svn commit: r327917 - head/sys/kern

[Konstantin Belousov]

Author: kib
Date: Sat Jan 13 11:59:49 2018
New Revision: 327917
URL: https://svnweb.freebsd.org/changeset/base/327917

Log:
  Add sysctl debug.kdb.stack_overflow to conveniently test kernel
  handling of the kstack overflow.
  
  Sponsored by: The FreeBSD Foundation
  MFC after:    1 week

Modified:
  head/sys/kern/subr_kdb.c

Modified: head/sys/kern/subr_kdb.c
==============================================================================
--- head/sys/kern/subr_kdb.c    Sat Jan 13 09:30:34 2018        (r327916)
+++ head/sys/kern/subr_kdb.c    Sat Jan 13 11:59:49 2018        (r327917)
@@ -85,6 +85,7 @@ static int kdb_sysctl_enter(SYSCTL_HANDLER_ARGS);
 static int kdb_sysctl_panic(SYSCTL_HANDLER_ARGS);
 static int kdb_sysctl_trap(SYSCTL_HANDLER_ARGS);
 static int kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS);
+static int kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS);
 
 static SYSCTL_NODE(_debug, OID_AUTO, kdb, CTLFLAG_RW, NULL, "KDB nodes");
 
@@ -110,6 +111,10 @@ SYSCTL_PROC(_debug_kdb, OID_AUTO, trap_code,
     CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
     kdb_sysctl_trap_code, "I", "set to cause a page fault via code access");
 
+SYSCTL_PROC(_debug_kdb, OID_AUTO, stack_overflow,
+    CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_SECURE, NULL, 0,
+    kdb_sysctl_stack_overflow, "I", "set to cause a stack overflow");
+
 SYSCTL_INT(_debug_kdb, OID_AUTO, break_to_debugger,
     CTLFLAG_RWTUN | CTLFLAG_SECURE,
     &kdb_break_to_debugger, 0, "Enable break to debugger");
@@ -224,6 +229,36 @@ kdb_sysctl_trap_code(SYSCTL_HANDLER_ARGS)
        (*fp)(0x11111111, 0x22222222, 0x33333333);
        return (0);
 }
+
+static void kdb_stack_overflow(volatile int *x)  __noinline;
+static void
+kdb_stack_overflow(volatile int *x)
+{
+
+       if (*x > 10000000)
+               return;
+       kdb_stack_overflow(x);
+       *x += PCPU_GET(cpuid) / 1000000;
+}
+
+static int
+kdb_sysctl_stack_overflow(SYSCTL_HANDLER_ARGS)
+{
+       int error, i;
+       volatile int x;
+
+       error = sysctl_wire_old_buffer(req, sizeof(int));
+       if (error == 0) {
+               i = 0;
+               error = sysctl_handle_int(oidp, &i, 0, req);
+       }
+       if (error != 0 || req->newptr == NULL)
+               return (error);
+       x = 0;
+       kdb_stack_overflow(&x);
+       return (0);
+}
+
 
 void
 kdb_panic(const char *msg)
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