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tracehook: asm/syscall.h

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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: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2008-07-25 19:45:57 -07:00 committed by Linus Torvalds
parent 64b1208d5b
commit 828c365cc8
2 changed files with 143 additions and 1 deletions
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141
include/asm-generic/syscall.h Normal file
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@ -0,0 +1,141 @@
/*
* 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 */

3
include/linux/tracehook.h
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@ -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.
*/