Add basic ARM support to the seccomp-bpf sandbox.

BUG=141157
TEST=unit tests on daisy.


Review URL: https://chromiumcodereview.appspot.com/10827223

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151007 0039d316-1c4b-4281-b951-d872f2087c98

4 files changed, 86 insertions, 31 deletions

diff --git a/sandbox/linux/sandbox_linux.gypi b/sandbox/linux/sandbox_linux.gypi
index e124007..fb68c73c 100644
--- a/sandbox/linux/sandbox_linux.gypi
+++ b/sandbox/linux/sandbox_linux.gypi
@@ -24,7 +24,8 @@
           ],
         }],
         # Similarly, compile seccomp BPF when we support it
-        [ 'OS=="linux" and (target_arch=="ia32" or target_arch=="x64")', {
+        [ 'OS=="linux" and (target_arch=="ia32" or target_arch=="x64" '
+                           'or target_arch=="arm")', {
           'type': 'static_library',
           'dependencies': [
             'seccomp_bpf',
@@ -47,7 +48,8 @@
         '../..',
       ],
       'conditions': [
-        [ 'OS=="linux" and (target_arch=="ia32" or target_arch=="x64")', {
+        [ 'OS=="linux" and (target_arch=="ia32" or target_arch=="x64" '
+                           'or target_arch=="arm")', {
           'sources': [
             'seccomp-bpf/sandbox_bpf_unittest.cc',
           ],
diff --git a/sandbox/linux/seccomp-bpf/sandbox_bpf.cc b/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
index 9599544..dd6ad94 100644
--- a/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
+++ b/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
@@ -602,8 +602,8 @@ void Sandbox::sigSys(int nr, siginfo_t *info, void *void_context) {
   memcpy(&sigsys, &info->_sifields, sizeof(sigsys));
 
   // Some more sanity checks.
-  if (sigsys.ip != reinterpret_cast<void *>(ctx->uc_mcontext.gregs[REG_IP]) ||
-      sigsys.nr != static_cast<int>(ctx->uc_mcontext.gregs[REG_SYSCALL]) ||
+  if (sigsys.ip != reinterpret_cast<void *>(SECCOMP_IP(ctx)) ||
+      sigsys.nr != static_cast<int>(SECCOMP_SYSCALL(ctx)) ||
       sigsys.arch != SECCOMP_ARCH) {
     goto sigsys_err;
   }
@@ -616,12 +616,12 @@ void Sandbox::sigSys(int nr, siginfo_t *info, void *void_context) {
     SECCOMP_ARCH,
     reinterpret_cast<uint64_t>(sigsys.ip),
     {
-      static_cast<uint64_t>(ctx->uc_mcontext.gregs[REG_PARM1]),
-      static_cast<uint64_t>(ctx->uc_mcontext.gregs[REG_PARM2]),
-      static_cast<uint64_t>(ctx->uc_mcontext.gregs[REG_PARM3]),
-      static_cast<uint64_t>(ctx->uc_mcontext.gregs[REG_PARM4]),
-      static_cast<uint64_t>(ctx->uc_mcontext.gregs[REG_PARM5]),
-      static_cast<uint64_t>(ctx->uc_mcontext.gregs[REG_PARM6])
+      static_cast<uint64_t>(SECCOMP_PARM1(ctx)),
+      static_cast<uint64_t>(SECCOMP_PARM2(ctx)),
+      static_cast<uint64_t>(SECCOMP_PARM3(ctx)),
+      static_cast<uint64_t>(SECCOMP_PARM4(ctx)),
+      static_cast<uint64_t>(SECCOMP_PARM5(ctx)),
+      static_cast<uint64_t>(SECCOMP_PARM6(ctx))
     }
   };
 
@@ -633,8 +633,8 @@ void Sandbox::sigSys(int nr, siginfo_t *info, void *void_context) {
   // Update the CPU register that stores the return code of the system call
   // that we just handled, and restore "errno" to the value that it had
   // before entering the signal handler.
-  ctx->uc_mcontext.gregs[REG_RESULT] = static_cast<greg_t>(rc);
-  errno                              = old_errno;
+  SECCOMP_RESULT(ctx) = static_cast<greg_t>(rc);
+  errno               = old_errno;
 
   return;
 }
diff --git a/sandbox/linux/seccomp-bpf/sandbox_bpf.h b/sandbox/linux/seccomp-bpf/sandbox_bpf.h
index 414327d..eb99d99 100644
--- a/sandbox/linux/seccomp-bpf/sandbox_bpf.h
+++ b/sandbox/linux/seccomp-bpf/sandbox_bpf.h
@@ -83,30 +83,65 @@
 #define MIN_SYSCALL  0u
 #define MAX_SYSCALL  1024u
 #define SECCOMP_ARCH AUDIT_ARCH_I386
-#define REG_RESULT   REG_EAX
-#define REG_SYSCALL  REG_EAX
-#define REG_IP       REG_EIP
-#define REG_PARM1    REG_EBX
-#define REG_PARM2    REG_ECX
-#define REG_PARM3    REG_EDX
-#define REG_PARM4    REG_ESI
-#define REG_PARM5    REG_EDI
-#define REG_PARM6    REG_EBP
+
+#define SECCOMP_REG(_ctx, _reg) ((_ctx)->uc_mcontext.gregs[(_reg)])
+#define SECCOMP_RESULT(_ctx)    SECCOMP_REG(_ctx, REG_EAX)
+#define SECCOMP_SYSCALL(_ctx)   SECCOMP_REG(_ctx, REG_EAX)
+#define SECCOMP_IP(_ctx)        SECCOMP_REG(_ctx, REG_EIP)
+#define SECCOMP_PARM1(_ctx)     SECCOMP_REG(_ctx, REG_EBX)
+#define SECCOMP_PARM2(_ctx)     SECCOMP_REG(_ctx, REG_ECX)
+#define SECCOMP_PARM3(_ctx)     SECCOMP_REG(_ctx, REG_EDX)
+#define SECCOMP_PARM4(_ctx)     SECCOMP_REG(_ctx, REG_ESI)
+#define SECCOMP_PARM5(_ctx)     SECCOMP_REG(_ctx, REG_EDI)
+#define SECCOMP_PARM6(_ctx)     SECCOMP_REG(_ctx, REG_EBP)
+
 #elif defined(__x86_64__)
 #define MIN_SYSCALL  0u
 #define MAX_SYSCALL  1024u
 #define SECCOMP_ARCH AUDIT_ARCH_X86_64
-#define REG_RESULT   REG_RAX
-#define REG_SYSCALL  REG_RAX
-#define REG_IP       REG_RIP
-#define REG_PARM1    REG_RDI
-#define REG_PARM2    REG_RSI
-#define REG_PARM3    REG_RDX
-#define REG_PARM4    REG_R10
-#define REG_PARM5    REG_R8
-#define REG_PARM6    REG_R9
+
+#define SECCOMP_REG(_ctx, _reg) ((_ctx)->uc_mcontext.gregs[(_reg)])
+#define SECCOMP_RESULT(_ctx)    SECCOMP_REG(_ctx, REG_RAX)
+#define SECCOMP_SYSCALL(_ctx)   SECCOMP_REG(_ctx, REG_RAX)
+#define SECCOMP_IP(_ctx)        SECCOMP_REG(_ctx, REG_RIP)
+#define SECCOMP_PARM1(_ctx)     SECCOMP_REG(_ctx, REG_RDI)
+#define SECCOMP_PARM2(_ctx)     SECCOMP_REG(_ctx, REG_RSI)
+#define SECCOMP_PARM3(_ctx)     SECCOMP_REG(_ctx, REG_RDX)
+#define SECCOMP_PARM4(_ctx)     SECCOMP_REG(_ctx, REG_R10)
+#define SECCOMP_PARM5(_ctx)     SECCOMP_REG(_ctx, REG_R8)
+#define SECCOMP_PARM6(_ctx)     SECCOMP_REG(_ctx, REG_R9)
+
+#elif defined(__arm__) && (defined(__thumb__) || defined(__ARM_EABI__))
+// ARM EABI includes "ARM private" system calls starting at |__ARM_NR_BASE|,
+// and a "ghost syscall private to the kernel", cmpxchg,
+// at |__ARM_NR_BASE+0x00fff0|.
+// See </arch/arm/include/asm/unistd.h> in the Linux kernel.
+#define MIN_SYSCALL  ((unsigned int)__NR_SYSCALL_BASE)
+#define MAX_SYSCALL  ((unsigned int)__ARM_NR_BASE + 0x00ffffu)
+// <linux/audit.h> includes <linux/elf-em.h>, which does not define EM_ARM.
+// <linux/elf.h> only includes <asm/elf.h> if we're in the kernel.
+# if !defined(EM_ARM)
+# define EM_ARM 40
+# endif
+#define SECCOMP_ARCH AUDIT_ARCH_ARM
+
+// ARM sigcontext_t is different from i386/x86_64.
+// See </arch/arm/include/asm/sigcontext.h> in the Linux kernel.
+#define SECCOMP_REG(_ctx, _reg) ((_ctx)->uc_mcontext.arm_##_reg)
+// ARM EABI syscall convention.
+#define SECCOMP_RESULT(_ctx)     SECCOMP_REG(_ctx, r0)
+#define SECCOMP_SYSCALL(_ctx)    SECCOMP_REG(_ctx, r7)
+#define SECCOMP_IP(_ctx)         SECCOMP_REG(_ctx, pc)
+#define SECCOMP_PARM1(_ctx)      SECCOMP_REG(_ctx, r0)
+#define SECCOMP_PARM2(_ctx)      SECCOMP_REG(_ctx, r1)
+#define SECCOMP_PARM3(_ctx)      SECCOMP_REG(_ctx, r2)
+#define SECCOMP_PARM4(_ctx)      SECCOMP_REG(_ctx, r3)
+#define SECCOMP_PARM5(_ctx)      SECCOMP_REG(_ctx, r4)
+#define SECCOMP_PARM6(_ctx)      SECCOMP_REG(_ctx, r5)
+
 #else
 #error Unsupported target platform
+
 #endif
 
 struct arch_seccomp_data {
diff --git a/sandbox/linux/seccomp-bpf/sandbox_bpf_unittest.cc b/sandbox/linux/seccomp-bpf/sandbox_bpf_unittest.cc
index b8ae3b7..54fe7a7 100644
--- a/sandbox/linux/seccomp-bpf/sandbox_bpf_unittest.cc
+++ b/sandbox/linux/seccomp-bpf/sandbox_bpf_unittest.cc
@@ -13,6 +13,9 @@ using namespace playground2;
 namespace {
 
 const int kExpectedReturnValue = 42;
+#if defined(__arm__)
+const int kArmPublicSysnoCeiling = __NR_SYSCALL_BASE + 1024;
+#endif
 
 TEST(SandboxBpf, CallSupports) {
   // We check that we don't crash, but it's ok if the kernel doesn't
@@ -234,6 +237,13 @@ Sandbox::ErrorCode SyntheticPolicy(int sysno) {
     // FIXME: we should really not have to do that in a trivial policy.
     return ENOSYS;
   }
+
+  // TODO(jorgelo): remove this restriction once crbug.com/141694 is fixed.
+#if defined(__arm__)
+  if (sysno > kArmPublicSysnoCeiling)
+    return ENOSYS;
+#endif
+
   if (sysno == __NR_exit_group) {
     // exit_group() is special, we really need it to work.
     return Sandbox::SB_ALLOWED;
@@ -249,8 +259,16 @@ void SyntheticProcess(void) {
       static_cast<int>(MAX_SYSCALL)) {
     ExitGroup(1);
   }
+
+  // TODO(jorgelo): remove this limit once crbug.com/141694 is fixed.
+#if defined(__arm__)
+  const int sysno_ceiling = kArmPublicSysnoCeiling;
+#else
+  const int sysno_ceiling = static_cast<int>(MAX_SYSCALL);
+#endif
+
   for (int syscall_number =  static_cast<int>(MIN_SYSCALL);
-           syscall_number <= static_cast<int>(MAX_SYSCALL);
+           syscall_number <= sysno_ceiling;
          ++syscall_number) {
     if (syscall_number == __NR_exit_group) {
       // exit_group() is special