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From: Andy Lutomirski <luto@kernel.org>
To: x86@kernel.org
Cc: Borislav Petkov <bp@alien8.de>,
	Shuah Khan <shuahkh@osg.samsung.com>,
	linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>
Subject: [PATCH] selftests/x86: Disable ldt_gdt_64 for now
Date: Wed,  6 Jan 2016 11:51:13 -0800	[thread overview]
Message-ID: <8dd42ba6434d84eefe6d864fb453fbe34d43098c.1452109816.git.luto@kernel.org> (raw)

ldt_gdt.c relies on cross-cpu invalidation of SS to do one of its
tests.  On 32-bit builds, this works fine, but on 64-bit builds, it
only works if the kernel has proper SS sigcontext handling for
64-bit user programs.

Since the SS fixes are currently reverted, restrict the test case to
32 bits for now.

In principle, I could change the test to use a different segment
register, but it would be messy: CS can't point to the LDT for
64-bit code, and the other registers don't result in immediate
faults because they aren't reloaded on kernel -> user transitions.

When we fix sigcontext (in 4.6?), we can revert this.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 tools/testing/selftests/x86/Makefile | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 3d1a8ef500a0..c0c15ff179b7 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -4,10 +4,11 @@ include ../lib.mk
 
 .PHONY: all all_32 all_64 warn_32bit_failure clean
 
-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs ldt_gdt syscall_nt ptrace_syscall
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall
 TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso unwind_vdso \
 			test_FCMOV test_FCOMI test_FISTTP \
-			vdso_restorer
+			vdso_restorer \
+			ldt_gdt
 
 TARGETS_C_32BIT_ALL := $(TARGETS_C_BOTHBITS) $(TARGETS_C_32BIT_ONLY)
 BINARIES_32 := $(TARGETS_C_32BIT_ALL:%=%_32)
-- 
2.5.0


             reply	other threads:[~2016-01-06 19:51 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-06 19:51 Andy Lutomirski [this message]
2016-01-07 20:49 ` [PATCH] selftests/x86: Disable ldt_gdt_64 for now Shuah Khan
2016-01-11 10:59   ` Ingo Molnar
2016-01-12  1:25     ` Andy Lutomirski
2016-01-12 10:45       ` Ingo Molnar

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