[PATCH] Use %ebp rather than %ebx for thread_info pointer

This patch changes assembly code that accesses thread_info to use %ebp
rather than %ebx.

This allows me to take advantage of the fact that %ebp is restored by
user mode in the sysenter register pop removal patch.

vm86() direct return code updated to match [ Linus ]

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 198def80785056e4615bcb8bb7b5b69e90fe7a01..0993b024cd274364a8d06401133f0167434436b3 100644 (file)
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -145,16 +145,16 @@ ENTRY(lcall7)
                                # gates, which has to be cleaned up later..
        pushl %eax
        SAVE_ALL
-       movl %esp, %ebx
-       pushl %ebx
+       movl %esp, %ebp
+       pushl %ebp
        pushl $0x7
 do_lcall:
-       movl EIP(%ebx), %eax    # due to call gates, this is eflags, not eip..
-       movl CS(%ebx), %edx     # this is eip..
-       movl EFLAGS(%ebx), %ecx # and this is cs..
-       movl %eax,EFLAGS(%ebx)  #
-       movl %edx,EIP(%ebx)     # Now we move them to their "normal" places
-       movl %ecx,CS(%ebx)      #
+       movl EIP(%ebp), %eax    # due to call gates, this is eflags, not eip..
+       movl CS(%ebp), %edx     # this is eip..
+       movl EFLAGS(%ebp), %ecx # and this is cs..
+       movl %eax,EFLAGS(%ebp)  #
+       movl %edx,EIP(%ebp)     # Now we move them to their "normal" places
+       movl %ecx,CS(%ebp)      #
 
        #
        # Call gates don't clear TF and NT in eflags like
@@ -166,8 +166,8 @@ do_lcall:
        pushl %eax
        popfl
 
-       andl $-8192, %ebx       # GET_THREAD_INFO
-       movl TI_EXEC_DOMAIN(%ebx), %edx # Get the execution domain
+       andl $-8192, %ebp       # GET_THREAD_INFO
+       movl TI_EXEC_DOMAIN(%ebp), %edx # Get the execution domain
        call *4(%edx)           # Call the lcall7 handler for the domain
        addl $4, %esp
        popl %eax
@@ -178,8 +178,8 @@ ENTRY(lcall27)
                                # gates, which has to be cleaned up later..
        pushl %eax
        SAVE_ALL
-       movl %esp, %ebx
-       pushl %ebx
+       movl %esp, %ebp
+       pushl %ebp
        pushl $0x27
        jmp do_lcall
 
@@ -187,7 +187,7 @@ ENTRY(lcall27)
 ENTRY(ret_from_fork)
        # NOTE: this function takes a parameter but it's unused on x86.
        call schedule_tail
-       GET_THREAD_INFO(%ebx)
+       GET_THREAD_INFO(%ebp)
        jmp syscall_exit
 
 /*
@@ -202,7 +202,7 @@ ENTRY(ret_from_fork)
 ret_from_exception:
        preempt_stop
 ret_from_intr:
-       GET_THREAD_INFO(%ebx)
+       GET_THREAD_INFO(%ebp)
        movl EFLAGS(%esp), %eax         # mix EFLAGS and CS
        movb CS(%esp), %al
        testl $(VM_MASK | 3), %eax
@@ -211,7 +211,7 @@ ENTRY(resume_userspace)
        cli                             # make sure we don't miss an interrupt
                                        # setting need_resched or sigpending
                                        # between sampling and the iret
-       movl TI_FLAGS(%ebx), %ecx
+       movl TI_FLAGS(%ebp), %ecx
        andl $_TIF_WORK_MASK, %ecx      # is there any work to be done on
                                        # int/exception return?
        jne work_pending
@@ -219,18 +219,18 @@ ENTRY(resume_userspace)
 
 #ifdef CONFIG_PREEMPT
 ENTRY(resume_kernel)
-       cmpl $0,TI_PRE_COUNT(%ebx)      # non-zero preempt_count ?
+       cmpl $0,TI_PRE_COUNT(%ebp)      # non-zero preempt_count ?
        jnz restore_all
 need_resched:
-       movl TI_FLAGS(%ebx), %ecx       # need_resched set ?
+       movl TI_FLAGS(%ebp), %ecx       # need_resched set ?
        testb $_TIF_NEED_RESCHED, %cl
        jz restore_all
        testl $IF_MASK,EFLAGS(%esp)     # interrupts off (execption path) ?
        jz restore_all
-       movl $PREEMPT_ACTIVE,TI_PRE_COUNT(%ebx)
+       movl $PREEMPT_ACTIVE,TI_PRE_COUNT(%ebp)
        sti
        call schedule
-       movl $0,TI_PRE_COUNT(%ebx) 
+       movl $0,TI_PRE_COUNT(%ebp)
        cli
        jmp need_resched
 #endif
@@ -262,16 +262,16 @@ ENTRY(sysenter_entry)
 
        pushl %eax
        SAVE_ALL
-       GET_THREAD_INFO(%ebx)
+       GET_THREAD_INFO(%ebp)
        cmpl $(NR_syscalls), %eax
        jae syscall_badsys
 
-       testb $_TIF_SYSCALL_TRACE,TI_FLAGS(%ebx)
+       testb $_TIF_SYSCALL_TRACE,TI_FLAGS(%ebp)
        jnz syscall_trace_entry
        call *sys_call_table(,%eax,4)
        movl %eax,EAX(%esp)
        cli
-       movl TI_FLAGS(%ebx), %ecx
+       movl TI_FLAGS(%ebp), %ecx
        testw $_TIF_ALLWORK_MASK, %cx
        jne syscall_exit_work
        RESTORE_INT_REGS
@@ -286,11 +286,11 @@ ENTRY(sysenter_entry)
 ENTRY(system_call)
        pushl %eax                      # save orig_eax
        SAVE_ALL
-       GET_THREAD_INFO(%ebx)
+       GET_THREAD_INFO(%ebp)
        cmpl $(NR_syscalls), %eax
        jae syscall_badsys
                                        # system call tracing in operation
-       testb $_TIF_SYSCALL_TRACE,TI_FLAGS(%ebx)
+       testb $_TIF_SYSCALL_TRACE,TI_FLAGS(%ebp)
        jnz syscall_trace_entry
 syscall_call:
        call *sys_call_table(,%eax,4)
@@ -299,7 +299,7 @@ syscall_exit:
        cli                             # make sure we don't miss an interrupt
                                        # setting need_resched or sigpending
                                        # between sampling and the iret
-       movl TI_FLAGS(%ebx), %ecx
+       movl TI_FLAGS(%ebp), %ecx
        testw $_TIF_ALLWORK_MASK, %cx   # current->work
        jne syscall_exit_work
 restore_all:
@@ -315,7 +315,7 @@ work_resched:
        cli                             # make sure we don't miss an interrupt
                                        # setting need_resched or sigpending
                                        # between sampling and the iret
-       movl TI_FLAGS(%ebx), %ecx
+       movl TI_FLAGS(%ebp), %ecx
        andl $_TIF_WORK_MASK, %ecx      # is there any work to be done other
                                        # than syscall tracing?
        jz restore_all
@@ -370,7 +370,7 @@ syscall_exit_work:
 syscall_fault:
        pushl %eax                      # save orig_eax
        SAVE_ALL
-       GET_THREAD_INFO(%ebx)
+       GET_THREAD_INFO(%ebp)
        movl $-EFAULT,EAX(%esp)
        jmp resume_userspace
 

diff --git a/arch/i386/kernel/vm86.c b/arch/i386/kernel/vm86.c
index 9d6a68f1948a5ba514a35a3d08334e9647d25355..facb01379561c57ad077615038bbedcaa8560ead 100644 (file)
--- a/arch/i386/kernel/vm86.c
+++ b/arch/i386/kernel/vm86.c
@@ -298,9 +298,10 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
        __asm__ __volatile__(
                "xorl %%eax,%%eax; movl %%eax,%%fs; movl %%eax,%%gs\n\t"
                "movl %0,%%esp\n\t"
+               "movl %1,%%ebp\n\t"
                "jmp resume_userspace"
                : /* no outputs */
-               :"r" (&info->regs), "b" (tsk->thread_info) : "ax");
+               :"r" (&info->regs), "r" (tsk->thread_info) : "ax");
        /* we never return here */
 }
 
@@ -311,8 +312,9 @@ static inline void return_to_32bit(struct kernel_vm86_regs * regs16, int retval)
        regs32 = save_v86_state(regs16);
        regs32->eax = retval;
        __asm__ __volatile__("movl %0,%%esp\n\t"
+               "movl %1,%%ebp\n\t"
                "jmp resume_userspace"
-               : : "r" (regs32), "b" (current_thread_info()));
+               : : "r" (regs32), "r" (current_thread_info()));
 }
 
 static inline void set_IF(struct kernel_vm86_regs * regs)