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Subject[PATCH] [re-xmit] kprobes for 2.5.58
Linus,

Here is the kprobes patch for 2.5.58.

This has incorporated all your feedback to unconditionally turn
trap1 and trap3 to ring3 interrupt gates and DaveM's (who wanted
the arch-indep bits for sparc).

kprobes allows trapping at almost any kernel address, useful for
various kernel-hacking tasks, and building on for more
infrastructure. This patch is x86 only, but other archs can add
support as required (s390 and ppc support is almost done, will be
submitted once this patch is in).

Rusty Lynch has built a sysfs-based module to use kprobes to
dynamically insert printks in running kernels. Other tools
that build on top of kprobes infrastructure, including
support for user space probes, are available/in development.

Please apply.

Thanks,
Vamsi.
--
Vamsi Krishna S.
Linux Technology Center,
IBM Software Lab, Bangalore.
Ph: +91 80 5044959
Internet: vamsi@in.ibm.com
--
[vamsi@vamsiks] ~$ diffstat -p1 /patches/kprobes-2558-1.patch
arch/i386/Kconfig | 9 ++
arch/i386/kernel/Makefile | 1
arch/i386/kernel/entry.S | 22 +++++-
arch/i386/kernel/kprobes.c | 160 +++++++++++++++++++++++++++++++++++++++++++++
arch/i386/kernel/traps.c | 36 ++++++++--
arch/i386/mm/fault.c | 4 +
include/asm-i386/kprobes.h | 34 +++++++++
include/linux/kprobes.h | 60 ++++++++++++++++
kernel/Makefile | 1
kernel/kprobes.c | 89 +++++++++++++++++++++++++
10 files changed, 405 insertions(+), 11 deletions(-)
--
diff -urN -X /home/vamsi/.dontdiff 58-pure/arch/i386/Kconfig 58-kprobes/arch/i386/Kconfig
--- 58-pure/arch/i386/Kconfig 2003-01-14 11:28:12.000000000 +0530
+++ 58-kprobes/arch/i386/Kconfig 2003-01-14 16:46:17.000000000 +0530
@@ -1543,6 +1543,15 @@
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.

+config KPROBES
+ bool "Kprobes"
+ depends on DEBUG_KERNEL
+ help
+ 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".
+
config DEBUG_STACKOVERFLOW
bool "Check for stack overflows"
depends on DEBUG_KERNEL
diff -urN -X /home/vamsi/.dontdiff 58-pure/arch/i386/kernel/entry.S 58-kprobes/arch/i386/kernel/entry.S
--- 58-pure/arch/i386/kernel/entry.S 2003-01-14 11:28:26.000000000 +0530
+++ 58-kprobes/arch/i386/kernel/entry.S 2003-01-14 16:46:17.000000000 +0530
@@ -471,9 +471,16 @@
jmp ret_from_exception

ENTRY(debug)
+ pushl $-1 # mark this as an int
+ SAVE_ALL
+ movl %esp,%edx
pushl $0
- pushl $do_debug
- jmp error_code
+ pushl %edx
+ call do_debug
+ addl $8,%esp
+ testl %eax,%eax
+ jnz restore_all
+ jmp ret_from_exception

ENTRY(nmi)
pushl %eax
@@ -486,9 +493,16 @@
RESTORE_ALL

ENTRY(int3)
+ pushl $-1 # mark this as an int
+ SAVE_ALL
+ movl %esp,%edx
pushl $0
- pushl $do_int3
- jmp error_code
+ pushl %edx
+ call do_int3
+ addl $8,%esp
+ testl %eax,%eax
+ jnz restore_all
+ jmp ret_from_exception

ENTRY(overflow)
pushl $0
diff -urN -X /home/vamsi/.dontdiff 58-pure/arch/i386/kernel/kprobes.c 58-kprobes/arch/i386/kernel/kprobes.c
--- 58-pure/arch/i386/kernel/kprobes.c 1970-01-01 05:30:00.000000000 +0530
+++ 58-kprobes/arch/i386/kernel/kprobes.c 2003-01-14 16:46:17.000000000 +0530
@@ -0,0 +1,160 @@
+/*
+ * Support for kernel probes.
+ * (C) 2002 Vamsi Krishna S <vamsi_krishna@in.ibm.com>.
+ */
+
+#include <linux/config.h>
+#include <linux/kprobes.h>
+#include <linux/ptrace.h>
+#include <linux/spinlock.h>
+#include <linux/preempt.h>
+
+/* kprobe_status settings */
+#define KPROBE_HIT_ACTIVE 0x00000001
+#define KPROBE_HIT_SS 0x00000002
+
+static struct kprobe *current_kprobe;
+static unsigned long kprobe_status, kprobe_old_eflags, kprobe_saved_eflags;
+
+/*
+ * 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.
+ */
+int kprobe_handler(struct pt_regs *regs)
+{
+ struct kprobe *p;
+ int ret = 0;
+ u8 *addr = (u8 *)(regs->eip-1);
+
+ /* We're in an interrupt, but this is clear and BUG()-safe. */
+ preempt_disable();
+
+ /* 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);
+ if (p) {
+ disarm_kprobe(p, regs);
+ ret = 1;
+ }
+ /* If it's not ours, can't be delete race, (we hold lock). */
+ goto no_kprobe;
+ }
+
+ lock_kprobes();
+ p = get_kprobe(addr);
+ if (!p) {
+ unlock_kprobes();
+ /* Unregistered (on another cpu) after this hit? Ignore */
+ if (*addr != BREAKPOINT_INSTRUCTION)
+ ret = 1;
+ /* Not one of ours: let kernel handle it */
+ goto no_kprobe;
+ }
+
+ kprobe_status = KPROBE_HIT_ACTIVE;
+ current_kprobe = p;
+ kprobe_saved_eflags = kprobe_old_eflags
+ = (regs->eflags & (TF_MASK|IF_MASK));
+ if (is_IF_modifier(p->opcode))
+ kprobe_saved_eflags &= ~IF_MASK;
+
+ p->pre_handler(p, regs);
+
+ regs->eflags |= TF_MASK;
+ regs->eflags &= ~IF_MASK;
+
+ /* We hold lock, now we remove breakpoint and single step. */
+ disarm_kprobe(p, regs);
+ kprobe_status = KPROBE_HIT_SS;
+ return 1;
+
+no_kprobe:
+ preempt_enable_no_resched();
+ return ret;
+}
+
+static void rearm_kprobe(struct kprobe *p, struct pt_regs *regs)
+{
+ regs->eflags &= ~TF_MASK;
+ *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.
+ */
+int post_kprobe_handler(struct pt_regs *regs)
+{
+ if (!kprobe_running())
+ return 0;
+
+ 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.
+ * Note that regs->esp is actually the top of the stack when the
+ * trap occurs in kernel space.
+ */
+ if (current_kprobe->opcode == 0x9c) { /* pushfl */
+ regs->esp &= ~(TF_MASK | IF_MASK);
+ regs->esp |= kprobe_old_eflags;
+ }
+
+ rearm_kprobe(current_kprobe, regs);
+ regs->eflags |= kprobe_saved_eflags;
+
+ unlock_kprobes();
+ preempt_enable_no_resched();
+
+ /*
+ * 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 & TF_MASK)
+ 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();
+ preempt_enable_no_resched();
+ }
+ return 0;
+}
diff -urN -X /home/vamsi/.dontdiff 58-pure/arch/i386/kernel/Makefile 58-kprobes/arch/i386/kernel/Makefile
--- 58-pure/arch/i386/kernel/Makefile 2003-01-14 11:28:21.000000000 +0530
+++ 58-kprobes/arch/i386/kernel/Makefile 2003-01-14 16:46:53.000000000 +0530
@@ -29,6 +29,7 @@
obj-$(CONFIG_X86_NUMAQ) += numaq.o
obj-$(CONFIG_PROFILING) += profile.o
obj-$(CONFIG_EDD) += edd.o
+obj-$(CONFIG_KPROBES) += kprobes.o
obj-$(CONFIG_MODULES) += module.o
obj-y += sysenter.o

diff -urN -X /home/vamsi/.dontdiff 58-pure/arch/i386/kernel/traps.c 58-kprobes/arch/i386/kernel/traps.c
--- 58-pure/arch/i386/kernel/traps.c 2003-01-14 11:28:20.000000000 +0530
+++ 58-kprobes/arch/i386/kernel/traps.c 2003-01-14 16:48:24.000000000 +0530
@@ -24,6 +24,7 @@
#include <linux/interrupt.h>
#include <linux/highmem.h>
#include <linux/kallsyms.h>
+#include <linux/kprobes.h>

#ifdef CONFIG_EISA
#include <linux/ioport.h>
@@ -344,7 +345,6 @@
}

DO_VM86_ERROR_INFO( 0, SIGFPE, "divide error", divide_error, FPE_INTDIV, regs->eip)
-DO_VM86_ERROR( 3, SIGTRAP, "int3", int3)
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)
@@ -360,6 +360,9 @@
{
if (regs->eflags & VM_MASK)
goto gp_in_vm86;
+
+ if (kprobe_running() && kprobe_fault_handler(regs, 13))
+ return;

if (!(regs->xcs & 3))
goto gp_in_kernel;
@@ -484,6 +487,17 @@
nmi_callback = dummy_nmi_callback;
}

+asmlinkage int do_int3(struct pt_regs *regs, long error_code)
+{
+ if (kprobe_handler(regs))
+ return 1;
+ /* This is an interrupt gate, because kprobes wants interrupts
+ disabled. Normal trap handlers don't. */
+ restore_interrupts(regs);
+ do_trap(3, SIGTRAP, "int3", 1, regs, error_code, NULL);
+ return 0;
+}
+
/*
* Our handling of the processor debug registers is non-trivial.
* We do not clear them on entry and exit from the kernel. Therefore
@@ -506,7 +520,7 @@
* 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;
@@ -514,6 +528,12 @@

__asm__ __volatile__("movl %%db6,%0" : "=r" (condition));

+ if (post_kprobe_handler(regs))
+ return 1;
+
+ /* Interrupts not disabled for normal trap handling. */
+ restore_interrupts(regs);
+
/* Mask out spurious debug traps due to lazy DR7 setting */
if (condition & (DR_TRAP0|DR_TRAP1|DR_TRAP2|DR_TRAP3)) {
if (!tsk->thread.debugreg[7])
@@ -564,17 +584,17 @@
__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_reenable:
set_tsk_thread_flag(tsk, TIF_SINGLESTEP);
clear_TF:
regs->eflags &= ~TF_MASK;
- return;
+ return 0;
}

/*
@@ -738,6 +758,8 @@
struct task_struct *tsk = current;
clts(); /* Allow maths ops (or we recurse) */

+ if (kprobe_running() && kprobe_fault_handler(&regs, 7))
+ return;
if (!tsk->used_math)
init_fpu(tsk);
restore_fpu(tsk);
@@ -831,9 +853,9 @@
#endif

set_trap_gate(0,&divide_error);
- set_trap_gate(1,&debug);
+ _set_gate(idt_table+1,14,3,&debug); /* debug trap for kprobes */
set_intr_gate(2,&nmi);
- set_system_gate(3,&int3); /* int3-5 can be called from all */
+ _set_gate(idt_table+3,14,3,&int3); /* int3-5 can be called from all */
set_system_gate(4,&overflow);
set_system_gate(5,&bounds);
set_trap_gate(6,&invalid_op);
diff -urN -X /home/vamsi/.dontdiff 58-pure/arch/i386/mm/fault.c 58-kprobes/arch/i386/mm/fault.c
--- 58-pure/arch/i386/mm/fault.c 2003-01-14 11:28:03.000000000 +0530
+++ 58-kprobes/arch/i386/mm/fault.c 2003-01-14 16:49:00.000000000 +0530
@@ -20,6 +20,7 @@
#include <linux/tty.h>
#include <linux/vt_kern.h> /* For unblank_screen() */
#include <linux/module.h>
+#include <linux/kprobes.h>

#include <asm/system.h>
#include <asm/uaccess.h>
@@ -161,6 +162,9 @@
/* get the address */
__asm__("movl %%cr2,%0":"=r" (address));

+ if (kprobe_running() && kprobe_fault_handler(regs, 14))
+ return;
+
/* It's safe to allow irq's after cr2 has been saved */
if (regs->eflags & X86_EFLAGS_IF)
local_irq_enable();
diff -urN -X /home/vamsi/.dontdiff 58-pure/include/asm-i386/kprobes.h 58-kprobes/include/asm-i386/kprobes.h
--- 58-pure/include/asm-i386/kprobes.h 1970-01-01 05:30:00.000000000 +0530
+++ 58-kprobes/include/asm-i386/kprobes.h 2003-01-14 16:46:17.000000000 +0530
@@ -0,0 +1,34 @@
+#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/types.h>
+#include <linux/ptrace.h>
+
+struct pt_regs;
+
+typedef u8 kprobe_opcode_t;
+#define BREAKPOINT_INSTRUCTION 0xcc
+
+/* trap3/1 are intr gates for kprobes. 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 & IF_MASK)
+ __asm__ __volatile__ ("sti");
+}
+
+#ifdef CONFIG_KPROBES
+extern int kprobe_fault_handler(struct pt_regs *regs, int trapnr);
+extern int post_kprobe_handler(struct pt_regs *regs);
+extern int kprobe_handler(struct pt_regs *regs);
+#else /* !CONFIG_KPROBES */
+static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) { return 0; }
+static inline int post_kprobe_handler(struct pt_regs *regs) { return 0; }
+static inline int kprobe_handler(struct pt_regs *regs) { return 0; }
+#endif
+#endif /* _ASM_KPROBES_H */
diff -urN -X /home/vamsi/.dontdiff 58-pure/include/linux/kprobes.h 58-kprobes/include/linux/kprobes.h
--- 58-pure/include/linux/kprobes.h 1970-01-01 05:30:00.000000000 +0530
+++ 58-kprobes/include/linux/kprobes.h 2003-01-14 16:46:17.000000000 +0530
@@ -0,0 +1,60 @@
+#ifndef _LINUX_KPROBES_H
+#define _LINUX_KPROBES_H
+#include <linux/config.h>
+#include <linux/list.h>
+#include <linux/notifier.h>
+#include <linux/smp.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? */
+static inline int kprobe_running(void)
+{
+ extern unsigned int kprobe_cpu;
+ return kprobe_cpu == smp_processor_id();
+}
+
+/* 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 kprobe *p) { return -ENOSYS; }
+static inline void unregister_kprobe(struct kprobe *p) { }
+#endif
+#endif /* _LINUX_KPROBES_H */
diff -urN -X /home/vamsi/.dontdiff 58-pure/kernel/kprobes.c 58-kprobes/kernel/kprobes.c
--- 58-pure/kernel/kprobes.c 1970-01-01 05:30:00.000000000 +0530
+++ 58-kprobes/kernel/kprobes.c 2003-01-14 16:46:17.000000000 +0530
@@ -0,0 +1,89 @@
+/* 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];
+
+unsigned int kprobe_cpu = NR_CPUS;
+static spinlock_t kprobe_lock = SPIN_LOCK_UNLOCKED;
+
+/* 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 -urN -X /home/vamsi/.dontdiff 58-pure/kernel/Makefile 58-kprobes/kernel/Makefile
--- 58-pure/kernel/Makefile 2003-01-14 11:28:24.000000000 +0530
+++ 58-kprobes/kernel/Makefile 2003-01-14 16:46:17.000000000 +0530
@@ -22,6 +22,7 @@
obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
obj-$(CONFIG_SOFTWARE_SUSPEND) += suspend.o
obj-$(CONFIG_COMPAT) += compat.o
+obj-$(CONFIG_KPROBES) += kprobes.o

ifneq ($(CONFIG_IA64),y)
# According to Alan Modra <alan@linuxcare.com.au>, the -fno-omit-frame-pointer is
-
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