Messages in this thread | | | Date | Tue, 27 Dec 2005 14:12:03 -0700 | From | Frank Sorenson <> | Subject | Re: 4k stacks |
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Andrew James Wade wrote: > I've modified stack.c to handle 4k stacks. It can also provide information > for 8k stacks (fwiw) by changing STACK_GRANULARITY. > > It found one stack with only 756 bytes left. I hope it's just due to a > greedy boot-time function as I'm not running anything particularly exotic. > (CIFS & Reiser4).
Yes, it does appear to be a boot-time function. It eventually becomes PID 1, and the stack usage shrinks considerably.
Here is a different approach that uses a kernel module, rather than /dev/mem. This module will display current stack usage for each PID, as well as the maximum usage if the kernel has the stack-poison patch. Also, the current call trace for each PID can be displayed if loaded with "verbose=1".
for example: 1: init - free stack now: 3640, at max usage: 740 2: ksoftirqd/0 - free stack now: 3880, at max usage: 3788 3: watchdog/0 - free stack now: 3828, at max usage: 3736 4: events/0 - free stack now: 3784, at max usage: 3012 ...
Disclaimer: This seems to work for me, but I'm not a very experienced kernel hacker, so if it breaks, take care that you don't get hurt.
Comments and fixes are welcome.
Thanks,
Frank - -- Frank Sorenson - KD7TZK Systems Manager, Computer Science Department Brigham Young University frank@tuxrocks.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org
iD8DBQFDsa4iaI0dwg4A47wRAo14AKCbaraQkijBHpzSJdFzoTG1L/MXjgCg8VDe 130LL3/dMhRjVw4Wp8IN0a8= =skKB -----END PGP SIGNATURE----- /* * stack_avail - A linux kernel module to display available stack * If the kernel stack-poison patch has been applied, this * module also displays available stack at maximum usage * Copyright Frank Sorenson <frank@tuxrocks.com> 2005 * * Permission is hereby granted to copy, modify and redistribute this code * in terms of the GNU Library General Public License, Version 2 or later, * at your option. * */
#include <linux/module.h> #include <linux/kallsyms.h>
static int verbose = 0;
static unsigned long sinittext; static unsigned long einittext; static unsigned long stext; static unsigned long etext;
// task_struct - /UML/Source/Host/linux-2.6.15-rc5-mm3+fs3/include/linux/sched.h // thread_struct - /UML/Source/Host/linux-2.6.15-rc5-mm3+fs3/include/asm-i386/processor.h // thread_info - /UML/Source/Host/linux-2.6.15-rc5-mm3+fs3/include/asm-i386/thread_info.h
static inline int valid_stack_ptr(struct thread_info *tinfo, void *p) { return p > (void *)tinfo && p < (void *)tinfo + THREAD_SIZE - 3; }
static int core_kernel_text(unsigned long addr) { if (addr >= (unsigned long)stext && addr <= (unsigned long)etext) return 1;
if (addr >= (unsigned long)sinittext && addr <= (unsigned long)einittext) return 1; return 0; }
int my_kernel_text_address(unsigned long addr) { if (core_kernel_text(addr)) return 1; return 0; // return __module_text_address(addr) != NULL; }
static inline unsigned long print_context_stack(struct thread_info *tinfo, unsigned long *stack, unsigned long ebp) { unsigned long addr; #ifdef CONFIG_FRAME_POINTER while (valid_stack_ptr(tinfo, (void *)ebp)) { addr = *(unsigned long *)(ebp + 4); printk(" [<%08lx>] ", addr); print_symbol("%s", addr); printk("\n"); ebp = *(unsigned long *)ebp; } #else while (valid_stack_ptr(tinfo, stack)) { addr = *stack++; if (my_kernel_text_address(addr)) { printk(" [<%08lx>]", addr); print_symbol(" %s", addr); printk("\n"); } } #endif return ebp; }
void show_trace(struct task_struct *task, unsigned long * stack) { unsigned long ebp;
ebp = *(unsigned long *) task->thread.esp;
while (1) { struct thread_info *context; context = (struct thread_info *) ((unsigned long)stack & (~(THREAD_SIZE - 1))); ebp = print_context_stack(context, stack, ebp); stack = (unsigned long*)context->previous_esp; if (!stack) break; printk(" =======================\n"); } }
static int stack_avail_load(void) { struct task_struct *task; unsigned char *base_addr; unsigned char *max_addr; unsigned char *ptr; unsigned long current_avail; unsigned long poisoned_avail;
sinittext = kallsyms_lookup_name("_sinittext"); einittext = kallsyms_lookup_name("_einittext"); stext = kallsyms_lookup_name("_stext"); etext = kallsyms_lookup_name("_etext");
printk("Displaying stack space available:\n");
for_each_process(task) { printk("%d: %s", task->pid, task->comm);
base_addr = (unsigned char *)(task->thread.esp & 0xFFFFF000); max_addr = base_addr + THREAD_SIZE - 1; ptr = base_addr + sizeof(struct thread_info); while (*ptr == 'Q') { ptr ++; } current_avail = (unsigned long)(task->thread.esp) - (unsigned long)(base_addr) - sizeof(struct thread_info); poisoned_avail = THREAD_SIZE - ((unsigned long)(max_addr - ptr)) - sizeof(struct thread_info) - 1;
printk(" - free stack now: %lu", current_avail); if (poisoned_avail != 0) printk(", at max usage: %lu", poisoned_avail);
if (verbose) { printk("\nCurrent call Trace:\n"); show_trace(task, (unsigned long *)(task->thread.esp)); } printk("\n"); } return 0; }
static void stack_avail_unload(void) { printk("stack_avail module unloading\n"); }
module_init(stack_avail_load); module_exit(stack_avail_unload); module_param(verbose, int, 0);
MODULE_AUTHOR ("Frank Sorenson, frank@tuxrocks.com"); MODULE_DESCRIPTION ("Displays available stack space"); MODULE_LICENSE("GPL"); KVER := $(shell uname -r) KSRC := /lib/modules/$(KVER)/build
PWD = $(shell pwd)
obj-m += stack_avail.o
all: modules
modules: $(MAKE) -C $(KSRC) SUBDIRS=$(PWD) BUILD_DIR=$(PWD) modules
ioctl: ioctl.c $(CC) $< -o $@
clean: @find . \ \( -name '*.ko' -o -name '.*.cmd' \ -o -name '*.o' -o -name '*.mod.c' \) \ -type f -print | xargs rm -f
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