Commit 5045b46803 added a check that cs.dpl equals cs.rpl during task-switch.
This is a wrong check, and this test introduces a test in which cs.dpl !=
cs.rpl. To do so, it configures tss.cs to be conforming with rpl=3 and dpl=0.
Since the cpl after calling is 3, it does not make any prints in the callee.
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
---
x86/taskswitch2.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/x86/taskswitch2.c b/x86/taskswitch2.c
index 92fc941..d96853f 100644
--- a/x86/taskswitch2.c
+++ b/x86/taskswitch2.c
@@ -7,6 +7,8 @@
#define MAIN_TSS_SEL (FIRST_SPARE_SEL + 0)
#define VM86_TSS_SEL (FIRST_SPARE_SEL + 8)
+#define USER_CS_SEL (FIRST_SPARE_SEL + 16)
+#define USER_DS_SEL (FIRST_SPARE_SEL + 24)
static volatile int test_count;
static volatile unsigned int test_divider;
@@ -102,6 +104,14 @@ start:
goto start;
}
+static void user_tss(void)
+{
+start:
+ test_count++;
+ asm volatile ("iret");
+ goto start;
+}
+
void test_kernel_mode_int()
{
unsigned int res;
@@ -201,6 +211,18 @@ void test_kernel_mode_int()
asm volatile ("ljmp $" xstr(TSS_INTR) ", $0xf4f4f4f4");
printf("Jump back succeeded\n");
report("ljmp", test_count == 1);
+
+ /* test lcall with conforming segment, cs.dpl != cs.rpl */
+ test_count = 0;
+ set_intr_task_gate(0, user_tss);
+
+ tss_intr.cs = USER_CS_SEL | 3;
+ tss_intr.ss = USER_DS_SEL | 3;
+ tss_intr.ds = tss_intr.gs = tss_intr.fs = tss_intr.ss;
+ set_gdt_entry(USER_CS_SEL, 0, 0xffffffff, 0x9f, 0xc0);
+ set_gdt_entry(USER_DS_SEL, 0, 0xffffffff, 0xf3, 0xc0);
+ asm volatile("lcall $" xstr(TSS_INTR) ", $0xf4f4f4f4");
+ report("lcall when cs.rpl != cs.dpl", test_count == 1);
}
void test_vm86_switch(void)
--
1.9.1
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