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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>
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1 parent fb45550 commit a74fb73c12398b250fdc5e333a11e15a9e3a84fc Al Viro committed Oct 11, 2012
Showing with 27 additions and 8 deletions.
  1. +3 −0 arch/Kconfig
  2. +8 −0 include/linux/syscalls.h
  3. +12 −8 init/main.c
  4. +3 −0 kernel/kmod.c
  5. +1 −0 kernel/kthread.c
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3 arch/Kconfig
@@ -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
View
8 include/linux/syscalls.h
@@ -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(
View
20 init/main.c
@@ -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.");
View
3 kernel/kmod.c
@@ -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:
View
1 kernel/kthread.c
@@ -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);

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