PR10650: markup some unprivileged-safe tapset functions

Add /* unprivileged */ to a variety of tapset embedded-c functions,
together with uid-assertion-checking code as needed.  This is only
an initial set, and may need to grow or shrink after further testing.

Prototyped-By: Dave Brolley <brolley@redhat.com>

* runtime/runtime.h (is_myproc, assert_is_myproc): New macros.
* runtime/addr-map.c (lookup_bad_addr): Reject if !is_myproc
  in unprivileged mode.
* runtime/print.c (_stp_print_kernel_info): Add unprivileged
  mode info.
* tapset/DEVGUIDE: Document /* pure */ and /* unprivileged */.
* tapset/*.stp: Add /* unprivileged */ here and there, in
  questionable cases along with an assert_is_myproc().

1 files changed, 21 insertions, 6 deletions

diff --git a/tapset/utrace.stp b/tapset/utrace.stp
index 0d26ed5f..4f841b30 100644
--- a/tapset/utrace.stp
+++ b/tapset/utrace.stp
@@ -4,23 +4,38 @@
 #include "syscall.h"
 %}
 
-function _utrace_syscall_nr:long () %{		/* pure */
-    THIS->__retvalue = syscall_get_nr(current, CONTEXT->regs);
+function _utrace_syscall_nr:long () %{		/* pure */ /* unprivileged */
+    assert_is_myproc();
+    if (! CONTEXT->regs) {
+       CONTEXT->last_error = "invalid call without context registers";
+    } else {
+       THIS->__retvalue = syscall_get_nr(current, CONTEXT->regs);
+    }
 %}
 
-function _utrace_syscall_arg:long (n:long) %{	/* pure */
+function _utrace_syscall_arg:long (n:long) %{	/* pure */ /* unprivileged */
     unsigned long arg = 0;
-    syscall_get_arguments(current, CONTEXT->regs, (int)THIS->n, 1, &arg);
+    assert_is_myproc();
+    if (! CONTEXT->regs) {
+       CONTEXT->last_error = "invalid call without context registers";
+    } else {
+       syscall_get_arguments(current, CONTEXT->regs, (int)THIS->n, 1, &arg);
+    }
     THIS->__retvalue = arg;
 %}
 
-function _utrace_syscall_return:long () %{	/* pure */
+function _utrace_syscall_return:long () %{	/* pure */ /* unprivileged */
     /*
      * Here's the reason for the "unsigned long" cast.  Since all
      * values inside systemtap are 64-bit numbers, return values were
      * getting sign extended.  This caused return values to not match
      * up with the same values passes as arguments.
      */
-    THIS->__retvalue = (unsigned long)syscall_get_return_value(current,
+    assert_is_myproc();
+    if (! CONTEXT->regs) {
+       CONTEXT->last_error = "invalid call without context registers";
+    } else {
+       THIS->__retvalue = (unsigned long)syscall_get_return_value(current,
 							       CONTEXT->regs);
+    }
 %}