rhbz1972805: add basic syscall-in-ptregs support for s390x

Akin to commit 7be7af0fda36 for ARM, add basic syscalls via
tracepoints / CONTEXT->sregs support for s390x.  The argno=6 case is
funny because for syscalls they travel in registers, whereas normally
they hop onto the stack.

diff --git a/tapset/s390/registers.stp b/tapset/s390/registers.stp
index b3986cdd975c94e64e5fc9ad1cc5497772d852dc..cbe7e84835b597e083c30b3d9efcd6637af532eb 100644 (file)
--- a/tapset/s390/registers.stp
+++ b/tapset/s390/registers.stp
@@ -136,7 +136,10 @@ function uarch_bytes:long() {
 function _stp_get_register_by_offset:long (offset:long) %{ /* pure */
        long value;
        struct pt_regs *regs;
-       regs = (CONTEXT->user_mode_p ? CONTEXT->uregs : CONTEXT->kregs);
+       if (CONTEXT->sregs)
+         regs = CONTEXT->sregs;
+       else
+         regs = (CONTEXT->user_mode_p ? CONTEXT->uregs : CONTEXT->kregs);
        if (!regs) {
                CONTEXT->last_error = "No registers available in this context";
                return;
@@ -169,9 +172,10 @@ function _stp_sign_extend32:long (value:long) {
 }
 
 function _stp_register:long (name:string, sign_extend:long) {
-  assert(registers_valid(), "cannot access CPU registers in this context")
+       # don't assert this: will get *regs state checked in _stp_get_register_by_offset, and better
+       # assert(registers_valid(), "cannot access CPU registers in this context")
        offset = _reg_offsets[name]
-  assert(offset != 0 || (name in _reg_offsets), "Unknown register: " . name)
+       assert(offset != 0 || (name in _reg_offsets), "Unknown register: " . name)
        value = _stp_get_register_by_offset(offset)
        if (probing_32bit_app()) {
                if (sign_extend)
@@ -235,8 +239,10 @@ function _stp_arg2:long (argnum:long, sign_extend:long, truncate:long,
                val = u_register("r5")
        else if (argnum == 5)
                val = u_register("r6")
+       else if (argnum == 6 && %{ CONTEXT->sregs != NULL %} ) // linux syscall arg6 goes into r7
+               val = u_register("r7")
        else if (argnum >= 6)
-               val = _stp_get_kernel_stack_param(argnum - 6)
+               val = _stp_get_kernel_stack_param(argnum - 6);
 
        if ((truncate || @__compat_task) && !force64) {
                /* High bits may be garbage. */