From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH kvm-unit-tests] x86: Test task-switch with cs.rpl != cs.dpl Date: Tue, 19 Aug 2014 12:27:05 +0200 Message-ID: <53F32679.6030607@redhat.com> References: <1408303946-2796-1-git-send-email-namit@cs.technion.ac.il> <1408304076-2862-1-git-send-email-namit@cs.technion.ac.il> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Cc: kvm@vger.kernel.org To: Nadav Amit Return-path: Received: from mail-we0-f182.google.com ([74.125.82.182]:55512 "EHLO mail-we0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbaHSK1K (ORCPT ); Tue, 19 Aug 2014 06:27:10 -0400 Received: by mail-we0-f182.google.com with SMTP id k48so6249856wev.13 for ; Tue, 19 Aug 2014 03:27:08 -0700 (PDT) In-Reply-To: <1408304076-2862-1-git-send-email-namit@cs.technion.ac.il> Sender: kvm-owner@vger.kernel.org List-ID: 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 > --- > 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) >