#include <errno.h>
#include "base/basictypes.h"
+#include "base/logging.h"
+#include "sandbox/linux/seccomp-bpf/linux_seccomp.h"
namespace sandbox {
namespace {
+#if defined(ARCH_CPU_X86_FAMILY) || defined(ARCH_CPU_ARM_FAMILY) || \
+ defined(ARCH_CPU_MIPS_FAMILY)
+// Number that's not currently used by any Linux kernel ABIs.
+const int kInvalidSyscallNumber = 0x351d3;
+#else
+#error Unrecognized architecture
+#endif
+
asm(// We need to be able to tell the kernel exactly where we made a
// system call. The C++ compiler likes to sometimes clone or
// inline code, which would inadvertently end up duplicating
// that are used internally (e.g. %ebx for position-independent
// code, and %ebp for the frame pointer), and as we need to keep at
// least a few registers available for the register allocator.
- "1:push %esi; .cfi_adjust_cfa_offset 4\n"
- "push %edi; .cfi_adjust_cfa_offset 4\n"
- "push %ebx; .cfi_adjust_cfa_offset 4\n"
- "push %ebp; .cfi_adjust_cfa_offset 4\n"
+ "1:push %esi; .cfi_adjust_cfa_offset 4; .cfi_rel_offset esi, 0\n"
+ "push %edi; .cfi_adjust_cfa_offset 4; .cfi_rel_offset edi, 0\n"
+ "push %ebx; .cfi_adjust_cfa_offset 4; .cfi_rel_offset ebx, 0\n"
+ "push %ebp; .cfi_adjust_cfa_offset 4; .cfi_rel_offset ebp, 0\n"
// Copy entries from the array holding the arguments into the
// correct CPU registers.
"movl 0(%edi), %ebx\n"
"2:"
// Restore any clobbered registers that we didn't declare to the
// compiler.
- "pop %ebp; .cfi_adjust_cfa_offset -4\n"
- "pop %ebx; .cfi_adjust_cfa_offset -4\n"
- "pop %edi; .cfi_adjust_cfa_offset -4\n"
- "pop %esi; .cfi_adjust_cfa_offset -4\n"
+ "pop %ebp; .cfi_restore ebp; .cfi_adjust_cfa_offset -4\n"
+ "pop %ebx; .cfi_restore ebx; .cfi_adjust_cfa_offset -4\n"
+ "pop %edi; .cfi_restore edi; .cfi_adjust_cfa_offset -4\n"
+ "pop %esi; .cfi_restore esi; .cfi_adjust_cfa_offset -4\n"
"ret\n"
".cfi_endproc\n"
"9:.size SyscallAsm, 9b-SyscallAsm\n"
#endif
".fnend\n"
"9:.size SyscallAsm, 9b-SyscallAsm\n"
+#elif defined(__mips__)
+ ".text\n"
+ ".align 4\n"
+ ".type SyscallAsm, @function\n"
+ "SyscallAsm:.ent SyscallAsm\n"
+ ".frame $sp, 40, $ra\n"
+ ".set push\n"
+ ".set noreorder\n"
+ "addiu $sp, $sp, -40\n"
+ "sw $ra, 36($sp)\n"
+ // Check if "v0" is negative. If so, do not attempt to make a
+ // system call. Instead, compute the return address that is visible
+ // to the kernel after we execute "syscall". This address can be
+ // used as a marker that BPF code inspects.
+ "bgez $v0, 1f\n"
+ " nop\n"
+ "la $v0, 2f\n"
+ "b 2f\n"
+ " nop\n"
+ // On MIPS first four arguments go to registers a0 - a3 and any
+ // argument after that goes to stack. We can go ahead and directly
+ // copy the entries from the arguments array into the appropriate
+ // CPU registers and on the stack.
+ "1:lw $a3, 28($a0)\n"
+ "lw $a2, 24($a0)\n"
+ "lw $a1, 20($a0)\n"
+ "lw $t0, 16($a0)\n"
+ "sw $a3, 28($sp)\n"
+ "sw $a2, 24($sp)\n"
+ "sw $a1, 20($sp)\n"
+ "sw $t0, 16($sp)\n"
+ "lw $a3, 12($a0)\n"
+ "lw $a2, 8($a0)\n"
+ "lw $a1, 4($a0)\n"
+ "lw $a0, 0($a0)\n"
+ // Enter the kernel
+ "syscall\n"
+ // This is our "magic" return address that the BPF filter sees.
+ // Restore the return address from the stack.
+ "2:lw $ra, 36($sp)\n"
+ "jr $ra\n"
+ " addiu $sp, $sp, 40\n"
+ ".set pop\n"
+ ".end SyscallAsm\n"
+ ".size SyscallAsm,.-SyscallAsm\n"
#endif
); // asm
} // namespace
+intptr_t Syscall::InvalidCall() {
+ // Explicitly pass eight zero arguments just in case.
+ return Call(kInvalidSyscallNumber, 0, 0, 0, 0, 0, 0, 0, 0);
+}
+
intptr_t Syscall::Call(int nr,
intptr_t p0,
intptr_t p1,
intptr_t p2,
intptr_t p3,
intptr_t p4,
- intptr_t p5) {
+ intptr_t p5,
+ intptr_t p6,
+ intptr_t p7) {
// We rely on "intptr_t" to be the exact size as a "void *". This is
// typically true, but just in case, we add a check. The language
// specification allows platforms some leeway in cases, where
COMPILE_ASSERT(sizeof(void*) == sizeof(intptr_t),
pointer_types_and_intptr_must_be_exactly_the_same_size);
+ // TODO(nedeljko): Enable use of more than six parameters on architectures
+ // where that makes sense.
+#if defined(__mips__)
+ const intptr_t args[8] = {p0, p1, p2, p3, p4, p5, p6, p7};
+#else
+ DCHECK_EQ(p6, 0) << " Support for syscalls with more than six arguments not "
+ "added for this architecture";
+ DCHECK_EQ(p7, 0) << " Support for syscalls with more than six arguments not "
+ "added for this architecture";
const intptr_t args[6] = {p0, p1, p2, p3, p4, p5};
+#endif // defined(__mips__)
// Invoke our file-scope assembly code. The constraints have been picked
// carefully to match what the rest of the assembly code expects in input,
);
ret = inout;
}
+#elif defined(__mips__)
+ int err_status;
+ intptr_t ret = Syscall::SandboxSyscallRaw(nr, args, &err_status);
+
+ if (err_status) {
+ // On error, MIPS returns errno from syscall instead of -errno.
+ // The purpose of this negation is for SandboxSyscall() to behave
+ // more like it would on other architectures.
+ ret = -ret;
+ }
#else
#error "Unimplemented architecture"
#endif
return ret;
}
+void Syscall::PutValueInUcontext(intptr_t ret_val, ucontext_t* ctx) {
+#if defined(__mips__)
+ // Mips ABI states that on error a3 CPU register has non zero value and if
+ // there is no error, it should be zero.
+ if (ret_val <= -1 && ret_val >= -4095) {
+ // |ret_val| followes the Syscall::Call() convention of being -errno on
+ // errors. In order to write correct value to return register this sign
+ // needs to be changed back.
+ ret_val = -ret_val;
+ SECCOMP_PARM4(ctx) = 1;
+ } else
+ SECCOMP_PARM4(ctx) = 0;
+#endif
+ SECCOMP_RESULT(ctx) = static_cast<greg_t>(ret_val);
+}
+
+#if defined(__mips__)
+intptr_t Syscall::SandboxSyscallRaw(int nr,
+ const intptr_t* args,
+ intptr_t* err_ret) {
+ register intptr_t ret __asm__("v0") = nr;
+ // a3 register becomes non zero on error.
+ register intptr_t err_stat __asm__("a3") = 0;
+ {
+ register const intptr_t* data __asm__("a0") = args;
+ asm volatile(
+ "la $t9, SyscallAsm\n"
+ "jalr $t9\n"
+ " nop\n"
+ : "=r"(ret), "=r"(err_stat)
+ : "0"(ret),
+ "r"(data)
+ // a2 is in the clober list so inline assembly can not change its
+ // value.
+ : "memory", "ra", "t9", "a2");
+ }
+
+ // Set an error status so it can be used outside of this function
+ *err_ret = err_stat;
+
+ return ret;
+}
+#endif // defined(__mips__)
+
} // namespace sandbox
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