mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-11-19 02:04:19 +08:00
b35f549df1
At Linux Plumbers, Andy Lutomirski approached me and pointed out that the function call syscall_get_arguments() implemented in x86 was horribly written and not optimized for the standard case of passing in 0 and 6 for the starting index and the number of system calls to get. When looking at all the users of this function, I discovered that all instances pass in only 0 and 6 for these arguments. Instead of having this function handle different cases that are never used, simply rewrite it to return the first 6 arguments of a system call. This should help out the performance of tracing system calls by ptrace, ftrace and perf. Link: http://lkml.kernel.org/r/20161107213233.754809394@goodmis.org Cc: Oleg Nesterov <oleg@redhat.com> Cc: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Dominik Brodowski <linux@dominikbrodowski.net> Cc: Dave Martin <dave.martin@arm.com> Cc: "Dmitry V. Levin" <ldv@altlinux.org> Cc: x86@kernel.org Cc: linux-snps-arc@lists.infradead.org Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-c6x-dev@linux-c6x.org Cc: uclinux-h8-devel@lists.sourceforge.jp Cc: linux-hexagon@vger.kernel.org Cc: linux-ia64@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: nios2-dev@lists.rocketboards.org Cc: openrisc@lists.librecores.org Cc: linux-parisc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-riscv@lists.infradead.org Cc: linux-s390@vger.kernel.org Cc: linux-sh@vger.kernel.org Cc: sparclinux@vger.kernel.org Cc: linux-um@lists.infradead.org Cc: linux-xtensa@linux-xtensa.org Cc: linux-arch@vger.kernel.org Acked-by: Paul Burton <paul.burton@mips.com> # MIPS parts Acked-by: Max Filippov <jcmvbkbc@gmail.com> # For xtensa changes Acked-by: Will Deacon <will.deacon@arm.com> # For the arm64 bits Reviewed-by: Thomas Gleixner <tglx@linutronix.de> # for x86 Reviewed-by: Dmitry V. Levin <ldv@altlinux.org> Reported-by: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
82 lines
2.5 KiB
C
82 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/ptrace.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/sched/task_stack.h>
|
|
#include <linux/export.h>
|
|
#include <asm/syscall.h>
|
|
|
|
static int collect_syscall(struct task_struct *target, struct syscall_info *info)
|
|
{
|
|
struct pt_regs *regs;
|
|
|
|
if (!try_get_task_stack(target)) {
|
|
/* Task has no stack, so the task isn't in a syscall. */
|
|
memset(info, 0, sizeof(*info));
|
|
info->data.nr = -1;
|
|
return 0;
|
|
}
|
|
|
|
regs = task_pt_regs(target);
|
|
if (unlikely(!regs)) {
|
|
put_task_stack(target);
|
|
return -EAGAIN;
|
|
}
|
|
|
|
info->sp = user_stack_pointer(regs);
|
|
info->data.instruction_pointer = instruction_pointer(regs);
|
|
|
|
info->data.nr = syscall_get_nr(target, regs);
|
|
if (info->data.nr != -1L)
|
|
syscall_get_arguments(target, regs,
|
|
(unsigned long *)&info->data.args[0]);
|
|
|
|
put_task_stack(target);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* task_current_syscall - Discover what a blocked task is doing.
|
|
* @target: thread to examine
|
|
* @info: structure with the following fields:
|
|
* .sp - filled with user stack pointer
|
|
* .data.nr - filled with system call number or -1
|
|
* .data.args - filled with @maxargs system call arguments
|
|
* .data.instruction_pointer - filled with user PC
|
|
*
|
|
* If @target is blocked in a system call, returns zero with @info.data.nr
|
|
* set to the the call's number and @info.data.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 *@info.data.nr set to -1 and does not fill in
|
|
* @info.data.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.
|
|
*/
|
|
int task_current_syscall(struct task_struct *target, struct syscall_info *info)
|
|
{
|
|
long state;
|
|
unsigned long ncsw;
|
|
|
|
if (target == current)
|
|
return collect_syscall(target, info);
|
|
|
|
state = target->state;
|
|
if (unlikely(!state))
|
|
return -EAGAIN;
|
|
|
|
ncsw = wait_task_inactive(target, state);
|
|
if (unlikely(!ncsw) ||
|
|
unlikely(collect_syscall(target, info)) ||
|
|
unlikely(wait_task_inactive(target, state) != ncsw))
|
|
return -EAGAIN;
|
|
|
|
return 0;
|
|
}
|