diff options
| -rw-r--r-- | include/linux/ptrace.h | 4 | ||||
| -rw-r--r-- | lib/Makefile | 2 | ||||
| -rw-r--r-- | lib/syscall.c | 75 |
3 files changed, 81 insertions, 0 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index ed69c03..fd31756 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -314,6 +314,10 @@ static inline void user_enable_block_step(struct task_struct *task) #define arch_ptrace_stop(code, info) do { } while (0) #endif +extern int task_current_syscall(struct task_struct *target, long *callno, + unsigned long args[6], unsigned int maxargs, + unsigned long *sp, unsigned long *pc); + #endif #endif diff --git a/lib/Makefile b/lib/Makefile index 9085ad6..942c725 100644 --- a/lib/Makefile +++ b/lib/Makefile @@ -78,6 +78,8 @@ lib-$(CONFIG_GENERIC_BUG) += bug.o obj-$(CONFIG_HAVE_LMB) += lmb.o +obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o + hostprogs-y := gen_crc32table clean-files := crc32table.h diff --git a/lib/syscall.c b/lib/syscall.c new file mode 100644 index 0000000..a4f7067 --- /dev/null +++ b/lib/syscall.c @@ -0,0 +1,75 @@ +#include <linux/ptrace.h> +#include <linux/sched.h> +#include <linux/module.h> +#include <asm/syscall.h> + +static int collect_syscall(struct task_struct *target, long *callno, + unsigned long args[6], unsigned int maxargs, + unsigned long *sp, unsigned long *pc) +{ + struct pt_regs *regs = task_pt_regs(target); + if (unlikely(!regs)) + return -EAGAIN; + + *sp = user_stack_pointer(regs); + *pc = instruction_pointer(regs); + + *callno = syscall_get_nr(target, regs); + if (*callno != -1L && maxargs > 0) + syscall_get_arguments(target, regs, 0, maxargs, args); + + return 0; +} + +/** + * task_current_syscall - Discover what a blocked task is doing. + * @target: thread to examine + * @callno: filled with system call number or -1 + * @args: filled with @maxargs system call arguments + * @maxargs: number of elements in @args to fill + * @sp: filled with user stack pointer + * @pc: filled with user PC + * + * If @target is blocked in a system call, returns zero with *@callno + * set to the the call's number and @args filled in with its arguments. + * Registers not used for system call arguments may not be available and + * it is not kosher to use &struct user_regset calls while the system + * call is still in progress. Note we may get this result if @target + * has finished its system call but not yet returned to user mode, such + * as when it's stopped for signal handling or syscall exit tracing. + * + * If @target is blocked in the kernel during a fault or exception, + * returns zero with *@callno set to -1 and does not fill in @args. + * If so, it's now safe to examine @target using &struct user_regset + * get() calls as long as we're sure @target won't return to user mode. + * + * Returns -%EAGAIN if @target does not remain blocked. + * + * Returns -%EINVAL if @maxargs is too large (maximum is six). + */ +int task_current_syscall(struct task_struct *target, long *callno, + unsigned long args[6], unsigned int maxargs, + unsigned long *sp, unsigned long *pc) +{ + long state; + unsigned long ncsw; + + if (unlikely(maxargs > 6)) + return -EINVAL; + + if (target == current) + return collect_syscall(target, callno, args, maxargs, sp, pc); + + state = target->state; + if (unlikely(!state)) + return -EAGAIN; + + ncsw = wait_task_inactive(target, state); + if (unlikely(!ncsw) || + unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) || + unlikely(wait_task_inactive(target, state) != ncsw)) + return -EAGAIN; + + return 0; +} +EXPORT_SYMBOL_GPL(task_current_syscall); |