Il 17/08/2014 21:34, Nadav Amit ha scritto:
> 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)
Please call it CONFORM_CS_SEL since it's not really a user-mode selector
(DPL=0), it's just used as one (RPL=3).
> +#define USER_DS_SEL (FIRST_SPARE_SEL + 24)
Not needed, see below.
>
> static volatile int test_count;
> static volatile unsigned int test_divider;
> @@ -102,6 +104,14 @@ start:
> goto start;
> }
>
> +static void user_tss(void)
> +{
> +start:
Please add a printf and print_current_tss_info() here.
> + 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);
You can use USER_DS here. Also, please put the test in a separate
function and call it last (after test_vm86_switch), because a failure in
this test breaks test_vm86_switch too.
Paolo
> + asm volatile("lcall $" xstr(TSS_INTR) ", $0xf4f4f4f4");
> + report("lcall when cs.rpl != cs.dpl", test_count == 1);
> }
>
> void test_vm86_switch(void)
>
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