Commit 828c365c authored by Roland McGrath's avatar Roland McGrath Committed by Linus Torvalds
Browse files

tracehook: asm/syscall.h 



This adds asm-generic/syscall.h, which documents what a real
asm-ARCH/syscall.h file should define.  This is not used yet, but will
provide all the machine-dependent details of examining a user system call
about to begin, in progress, or just ended.

Each arch should add an asm-ARCH/syscall.h that defines all the entry
points documented in asm-generic/syscall.h, as short inlines if possible.
This lets us write new tracing code that understands user system call
registers, without any new arch-specific work.

Signed-off-by: default avatarRoland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 64b1208d

include/asm-generic/syscall.h

0 → 100644
+141 −0
Original line number Diff line number Diff line 
/*

 * Access to user system call parameters and results

 *

 * Copyright (C) 2008 Red Hat, Inc.  All rights reserved.

 *

 * This copyrighted material is made available to anyone wishing to use,

 * modify, copy, or redistribute it subject to the terms and conditions

 * of the GNU General Public License v.2.

 *

 * This file is a stub providing documentation for what functions

 * asm-ARCH/syscall.h files need to define.  Most arch definitions

 * will be simple inlines.

 *

 * All of these functions expect to be called with no locks,

 * and only when the caller is sure that the task of interest

 * cannot return to user mode while we are looking at it.

 */



#ifndef _ASM_SYSCALL_H

#define _ASM_SYSCALL_H	1



struct task_struct;

struct pt_regs;



/**

 * syscall_get_nr - find what system call a task is executing

 * @task:	task of interest, must be blocked

 * @regs:	task_pt_regs() of @task

 *

 * If @task is executing a system call or is at system call

 * tracing about to attempt one, returns the system call number.

 * If @task is not executing a system call, i.e. it's blocked

 * inside the kernel for a fault or signal, returns -1.

 *

 * It's only valid to call this when @task is known to be blocked.

 */

long syscall_get_nr(struct task_struct *task, struct pt_regs *regs);



/**

 * syscall_rollback - roll back registers after an aborted system call

 * @task:	task of interest, must be in system call exit tracing

 * @regs:	task_pt_regs() of @task

 *

 * It's only valid to call this when @task is stopped for system

 * call exit tracing (due to TIF_SYSCALL_TRACE or TIF_SYSCALL_AUDIT),

 * after tracehook_report_syscall_entry() returned nonzero to prevent

 * the system call from taking place.

 *

 * This rolls back the register state in @regs so it's as if the

 * system call instruction was a no-op.  The registers containing

 * the system call number and arguments are as they were before the

 * system call instruction.  This may not be the same as what the

 * register state looked like at system call entry tracing.

 */

void syscall_rollback(struct task_struct *task, struct pt_regs *regs);



/**

 * syscall_get_error - check result of traced system call

 * @task:	task of interest, must be blocked

 * @regs:	task_pt_regs() of @task

 *

 * Returns 0 if the system call succeeded, or -ERRORCODE if it failed.

 *

 * It's only valid to call this when @task is stopped for tracing on exit

 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.

 */

long syscall_get_error(struct task_struct *task, struct pt_regs *regs);



/**

 * syscall_get_return_value - get the return value of a traced system call

 * @task:	task of interest, must be blocked

 * @regs:	task_pt_regs() of @task

 *

 * Returns the return value of the successful system call.

 * This value is meaningless if syscall_get_error() returned nonzero.

 *

 * It's only valid to call this when @task is stopped for tracing on exit

 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.

 */

long syscall_get_return_value(struct task_struct *task, struct pt_regs *regs);



/**

 * syscall_set_return_value - change the return value of a traced system call

 * @task:	task of interest, must be blocked

 * @regs:	task_pt_regs() of @task

 * @error:	negative error code, or zero to indicate success

 * @val:	user return value if @error is zero

 *

 * This changes the results of the system call that user mode will see.

 * If @error is zero, the user sees a successful system call with a

 * return value of @val.  If @error is nonzero, it's a negated errno

 * code; the user sees a failed system call with this errno code.

 *

 * It's only valid to call this when @task is stopped for tracing on exit

 * from a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.

 */

void syscall_set_return_value(struct task_struct *task, struct pt_regs *regs,

			      int error, long val);



/**

 * syscall_get_arguments - extract system call parameter values

 * @task:	task of interest, must be blocked

 * @regs:	task_pt_regs() of @task

 * @i:		argument index [0,5]

 * @n:		number of arguments; n+i must be [1,6].

 * @args:	array filled with argument values

 *

 * Fetches @n arguments to the system call starting with the @i'th argument

 * (from 0 through 5).  Argument @i is stored in @args[0], and so on.

 * An arch inline version is probably optimal when @i and @n are constants.

 *

 * It's only valid to call this when @task is stopped for tracing on

 * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.

 * It's invalid to call this with @i + @n > 6; we only support system calls

 * taking up to 6 arguments.

 */

void syscall_get_arguments(struct task_struct *task, struct pt_regs *regs,

			   unsigned int i, unsigned int n, unsigned long *args);



/**

 * syscall_set_arguments - change system call parameter value

 * @task:	task of interest, must be in system call entry tracing

 * @regs:	task_pt_regs() of @task

 * @i:		argument index [0,5]

 * @n:		number of arguments; n+i must be [1,6].

 * @args:	array of argument values to store

 *

 * Changes @n arguments to the system call starting with the @i'th argument.

 * @n'th argument to @val.  Argument @i gets value @args[0], and so on.

 * An arch inline version is probably optimal when @i and @n are constants.

 *

 * It's only valid to call this when @task is stopped for tracing on

 * entry to a system call, due to %TIF_SYSCALL_TRACE or %TIF_SYSCALL_AUDIT.

 * It's invalid to call this with @i + @n > 6; we only support system calls

 * taking up to 6 arguments.

 */

void syscall_set_arguments(struct task_struct *task, struct pt_regs *regs,

			   unsigned int i, unsigned int n,

			   const unsigned long *args);



#endif	/* _ASM_SYSCALL_H */

include/linux/tracehook.h

+2 −1
Original line number Diff line number Diff line
@@ -103,7 +103,8 @@ static inline void ptrace_report_syscall(struct pt_regs *regs) 
 * the system call.  That must prevent normal entry so no system call is

 * made.  If @task ever returns to user mode after this, its register state

 * is unspecified, but should be something harmless like an %ENOSYS error

 * return.

 * return.  It should preserve enough information so that syscall_rollback()

 * can work (see asm-generic/syscall.h).

 *

 * Called without locks, just after entering kernel mode.

 */

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