The test checks that all registers are preserved across
32-bit syscalls. It tests syscalls through VDSO
(if available) and through INT 0x80, normally
and under ptrace.
If kernel is a 64-bit one, high registers (r8..r15) are poisoned
before call and checked afterwards. They must be either preserved,
or cleared to zero (but r11 is special); r12..15 must be preserved
for INT 0x80.
EFLAGS is checked for changes too, but change there is not considered
to be a bug (paravirt kernels do not preserve arithmetic flags).
Run-tested on 64-bit kernel:
$ ./test_syscall_vdso_32
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[NOTE] R11 has changed:0000000000200ed7 - assuming clobbered by SYSRET insn
[OK] R8..R15 did not leak kernel data
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
[RUN] Running tests under ptrace
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
On 32-bit paravirt kernel:
$ ./test_syscall_vdso_32
[NOTE] Not a 64-bit kernel, won't test R8..R15 leaks
[RUN] Executing 6-argument 32-bit syscall via VDSO
[WARN] Flags before=0000000000200ed7 id 0 00 o d i s z 0 a 0 p 1 c
[WARN] Flags after=0000000000200246 id 0 00 i z 0 0 p 1
[WARN] Flags change=0000000000000c91 0 00 o d s 0 a 0 0 c
[OK] Arguments are preserved across syscall
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[RUN] Running tests under ptrace
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
Signed-off-by: Denys Vlasenko <[email protected]>
CC: Linus Torvalds <[email protected]>
CC: Steven Rostedt <[email protected]>
CC: Ingo Molnar <[email protected]>
CC: Borislav Petkov <[email protected]>
CC: "H. Peter Anvin" <[email protected]>
CC: Andy Lutomirski <[email protected]>
CC: Oleg Nesterov <[email protected]>
CC: Frederic Weisbecker <[email protected]>
CC: Alexei Starovoitov <[email protected]>
CC: Will Drewry <[email protected]>
CC: Kees Cook <[email protected]>
CC: [email protected]
CC: [email protected]
---
Changes in v2:
does not fail if VDSO can't be found;
tests INT 80 syscall method;
tests syscalls under ptrace;
switched to /* */ comments
Changes in v3:
added checking for r8..r15 info leaks
tools/testing/selftests/x86/test_syscall_vdso.c | 401 ++++++++++++++++++++++++
tools/testing/selftests/x86/thunks_32.S | 55 ++++
2 files changed, 456 insertions(+)
create mode 100644 tools/testing/selftests/x86/test_syscall_vdso.c
create mode 100644 tools/testing/selftests/x86/thunks_32.S
diff --git a/tools/testing/selftests/x86/test_syscall_vdso.c b/tools/testing/selftests/x86/test_syscall_vdso.c
new file mode 100644
index 0000000..0792aef
--- /dev/null
+++ b/tools/testing/selftests/x86/test_syscall_vdso.c
@@ -0,0 +1,401 @@
+/*
+ * 32-bit syscall ABI conformance test.
+ *
+ * Copyright (c) 2015 Denys Vlasenko
+ *
+ * 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.
+ */
+/*
+ * Can be built statically:
+ * gcc -Os -Wall -static -m32 test_syscall_vdso.c thunks_32.S
+ */
+#undef _GNU_SOURCE
+#define _GNU_SOURCE 1
+#undef __USE_GNU
+#define __USE_GNU 1
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <signal.h>
+#include <sys/types.h>
+#include <sys/select.h>
+#include <sys/time.h>
+#include <elf.h>
+#include <sys/ptrace.h>
+#include <sys/wait.h>
+
+#if !defined(__i386__)
+int main(int argc, char **argv, char **envp)
+{
+ printf("[SKIP]\tNot a 32-bit x86 userspace\n");
+ return 0;
+}
+#else
+
+long syscall_addr;
+long get_syscall(char **envp)
+{
+ Elf32_auxv_t *auxv;
+ while (*envp++ != NULL)
+ continue;
+ for (auxv = (void *)envp; auxv->a_type != AT_NULL; auxv++)
+ if (auxv->a_type == AT_SYSINFO)
+ return auxv->a_un.a_val;
+ printf("[WARN]\tAT_SYSINFO not supplied\n");
+ return 0;
+}
+
+asm (
+ " .pushsection .text\n"
+ " .global int80\n"
+ "int80:\n"
+ " int $0x80\n"
+ " ret\n"
+ " .popsection\n"
+);
+extern char int80;
+
+struct regs64 {
+ uint64_t rax, rbx, rcx, rdx;
+ uint64_t rsi, rdi, rbp, rsp;
+ uint64_t r8, r9, r10, r11;
+ uint64_t r12, r13, r14, r15;
+};
+struct regs64 regs64;
+int kernel_is_64bit;
+
+asm (
+ " .pushsection .text\n"
+ " .code64\n"
+ "get_regs64:\n"
+ " push %rax\n"
+ " mov $regs64, %eax\n"
+ " pop 0*8(%rax)\n"
+ " movq %rbx, 1*8(%rax)\n"
+ " movq %rcx, 2*8(%rax)\n"
+ " movq %rdx, 3*8(%rax)\n"
+ " movq %rsi, 4*8(%rax)\n"
+ " movq %rdi, 5*8(%rax)\n"
+ " movq %rbp, 6*8(%rax)\n"
+ " movq %rsp, 7*8(%rax)\n"
+ " movq %r8, 8*8(%rax)\n"
+ " movq %r9, 9*8(%rax)\n"
+ " movq %r10, 10*8(%rax)\n"
+ " movq %r11, 11*8(%rax)\n"
+ " movq %r12, 12*8(%rax)\n"
+ " movq %r13, 13*8(%rax)\n"
+ " movq %r14, 14*8(%rax)\n"
+ " movq %r15, 15*8(%rax)\n"
+ " ret\n"
+ "poison_regs64:\n"
+ " movq $0x7f7f7f7f, %r8\n"
+ " shl $32, %r8\n"
+ " orq $0x7f7f7f7f, %r8\n"
+ " movq %r8, %r9\n"
+ " movq %r8, %r10\n"
+ " movq %r8, %r11\n"
+ " movq %r8, %r12\n"
+ " movq %r8, %r13\n"
+ " movq %r8, %r14\n"
+ " movq %r8, %r15\n"
+ " ret\n"
+ " .code32\n"
+ " .popsection\n"
+);
+extern void get_regs64(void);
+extern void poison_regs64(void);
+extern unsigned long call64_from_32(void (*function)(void));
+void print_regs64(void)
+{
+ if (!kernel_is_64bit)
+ return;
+ printf("ax:%016llx bx:%016llx cx:%016llx dx:%016llx\n", regs64.rax, regs64.rbx, regs64.rcx, regs64.rdx);
+ printf("si:%016llx di:%016llx bp:%016llx sp:%016llx\n", regs64.rsi, regs64.rdi, regs64.rbp, regs64.rsp);
+ printf(" 8:%016llx 9:%016llx 10:%016llx 11:%016llx\n", regs64.r8 , regs64.r9 , regs64.r10, regs64.r11);
+ printf("12:%016llx 13:%016llx 14:%016llx 15:%016llx\n", regs64.r12, regs64.r13, regs64.r14, regs64.r15);
+}
+
+int check_regs64(void)
+{
+ int err = 0;
+ int num = 8;
+ uint64_t *r64 = ®s64.r8;
+
+ if (!kernel_is_64bit)
+ return 0;
+
+ do {
+ if (*r64 == 0x7f7f7f7f7f7f7f7fULL)
+ continue; /* register did not change */
+ if (syscall_addr != (long)&int80) {
+ /*
+ * Non-INT80 syscall entrypoints are allowed to clobber R8+ regs:
+ * either clear them to 0, or for R11, load EFLAGS.
+ */
+ if (*r64 == 0)
+ continue;
+ if (num == 11) {
+ printf("[NOTE]\tR11 has changed:%016llx - assuming clobbered by SYSRET insn\n", *r64);
+ continue;
+ }
+ } else {
+ /* INT80 syscall entrypoint can be used by
+ * 64-bit programs too, unlike SYSCALL/SYSENTER.
+ * Therefore it must preserve R12+
+ * (they are callee-saved registers in 64-bit C ABI).
+ *
+ * This was probably historically not intended,
+ * but R8..11 are clobbered (cleared to 0).
+ * IOW: they are the only registers which aren't
+ * preserved across INT80 syscall.
+ */
+ if (*r64 == 0 && num <= 11)
+ continue;
+ }
+ printf("[FAIL]\tR%d has changed:%016llx\n", num, *r64);
+ err++;
+ } while (r64++, ++num < 16);
+
+ if (!err)
+ printf("[OK]\tR8..R15 did not leak kernel data\n");
+ return err;
+}
+
+int nfds;
+fd_set rfds;
+fd_set wfds;
+fd_set efds;
+struct timespec timeout;
+sigset_t sigmask;
+struct {
+ sigset_t *sp;
+ int sz;
+} sigmask_desc;
+
+void prep_args()
+{
+ nfds = 42;
+ FD_ZERO(&rfds);
+ FD_ZERO(&wfds);
+ FD_ZERO(&efds);
+ FD_SET(0, &rfds);
+ FD_SET(1, &wfds);
+ FD_SET(2, &efds);
+ timeout.tv_sec = 0;
+ timeout.tv_nsec = 123;
+ sigemptyset(&sigmask);
+ sigaddset(&sigmask, SIGINT);
+ sigaddset(&sigmask, SIGUSR2);
+ sigaddset(&sigmask, SIGRTMAX);
+ sigmask_desc.sp = &sigmask;
+ sigmask_desc.sz = 8; /* bytes */
+}
+
+static void print_flags(const char *name, unsigned long r)
+{
+ static const char *bitarray[] = {
+ "\n" ,"c\n" ,/* Carry Flag */
+ "0 " ,"1 " ,/* Bit 1 - always on */
+ "" ,"p " ,/* Parity Flag */
+ "0 " ,"3? " ,
+ "" ,"a " ,/* Auxiliary carry Flag */
+ "0 " ,"5? " ,
+ "" ,"z " ,/* Zero Flag */
+ "" ,"s " ,/* Sign Flag */
+ "" ,"t " ,/* Trap Flag */
+ "" ,"i " ,/* Interrupt Flag */
+ "" ,"d " ,/* Direction Flag */
+ "" ,"o " ,/* Overflow Flag */
+ "0 " ,"1 " ,/* I/O Privilege Level (2 bits) */
+ "0" ,"1" ,/* I/O Privilege Level (2 bits) */
+ "" ,"n " ,/* Nested Task */
+ "0 " ,"15? ",
+ "" ,"r " ,/* Resume Flag */
+ "" ,"v " ,/* Virtual Mode */
+ "" ,"ac " ,/* Alignment Check/Access Control */
+ "" ,"vif ",/* Virtual Interrupt Flag */
+ "" ,"vip ",/* Virtual Interrupt Pending */
+ "" ,"id " ,/* CPUID detection */
+ NULL
+ };
+ const char **bitstr;
+ int bit;
+
+ printf("%s=%016lx ", name, r);
+ bitstr = bitarray + 42;
+ bit = 21;
+ if ((r >> 22) != 0)
+ printf("(extra bits are set) ");
+ do {
+ if (bitstr[(r >> bit) & 1][0])
+ printf(bitstr[(r >> bit) & 1]);
+ bitstr -= 2;
+ bit--;
+ } while (bit >= 0);
+}
+
+int run_syscall(void)
+{
+ long flags, bad_arg;
+
+ prep_args();
+
+ if (kernel_is_64bit)
+ call64_from_32(poison_regs64);
+ /*print_regs64();*/
+
+ asm("\n"
+ /* Try 6-arg syscall: pselect. It should return quickly */
+ " push %%ebp\n"
+ " mov $308, %%eax\n" /* PSELECT */
+ " mov nfds, %%ebx\n" /* ebx arg1 */
+ " mov $rfds, %%ecx\n" /* ecx arg2 */
+ " mov $wfds, %%edx\n" /* edx arg3 */
+ " mov $efds, %%esi\n" /* esi arg4 */
+ " mov $timeout, %%edi\n" /* edi arg5 */
+ " mov $sigmask_desc, %%ebp\n" /* %ebp arg6 */
+ " push $0x200ed7\n" /* set almost all flags */
+ " popf\n" /* except TF, IOPL, NT, RF, VM, AC, VIF, VIP */
+ " call *syscall_addr\n"
+ /* Check that registers are not clobbered */
+ " pushf\n"
+ " pop %%eax\n"
+ " cld\n"
+ " cmp nfds, %%ebx\n" /* ebx arg1 */
+ " mov $1, %%ebx\n"
+ " jne 1f\n"
+ " cmp $rfds, %%ecx\n" /* ecx arg2 */
+ " mov $2, %%ebx\n"
+ " jne 1f\n"
+ " cmp $wfds, %%edx\n" /* edx arg3 */
+ " mov $3, %%ebx\n"
+ " jne 1f\n"
+ " cmp $efds, %%esi\n" /* esi arg4 */
+ " mov $4, %%ebx\n"
+ " jne 1f\n"
+ " cmp $timeout, %%edi\n" /* edi arg5 */
+ " mov $5, %%ebx\n"
+ " jne 1f\n"
+ " cmpl $sigmask_desc, %%ebp\n" /* %ebp arg6 */
+ " mov $6, %%ebx\n"
+ " jne 1f\n"
+ " mov $0, %%ebx\n"
+ "1:\n"
+ " pop %%ebp\n"
+ : "=a" (flags), "=b" (bad_arg)
+ :
+ : "cx", "dx", "si", "di"
+ );
+
+ if (kernel_is_64bit) {
+ memset(®s64, 0x77, sizeof(regs64));
+ call64_from_32(get_regs64);
+ /*print_regs64();*/
+ }
+
+ /*
+ * On paravirt kernels, flags are not preserved across syscalls.
+ * Thus, we do not consider it a bug if some are changed.
+ * We just show ones which do.
+ */
+ if ((0x200ed7 ^ flags) != 0) {
+ print_flags("[WARN]\tFlags before", 0x200ed7);
+ print_flags("[WARN]\tFlags after", flags);
+ print_flags("[WARN]\tFlags change", (0x200ed7 ^ flags));
+ }
+
+ if (bad_arg) {
+ printf("[FAIL]\targ#%ld clobbered\n", bad_arg);
+ return 1;
+ }
+ printf("[OK]\tArguments are preserved across syscall\n");
+
+ return check_regs64();
+}
+
+int run_syscall_twice()
+{
+ int exitcode = 0;
+ long sv;
+
+ if (syscall_addr) {
+ printf("[RUN]\tExecuting 6-argument 32-bit syscall via VDSO\n");
+ exitcode = run_syscall();
+ }
+ sv = syscall_addr;
+ syscall_addr = (long)&int80;
+ printf("[RUN]\tExecuting 6-argument 32-bit syscall via INT 80\n");
+ exitcode += run_syscall();
+ syscall_addr = sv;
+ return exitcode;
+}
+
+void ptrace_me()
+{
+ pid_t pid;
+
+ fflush(NULL);
+ pid = fork();
+ if (pid < 0)
+ exit(1);
+ if (pid == 0) {
+ /* child */
+ if (ptrace(PTRACE_TRACEME, 0L, 0L, 0L) != 0)
+ exit(0);
+ raise(SIGSTOP);
+ return;
+ }
+ /* parent */
+ printf("[RUN]\tRunning tests under ptrace\n");
+ while (1) {
+ int status;
+ pid = waitpid(-1, &status, __WALL);
+ if (WIFEXITED(status))
+ exit(WEXITSTATUS(status));
+ if (WIFSIGNALED(status))
+ exit(WTERMSIG(status));
+ if (pid <= 0 || !WIFSTOPPED(status)) /* paranoia */
+ exit(255);
+ /*
+ * Note: we do not inject sig = WSTOPSIG(status).
+ * We probably should, but careful: do not inject SIGTRAP
+ * generated by syscall entry/exit stops.
+ * That kills the child.
+ */
+ ptrace(PTRACE_SYSCALL, pid, 0L, 0L /*sig*/);
+ }
+}
+
+int main(int argc, char **argv, char **envp)
+{
+ int exitcode = 0;
+ int cs;
+
+ asm("\n"
+ " movl %%cs, %%eax\n"
+ : "=a" (cs)
+ );
+ kernel_is_64bit = (cs == 0x23);
+ if (!kernel_is_64bit)
+ printf("[NOTE]\tNot a 64-bit kernel, won't test R8..R15 leaks\n");
+
+ /* This only works for non-static builds:
+ * syscall_addr = dlsym(dlopen("linux-gate.so.1", RTLD_NOW), "__kernel_vsyscall");
+ */
+ syscall_addr = get_syscall(envp);
+
+ exitcode += run_syscall_twice();
+ ptrace_me();
+ exitcode += run_syscall_twice();
+
+ return exitcode;
+}
+#endif
diff --git a/tools/testing/selftests/x86/thunks_32.S b/tools/testing/selftests/x86/thunks_32.S
new file mode 100644
index 0000000..77e9159
--- /dev/null
+++ b/tools/testing/selftests/x86/thunks_32.S
@@ -0,0 +1,55 @@
+/*
+ * thunks_32.S - assembly helpers for mixed-bitness code
+ * Copyright (c) 2015 2015 Denys Vlasenko
+ *
+ * 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.
+ *
+ * These are little helpers that make it easier to switch bitness on
+ * the fly.
+ */
+
+ .text
+ .code32
+
+ .global call64_from_32
+ .type call32_from_64, @function
+
+ // 4(%esp): function to call
+call64_from_32:
+ // Fetch function address
+ mov 4(%esp), %eax
+
+ // Save registers which are callee-clobbered by 64-bit ABI
+ push %ecx
+ push %edx
+ push %esi
+ push %edi
+
+ // Switch to long mode
+ jmp $0x33,$1f
+1: .code64
+
+ // Call the function
+ call *%rax
+
+ // Switch to compatibility mode
+ push $0x23 /* USER32_CS */
+ .code32; push $1f; .code64 /* hack: can't have X86_64_32S relocation in 32-bit ELF */
+ lretq
+1: .code32
+
+ pop %edi
+ pop %esi
+ pop %edx
+ pop %ecx
+
+ ret
+
+.size call64_from_32, .-call64_from_32
--
1.8.1.4
* Denys Vlasenko <[email protected]> wrote:
> The test checks that all registers are preserved across
> 32-bit syscalls. It tests syscalls through VDSO
> (if available) and through INT 0x80, normally
> and under ptrace.
>
> If kernel is a 64-bit one, high registers (r8..r15) are poisoned
> before call and checked afterwards. They must be either preserved,
> or cleared to zero (but r11 is special); r12..15 must be preserved
> for INT 0x80.
>
> EFLAGS is checked for changes too, but change there is not considered
> to be a bug (paravirt kernels do not preserve arithmetic flags).
>
> Run-tested on 64-bit kernel:
>
> $ ./test_syscall_vdso_32
> [RUN] Executing 6-argument 32-bit syscall via VDSO
> [OK] Arguments are preserved across syscall
> [NOTE] R11 has changed:0000000000200ed7 - assuming clobbered by SYSRET insn
> [OK] R8..R15 did not leak kernel data
> [RUN] Executing 6-argument 32-bit syscall via INT 80
> [OK] Arguments are preserved across syscall
> [OK] R8..R15 did not leak kernel data
> [RUN] Running tests under ptrace
> [RUN] Executing 6-argument 32-bit syscall via VDSO
> [OK] Arguments are preserved across syscall
> [OK] R8..R15 did not leak kernel data
> [RUN] Executing 6-argument 32-bit syscall via INT 80
> [OK] Arguments are preserved across syscall
> [OK] R8..R15 did not leak kernel data
>
> On 32-bit paravirt kernel:
>
> $ ./test_syscall_vdso_32
> [NOTE] Not a 64-bit kernel, won't test R8..R15 leaks
> [RUN] Executing 6-argument 32-bit syscall via VDSO
> [WARN] Flags before=0000000000200ed7 id 0 00 o d i s z 0 a 0 p 1 c
> [WARN] Flags after=0000000000200246 id 0 00 i z 0 0 p 1
> [WARN] Flags change=0000000000000c91 0 00 o d s 0 a 0 0 c
> [OK] Arguments are preserved across syscall
> [RUN] Executing 6-argument 32-bit syscall via INT 80
> [OK] Arguments are preserved across syscall
> [RUN] Running tests under ptrace
> [RUN] Executing 6-argument 32-bit syscall via VDSO
> [OK] Arguments are preserved across syscall
> [RUN] Executing 6-argument 32-bit syscall via INT 80
> [OK] Arguments are preserved across syscall
>
> Signed-off-by: Denys Vlasenko <[email protected]>
> CC: Linus Torvalds <[email protected]>
> CC: Steven Rostedt <[email protected]>
> CC: Ingo Molnar <[email protected]>
> CC: Borislav Petkov <[email protected]>
> CC: "H. Peter Anvin" <[email protected]>
> CC: Andy Lutomirski <[email protected]>
> CC: Oleg Nesterov <[email protected]>
> CC: Frederic Weisbecker <[email protected]>
> CC: Alexei Starovoitov <[email protected]>
> CC: Will Drewry <[email protected]>
> CC: Kees Cook <[email protected]>
> CC: [email protected]
> CC: [email protected]
> ---
>
> Changes in v2:
> does not fail if VDSO can't be found;
> tests INT 80 syscall method;
> tests syscalls under ptrace;
> switched to /* */ comments
>
> Changes in v3:
> added checking for r8..r15 info leaks
>
> tools/testing/selftests/x86/test_syscall_vdso.c | 401 ++++++++++++++++++++++++
> tools/testing/selftests/x86/thunks_32.S | 55 ++++
> 2 files changed, 456 insertions(+)
> create mode 100644 tools/testing/selftests/x86/test_syscall_vdso.c
> create mode 100644 tools/testing/selftests/x86/thunks_32.S
Hm, what I don't see is any Makefile integration. How am I supposed to build this
test, and how will automated tests pick this testcase up?
Thanks,
Ingo
* Ingo Molnar <[email protected]> wrote:
> > tools/testing/selftests/x86/test_syscall_vdso.c | 401 ++++++++++++++++++++++++
> > tools/testing/selftests/x86/thunks_32.S | 55 ++++
> > 2 files changed, 456 insertions(+)
> > create mode 100644 tools/testing/selftests/x86/test_syscall_vdso.c
> > create mode 100644 tools/testing/selftests/x86/thunks_32.S
>
> Hm, what I don't see is any Makefile integration. How am I supposed to build this
> test, and how will automated tests pick this testcase up?
Note that I prettied up its changelog (attached below), please use this for the
next submission.
Thanks,
Ingo
=======================>
Subject: x86/asm/entry/32, selftests: Add 'test_syscall_vdso' test
From: Denys Vlasenko <[email protected]>
Date: Fri, 3 Jul 2015 22:02:52 +0200
This new test checks that all x86 registers are preserved across
32-bit syscalls. It tests syscalls through VDSO (if available)
and through INT 0x80, normally and under ptrace.
If kernel is a 64-bit one, high registers (r8..r15) are poisoned
before the syscall is called and are checked afterwards.
They must be either preserved, or cleared to zero (but r11 is special);
r12..15 must be preserved for INT 0x80.
EFLAGS is checked for changes too, but change there is not
considered to be a bug (paravirt kernels do not preserve
arithmetic flags).
Run-tested on 64-bit kernel:
$ ./test_syscall_vdso_32
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[NOTE] R11 has changed:0000000000200ed7 - assuming clobbered by SYSRET insn
[OK] R8..R15 did not leak kernel data
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
[RUN] Running tests under ptrace
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
On 32-bit paravirt kernel:
$ ./test_syscall_vdso_32
[NOTE] Not a 64-bit kernel, won't test R8..R15 leaks
[RUN] Executing 6-argument 32-bit syscall via VDSO
[WARN] Flags before=0000000000200ed7 id 0 00 o d i s z 0 a 0 p 1 c
[WARN] Flags after=0000000000200246 id 0 00 i z 0 0 p 1
[WARN] Flags change=0000000000000c91 0 00 o d s 0 a 0 0 c
[OK] Arguments are preserved across syscall
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[RUN] Running tests under ptrace
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
On 07/06/2015 02:46 PM, Ingo Molnar wrote:
>
> * Ingo Molnar <[email protected]> wrote:
>
>>> tools/testing/selftests/x86/test_syscall_vdso.c | 401 ++++++++++++++++++++++++
>>> tools/testing/selftests/x86/thunks_32.S | 55 ++++
>>> 2 files changed, 456 insertions(+)
>>> create mode 100644 tools/testing/selftests/x86/test_syscall_vdso.c
>>> create mode 100644 tools/testing/selftests/x86/thunks_32.S
>>
>> Hm, what I don't see is any Makefile integration. How am I supposed to build this
>> test, and how will automated tests pick this testcase up?
> Note that I prettied up its changelog (attached below), please use this for the
> next submission.
I just sent v4. Sorry.