From 9786a8f3cbc61f990266e23ffdb338ee3118b03d Mon Sep 17 00:00:00 2001 From: Bodo Stroesser Date: Thu, 7 Jul 2005 17:56:50 -0700 Subject: [PATCH] uml: Proper clone support for skas0 This patch implements the clone-stub mechanism, which allows skas0 to run with proc_mm==0, even if the clib in UML uses modify_ldt. Note: There is a bug in skas3.v7 host patch, that avoids UML-skas from running properly on a SMP-box. In full skas3, I never really saw problems, but in skas0 they showed up. More commentary by jdike - What this patch does is makes sure that the host parent of each new host process matches the UML parent of the corresponding UML process. This ensures that any changed LDTs are inherited. This is done by having clone actually called by the UML process from its stub, rather than by the kernel. We have special syscall stubs that are loaded onto the stub code page because that code must be completely self-contained. These stubs are given C interfaces, and used like normal C functions, but there are subtleties. Principally, we have to be careful about stack variables in stub_clone_handler after the clone. The code is written so that there aren't any - everything boils down to a fixed address. If there were any locals, references to them after the clone would be wrong because the stack just changed. Signed-off-by: Bodo Stroesser Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/um/kernel/skas/include/skas.h | 1 + arch/um/kernel/skas/include/stub-data.h | 18 ++++++++++++++++++ 2 files changed, 19 insertions(+) create mode 100644 arch/um/kernel/skas/include/stub-data.h (limited to 'arch/um/kernel/skas/include') diff --git a/arch/um/kernel/skas/include/skas.h b/arch/um/kernel/skas/include/skas.h index d91a60f3830..d983ea84254 100644 --- a/arch/um/kernel/skas/include/skas.h +++ b/arch/um/kernel/skas/include/skas.h @@ -32,6 +32,7 @@ extern int protect(struct mm_id * mm_idp, unsigned long addr, extern void user_signal(int sig, union uml_pt_regs *regs, int pid); extern int new_mm(int from); extern int start_userspace(unsigned long stub_stack); +extern int copy_context_skas0(unsigned long stack, int pid); extern void get_skas_faultinfo(int pid, struct faultinfo * fi); extern long execute_syscall_skas(void *r); extern unsigned long current_stub_stack(void); diff --git a/arch/um/kernel/skas/include/stub-data.h b/arch/um/kernel/skas/include/stub-data.h new file mode 100644 index 00000000000..f6ed92c3727 --- /dev/null +++ b/arch/um/kernel/skas/include/stub-data.h @@ -0,0 +1,18 @@ +/* + * Copyright (C) 2005 Jeff Dike (jdike@karaya.com) + * Licensed under the GPL + */ + +#ifndef __STUB_DATA_H +#define __STUB_DATA_H + +#include + +struct stub_data { + long offset; + int fd; + struct itimerval timer; + long err; +}; + +#endif -- cgit v1.2.3