Check whether reading/writing DR4 generates an undefined opcode exception.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
x86/debug.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/x86/debug.c b/x86/debug.c
index 9798e62..382fdde 100644
--- a/x86/debug.c
+++ b/x86/debug.c
@@ -18,6 +18,14 @@ static volatile unsigned long db_addr[10], dr6[10];
static volatile unsigned int n;
static volatile unsigned long value;
+static unsigned long get_dr4(void)
+{
+ unsigned long value;
+
+ asm volatile("mov %%dr4, %0" : "=r" (value));
+ return value;
+}
+
static unsigned long get_dr6(void)
{
unsigned long value;
@@ -36,6 +44,11 @@ static void set_dr1(void *value)
asm volatile("mov %0,%%dr1" : : "r" (value));
}
+static void set_dr4(unsigned long value)
+{
+ asm volatile("mov %0,%%dr4" : : "r" (value));
+}
+
static void set_dr6(unsigned long value)
{
asm volatile("mov %0,%%dr6" : : "r" (value));
@@ -72,12 +85,35 @@ static void handle_bp(struct ex_regs *regs)
bp_addr = regs->rip;
}
+bool got_ud;
+static void handle_ud(struct ex_regs *regs)
+{
+ unsigned long cr4 = read_cr4();
+ write_cr4(cr4 & ~X86_CR4_DE);
+ got_ud = 1;
+}
+
int main(int ac, char **av)
{
unsigned long start;
+ unsigned long cr4;
handle_exception(DB_VECTOR, handle_db);
handle_exception(BP_VECTOR, handle_bp);
+ handle_exception(UD_VECTOR, handle_ud);
+
+ got_ud = 0;
+ cr4 = read_cr4();
+ write_cr4(cr4 & ~X86_CR4_DE);
+ set_dr4(0);
+ set_dr6(0xffff4ff2);
+ report(get_dr4() == 0xffff4ff2 && !got_ud, "reading DR4 with CR4.DE == 0");
+
+ cr4 = read_cr4();
+ write_cr4(cr4 | X86_CR4_DE);
+ get_dr4();
+ report(got_ud, "reading DR4 with CR4.DE == 1");
+ set_dr6(0);
extern unsigned char sw_bp;
asm volatile("int3; sw_bp:");
--
2.26.2
