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: Al Viro <viro@zeniv.linux.org.uk>

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: Al Viro <viro@zeniv.linux.org.uk>
Al Viro
1 parent fb45550d76
Showing 5 changed files with 27 additions and 8 deletions Side-by-side Diff
arch/Kconfig
include/linux/syscalls.h
init/main.c
kernel/kmod.c
kernel/kthread.c
@@ -261,6 +261,9 @@
 config GENERIC_KERNEL_THREAD
 	bool
  
+config GENERIC_KERNEL_EXECVE
+	bool
+
 config HAVE_ARCH_SECCOMP_FILTER
 	bool
 	help
@@ -827,7 +827,15 @@
 				  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(
@@ -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 @@
 		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 @@
 	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 @@
 	 * 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.");
@@ -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 @@
 	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:
@@ -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);
...	...	@@ -261,6 +261,9 @@
261	261	config GENERIC_KERNEL_THREAD
262	262	bool
263	263
	264	+config GENERIC_KERNEL_EXECVE
	265	+ bool
	266	+
264	267	config HAVE_ARCH_SECCOMP_FILTER
265	268	bool
266	269	help
...	...	@@ -827,7 +827,15 @@
827	827	const char __user *pathname);
828	828	asmlinkage long sys_syncfs(int fd);
829	829
	830	+#ifndef CONFIG_GENERIC_KERNEL_EXECVE
830	831	int kernel_execve(const char filename, const char const argv[], const char *const envp[]);
	832	+#else
	833	+#define kernel_execve(filename, argv, envp) \
	834	+ do_execve(filename, \
	835	+ (const char __user const __user )argv, \
	836	+ (const char __user const __user )envp, \
	837	+ current_pt_regs())
	838	+#endif
831	839
832	840
833	841	asmlinkage long sys_perf_event_open(
...	...	@@ -69,6 +69,7 @@
69	69	#include <linux/slab.h>
70	70	#include <linux/perf_event.h>
71	71	#include <linux/file.h>
	72	+#include <linux/ptrace.h>
72	73
73	74	#include <asm/io.h>
74	75	#include <asm/bugs.h>
75	76
...	...	@@ -788,10 +789,10 @@
788	789	do_one_initcall(*fn);
789	790	}
790	791
791		-static void run_init_process(const char *init_filename)
	792	+static int run_init_process(const char *init_filename)
792	793	{
793	794	argv_init[0] = init_filename;
794		- kernel_execve(init_filename, argv_init, envp_init);
	795	+ return kernel_execve(init_filename, argv_init, envp_init);
795	796	}
796	797
797	798	static void __init kernel_init_freeable(void);
...	...	@@ -810,7 +811,8 @@
810	811	flush_delayed_fput();
811	812
812	813	if (ramdisk_execute_command) {
813		- run_init_process(ramdisk_execute_command);
	814	+ if (!run_init_process(ramdisk_execute_command))
	815	+ return 0;
814	816	printk(KERN_WARNING "Failed to execute %s\n",
815	817	ramdisk_execute_command);
816	818	}
817	819
...	...	@@ -822,14 +824,16 @@
822	824	* trying to recover a really broken machine.
823	825	*/
824	826	if (execute_command) {
825		- run_init_process(execute_command);
	827	+ if (!run_init_process(execute_command))
	828	+ return 0;
826	829	printk(KERN_WARNING "Failed to execute %s. Attempting "
827	830	"defaults...\n", execute_command);
828	831	}
829		- run_init_process("/sbin/init");
830		- run_init_process("/etc/init");
831		- run_init_process("/bin/init");
832		- run_init_process("/bin/sh");
	832	+ if (!run_init_process("/sbin/init") \|\|
	833	+ !run_init_process("/etc/init") \|\|
	834	+ !run_init_process("/bin/init") \|\|
	835	+ !run_init_process("/bin/sh"))
	836	+ return 0;
833	837
834	838	panic("No init found. Try passing init= option to kernel. "
835	839	"See Linux Documentation/init.txt for guidance.");
...	...	@@ -37,6 +37,7 @@
37	37	#include <linux/notifier.h>
38	38	#include <linux/suspend.h>
39	39	#include <linux/rwsem.h>
	40	+#include <linux/ptrace.h>
40	41	#include <asm/uaccess.h>
41	42
42	43	#include <trace/events/module.h>
...	...	@@ -221,6 +222,8 @@
221	222	retval = kernel_execve(sub_info->path,
222	223	(const char const )sub_info->argv,
223	224	(const char const )sub_info->envp);
	225	+ if (!retval)
	226	+ return 0;
224	227
225	228	/* Exec failed? */
226	229	fail:
...	...	@@ -16,6 +16,7 @@
16	16	#include <linux/mutex.h>
17	17	#include <linux/slab.h>
18	18	#include <linux/freezer.h>
	19	+#include <linux/ptrace.h>
19	20	#include <trace/events/sched.h>
20	21
21	22	static DEFINE_SPINLOCK(kthread_create_lock);