9786a8f3cb
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 <bstroesser@fujitsu-siemens.com> Signed-off-by: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
66 lines
1.8 KiB
C
66 lines
1.8 KiB
C
/*
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* Copyright (C) 2004 Jeff Dike (jdike@addtoit.com)
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* Licensed under the GPL
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*/
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#ifndef __SYSDEP_STUB_H
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#define __SYSDEP_STUB_H
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#include <asm/ptrace.h>
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#include <asm/unistd.h>
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extern void stub_segv_handler(int sig);
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extern void stub_clone_handler(void);
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#define STUB_SYSCALL_RET EAX
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#define STUB_MMAP_NR __NR_mmap2
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#define MMAP_OFFSET(o) ((o) >> PAGE_SHIFT)
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static inline long stub_syscall2(long syscall, long arg1, long arg2)
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{
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long ret;
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__asm__("movl %0, %%ecx; " : : "g" (arg2) : "%ecx");
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__asm__("movl %0, %%ebx; " : : "g" (arg1) : "%ebx");
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__asm__("movl %0, %%eax; " : : "g" (syscall) : "%eax");
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__asm__("int $0x80;" : : : "%eax");
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__asm__ __volatile__("movl %%eax, %0; " : "=g" (ret) :);
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return(ret);
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}
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static inline long stub_syscall3(long syscall, long arg1, long arg2, long arg3)
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{
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__asm__("movl %0, %%edx; " : : "g" (arg3) : "%edx");
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return(stub_syscall2(syscall, arg1, arg2));
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}
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static inline long stub_syscall4(long syscall, long arg1, long arg2, long arg3,
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long arg4)
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{
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__asm__("movl %0, %%esi; " : : "g" (arg4) : "%esi");
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return(stub_syscall3(syscall, arg1, arg2, arg3));
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}
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static inline long stub_syscall6(long syscall, long arg1, long arg2, long arg3,
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long arg4, long arg5, long arg6)
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{
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long ret;
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__asm__("movl %0, %%eax; " : : "g" (syscall) : "%eax");
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__asm__("movl %0, %%ebx; " : : "g" (arg1) : "%ebx");
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__asm__("movl %0, %%ecx; " : : "g" (arg2) : "%ecx");
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__asm__("movl %0, %%edx; " : : "g" (arg3) : "%edx");
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__asm__("movl %0, %%esi; " : : "g" (arg4) : "%esi");
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__asm__("movl %0, %%edi; " : : "g" (arg5) : "%edi");
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__asm__ __volatile__("pushl %%ebp ; movl %1, %%ebp; "
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"int $0x80; popl %%ebp ; "
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"movl %%eax, %0; " : "=g" (ret) : "g" (arg6) : "%eax");
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return(ret);
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}
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static inline void trap_myself(void)
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{
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__asm("int3");
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}
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#endif
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