In message <20020801.191449.101696880.davem@redhat.com> you write:
> From: Rusty Russell <rusty@rustcorp.com.au>
> Date: Fri, 02 Aug 2002 12:11:47 +1000
>
> Vamsi's kernel probes again, this time with EXPORT_SYMBOL_GPL
> so people don't think this is blanket permission to hook into
> arbitrary parts of the kernel (as separate from debugging, testing,
> diagnostics, etc).
>
> A nice enhancement would be to move the kprobe table and
> other generic bits into a common area so that it did not
> need to be duplicated as other arches add kprobe support.
Done. Look better?
Rusty.
-- Anyone who quotes me in their sig is an idiot. -- Rusty Russell.Name: Kprobes for i386 Author: Vamsi Krishna S Status: Experimental
D: This patch allows trapping at almost any kernel address, useful for D: various kernel-hacking tasks, and building on for more D: infrastructure. This patch is x86 only, but other archs can add D: support as required.
diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/arch/i386/Config.help working-2.5.30-kprobes/arch/i386/Config.help --- linux-2.5.30/arch/i386/Config.help Mon Jun 17 23:19:15 2002 +++ working-2.5.30-kprobes/arch/i386/Config.help Fri Aug 2 15:36:03 2002 @@ -967,3 +967,9 @@ CONFIG_SOFTWARE_SUSPEND absence of features. For more information take a look at Documentation/swsusp.txt. + +CONFIG_KPROBES + Kprobes allows you to trap at almost any kernel address, using + register_kprobe(), and providing a callback function. This is useful + for kernel debugging, non-intrusive instrumentation and testing. If + in doubt, say "N". diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/include/linux/kprobes.h working-2.5.30-kprobes/include/linux/kprobes.h --- linux-2.5.30/include/linux/kprobes.h Thu Jan 1 10:00:00 1970 +++ working-2.5.30-kprobes/include/linux/kprobes.h Mon Aug 5 10:56:44 2002 @@ -0,0 +1,54 @@ +#ifndef _LINUX_KPROBES_H +#define _LINUX_KPROBES_H +#include <linux/config.h> +#include <linux/list.h> +#include <asm/kprobes.h> + +struct kprobe; +struct pt_regs; + +typedef void (*kprobe_pre_handler_t)(struct kprobe *, struct pt_regs *); +typedef void (*kprobe_post_handler_t)(struct kprobe *, struct pt_regs *, + unsigned long flags); +typedef int (*kprobe_fault_handler_t)(struct kprobe *, struct pt_regs *, + int trapnr); + +struct kprobe { + struct list_head list; + + /* location of the probe point */ + kprobe_opcode_t *addr; + + /* Called before addr is executed. */ + kprobe_pre_handler_t pre_handler; + + /* Called after addr is executed, unless... */ + kprobe_post_handler_t post_handler; + + /* ... called if executing addr causes a fault (eg. page fault). + * Return 1 if it handled fault, otherwise kernel will see it. */ + kprobe_fault_handler_t fault_handler; + + /* Saved opcode (which has been replaced with breakpoint) */ + kprobe_opcode_t opcode; +}; + +#ifdef CONFIG_KPROBES +/* Locks kprobe: irq must be disabled */ +void lock_kprobes(void); +void unlock_kprobes(void); + +/* kprobe running now on this CPU? */ +int kprobe_running(void); + +/* Get the kprobe at this addr (if any). Must have called lock_kprobes */ +struct kprobe *get_kprobe(void *addr); + +int register_kprobe(struct kprobe *p); +void unregister_kprobe(struct kprobe *p); +#else +static inline int kprobe_running(void) { return 0; } +static inline int register_kprobe(struct probe_struct *p) { return -ENOSYS; } +static inline void unregister_kprobe(struct probe_struct *p) { } +#endif +#endif /* _LINUX_KPROBES_H */ diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/kernel/Makefile working-2.5.30-kprobes/kernel/Makefile --- linux-2.5.30/kernel/Makefile Sat Jul 27 15:24:39 2002 +++ working-2.5.30-kprobes/kernel/Makefile Fri Aug 2 15:36:03 2002 @@ -10,7 +10,7 @@ O_TARGET := kernel.o export-objs = signal.o sys.o kmod.o context.o ksyms.o pm.o exec_domain.o \ - printk.o platform.o suspend.o + printk.o platform.o suspend.o kprobes.o obj-y = sched.o dma.o fork.o exec_domain.o panic.o printk.o \ module.o exit.o itimer.o time.o softirq.o resource.o \ @@ -23,6 +23,7 @@ obj-$(CONFIG_MODULES) += ksyms.o obj-$(CONFIG_PM) += pm.o obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o obj-$(CONFIG_SOFTWARE_SUSPEND) += suspend.o +obj-$(CONFIG_KPROBES) += kprobes.o ifneq ($(CONFIG_IA64),y) # According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/kernel/kprobes.c working-2.5.30-kprobes/kernel/kprobes.c --- linux-2.5.30/kernel/kprobes.c Thu Jan 1 10:00:00 1970 +++ working-2.5.30-kprobes/kernel/kprobes.c Fri Aug 2 15:45:13 2002 @@ -0,0 +1,94 @@ +/* Support for kernel probes. + (C) 2002 Vamsi Krishna S <vamsi_krishna@in.ibm.com>. +*/ +#include <linux/kprobes.h> +#include <linux/spinlock.h> +#include <linux/hash.h> +#include <linux/init.h> +#include <linux/module.h> +#include <asm/cacheflush.h> +#include <asm/errno.h> + +#define KPROBE_HASH_BITS 6 +#define KPROBE_TABLE_SIZE (1 << KPROBE_HASH_BITS) + +static struct list_head kprobe_table[KPROBE_TABLE_SIZE]; + +static unsigned int kprobe_cpu = NR_CPUS; +static spinlock_t kprobe_lock = SPIN_LOCK_UNLOCKED; + +int kprobe_running(void) +{ + return kprobe_cpu == smp_processor_id(); +} + +/* Locks kprobe: irqs must be disabled */ +void lock_kprobes(void) +{ + spin_lock(&kprobe_lock); + kprobe_cpu = smp_processor_id(); +} + +void unlock_kprobes(void) +{ + kprobe_cpu = NR_CPUS; + spin_unlock(&kprobe_lock); +} + +/* You have to be holding the kprobe_lock */ +struct kprobe *get_kprobe(void *addr) +{ + struct list_head *head, *tmp; + + head = &kprobe_table[hash_ptr(addr, KPROBE_HASH_BITS)]; + list_for_each(tmp, head) { + struct kprobe *p = list_entry(tmp, struct kprobe, list); + if (p->addr == addr) + return p; + } + return NULL; +} + +int register_kprobe(struct kprobe *p) +{ + int ret = 0; + + spin_lock_irq(&kprobe_lock); + if (get_kprobe(p->addr)) { + ret = -EEXIST; + goto out; + } + list_add(&p->list, &kprobe_table[hash_ptr(p->addr, KPROBE_HASH_BITS)]); + + p->opcode = *p->addr; + *p->addr = BREAKPOINT_INSTRUCTION; + flush_icache_range(p->addr, p->addr + sizeof(kprobe_opcode_t)); + out: + spin_unlock_irq(&kprobe_lock); + return ret; +} + +void unregister_kprobe(struct kprobe *p) +{ + spin_lock_irq(&kprobe_lock); + *p->addr = p->opcode; + list_del(&p->list); + flush_icache_range(p->addr, p->addr + sizeof(kprobe_opcode_t)); + spin_unlock_irq(&kprobe_lock); +} + +static int __init init_kprobes(void) +{ + int i; + + /* FIXME allocate the probe table, currently defined statically */ + /* initialize all list heads */ + for (i = 0; i < KPROBE_TABLE_SIZE; i++) + INIT_LIST_HEAD(&kprobe_table[i]); + + return 0; +} +__initcall(init_kprobes); + +EXPORT_SYMBOL_GPL(register_kprobe); +EXPORT_SYMBOL_GPL(unregister_kprobe); diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/arch/i386/config.in working-2.5.30-kprobes/arch/i386/config.in --- linux-2.5.30/arch/i386/config.in Sat Jul 27 15:24:35 2002 +++ working-2.5.30-kprobes/arch/i386/config.in Fri Aug 2 15:36:03 2002 @@ -415,6 +415,7 @@ if [ "$CONFIG_DEBUG_KERNEL" != "n" ]; th if [ "$CONFIG_HIGHMEM" = "y" ]; then bool ' Highmem debugging' CONFIG_DEBUG_HIGHMEM fi + bool ' Probes' CONFIG_KPROBES fi endmenu diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/arch/i386/kernel/entry.S working-2.5.30-kprobes/arch/i386/kernel/entry.S --- linux-2.5.30/arch/i386/kernel/entry.S Fri Aug 2 11:15:05 2002 +++ working-2.5.30-kprobes/arch/i386/kernel/entry.S Fri Aug 2 15:36:03 2002 @@ -430,9 +430,22 @@ device_not_available_emulate: jmp ret_from_exception ENTRY(debug) +#ifdef CONFIG_KPROBES + pushl %eax + SAVE_ALL + movl %esp,%edx + pushl $0 + pushl %edx + call do_debug + addl $8,%esp + cmpl $0,%eax + jnz restore_all + jmp ret_from_exception +#else pushl $0 pushl $do_debug jmp error_code +#endif ENTRY(nmi) pushl %eax @@ -445,9 +460,22 @@ ENTRY(nmi) RESTORE_ALL ENTRY(int3) +#ifdef CONFIG_KPROBES + pushl %eax + SAVE_ALL + movl %esp,%edx + pushl $0 + pushl %edx + call do_int3 + addl $8,%esp + cmpl $0,%eax + jnz restore_all + jmp ret_from_exception +#else pushl $0 pushl $do_int3 jmp error_code +#endif ENTRY(overflow) pushl $0 diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/arch/i386/kernel/traps.c working-2.5.30-kprobes/arch/i386/kernel/traps.c --- linux-2.5.30/arch/i386/kernel/traps.c Sat Jul 27 15:24:35 2002 +++ working-2.5.30-kprobes/arch/i386/kernel/traps.c Fri Aug 2 17:38:56 2002 @@ -5,6 +5,9 @@ * * Pentium III FXSR, SSE support * Gareth Hughes <gareth@valinux.com>, May 2000 + * + * Dynamic Probes (kprobes) support + * Vamsi Krishna S <vamsi_krishna@in.ibm.com>, July, 2002 */ /* @@ -24,6 +27,7 @@ #include <linux/spinlock.h> #include <linux/interrupt.h> #include <linux/highmem.h> +#include <linux/kprobes.h> #ifdef CONFIG_EISA #include <linux/ioport.h> @@ -50,6 +54,7 @@ #include <asm/cobalt.h> #include <asm/lithium.h> #endif +#include <linux/hash.h> #include <linux/irq.h> #include <linux/module.h> @@ -297,6 +302,158 @@ static inline void die_if_kernel(const c die(str, regs, err); } +#ifdef CONFIG_KPROBES +/* kprobe_status settings */ +#define KPROBE_HIT_ACTIVE 0x00000001 +#define KPROBE_HIT_SS 0x00000002 + +#define EF_TF 0x00000100 +#define EF_IE 0x00000200 + +static struct kprobe *current_kprobe; +static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags; + +/* + * We changed trap3/1 to an intr gate. So, restore the status of IF, + * if necessary, before executing the original int3/1 (trap) handler. + */ +static inline void restore_interrupts(struct pt_regs *regs) +{ + if (regs->eflags & EF_IE) + __asm__ __volatile__ ("sti"); +} + +/* + * returns non-zero if opcode modifies the interrupt flag. + */ +static inline int is_IF_modifier(u8 opcode) +{ + switch(opcode) { + case 0xfa: /* cli */ + case 0xfb: /* sti */ + case 0xcf: /* iret/iretd */ + case 0x9d: /* popf/popfd */ + return 1; + } + return 0; +} + +static inline void disarm_kprobe(struct kprobe *p, struct pt_regs *regs) +{ + *p->addr = p->opcode; + regs->eip = (unsigned long)p->addr; +} + +/* + * Interrupts are disabled on entry as trap3 is an interrupt gate and they + * remain disabled thorough out this function. + */ +static int kprobe_handler(struct pt_regs * regs) +{ + struct kprobe *p; + u8 *addr = (u8 *)(regs->eip-1); + + /* Lock, check we're not actually recursing */ + if (kprobe_running()) { + /* We *are* holding lock here, so this is safe. + Disarm the probe we just hit, and ignore it. */ + p = get_kprobe(addr); + /* Not ours? Can't be delete race, since we hold lock. */ + if (!p) + return 0; + disarm_kprobe(p, regs); + return 1; + } + + lock_kprobes(); + p = get_kprobe(addr); + if (!p) { + unlock_kprobes(); + /* Unregistered (on another cpu) after this hit? Ignore */ + if (*addr != BREAKPOINT_INSTRUCTION) + return 1; + /* Not one of ours: let kernel handle it */ + restore_interrupts(regs); + return 0; + } + + kprobe_status = KPROBE_HIT_ACTIVE; + current_kprobe = p; + kprobe_saved_eflags = kprobe_old_eflags = regs->eflags & (EF_TF|EF_IE); + if (is_IF_modifier(p->opcode)) + kprobe_saved_eflags &= ~EF_IE; + + p->pre_handler(p, regs); + + regs->eflags |= EF_TF; + regs->eflags &= ~EF_IE; + + /* We hold lock, now we remove breakpoint and single step. */ + disarm_kprobe(p, regs); + kprobe_status = KPROBE_HIT_SS; + return 1; +} + +static void rearm_kprobe(struct kprobe *p, struct pt_regs *regs) +{ + regs->eflags &= ~EF_TF; + *p->addr = BREAKPOINT_INSTRUCTION; +} + +/* + * Interrupts are disabled on entry as trap1 is an interrupt gate and they + * remain disabled thorough out this function. And we hold kprobe lock. + */ +static int post_kprobe_handler(struct pt_regs *regs) +{ + if (current_kprobe->post_handler) + current_kprobe->post_handler(current_kprobe, regs, 0); + + /* + * We singlestepped with interrupts disabled. So, the result on + * the stack would be incorrect for "pushfl" instruction. + */ + if (current_kprobe->opcode == 0x9c) { /* pushfl */ + regs->esp &= ~(EF_TF | EF_IE); + regs->esp |= kprobe_old_eflags; + } + + rearm_kprobe(current_kprobe, regs); + regs->eflags |= kprobe_saved_eflags; + + unlock_kprobes(); + + /* + * if somebody else is singlestepping across a probe point, eflags + * will have TF set, in which case, continue the remaining processing + * of do_debug, as if this is not a probe hit. + */ + if (regs->eflags & EF_TF) { + restore_interrupts(regs); + return 0; + } + return 1; +} + +/* Interrupts disabled, kprobe_lock held. */ +int kprobe_fault_handler(struct pt_regs *regs, int trapnr) +{ + if (current_kprobe->fault_handler + && current_kprobe->fault_handler(current_kprobe, regs, trapnr)) + return 1; + + if (kprobe_status & KPROBE_HIT_SS) { + rearm_kprobe(current_kprobe, regs); + regs->eflags |= kprobe_old_eflags; + + unlock_kprobes(); + } + return 0; +} +#else +static inline int post_kprobe_handler(struct pt_regs *regs) { return 0; } +#endif /* CONFIG_KPROBES */ + static inline unsigned long get_cr2(void) { unsigned long address; @@ -326,6 +483,8 @@ static void inline do_trap(int trapnr, i panic("do_trap: can't hit this"); } #endif + if (kprobe_fault(regs, trapnr)) + return; if (!(regs->xcs & 3)) goto kernel_trap; @@ -392,7 +551,9 @@ asmlinkage void do_##name(struct pt_regs } DO_VM86_ERROR_INFO( 0, SIGFPE, "divide error", divide_error, FPE_INTDIV, regs->eip) +#ifndef CONFIG_KPROBES DO_VM86_ERROR( 3, SIGTRAP, "int3", int3) +#endif DO_VM86_ERROR( 4, SIGSEGV, "overflow", overflow) DO_VM86_ERROR( 5, SIGSEGV, "bounds", bounds) DO_ERROR_INFO( 6, SIGILL, "invalid operand", invalid_op, ILL_ILLOPN, regs->eip) @@ -408,6 +569,9 @@ asmlinkage void do_general_protection(st { if (regs->eflags & VM_MASK) goto gp_in_vm86; + + if (kprobe_fault(regs, 13)) + return; if (!(regs->xcs & 3)) goto gp_in_kernel; @@ -508,6 +672,16 @@ asmlinkage void do_nmi(struct pt_regs * inb(0x71); /* dummy */ } +#ifdef CONFIG_KPROBES +asmlinkage int do_int3(struct pt_regs * regs, long error_code) +{ + if (kprobe_handler(regs)) + return 1; + do_trap(3, SIGTRAP, "int3", 1, regs, error_code, NULL); + return 0; +} +#endif + /* * Our handling of the processor debug registers is non-trivial. * We do not clear them on entry and exit from the kernel. Therefore @@ -530,7 +704,7 @@ asmlinkage void do_nmi(struct pt_regs * * find every occurrence of the TF bit that could be saved away even * by user code) */ -asmlinkage void do_debug(struct pt_regs * regs, long error_code) +asmlinkage int do_debug(struct pt_regs * regs, long error_code) { unsigned int condition; struct task_struct *tsk = current; @@ -552,6 +726,8 @@ asmlinkage void do_debug(struct pt_regs /* Mask out spurious TF errors due to lazy TF clearing */ if (condition & DR_STEP) { + if (kprobe_running() && post_kprobe_handler(regs)) + return 1; /* * The TF error should be masked out only if the current * process is not traced and if the TRAP flag has been set @@ -588,15 +764,15 @@ clear_dr7: __asm__("movl %0,%%db7" : /* no output */ : "r" (0)); - return; + return 0; debug_vm86: handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1); - return; + return 0; clear_TF: regs->eflags &= ~TF_MASK; - return; + return 0; } /* @@ -760,6 +936,8 @@ asmlinkage void math_state_restore(struc struct task_struct *tsk = current; clts(); /* Allow maths ops (or we recurse) */ + if (kprobe_fault(®s, 7)) + return; if (!tsk->used_math) init_fpu(tsk); restore_fpu(tsk); @@ -943,9 +1121,17 @@ void __init trap_init(void) #endif set_trap_gate(0,÷_error); +#ifndef CONFIG_KPROBES set_trap_gate(1,&debug); +#else + _set_gate(idt_table+1,14,3,&debug); +#endif set_intr_gate(2,&nmi); +#ifndef CONFIG_KPROBES set_system_gate(3,&int3); /* int3-5 can be called from all */ +#else + _set_gate(idt_table+3,14,3,&int3); +#endif set_system_gate(4,&overflow); set_system_gate(5,&bounds); set_trap_gate(6,&invalid_op); diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/arch/i386/mm/fault.c working-2.5.30-kprobes/arch/i386/mm/fault.c --- linux-2.5.30/arch/i386/mm/fault.c Sat Jul 27 15:24:35 2002 +++ working-2.5.30-kprobes/arch/i386/mm/fault.c Mon Aug 5 10:57:18 2002 @@ -19,6 +19,7 @@ #include <linux/init.h> #include <linux/tty.h> #include <linux/vt_kern.h> /* For unblank_screen() */ +#include <linux/kprobes.h> #include <asm/system.h> #include <asm/uaccess.h> @@ -154,6 +155,9 @@ asmlinkage void do_page_fault(struct pt_ /* get the address */ __asm__("movl %%cr2,%0":"=r" (address)); + + if (kprobe_fault(regs, 14)) + return; /* It's safe to allow irq's after cr2 has been saved */ if (regs->eflags & X86_EFLAGS_IF) diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/fs/partitions/check.c working-2.5.30-kprobes/fs/partitions/check.c --- linux-2.5.30/fs/partitions/check.c Fri Aug 2 11:15:09 2002 +++ working-2.5.30-kprobes/fs/partitions/check.c Fri Aug 2 17:30:34 2002 @@ -467,7 +467,7 @@ void devfs_register_partitions (struct g for (part = 1; part < max_p; part++) { if ( unregister || (p[part].nr_sects < 1) ) { devfs_unregister(p[part].de); - dev->part[p].de = NULL; + dev->part[part].de = NULL; continue; } devfs_register_partition (dev, minor, part); diff -urNp -I \$.*\$ --exclude TAGS -X /home/rusty/current-dontdiff --minimal linux-2.5.30/include/asm-i386/kprobes.h working-2.5.30-kprobes/include/asm-i386/kprobes.h --- linux-2.5.30/include/asm-i386/kprobes.h Thu Jan 1 10:00:00 1970 +++ working-2.5.30-kprobes/include/asm-i386/kprobes.h Fri Aug 2 15:40:33 2002 @@ -0,0 +1,28 @@ +#ifndef _ASM_KPROBES_H +#define _ASM_KPROBES_H +/* + * Dynamic Probes (kprobes) support + * Vamsi Krishna S <vamsi_krishna@in.ibm.com>, July, 2002 + * Mailing list: dprobes@www-124.ibm.com + */ +#include <linux/smp.h> +#include <linux/types.h> + +struct pt_regs; + +#ifdef CONFIG_KPROBES +typedef u8 kprobe_opcode_t; + +#define BREAKPOINT_INSTRUCTION 0xcc + +extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr); + +/* kprobe_running() not defined yet, so this is a macro. */ +#define kprobe_fault(regs, trapnr) \ + (kprobe_running() && kprobe_fault_handler(regs, trapnr)) + +#else /* !CONFIG_KPROBES */ +static inline int kprobe_fault(struct pt_regs *regs, int trapnr) { return 0; } +#endif + +#endif /* _ASM_KPROBES_H */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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