[S390] fix system call parameter functions.

syscall_get_nr() currently returns a valid result only if the call
chain of the traced process includes do_syscall_trace_enter(). But
collect_syscall() can be called for any sleeping task, the result of
syscall_get_nr() in general is completely bogus.

To make syscall_get_nr() work for any sleeping task the traps field
in pt_regs is replace with svcnr - the system call number the process
is executing. If svcnr == 0 the process is not on a system call path.

The syscall_get_arguments and syscall_set_arguments use regs->gprs[2]
for the first system call parameter. This is incorrect since gprs[2]
may have been overwritten with the system call number if the call
chain includes do_syscall_trace_enter. Use regs->orig_gprs2 instead.

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

1 files changed, 11 insertions, 10 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 08844fc24a2e..198ea18a534d 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -46,7 +46,7 @@ SP_R14	     =	STACK_FRAME_OVERHEAD + __PT_GPRS + 56
 SP_R15       =  STACK_FRAME_OVERHEAD + __PT_GPRS + 60
 SP_ORIG_R2   =  STACK_FRAME_OVERHEAD + __PT_ORIG_GPR2
 SP_ILC       =  STACK_FRAME_OVERHEAD + __PT_ILC
-SP_TRAP      =  STACK_FRAME_OVERHEAD + __PT_TRAP
+SP_SVCNR     =  STACK_FRAME_OVERHEAD + __PT_SVCNR
 SP_SIZE      =  STACK_FRAME_OVERHEAD + __PT_SIZE
 
 _TIF_WORK_SVC = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
@@ -183,11 +183,10 @@ STACK_SIZE  = 1 << STACK_SHIFT
         .macro  CREATE_STACK_FRAME psworg,savearea
         s       %r15,BASED(.Lc_spsize)  # make room for registers & psw
         mvc     SP_PSW(8,%r15),0(%r12)  # move user PSW to stack
-        la      %r12,\psworg
         st      %r2,SP_ORIG_R2(%r15)    # store original content of gpr 2
-        icm     %r12,12,__LC_SVC_ILC
+        icm     %r12,3,__LC_SVC_ILC
         stm     %r0,%r11,SP_R0(%r15)    # store gprs %r0-%r11 to kernel stack
-        st      %r12,SP_ILC(%r15)
+        st      %r12,SP_SVCNR(%r15)
         mvc     SP_R12(16,%r15),\savearea # move %r12-%r15 to stack
         la      %r12,0
         st      %r12,__SF_BACKCHAIN(%r15)       # clear back chain
@@ -264,16 +263,17 @@ sysc_update:
 #endif
 sysc_do_svc:
         l       %r9,__LC_THREAD_INFO    # load pointer to thread_info struct
-        sla     %r7,2                   # *4 and test for svc 0
+        ltr     %r7,%r7                 # test for svc 0
         bnz     BASED(sysc_nr_ok)       # svc number > 0
         # svc 0: system call number in %r1
         cl      %r1,BASED(.Lnr_syscalls)
         bnl     BASED(sysc_nr_ok)
         lr      %r7,%r1           # copy svc number to %r7
-        sla     %r7,2             # *4
 sysc_nr_ok:
         mvc     SP_ARGS(4,%r15),SP_R7(%r15)
 sysc_do_restart:
+        sth     %r7,SP_SVCNR(%r15)
+        sll     %r7,2             # svc number *4
         l       %r8,BASED(.Lsysc_table)
         tm      __TI_flags+3(%r9),(_TIF_SYSCALL_TRACE|_TIF_SYSCALL_AUDIT)
         l       %r8,0(%r7,%r8)    # get system call addr.
@@ -376,7 +376,6 @@ sysc_notify_resume:
 sysc_restart:
         ni      __TI_flags+3(%r9),255-_TIF_RESTART_SVC # clear TIF_RESTART_SVC
         l       %r7,SP_R2(%r15)         # load new svc number
-        sla     %r7,2
         mvc     SP_R2(4,%r15),SP_ORIG_R2(%r15) # restore first argument
         lm      %r2,%r6,SP_R2(%r15)     # load svc arguments
         b       BASED(sysc_do_restart)  # restart svc
@@ -386,7 +385,8 @@ sysc_restart:
 #
 sysc_singlestep:
         ni      __TI_flags+3(%r9),255-_TIF_SINGLE_STEP # clear TIF_SINGLE_STEP
-        mvi     SP_TRAP+1(%r15),0x28    # set trap indication to pgm check
+        mvi     SP_SVCNR(%r15),0xff     # set trap indication to pgm check
+        mvi     SP_SVCNR+1(%r15),0xff
         la      %r2,SP_PTREGS(%r15)     # address of register-save area
         l       %r1,BASED(.Lhandle_per) # load adr. of per handler
         la      %r14,BASED(sysc_return) # load adr. of system return
@@ -407,7 +407,7 @@ sysc_tracesys:
         bnl     BASED(sysc_tracenogo)
         l       %r8,BASED(.Lsysc_table)
         lr      %r7,%r2
-        sll     %r7,2                   # *4
+        sll     %r7,2                   # svc number *4
         l       %r8,0(%r7,%r8)
 sysc_tracego:
         lm      %r3,%r6,SP_R3(%r15)
@@ -586,7 +586,8 @@ pgm_svcper:
 # per was called from kernel, must be kprobes
 #
 kernel_per:
-        mvi     SP_TRAP+1(%r15),0x28    # set trap indication to pgm check
+        mvi     SP_SVCNR(%r15),0xff     # set trap indication to pgm check
+        mvi     SP_SVCNR+1(%r15),0xff
         la      %r2,SP_PTREGS(%r15)     # address of register-save area
         l       %r1,BASED(.Lhandle_per) # load adr. of per handler
         la      %r14,BASED(sysc_restore)# load adr. of system return