[Xen-devel] [PATCH] xen: make debugger support configurable

[Juergen Gross <jgross@xxxxxxxx>]

Debugger support in the hypervisor is rarely used and it is opening a
way for dom0 to modify the running hypervisor by very easy means.

Add a Kconfig option to control support of gdbsx. Default is off.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/Kconfig.debug              |  4 ++++
 xen/arch/x86/Kconfig           |  1 -
 xen/arch/x86/domctl.c          |  4 ++++
 xen/common/Kconfig             |  3 ---
 xen/common/domain.c            |  2 +-
 xen/include/asm-x86/debugger.h | 30 ++++++++++++++++++------------
 xen/include/xen/sched.h        |  4 ++++
 7 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/xen/Kconfig.debug b/xen/Kconfig.debug
index 22573e74db..84a6e1b8eb 100644
--- a/xen/Kconfig.debug
+++ b/xen/Kconfig.debug
@@ -13,9 +13,13 @@ config DEBUG
 
 if DEBUG || EXPERT = "y"
 
+config GDBSX
+       bool
+
 config CRASH_DEBUG
        bool "Crash Debugging Support"
        depends on X86
+       select GDBSX
        ---help---
          If you want to attach gdb to Xen to debug Xen if it crashes
          then say Y.
diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 28b3b4692a..c72da8964a 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -13,7 +13,6 @@ config X86
        select HAS_EHCI
        select HAS_EX_TABLE
        select HAS_FAST_MULTIPLY
-       select HAS_GDBSX
        select HAS_IOPORTS
        select HAS_KEXEC
        select MEM_ACCESS_ALWAYS_ON
diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 43e368d63b..90e36b9ad8 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -36,6 +36,7 @@
 #include <asm/psr.h>
 #include <asm/cpuid.h>
 
+#ifdef CONFIG_GDBSX
 static int gdbsx_guest_mem_io(domid_t domid, struct xen_domctl_gdbsx_memio 
*iop)
 {
     void * __user gva = (void *)iop->gva, * __user uva = (void *)iop->uva;
@@ -45,6 +46,7 @@ static int gdbsx_guest_mem_io(domid_t domid, struct 
xen_domctl_gdbsx_memio *iop)
 
     return iop->remain ? -EFAULT : 0;
 }
+#endif
 
 static void domain_cpu_policy_changed(struct domain *d)
 {
@@ -912,6 +914,7 @@ long arch_do_domctl(
     }
 #endif
 
+#ifdef CONFIG_GDBSX
     case XEN_DOMCTL_gdbsx_guestmemio:
         domctl->u.gdbsx_guest_memio.remain = domctl->u.gdbsx_guest_memio.len;
         ret = gdbsx_guest_mem_io(domctl->domain, &domctl->u.gdbsx_guest_memio);
@@ -976,6 +979,7 @@ long arch_do_domctl(
         copyback = true;
         break;
     }
+#endif
 
     case XEN_DOMCTL_setvcpuextstate:
     case XEN_DOMCTL_getvcpuextstate:
diff --git a/xen/common/Kconfig b/xen/common/Kconfig
index f754741972..7bde6aff02 100644
--- a/xen/common/Kconfig
+++ b/xen/common/Kconfig
@@ -57,9 +57,6 @@ config HAS_UBSAN
 config HAS_KEXEC
        bool
 
-config HAS_GDBSX
-       bool
-
 config HAS_IOPORTS
        bool
 
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 611116c7fc..b4e041ffd0 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -915,7 +915,7 @@ void vcpu_end_shutdown_deferral(struct vcpu *v)
         vcpu_check_shutdown(v);
 }
 
-#ifdef CONFIG_HAS_GDBSX
+#ifdef CONFIG_GDBSX
 void domain_pause_for_debugger(void)
 {
     struct vcpu *curr = current;
diff --git a/xen/include/asm-x86/debugger.h b/xen/include/asm-x86/debugger.h
index b1b627f1fa..4a8f226b86 100644
--- a/xen/include/asm-x86/debugger.h
+++ b/xen/include/asm-x86/debugger.h
@@ -47,18 +47,6 @@ static inline bool debugger_trap_fatal(
 /* Int3 is a trivial way to gather cpu_user_regs context. */
 #define debugger_trap_immediate() __asm__ __volatile__ ( "int3" );
 
-#else
-
-static inline bool debugger_trap_fatal(
-    unsigned int vector, struct cpu_user_regs *regs)
-{
-    return false;
-}
-
-#define debugger_trap_immediate() ((void)0)
-
-#endif
-
 static inline bool debugger_trap_entry(
     unsigned int vector, struct cpu_user_regs *regs)
 {
@@ -88,4 +76,22 @@ unsigned int dbg_rw_mem(void * __user addr, void * __user 
buf,
                         unsigned int len, domid_t domid, bool toaddr,
                         uint64_t pgd3);
 
+#else
+
+static inline bool debugger_trap_fatal(
+    unsigned int vector, struct cpu_user_regs *regs)
+{
+    return false;
+}
+
+#define debugger_trap_immediate() ((void)0)
+
+static inline bool debugger_trap_entry(
+    unsigned int vector, struct cpu_user_regs *regs)
+{
+    return false;
+}
+
+#endif
+
 #endif /* __X86_DEBUGGER_H__ */
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 9f7bc69293..094003f562 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -652,7 +652,11 @@ void domain_destroy(struct domain *d);
 int domain_kill(struct domain *d);
 int domain_shutdown(struct domain *d, u8 reason);
 void domain_resume(struct domain *d);
+#ifdef CONFIG_GDBSX
 void domain_pause_for_debugger(void);
+#else
+static inline void domain_pause_for_debugger(void) { }
+#endif
 
 int domain_soft_reset(struct domain *d);
 
-- 
2.16.4


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