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

* [Xen-devel] [PATCH] xen: make debugger support configurable
@ 2019-11-13 16:22 Juergen Gross
  2019-11-13 16:59 ` Jan Beulich
  2019-11-13 17:26 ` Andrew Cooper
  0 siblings, 2 replies; 4+ messages in thread
From: Juergen Gross @ 2019-11-13 16:22 UTC (permalink / raw)
  To: xen-devel
  Cc: Juergen Gross, Stefano Stabellini, Julien Grall, Wei Liu,
	Konrad Rzeszutek Wilk, George Dunlap, Andrew Cooper, Ian Jackson,
	Jan Beulich, Roger Pau Monné

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@suse.com>
---
 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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