Prev kernel_execve() ensured return to userland using asm glue ret_from_kernel_execve(). However given that -kernel_execve() is always called from inside a kernel_thread -and that a real kernel thread never directly "falls-off" into ret_from_kernel_thread() - either never return such as kthreadd or use kthread() wrapper which ensures tailing to do_exit. -core kernel enables returning from kernel_execve( ) path - by removing __init annotation from kernel_init() Thus we can utilize the thread-falling-off for returning to userland. In summary: A thread starts from ret_from_kernel_thread trampoline - leading to kernel_execve. By making sure kernel_execve returns we end back into ret_from_kernel_thread - which now returns as if from syscall - enabling return to usermode. Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> --- arch/arc/Kconfig | 1 + arch/arc/include/asm/unistd.h | 1 - arch/arc/kernel/entry.S | 12 +----------- 3 files changed, 2 insertions(+), 12 deletions(-) diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig index 5588cee..3d5f940 100644 --- a/arch/arc/Kconfig +++ b/arch/arc/Kconfig @@ -17,6 +17,7 @@ config ARC select GENERIC_FIND_FIRST_BIT # for now, we don't need GENERIC_IRQ_PROBE, CONFIG_GENERIC_IRQ_CHIP select GENERIC_IRQ_SHOW + select GENERIC_KERNEL_EXECVE select GENERIC_KERNEL_THREAD select GENERIC_PENDING_IRQ if SMP select GENERIC_SMP_IDLE_THREAD diff --git a/arch/arc/include/asm/unistd.h b/arch/arc/include/asm/unistd.h index 003b2cf..7841827 100644 --- a/arch/arc/include/asm/unistd.h +++ b/arch/arc/include/asm/unistd.h @@ -8,7 +8,6 @@ /******** no-legacy-syscalls-ABI *******/ -#define __ARCH_WANT_KERNEL_EXECVE #define __ARCH_WANT_SYS_EXECVE #define sys_mmap2 sys_mmap_pgoff diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S index d2cad3c..b2291fc 100644 --- a/arch/arc/kernel/entry.S +++ b/arch/arc/kernel/entry.S @@ -583,19 +583,9 @@ ARC_ENTRY ret_from_kernel_thread bl @schedule_tail jl.d [r14] ; kernel_thread "payload" mov r0, r13 ; arg to payload - j @sys_exit + b ret_from_exception ARC_EXIT ret_from_kernel_thread -; When we land here, pt_regs have already been updated in-place correctly -; for return to user mode. -; However the call stack leading to kernel_execve() from say -; ____call_usermodehelper() would make SP != pt_regs. -; Thus we need to set SP to pt_regs as passed by kernel_execve() to us. -ARC_ENTRY ret_from_kernel_execve - b.d ret_from_exception - mov sp, r0 -ARC_EXIT ret_from_kernel_execve - ;################### Special Sys Call Wrappers ########################## ; TBD: call do_fork directly from here -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
