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Date: Thu, 28 Jan 2016 15:11:20 -0800
From: Andy Lutomirski <luto@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, Brian Gerst <brgerst@...il.com>,
Borislav Petkov <bp@...en8.de>,
Frédéric Weisbecker <fweisbec@...il.com>,
Denys Vlasenko <dvlasenk@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 02/10] selftests/x86: Add check_initial_reg_state
This checks that ELF binaries are started with an appropriately
blank register state.
(There's currently a nasty special case in the entry asm to arrange
for this. I'm planning on removing the special case, and this will
help make sure I don't break it.)
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
tools/testing/selftests/x86/Makefile | 9 +-
.../selftests/x86/check_initial_reg_state.c | 109 +++++++++++++++++++++
2 files changed, 117 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/x86/check_initial_reg_state.c
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 9c81f263a396..df4f767f48da 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -4,7 +4,8 @@ include ../lib.mk
.PHONY: all all_32 all_64 warn_32bit_failure clean
-TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall
+TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall \
+ check_initial_reg_state
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault sigreturn test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
ldt_gdt \
@@ -66,3 +67,9 @@ endif
sysret_ss_attrs_64: thunks.S
ptrace_syscall_32: raw_syscall_helper_32.S
test_syscall_vdso_32: thunks_32.S
+
+# check_initial_reg_state is special: it needs a custom entry, and it
+# needs to be static so that its interpreter doesn't destroy its initial
+# state.
+check_initial_reg_state_32: CFLAGS += -Wl,-ereal_start -static
+check_initial_reg_state_64: CFLAGS += -Wl,-ereal_start -static
diff --git a/tools/testing/selftests/x86/check_initial_reg_state.c b/tools/testing/selftests/x86/check_initial_reg_state.c
new file mode 100644
index 000000000000..6aaed9b85baf
--- /dev/null
+++ b/tools/testing/selftests/x86/check_initial_reg_state.c
@@ -0,0 +1,109 @@
+/*
+ * check_initial_reg_state.c - check that execve sets the correct state
+ * Copyright (c) 2014-2016 Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+
+unsigned long ax, bx, cx, dx, si, di, bp, sp, flags;
+unsigned long r8, r9, r10, r11, r12, r13, r14, r15;
+
+asm (
+ ".pushsection .text\n\t"
+ ".type real_start, @function\n\t"
+ ".global real_start\n\t"
+ "real_start:\n\t"
+#ifdef __x86_64__
+ "mov %rax, ax\n\t"
+ "mov %rbx, bx\n\t"
+ "mov %rcx, cx\n\t"
+ "mov %rdx, dx\n\t"
+ "mov %rsi, si\n\t"
+ "mov %rdi, di\n\t"
+ "mov %rbp, bp\n\t"
+ "mov %rsp, sp\n\t"
+ "mov %r8, r8\n\t"
+ "mov %r9, r9\n\t"
+ "mov %r10, r10\n\t"
+ "mov %r11, r11\n\t"
+ "mov %r12, r12\n\t"
+ "mov %r13, r13\n\t"
+ "mov %r14, r14\n\t"
+ "mov %r15, r15\n\t"
+ "pushfq\n\t"
+ "popq flags\n\t"
+#else
+ "mov %eax, ax\n\t"
+ "mov %ebx, bx\n\t"
+ "mov %ecx, cx\n\t"
+ "mov %edx, dx\n\t"
+ "mov %esi, si\n\t"
+ "mov %edi, di\n\t"
+ "mov %ebp, bp\n\t"
+ "mov %esp, sp\n\t"
+ "pushfl\n\t"
+ "popl flags\n\t"
+#endif
+ "jmp _start\n\t"
+ ".size real_start, . - real_start\n\t"
+ ".popsection");
+
+int main()
+{
+ int nerrs = 0;
+
+ if (sp == 0) {
+ printf("[FAIL]\tTest was built incorrectly\n");
+ return 1;
+ }
+
+ if (ax || bx || cx || dx || si || di || bp
+#ifdef __x86_64__
+ || r8 || r9 || r10 || r11 || r12 || r13 || r14 || r15
+#endif
+ ) {
+ printf("[FAIL]\tAll GPRs except SP should be 0\n");
+#define SHOW(x) printf("\t" #x " = 0x%lx\n", x);
+ SHOW(ax);
+ SHOW(bx);
+ SHOW(cx);
+ SHOW(dx);
+ SHOW(si);
+ SHOW(di);
+ SHOW(bp);
+ SHOW(sp);
+#ifdef __x86_64__
+ SHOW(r8);
+ SHOW(r9);
+ SHOW(r10);
+ SHOW(r11);
+ SHOW(r12);
+ SHOW(r13);
+ SHOW(r14);
+ SHOW(r15);
+#endif
+ nerrs++;
+ } else {
+ printf("[OK]\tAll GPRs except SP are 0\n");
+ }
+
+ if (flags != 0x202) {
+ printf("[FAIL]\tFLAGS is 0x%lx, but it should be 0x202\n", flags);
+ nerrs++;
+ } else {
+ printf("[OK]\tFLAGS is 0x202\n");
+ }
+
+ return nerrs ? 1 : 0;
+}
--
2.5.0
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