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Commit a74fb73c authored by Al Viro's avatar Al Viro
Browse files

infrastructure for saner ret_from_kernel_thread semantics 



* allow kernel_execve() leave the actual return to userland to
caller (selected by CONFIG_GENERIC_KERNEL_EXECVE).  Callers
updated accordingly.
* architecture that does select GENERIC_KERNEL_EXECVE in its
Kconfig should have its ret_from_kernel_thread() do this:
	call schedule_tail
	call the callback left for it by copy_thread(); if it ever
returns, that's because it has just done successful kernel_execve()
	jump to return from syscall
IOW, its only difference from ret_from_fork() is that it does call the
callback.
* such an architecture should also get rid of ret_from_kernel_execve()
and __ARCH_WANT_KERNEL_EXECVE

This is the last part of infrastructure patches in that area - from
that point on work on different architectures can live independently.

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent fb45550d

arch/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -261,6 +261,9 @@ config ARCH_WANT_OLD_COMPAT_IPC 
config GENERIC_KERNEL_THREAD

	bool



config GENERIC_KERNEL_EXECVE

	bool



config HAVE_ARCH_SECCOMP_FILTER

	bool

	help

include/linux/syscalls.h

+8 −0
Original line number Diff line number Diff line
@@ -827,7 +827,15 @@ asmlinkage long sys_fanotify_mark(int fanotify_fd, unsigned int flags, 
				  const char  __user *pathname);

asmlinkage long sys_syncfs(int fd);



#ifndef CONFIG_GENERIC_KERNEL_EXECVE

int kernel_execve(const char *filename, const char *const argv[], const char *const envp[]);

#else

#define kernel_execve(filename, argv, envp) \

	do_execve(filename, \

		(const char __user *const __user *)argv, \

		(const char __user *const __user *)envp, \

		current_pt_regs())

#endif





asmlinkage long sys_perf_event_open(

init/main.c

+12 −8
Original line number Diff line number Diff line
@@ -69,6 +69,7 @@ 
#include <linux/slab.h>

#include <linux/perf_event.h>

#include <linux/file.h>

#include <linux/ptrace.h>



#include <asm/io.h>

#include <asm/bugs.h>
@@ -788,10 +789,10 @@ static void __init do_pre_smp_initcalls(void) 
		do_one_initcall(*fn);

}



static void run_init_process(const char *init_filename)

static int run_init_process(const char *init_filename)

{

	argv_init[0] = init_filename;

	kernel_execve(init_filename, argv_init, envp_init);

	return kernel_execve(init_filename, argv_init, envp_init);

}



static void __init kernel_init_freeable(void);
@@ -810,7 +811,8 @@ static int __ref kernel_init(void *unused) 
	flush_delayed_fput();



	if (ramdisk_execute_command) {

		run_init_process(ramdisk_execute_command);

		if (!run_init_process(ramdisk_execute_command))

			return 0;

		printk(KERN_WARNING "Failed to execute %s\n",

				ramdisk_execute_command);

	}
@@ -822,14 +824,16 @@ static int __ref kernel_init(void *unused) 
	 * trying to recover a really broken machine.

	 */

	if (execute_command) {

		run_init_process(execute_command);

		if (!run_init_process(execute_command))

			return 0;

		printk(KERN_WARNING "Failed to execute %s.  Attempting "

					"defaults...\n", execute_command);

	}

	run_init_process("/sbin/init");

	run_init_process("/etc/init");

	run_init_process("/bin/init");

	run_init_process("/bin/sh");

	if (!run_init_process("/sbin/init") ||

	    !run_init_process("/etc/init") ||

	    !run_init_process("/bin/init") ||

	    !run_init_process("/bin/sh"))

		return 0;



	panic("No init found.  Try passing init= option to kernel. "

	      "See Linux Documentation/init.txt for guidance.");

kernel/kmod.c

+3 −0
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include <linux/notifier.h>

#include <linux/suspend.h>

#include <linux/rwsem.h>

#include <linux/ptrace.h>

#include <asm/uaccess.h>



#include <trace/events/module.h>
@@ -221,6 +222,8 @@ static int ____call_usermodehelper(void *data) 
	retval = kernel_execve(sub_info->path,

			       (const char *const *)sub_info->argv,

			       (const char *const *)sub_info->envp);

	if (!retval)

		return 0;



	/* Exec failed? */

fail:

kernel/kthread.c

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/mutex.h>

#include <linux/slab.h>

#include <linux/freezer.h>

#include <linux/ptrace.h>

#include <trace/events/sched.h>



static DEFINE_SPINLOCK(kthread_create_lock);