory when using IRQ stacks. cpu_possible_map is not now initialized in such a manner as to provide a meaningful indication of how many CPU's might be in the system, and features to appear in the sequel also require indirection, so they themselves are not allocatable as per_cpu variables, but rather only pointers to them.
arch/i386/kernel/irq.c +32 -15
@@ -17,9 +17,11 @@#include <linux/notifier.h> #include <linux/cpu.h> #include <linux/delay.h> +#include <linux/bootmem.h> #include <asm/apic.h> #include <asm/uaccess.h> +#include <asm/pgtable.h> DEFINE_PER_CPU (irq_cpustat_t, irq_stat)____cacheline_internodealigned_in_smp ;EXPORT_PER_CPU_SYMBOL (irq_stat);
@@ -56,8 +58,8 @@u32 stack[THREAD_SIZE /sizeof (u32)]; }; -static union irq_ctx *hardirq_ctx[NR_CPUS ]__read_mostly ; -static union irq_ctx *softirq_ctx[NR_CPUS ]__read_mostly ; +static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx); +static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);#endif /*
@@ -102,7 +104,7 @@#ifdef CONFIG_4KSTACKS curctx = (union irq_ctx *)current_thread_info (); - irqctx = hardirq_ctx[smp_processor_id ()]; + irqctx =per_cpu (hardirq_ctx,smp_processor_id ());/* * this is where we switch to the IRQ stack. However, if we are
@@ -150,11 +152,24 @@* These should really be __section__(".bss.page_aligned") as well, but * gcc's 3.0 and earlier don't handle that correctly. */ -static char softirq_stack[NR_CPUS * THREAD_SIZE] - __attribute__((__aligned__(THREAD_SIZE))); +static DEFINE_PER_CPU(char *, softirq_stack); +static DEFINE_PER_CPU(char *, hardirq_stack); -static char hardirq_stack[NR_CPUS * THREAD_SIZE] - __attribute__((__aligned__(THREAD_SIZE))); +static void *__init __alloc_irqstack (int cpu) +{ +if (!cpu) +return __alloc_bootmem (THREAD_SIZE ,THREAD_SIZE , +__pa (MAX_DMA_ADDRESS )); + +return (void *)__get_free_pages (GFP_KERNEL , +ilog2 (THREAD_SIZE /PAGE_SIZE )); +} + +static void __init alloc_irqstacks (int cpu) +{ +per_cpu (softirq_stack, cpu) =__alloc_irqstack (cpu); +per_cpu (hardirq_stack, cpu) =__alloc_irqstack (cpu); +}/* * allocate per-cpu stacks for hardirq and for softirq processing
@@ -163,34 +178,36 @@ {union irq_ctx *irqctx; -if (hardirq_ctx[cpu]) +if (per_cpu (hardirq_ctx, cpu))return ; - irqctx = (union irq_ctx *) &hardirq_stack[cpu*THREAD_SIZE ]; +alloc_irqstacks (cpu); + + irqctx = (union irq_ctx *)per_cpu (hardirq_stack, cpu); irqctx->tinfo.task =NULL ; irqctx->tinfo.exec_domain =NULL ; irqctx->tinfo.cpu = cpu; irqctx->tinfo.preempt_count =HARDIRQ_OFFSET ; irqctx->tinfo.addr_limit =MAKE_MM_SEG (0 ); - hardirq_ctx[cpu] = irqctx; +per_cpu (hardirq_ctx, cpu) = irqctx; - irqctx = (union irq_ctx *) &softirq_stack[cpu*THREAD_SIZE ]; + irqctx = (union irq_ctx *)per_cpu (softirq_stack, cpu); irqctx->tinfo.task =NULL ; irqctx->tinfo.exec_domain =NULL ; irqctx->tinfo.cpu = cpu; irqctx->tinfo.preempt_count =0 ; irqctx->tinfo.addr_limit =MAKE_MM_SEG (0 ); - softirq_ctx[cpu] = irqctx; +per_cpu (softirq_ctx, cpu) = irqctx;printk ("CPU %u irqstacks, hard=%p soft=%p\n" , - cpu,hardirq_ctx[cpu],softirq_ctx[cpu]); + cpu,per_cpu (hardirq_ctx, cpu),per_cpu (softirq_ctx, cpu)); }void irq_ctx_exit (int cpu) { - hardirq_ctx[cpu] =NULL ; +per_cpu (hardirq_ctx, cpu) =NULL ; } extern asmlinkage void __do_softirq(void);
@@ -209,7 +226,7 @@if (local_softirq_pending ()) { curctx =current_thread_info (); - irqctx = softirq_ctx[smp_processor_id ()]; + irqctx =per_cpu (softirq_ctx,smp_processor_id ()); irqctx->tinfo.task = curctx->task; irqctx->tinfo.previous_esp = current_stack_pointer;
PATCH 2/3 unconditional i386 IRQ stacks
IRQ stacks are a valuable stability feature. This patch makes them unconditional, as there is no circumstance under which they do not improve stability and they have no meaningful performance impact.
include/asm-i386/irq.h +3 -8
@@ -24,14 +24,9 @@# define ARCH_HAS_NMI_WATCHDOG /* See include/linux/nmi.h */ #endif -#ifdef CONFIG_4KSTACKS -extern void irq_ctx_init (int cpu); -extern void irq_ctx_exit (int cpu); -# define __ARCH_HAS_DO_SOFTIRQ -#else -# define irq_ctx_init (cpu) do { } while (0) -# define irq_ctx_exit (cpu) do { } while (0) -#endif +void irq_ctx_init (int ); +void irq_ctx_exit (int ); +#define __ARCH_HAS_DO_SOFTIRQ#ifdef CONFIG_IRQBALANCE extern int irqbalance_disable (char *str);
arch/i386/kernel/irq.c +0 -11
@@ -49,7 +49,6 @@#endif } -#ifdef CONFIG_4KSTACKS /* * per-CPU IRQ handling contexts (thread information and stack) */
@@ -60,7 +59,6 @@ static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx); static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx); -#endif /* * do_IRQ handles all normal device IRQ's (the special
@@ -73,10 +71,8 @@/* high bit used in ret_from_ code */ int irq = ~regs->orig_eax;struct irq_desc *desc = irq_desc + irq; -#ifdef CONFIG_4KSTACKS union irq_ctx *curctx, *irqctx;u32 *isp; -#endif if (unlikely ((unsigned )irq >=NR_IRQS )) { printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
@@ -100,9 +96,6 @@ } }#endif - -#ifdef CONFIG_4KSTACKS - curctx = (union irq_ctx *)current_thread_info (); irqctx =per_cpu (hardirq_ctx,smp_processor_id ());
@@ -138,7 +131,6 @@ : "memory", "cc" ); }else -#endif desc->handle_irq (irq, desc);irq_exit ();
@@ -146,8 +138,6 @@return 1 ; } -#ifdef CONFIG_4KSTACKS -/* * These should really be __section__(".bss.page_aligned") as well, but * gcc's 3.0 and earlier don't handle that correctly.
@@ -251,7 +241,6 @@ }EXPORT_SYMBOL (do_softirq); -#endif /* * Interrupt statistics:
PATCH 3/3 use vmalloc() to arrange guard pages for stacks
This patch introduces CONFIG_DEBUG_STACK, which vmalloc()'s task and IRQ stacks in order to establish guard pages. In such a manner any stack overflow that references pages immediately adjacent to the stack is immediately trapped with a fault, which precludes silent memory corruption or difficult-to-decipher failure modes resulting from stack corruption.
It furthermore adds a check to __pa() to catch drivers trying to DMA off the stack, which more generally flags incorrect attempts to use __pa() on vmallocspace addresses.
arch/i386/Kconfig.debug +10 -0
@@ -35,6 +35,16 @@ This option will slow down process creation somewhat. +config DEBUG_STACK + bool "Debug stack overflows" + depends on DEBUG_KERNEL + help + Allocates the stack physically discontiguously and from high + memory. Furthermore an unmapped guard page follows the stack, + which results in immediately trapping stack overflows instead + of silent corruption. This is not for end-users. It's intended + to trigger fatal system errors under various forms of stack abuse. + comment "Page alloc debug is incompatible with Software Suspend on i386" depends on DEBUG_KERNEL && SOFTWARE_SUSPEND
arch/i386/kernel/process.c +53 -0
65 lines not on this page · raw message
include/asm-i386/module.h +8 -1
@@ -68,6 +68,13 @@#define MODULE_STACKSIZE ""#endif -#define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE +#ifdef CONFIG_DEBUG_STACK +#define MODULE_DEBUG_STACK "DEBUG_STACKS " +#else +#define MODULE_DEBUG_STACK "" +#endif + +#define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE \ + MODULE_DEBUG_STACK#endif /* _ASM_I386_MODULE_H */
include/asm-i386/thread_info.h +6 -0
@@ -94,6 +94,11 @@ }/* thread information allocation */ +#ifdef CONFIG_DEBUG_STACK +struct task_struct ; +struct thread_info *alloc_thread_info (struct task_struct *); +void free_thread_info (struct thread_info *); +#else /* !CONFIG_DEBUG_STACK */ #ifdef CONFIG_DEBUG_STACK_USAGE #define alloc_thread_info (tsk) kzalloc(THREAD_SIZE, GFP_KERNEL)#else
@@ -101,6 +106,7 @@#endif #define free_thread_info (info) kfree(info) +#endif /* !CONFIG_DEBUG_STACK */ #else /* !__ASSEMBLY__ */
arch/i386/kernel/doublefault.c +1 -1
@@ -62,5 +62,5 @@ .ss = __KERNEL_DS, .ds = __USER_DS, - .__cr3 =__pa (swapper_pg_dir) + .__cr3 = (unsigned long)swapper_pg_dir - PAGE_OFFSET, };
arch/i386/kernel/irq.c +56 -1
75 lines not on this page · raw message
arch/i386/mm/pgtable.c +11 -0
@@ -181,6 +181,17 @@#endif } +#ifdef CONFIG_DEBUG_STACK +unsigned long __kvaddr_to_paddr (unsigned long kvaddr) +{ +if (high_memory) +BUG_ON (kvaddr >=VMALLOC_START ); +else +BUG_ON (kvaddr >= (unsigned long )__va (MAXMEM )); +return kvaddr -PAGE_OFFSET ; +} +#endif /* CONFIG_DEBUG_STACK */ +pte_t *pte_alloc_one_kernel (struct mm_struct *mm,unsigned long address) {return (pte_t *)__get_free_page (GFP_KERNEL |__GFP_REPEAT|__GFP_ZERO);
include/asm-i386/page.h +8 -2
@@ -118,11 +118,17 @@#define __PAGE_OFFSET ((unsigned long)CONFIG_PAGE_OFFSET)#endif -#define PAGE_OFFSET ((unsigned long)__PAGE_OFFSET) + +#if defined(CONFIG_DEBUG_STACK ) && !defined(__ASSEMBLY__) +unsigned long __kvaddr_to_paddr (unsigned long ); +#define __pa (x) __kvaddr_to_paddr((unsigned long)(x)) +#else /* !CONFIG_DEBUG_STACK */ +#define __pa (x) ((unsigned long)(x)-PAGE_OFFSET) +#endif /* !CONFIG_DEBUG_STACK */ +#define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE)#define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE) -#define __pa (x) ((unsigned long)(x)-PAGE_OFFSET)/* __pa_symbol should be used for C visible symbols. This seems to be the official gcc blessed way to do such arithmetic. */ #define __pa_symbol (x) __pa(RELOC_HIDE((unsigned long)(x),0))
Re: [3/3] use vmalloc() to arrange guard pages for stacks
Quoted 6 lines · Bill Irwin
This patch introduces
CONFIG_DEBUG_STACK, which vmalloc()'s task and IRQ stacks in order to establish guard pages. In such a manner any stack overflow that references pages immediately adjacent to the stack is immediately trapped with a fault, which precludes silent memory corruption or difficult-to-decipher failure modes resulting from stack corruption.
Is there a guard page below and above the stack? (I've seen stack underflow before, as well as overflow.)
Re: [3/3] use vmalloc() to arrange guard pages for stacks
Quoted 5 lines · Bill Irwin
Quoted 5 lines
This patch introduces
CONFIG_DEBUG_STACK, which vmalloc()'s task and IRQ stacks in order to establish guard pages. In such a manner any stack overflow that references pages immediately adjacent to the stack is immediately trapped with a fault, which precludes silent memory corruption or difficult-to-decipher failure modes resulting from stack corruption.
Quoted 2 lines · Chuck Ebbert
Is there a guard page below and above the stack? (I've seen stack underflow before, as well as overflow.)
vmallocspace allocations are always separated by at least a page, so this establishes guard pages both above and below the stack by virtue of such.
It's also notable that the option establishes guard pages for IRQ stacks in like fashion.
It's a shame that the resource scalability implications of vmallocspace allocations prevent this from being useful in production. One could, in principle, establish guard pages within ZONE_NORMAL, but for 4KB stacks it's somewhat awkward to dredge up 3 contigous pages, and 4 defeats the purpose. Alignment with 8KB stacks wants 2 contiguous order 1 pages that span an order 2 page boundary. I guess I could rewrite the page allocator (again), but people seem to feel safest with the buddy allocator affairs.
BTW, did the original patches for this prove to be of any use to you?
-- wli
Re: [3/3] use vmalloc() to arrange guard pages for stacks
Quoted 11 lines · Bill Irwin
It's a shame that the resource scalability implications of vmallocspace allocations prevent this from being useful in production. One could, in principle, establish guard pages within
ZONE_NORMAL, but for 4KB stacks it's somewhat awkward to dredge up 3 contigous pages, and 4 defeats the purpose. Alignment with 8KB stacks wants 2 contiguous order 1 pages that span an order 2 page boundary. I guess I could rewrite the page allocator (again), but people seem to feel safest with the buddy allocator affairs.BTW, did the original patches for this prove to be of any use to you?
No, I never tried them. Seems like I never get to anything these days but answering bug reports and merging fixes... Putting the feature in-kernel means I might get to use it though. :)
Re: [3/3] use vmalloc() to arrange guard pages for stacks
Quoted 8 lines · Bill Irwin
Quoted 8 lines
It's a shame that the resource scalability implications of vmallocspace allocations prevent this from being useful in production. One could, in principle, establish guard pages within
ZONE_NORMAL, but for 4KB stacks it's somewhat awkward to dredge up 3 contigous pages, and 4 defeats the purpose. Alignment with 8KB stacks wants 2 contiguous order 1 pages that span an order 2 page boundary. I guess I could rewrite the page allocator (again), but people seem to feel safest with the buddy allocator affairs. BTW, did the original patches for this prove to be of any use to you?
Quoted 3 lines · Chuck Ebbert
No, I never tried them. Seems like I never get to anything these days but answering bug reports and merging fixes... Putting the feature in-kernel means I might get to use it though. :)
Maybe it's a bit late for whatever bug you were hunting, but at least it'll help smoke out whatever other stack overflows you or anyone else might end up chasing down.
-- wli
Re: [1/3] dynamically allocate IRQ stacks
In reply to Bill Irwinarch/i386/kernel/irq.c line 166
Quoted 9 lines
arch/i386/kernel/irq.c +9
-0+static void *__init __alloc_irqstack (int cpu) +{ +if (!cpu) +return __alloc_bootmem (THREAD_SIZE ,THREAD_SIZE , +__pa (MAX_DMA_ADDRESS )); + +return (void *)__get_free_pages (GFP_KERNEL , +ilog2 (THREAD_SIZE /PAGE_SIZE )); +}
I think you should test for slab_is_available() instead of checking if the cpu number is 0.
Re: [1/3] dynamically allocate IRQ stacks
Quoted 9 lines · At some point in the past, I wrote:
Quoted 9 lines
(quoted diff) +9
-0+static void * __init __alloc_irqstack(int cpu) +{ + if (!cpu) + return __alloc_bootmem(THREAD_SIZE, THREAD_SIZE, + __pa(MAX_DMA_ADDRESS)); + + return (void *)__get_free_pages(GFP_KERNEL, + ilog2(THREAD_SIZE/PAGE_SIZE)); +}
Quoted 2 lines · Heiko Carstens
I think you should test for
slab_is_available()instead of checking if the cpu number is 0.
Plausible, though it would appear somewhat incongruous given that no direct calls to slab functions are made. The timing should still come out right, given that the vmallocspace variant needs to run late enough for mm/vmalloc.c's internal slab allocations to work.
The patches end up looking like the following MIME attachments with your suggested change.
-- wli
Subject: dynamically allocate IRQ stacks
Dynamically allocate IRQ stacks in order to conserve memory when using IRQ stacks. cpu_possible_map is not now initialized in such a manner as to provide a meaningful indication of how many CPU's might be in the system, and features to appear in the sequel also require indirection, so they themselves are not allocatable as per_cpu variables, but rather only pointers to them.
arch/i386/kernel/irq.c +32 -15
@@ -17,9 +17,11 @@#include <linux/notifier.h> #include <linux/cpu.h> #include <linux/delay.h> +#include <linux/bootmem.h> #include <asm/apic.h> #include <asm/uaccess.h> +#include <asm/pgtable.h> DEFINE_PER_CPU (irq_cpustat_t, irq_stat)____cacheline_internodealigned_in_smp ;EXPORT_PER_CPU_SYMBOL (irq_stat);
@@ -56,8 +58,8 @@u32 stack[THREAD_SIZE /sizeof (u32)]; }; -static union irq_ctx *hardirq_ctx[NR_CPUS ]__read_mostly ; -static union irq_ctx *softirq_ctx[NR_CPUS ]__read_mostly ; +static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx); +static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);#endif /*
@@ -102,7 +104,7 @@#ifdef CONFIG_4KSTACKS curctx = (union irq_ctx *)current_thread_info (); - irqctx = hardirq_ctx[smp_processor_id ()]; + irqctx =per_cpu (hardirq_ctx,smp_processor_id ());/* * this is where we switch to the IRQ stack. However, if we are
@@ -150,11 +152,24 @@* These should really be __section__(".bss.page_aligned") as well, but * gcc's 3.0 and earlier don't handle that correctly. */ -static char softirq_stack[NR_CPUS * THREAD_SIZE] - __attribute__((__aligned__(THREAD_SIZE))); +static DEFINE_PER_CPU(char *, softirq_stack); +static DEFINE_PER_CPU(char *, hardirq_stack); -static char hardirq_stack[NR_CPUS * THREAD_SIZE] - __attribute__((__aligned__(THREAD_SIZE))); +static void *__init __alloc_irqstack (int cpu) +{ +if (!slab_is_available ()) +return __alloc_bootmem (THREAD_SIZE ,THREAD_SIZE , +__pa (MAX_DMA_ADDRESS )); + +return (void *)__get_free_pages (GFP_KERNEL , +ilog2 (THREAD_SIZE /PAGE_SIZE )); +} + +static void __init alloc_irqstacks (int cpu) +{ +per_cpu (softirq_stack, cpu) =__alloc_irqstack (cpu); +per_cpu (hardirq_stack, cpu) =__alloc_irqstack (cpu); +}/* * allocate per-cpu stacks for hardirq and for softirq processing
@@ -163,34 +178,36 @@ {union irq_ctx *irqctx; -if (hardirq_ctx[cpu]) +if (per_cpu (hardirq_ctx, cpu))return ; - irqctx = (union irq_ctx *) &hardirq_stack[cpu*THREAD_SIZE ]; +alloc_irqstacks (cpu); + + irqctx = (union irq_ctx *)per_cpu (hardirq_stack, cpu); irqctx->tinfo.task =NULL ; irqctx->tinfo.exec_domain =NULL ; irqctx->tinfo.cpu = cpu; irqctx->tinfo.preempt_count =HARDIRQ_OFFSET ; irqctx->tinfo.addr_limit =MAKE_MM_SEG (0 ); - hardirq_ctx[cpu] = irqctx; +per_cpu (hardirq_ctx, cpu) = irqctx; - irqctx = (union irq_ctx *) &softirq_stack[cpu*THREAD_SIZE ]; + irqctx = (union irq_ctx *)per_cpu (softirq_stack, cpu); irqctx->tinfo.task =NULL ; irqctx->tinfo.exec_domain =NULL ; irqctx->tinfo.cpu = cpu; irqctx->tinfo.preempt_count =0 ; irqctx->tinfo.addr_limit =MAKE_MM_SEG (0 ); - softirq_ctx[cpu] = irqctx; +per_cpu (softirq_ctx, cpu) = irqctx;printk ("CPU %u irqstacks, hard=%p soft=%p\n" , - cpu,hardirq_ctx[cpu],softirq_ctx[cpu]); + cpu,per_cpu (hardirq_ctx, cpu),per_cpu (softirq_ctx, cpu)); }void irq_ctx_exit (int cpu) { - hardirq_ctx[cpu] =NULL ; +per_cpu (hardirq_ctx, cpu) =NULL ; } extern asmlinkage void __do_softirq(void);
@@ -209,7 +226,7 @@if (local_softirq_pending ()) { curctx =current_thread_info (); - irqctx = softirq_ctx[smp_processor_id ()]; + irqctx =per_cpu (softirq_ctx,smp_processor_id ()); irqctx->tinfo.task = curctx->task; irqctx->tinfo.previous_esp = current_stack_pointer;
IRQ stacks are a valuable stability feature. This patch makes them unconditional, as there is no circumstance under which they do not improve stability and they have no meaningful performance impact.
include/asm-i386/irq.h +3 -8
@@ -24,14 +24,9 @@# define ARCH_HAS_NMI_WATCHDOG /* See include/linux/nmi.h */ #endif -#ifdef CONFIG_4KSTACKS -extern void irq_ctx_init (int cpu); -extern void irq_ctx_exit (int cpu); -# define __ARCH_HAS_DO_SOFTIRQ -#else -# define irq_ctx_init (cpu) do { } while (0) -# define irq_ctx_exit (cpu) do { } while (0) -#endif +void irq_ctx_init (int ); +void irq_ctx_exit (int ); +#define __ARCH_HAS_DO_SOFTIRQ#ifdef CONFIG_IRQBALANCE extern int irqbalance_disable (char *str);
arch/i386/kernel/irq.c +0 -11
@@ -49,7 +49,6 @@#endif } -#ifdef CONFIG_4KSTACKS /* * per-CPU IRQ handling contexts (thread information and stack) */
@@ -60,7 +59,6 @@ static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx); static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx); -#endif /* * do_IRQ handles all normal device IRQ's (the special
@@ -73,10 +71,8 @@/* high bit used in ret_from_ code */ int irq = ~regs->orig_eax;struct irq_desc *desc = irq_desc + irq; -#ifdef CONFIG_4KSTACKS union irq_ctx *curctx, *irqctx;u32 *isp; -#endif if (unlikely ((unsigned )irq >=NR_IRQS )) { printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
@@ -100,9 +96,6 @@ } }#endif - -#ifdef CONFIG_4KSTACKS - curctx = (union irq_ctx *)current_thread_info (); irqctx =per_cpu (hardirq_ctx,smp_processor_id ());
@@ -138,7 +131,6 @@ : "memory", "cc" ); }else -#endif desc->handle_irq (irq, desc);irq_exit ();
@@ -146,8 +138,6 @@return 1 ; } -#ifdef CONFIG_4KSTACKS -/* * These should really be __section__(".bss.page_aligned") as well, but * gcc's 3.0 and earlier don't handle that correctly.
@@ -251,7 +241,6 @@ }EXPORT_SYMBOL (do_softirq); -#endif /* * Interrupt statistics:
This patch introduces CONFIG_DEBUG_STACK, which vmalloc()'s task and IRQ stacks in order to establish guard pages. In such a manner any stack overflow that references pages immediately adjacent to the stack is immediately trapped with a fault, which precludes silent memory corruption or difficult-to-decipher failure modes resulting from stack corruption.
It furthermore adds a check to __pa() to catch drivers trying to DMA off the stack, which more generally flags incorrect attempts to use __pa() on vmallocspace addresses.
arch/i386/Kconfig.debug +10 -0
@@ -35,6 +35,16 @@ This option will slow down process creation somewhat. +config DEBUG_STACK + bool "Debug stack overflows" + depends on DEBUG_KERNEL + help + Allocates the stack physically discontiguously and from high + memory. Furthermore an unmapped guard page follows the stack, + which results in immediately trapping stack overflows instead + of silent corruption. This is not for end-users. It's intended + to trigger fatal system errors under various forms of stack abuse. + comment "Page alloc debug is incompatible with Software Suspend on i386" depends on DEBUG_KERNEL && SOFTWARE_SUSPEND
arch/i386/kernel/process.c +53 -0
65 lines not on this page · raw message
include/asm-i386/module.h +8 -1
@@ -68,6 +68,13 @@#define MODULE_STACKSIZE ""#endif -#define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE +#ifdef CONFIG_DEBUG_STACK +#define MODULE_DEBUG_STACK "DEBUG_STACKS " +#else +#define MODULE_DEBUG_STACK "" +#endif + +#define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE \ + MODULE_DEBUG_STACK#endif /* _ASM_I386_MODULE_H */
include/asm-i386/thread_info.h +6 -0
@@ -94,6 +94,11 @@ }/* thread information allocation */ +#ifdef CONFIG_DEBUG_STACK +struct task_struct ; +struct thread_info *alloc_thread_info (struct task_struct *); +void free_thread_info (struct thread_info *); +#else /* !CONFIG_DEBUG_STACK */ #ifdef CONFIG_DEBUG_STACK_USAGE #define alloc_thread_info (tsk) kzalloc(THREAD_SIZE, GFP_KERNEL)#else
@@ -101,6 +106,7 @@#endif #define free_thread_info (info) kfree(info) +#endif /* !CONFIG_DEBUG_STACK */ #else /* !__ASSEMBLY__ */
arch/i386/kernel/doublefault.c +1 -1
@@ -62,5 +62,5 @@ .ss = __KERNEL_DS, .ds = __USER_DS, - .__cr3 =__pa (swapper_pg_dir) + .__cr3 = (unsigned long)swapper_pg_dir - PAGE_OFFSET, };
arch/i386/kernel/irq.c +56 -1
75 lines not on this page · raw message
arch/i386/mm/pgtable.c +11 -0
@@ -181,6 +181,17 @@#endif } +#ifdef CONFIG_DEBUG_STACK +unsigned long __kvaddr_to_paddr (unsigned long kvaddr) +{ +if (high_memory) +BUG_ON (kvaddr >=VMALLOC_START ); +else +BUG_ON (kvaddr >= (unsigned long )__va (MAXMEM )); +return kvaddr -PAGE_OFFSET ; +} +#endif /* CONFIG_DEBUG_STACK */ +pte_t *pte_alloc_one_kernel (struct mm_struct *mm,unsigned long address) {return (pte_t *)__get_free_page (GFP_KERNEL |__GFP_REPEAT|__GFP_ZERO);
include/asm-i386/page.h +8 -2
@@ -118,11 +118,17 @@#define __PAGE_OFFSET ((unsigned long)CONFIG_PAGE_OFFSET)#endif -#define PAGE_OFFSET ((unsigned long)__PAGE_OFFSET) + +#if defined(CONFIG_DEBUG_STACK ) && !defined(__ASSEMBLY__) +unsigned long __kvaddr_to_paddr (unsigned long ); +#define __pa (x) __kvaddr_to_paddr((unsigned long)(x)) +#else /* !CONFIG_DEBUG_STACK */ +#define __pa (x) ((unsigned long)(x)-PAGE_OFFSET) +#endif /* !CONFIG_DEBUG_STACK */ +#define VMALLOC_RESERVE ((unsigned long)__VMALLOC_RESERVE)#define MAXMEM (-__PAGE_OFFSET-__VMALLOC_RESERVE) -#define __pa (x) ((unsigned long)(x)-PAGE_OFFSET)/* __pa_symbol should be used for C visible symbols. This seems to be the official gcc blessed way to do such arithmetic. */ #define __pa_symbol (x) __pa(RELOC_HIDE((unsigned long)(x),0))