Changeset ae89656 in mainline

Timestamp:

2018-05-11T17:26:58Z (6 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

7473807

Parents:

8a8771c

Message:

Provide an empty #DB handler

Userspace can trigger a #DB exception just after the SYSENTER
instruction by setting the TF in EFLAGS. The #DB exception will appear
to have originated in the kernel so we must not panic in that case.

Location:

kernel/arch/ia32

Files:

• include/arch/interrupt.h (modified) (2 diffs)
• src/interrupt.c (modified) (2 diffs)

kernel/arch/ia32/include/arch/interrupt.h

@@ -51 +51 @@
 
 #define EXC_DE 0
+#define EXC_DB 1
 #define EXC_NM 7
 #define EXC_SS 12
@@ -73 +74 @@
 
 #define VECTOR_DE                 (IVT_EXCBASE + EXC_DE)
+#define VECTOR_DB                 (IVT_EXCBASE + EXC_DB)
 #define VECTOR_NM                 (IVT_EXCBASE + EXC_NM)
 #define VECTOR_SS                 (IVT_EXCBASE + EXC_SS)

kernel/arch/ia32/src/interrupt.c

@@ -112 +112 @@
 }
 
+static void db_exception(unsigned int n, istate_t *istate)
+{
+        /*
+         * We need to provide at least an empty handler that does not panic
+         * if the exception appears to come from the kernel because the
+         * userspace can inject a kernel-level #DB after e.g. the SYSENTER
+         * instruction if the EFLAGS.TF is set.
+         */
+}
+
 /** General Protection Fault. */
 static void gp_fault(unsigned int n __attribute__((unused)), istate_t *istate)
@@ -231 +241 @@
 
         exc_register(VECTOR_DE, "de_fault", true, (iroutine_t) de_fault);
+        exc_register(VECTOR_DB, "db_exc", true, (iroutine_t) db_exception);
         exc_register(VECTOR_NM, "nm_fault", true, (iroutine_t) nm_fault);
         exc_register(VECTOR_SS, "ss_fault", true, (iroutine_t) ss_fault);