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linux-next/include/linux/uprobes.h
Ravi Bangoria 1cc33161a8 uprobes: Support SDT markers having reference count (semaphore) 
Userspace Statically Defined Tracepoints[1] are dtrace style markers
inside userspace applications. Applications like PostgreSQL, MySQL,
Pthread, Perl, Python, Java, Ruby, Node.js, libvirt, QEMU, glib etc
have these markers embedded in them. These markers are added by developer
at important places in the code. Each marker source expands to a single
nop instruction in the compiled code but there may be additional
overhead for computing the marker arguments which expands to couple of
instructions. In case the overhead is more, execution of it can be
omitted by runtime if() condition when no one is tracing on the marker:

    if (reference_counter > 0) {
        Execute marker instructions;
    }

Default value of reference counter is 0. Tracer has to increment the
reference counter before tracing on a marker and decrement it when
done with the tracing.

Implement the reference counter logic in core uprobe. User will be
able to use it from trace_uprobe as well as from kernel module. New
trace_uprobe definition with reference counter will now be:

    <path>:<offset>[(ref_ctr_offset)]

where ref_ctr_offset is an optional field. For kernel module, new
variant of uprobe_register() has been introduced:

    uprobe_register_refctr(inode, offset, ref_ctr_offset, consumer)

No new variant for uprobe_unregister() because it's assumed to have
only one reference counter for one uprobe.

[1] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation

Note: 'reference counter' is called as 'semaphore' in original Dtrace
(or Systemtap, bcc and even in ELF) documentation and code. But the
term 'semaphore' is misleading in this context. This is just a counter
used to hold number of tracers tracing on a marker. This is not really
used for any synchronization. So we are calling it a 'reference counter'
in kernel / perf code.

Link: http://lkml.kernel.org/r/20180820044250.11659-2-ravi.bangoria@linux.ibm.com

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
[Only trace_uprobe.c]
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-09-24 04:44:53 -04:00

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#ifndef _LINUX_UPROBES_H
#define _LINUX_UPROBES_H
/*
* User-space Probes (UProbes)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright (C) IBM Corporation, 2008-2012
* Authors:
* Srikar Dronamraju
* Jim Keniston
* Copyright (C) 2011-2012 Red Hat, Inc., Peter Zijlstra
*/
#include <linux/errno.h>
#include <linux/rbtree.h>
#include <linux/types.h>
#include <linux/wait.h>
struct vm_area_struct;
struct mm_struct;
struct inode;
struct notifier_block;
struct page;
#define UPROBE_HANDLER_REMOVE 1
#define UPROBE_HANDLER_MASK 1
#define MAX_URETPROBE_DEPTH 64
enum uprobe_filter_ctx {
UPROBE_FILTER_REGISTER,
UPROBE_FILTER_UNREGISTER,
UPROBE_FILTER_MMAP,
};
struct uprobe_consumer {
int (*handler)(struct uprobe_consumer *self, struct pt_regs *regs);
int (*ret_handler)(struct uprobe_consumer *self,
unsigned long func,
struct pt_regs *regs);
bool (*filter)(struct uprobe_consumer *self,
enum uprobe_filter_ctx ctx,
struct mm_struct *mm);
struct uprobe_consumer *next;
};
#ifdef CONFIG_UPROBES
#include <asm/uprobes.h>
enum uprobe_task_state {
UTASK_RUNNING,
UTASK_SSTEP,
UTASK_SSTEP_ACK,
UTASK_SSTEP_TRAPPED,
};
/*
* uprobe_task: Metadata of a task while it singlesteps.
*/
struct uprobe_task {
enum uprobe_task_state state;
union {
struct {
struct arch_uprobe_task autask;
unsigned long vaddr;
};
struct {
struct callback_head dup_xol_work;
unsigned long dup_xol_addr;
};
};
struct uprobe *active_uprobe;
unsigned long xol_vaddr;
struct return_instance *return_instances;
unsigned int depth;
};
struct return_instance {
struct uprobe *uprobe;
unsigned long func;
unsigned long stack; /* stack pointer */
unsigned long orig_ret_vaddr; /* original return address */
bool chained; /* true, if instance is nested */
struct return_instance *next; /* keep as stack */
};
enum rp_check {
RP_CHECK_CALL,
RP_CHECK_CHAIN_CALL,
RP_CHECK_RET,
};
struct xol_area;
struct uprobes_state {
struct xol_area *xol_area;
};
extern int set_swbp(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long vaddr);
extern int set_orig_insn(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long vaddr);
extern bool is_swbp_insn(uprobe_opcode_t *insn);
extern bool is_trap_insn(uprobe_opcode_t *insn);
extern unsigned long uprobe_get_swbp_addr(struct pt_regs *regs);
extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs);
extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t);
extern int uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern int uprobe_register_refctr(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
extern int uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool);
extern void uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc);
extern int uprobe_mmap(struct vm_area_struct *vma);
extern void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end);
extern void uprobe_start_dup_mmap(void);
extern void uprobe_end_dup_mmap(void);
extern void uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm);
extern void uprobe_free_utask(struct task_struct *t);
extern void uprobe_copy_process(struct task_struct *t, unsigned long flags);
extern int uprobe_post_sstep_notifier(struct pt_regs *regs);
extern int uprobe_pre_sstep_notifier(struct pt_regs *regs);
extern void uprobe_notify_resume(struct pt_regs *regs);
extern bool uprobe_deny_signal(void);
extern bool arch_uprobe_skip_sstep(struct arch_uprobe *aup, struct pt_regs *regs);
extern void uprobe_clear_state(struct mm_struct *mm);
extern int arch_uprobe_analyze_insn(struct arch_uprobe *aup, struct mm_struct *mm, unsigned long addr);
extern int arch_uprobe_pre_xol(struct arch_uprobe *aup, struct pt_regs *regs);
extern int arch_uprobe_post_xol(struct arch_uprobe *aup, struct pt_regs *regs);
extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs *regs);
extern bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx, struct pt_regs *regs);
extern bool arch_uprobe_ignore(struct arch_uprobe *aup, struct pt_regs *regs);
extern void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
void *src, unsigned long len);
#else /* !CONFIG_UPROBES */
struct uprobes_state {
};
#define uprobe_get_trap_addr(regs) instruction_pointer(regs)
static inline int
uprobe_register(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
{
return -ENOSYS;
}
static inline int uprobe_register_refctr(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc)
{
return -ENOSYS;
}
static inline int
uprobe_apply(struct inode *inode, loff_t offset, struct uprobe_consumer *uc, bool add)
{
return -ENOSYS;
}
static inline void
uprobe_unregister(struct inode *inode, loff_t offset, struct uprobe_consumer *uc)
{
}
static inline int uprobe_mmap(struct vm_area_struct *vma)
{
return 0;
}
static inline void
uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned long end)
{
}
static inline void uprobe_start_dup_mmap(void)
{
}
static inline void uprobe_end_dup_mmap(void)
{
}
static inline void
uprobe_dup_mmap(struct mm_struct *oldmm, struct mm_struct *newmm)
{
}
static inline void uprobe_notify_resume(struct pt_regs *regs)
{
}
static inline bool uprobe_deny_signal(void)
{
return false;
}
static inline void uprobe_free_utask(struct task_struct *t)
{
}
static inline void uprobe_copy_process(struct task_struct *t, unsigned long flags)
{
}
static inline void uprobe_clear_state(struct mm_struct *mm)
{
}
#endif /* !CONFIG_UPROBES */
#endif /* _LINUX_UPROBES_H */
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