s390: store breaking event address only for program checks

The principles of operations specifies that the breaking event address
is stored to the address 0x110 in the prefix page only for program checks.
The last branch in user space is lost as soon as a branch in kernel space
is executed after e.g. an svc. This makes it impossible to accurately
maintain the breaking event address for a user space process.

Simplify the code, just copy the current breaking event address from
0x110 to the task structure for program checks from user space.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 97298c58b2bed2c58f2a67f87314b5b11dce7c62..f687f168c94d50030082654373b35d178da4930b 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -103,8 +103,7 @@ _PIF_WORK   = (_PIF_PER_TRAP)
        CHECK_STACK 1<<STACK_SHIFT,\savearea
        aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
        j       3f
-1:     LAST_BREAK %r14
-       UPDATE_VTIME %r14,%r15,\timer
+1:     UPDATE_VTIME %r14,%r15,\timer
 2:     lg      %r15,__LC_ASYNC_STACK   # load async stack
 3:     la      %r11,STACK_FRAME_OVERHEAD(%r15)
        .endm
@@ -121,18 +120,6 @@ _PIF_WORK  = (_PIF_PER_TRAP)
        mvc     __LC_LAST_UPDATE_TIMER(8),\enter_timer
        .endm
 
-       .macro  LAST_BREAK scratch
-       srag    \scratch,%r10,23
-#ifdef CONFIG_HAVE_MARCH_Z990_FEATURES
-       jz      .+10
-       stg     %r10,__TASK_thread+__THREAD_last_break(%r12)
-#else
-       jz      .+14
-       lghi    \scratch,__TASK_thread
-       stg     %r10,__THREAD_last_break(\scratch,%r12)
-#endif
-       .endm
-
        .macro REENABLE_IRQS
        stg     %r8,__LC_RETURN_PSW
        ni      __LC_RETURN_PSW,0xbf
@@ -278,15 +265,14 @@ ENTRY(system_call)
        stpt    __LC_SYNC_ENTER_TIMER
 .Lsysc_stmg:
        stmg    %r8,%r15,__LC_SAVE_AREA_SYNC
-       lg      %r10,__LC_LAST_BREAK
        lg      %r12,__LC_CURRENT
+       lghi    %r13,__TASK_thread
        lghi    %r14,_PIF_SYSCALL
 .Lsysc_per:
        lg      %r15,__LC_KERNEL_STACK
        la      %r11,STACK_FRAME_OVERHEAD(%r15) # pointer to pt_regs
-       LAST_BREAK %r13
 .Lsysc_vtime:
-       UPDATE_VTIME %r10,%r13,__LC_SYNC_ENTER_TIMER
+       UPDATE_VTIME %r8,%r9,__LC_SYNC_ENTER_TIMER
        stmg    %r0,%r7,__PT_R0(%r11)
        mvc     __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
        mvc     __PT_PSW(16,%r11),__LC_SVC_OLD_PSW
@@ -294,12 +280,7 @@ ENTRY(system_call)
        stg     %r14,__PT_FLAGS(%r11)
 .Lsysc_do_svc:
        # load address of system call table
-#ifdef CONFIG_HAVE_MARCH_Z990_FEATURES
-       lg      %r10,__TASK_thread+__THREAD_sysc_table(%r12)
-#else
-       lghi    %r13,__TASK_thread
        lg      %r10,__THREAD_sysc_table(%r13,%r12)
-#endif
        llgh    %r8,__PT_INT_CODE+2(%r11)
        slag    %r8,%r8,2                       # shift and test for svc 0
        jnz     .Lsysc_nr_ok
@@ -508,8 +489,7 @@ ENTRY(pgm_check_handler)
 1:     CHECK_STACK STACK_SIZE,__LC_SAVE_AREA_SYNC
        aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
        j       3f
-2:     LAST_BREAK %r14
-       UPDATE_VTIME %r14,%r15,__LC_SYNC_ENTER_TIMER
+2:     UPDATE_VTIME %r14,%r15,__LC_SYNC_ENTER_TIMER
        lg      %r15,__LC_KERNEL_STACK
        lgr     %r14,%r12
        aghi    %r14,__TASK_thread      # pointer to thread_struct
@@ -518,6 +498,7 @@ ENTRY(pgm_check_handler)
        jz      3f
        mvc     __THREAD_trap_tdb(256,%r14),0(%r13)
 3:     la      %r11,STACK_FRAME_OVERHEAD(%r15)
+       stg     %r10,__THREAD_last_break(%r14)
        stmg    %r0,%r7,__PT_R0(%r11)
        mvc     __PT_R8(64,%r11),__LC_SAVE_AREA_SYNC
        stmg    %r8,%r9,__PT_PSW(%r11)
@@ -576,7 +557,6 @@ ENTRY(io_int_handler)
        STCK    __LC_INT_CLOCK
        stpt    __LC_ASYNC_ENTER_TIMER
        stmg    %r8,%r15,__LC_SAVE_AREA_ASYNC
-       lg      %r10,__LC_LAST_BREAK
        lg      %r12,__LC_CURRENT
        larl    %r13,cleanup_critical
        lmg     %r8,%r9,__LC_IO_OLD_PSW
@@ -750,7 +730,6 @@ ENTRY(ext_int_handler)
        STCK    __LC_INT_CLOCK
        stpt    __LC_ASYNC_ENTER_TIMER
        stmg    %r8,%r15,__LC_SAVE_AREA_ASYNC
-       lg      %r10,__LC_LAST_BREAK
        lg      %r12,__LC_CURRENT
        larl    %r13,cleanup_critical
        lmg     %r8,%r9,__LC_EXT_OLD_PSW
@@ -893,7 +872,6 @@ ENTRY(mcck_int_handler)
        la      %r1,4095                # revalidate r1
        spt     __LC_CPU_TIMER_SAVE_AREA-4095(%r1)      # revalidate cpu timer
        lmg     %r0,%r15,__LC_GPREGS_SAVE_AREA-4095(%r1)# revalidate gprs
-       lg      %r10,__LC_LAST_BREAK
        lg      %r12,__LC_CURRENT
        larl    %r13,cleanup_critical
        lmg     %r8,%r9,__LC_MCK_OLD_PSW
@@ -1088,9 +1066,10 @@ cleanup_critical:
 0:     # check if base register setup + TIF bit load has been done
        clg     %r9,BASED(.Lcleanup_system_call_insn+16)
        jhe     0f
-       # set up saved registers r10 and r12
-       stg     %r10,16(%r11)           # r10 last break
-       stg     %r12,32(%r11)           # r12 task struct pointer
+       # set up saved register r12 task struct pointer
+       stg     %r12,32(%r11)
+       # set up saved register r13 __TASK_thread offset
+       mvc     40(8,%r11),BASED(.Lcleanup_system_call_const)
 0:     # check if the user time update has been done
        clg     %r9,BASED(.Lcleanup_system_call_insn+24)
        jh      0f
@@ -1107,14 +1086,7 @@ cleanup_critical:
        stg     %r15,__LC_SYSTEM_TIMER
 0:     # update accounting time stamp
        mvc     __LC_LAST_UPDATE_TIMER(8),__LC_SYNC_ENTER_TIMER
-       # do LAST_BREAK
-       lg      %r9,16(%r11)
-       srag    %r9,%r9,23
-       jz      0f
-       lgr     %r9,%r12
-       aghi    %r9,__TASK_thread
-       mvc     __THREAD_last_break(8,%r9),16(%r11)
-0:     # set up saved register r11
+       # set up saved register r11
        lg      %r15,__LC_KERNEL_STACK
        la      %r9,STACK_FRAME_OVERHEAD(%r15)
        stg     %r9,24(%r11)            # r11 pt_regs pointer
@@ -1136,6 +1108,8 @@ cleanup_critical:
        .quad   .Lsysc_per
        .quad   .Lsysc_vtime+36
        .quad   .Lsysc_vtime+42
+.Lcleanup_system_call_const:
+       .quad   __TASK_thread
 
 .Lcleanup_sysc_tif:
        larl    %r9,.Lsysc_tif