diff options
| -rw-r--r-- | include/asm-generic/syscall.h | 141 | ||||
| -rw-r--r-- | include/linux/tracehook.h | 3 |
2 files changed, 143 insertions, 1 deletions
diff --git a/include/asm-generic/syscall.h b/include/asm-generic/syscall.h new file mode 100644 index 00000000000..abcf34c2fdc --- /dev/null +++ b/include/asm-generic/syscall.h @@ -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 */ diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h index 32867ab86c7..589f429619c 100644 --- a/include/linux/tracehook.h +++ b/include/linux/tracehook.h @@ -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. */ |