From: Zachary Amsden These changes allow a sub-architecture to change the notion of privilege by running the kernel at CPL 0, 1, or 2. The make_kernel_segment() macro can be redefined by a subarchitecture to change the RPL on kernel segments to the appropriate value, and the tests user_mode() and user_mode_vm() may be similarly overridden. Changes to the assembly code are required to fully support this, and provided in a separate patch. Signed-off-by: Zachary Amsden Signed-off-by: Andrew Morton --- arch/i386/kernel/process.c | 2 - arch/i386/kernel/traps.c | 4 +-- include/asm-i386/mach-default/mach_segment.h | 28 +++++++++++++++++++++++++++ include/asm-i386/ptrace.h | 16 --------------- 4 files changed, 32 insertions(+), 18 deletions(-) diff -puN arch/i386/kernel/process.c~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at arch/i386/kernel/process.c --- devel/arch/i386/kernel/process.c~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at 2005-08-06 15:01:42.000000000 -0700 +++ devel-akpm/arch/i386/kernel/process.c 2005-08-06 15:01:42.000000000 -0700 @@ -355,7 +355,7 @@ int kernel_thread(int (*fn)(void *), voi regs.xes = __USER_DS; regs.orig_eax = -1; regs.eip = (unsigned long) kernel_thread_helper; - regs.xcs = __KERNEL_CS; + regs.xcs = make_kernel_segment(__KERNEL_CS); regs.eflags = X86_EFLAGS_IF | X86_EFLAGS_SF | X86_EFLAGS_PF | 0x2; /* Ok, create the new process.. */ diff -puN arch/i386/kernel/traps.c~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at arch/i386/kernel/traps.c --- devel/arch/i386/kernel/traps.c~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at 2005-08-06 15:01:42.000000000 -0700 +++ devel-akpm/arch/i386/kernel/traps.c 2005-08-06 15:01:42.000000000 -0700 @@ -938,10 +938,10 @@ fastcall void setup_x86_bogus_stack(unsi memcpy((void *)(stack_bot + iret_frame16_off), ®s->eip, 20); /* fill in the switch pointers */ switch16_ptr[0] = (regs->esp & 0xffff0000) | iret_frame16_off; - switch16_ptr[1] = __ESPFIX_SS; + switch16_ptr[1] = make_kernel_segment(__ESPFIX_SS); switch32_ptr[0] = (unsigned long)stk + sizeof(struct pt_regs) + 8 - CPU_16BIT_STACK_SIZE; - switch32_ptr[1] = __KERNEL_DS; + switch32_ptr[1] = make_kernel_segment(__KERNEL_DS); } fastcall unsigned char * fixup_x86_bogus_stack(unsigned short sp) diff -puN include/asm-i386/mach-default/mach_segment.h~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at include/asm-i386/mach-default/mach_segment.h --- devel/include/asm-i386/mach-default/mach_segment.h~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at 2005-08-06 15:01:42.000000000 -0700 +++ devel-akpm/include/asm-i386/mach-default/mach_segment.h 2005-08-06 15:01:42.000000000 -0700 @@ -0,0 +1,28 @@ +/* + * include/asm-i386/mach-default/mach_segment.h + * + * user_mode macros moved from include/asm-i386/ptrace.h 08/05 + */ + +#ifndef __MACH_SEGMENT_H +#define __MACH_SEGMENT_H + +/* + * user_mode_vm(regs) determines whether a register set came from user mode. + * This is true if V8086 mode was enabled OR if the register set was from + * protected mode with RPL-3 CS value. This tricky test checks that with + * one comparison. Many places in the kernel can bypass this full check + * if they have already ruled out V8086 mode, so user_mode(regs) can be used. + */ +static inline int user_mode(struct pt_regs *regs) +{ + return (regs->xcs & 3) != 0; +} +static inline int user_mode_vm(struct pt_regs *regs) +{ + return ((regs->xcs & 3) | (regs->eflags & VM_MASK)) != 0; +} + +#define make_kernel_segment(seg) (seg) + +#endif diff -puN include/asm-i386/ptrace.h~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at include/asm-i386/ptrace.h --- devel/include/asm-i386/ptrace.h~i386-transparent-paravirtualization-sub-arch-create-accessors-that-allow-the-i386-kernel-to-run-at 2005-08-06 15:01:42.000000000 -0700 +++ devel-akpm/include/asm-i386/ptrace.h 2005-08-06 15:01:42.000000000 -0700 @@ -57,25 +57,11 @@ struct pt_regs { #ifdef __KERNEL__ #include +#include struct task_struct; extern void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code); -/* - * user_mode_vm(regs) determines whether a register set came from user mode. - * This is true if V8086 mode was enabled OR if the register set was from - * protected mode with RPL-3 CS value. This tricky test checks that with - * one comparison. Many places in the kernel can bypass this full check - * if they have already ruled out V8086 mode, so user_mode(regs) can be used. - */ -static inline int user_mode(struct pt_regs *regs) -{ - return (regs->xcs & 3) != 0; -} -static inline int user_mode_vm(struct pt_regs *regs) -{ - return ((regs->xcs & 3) | (regs->eflags & VM_MASK)) != 0; -} #define instruction_pointer(regs) ((regs)->eip) #if defined(CONFIG_SMP) && defined(CONFIG_FRAME_POINTER) extern unsigned long profile_pc(struct pt_regs *regs); _