Index: sandbox/linux/seccomp-bpf/syscall.cc |
diff --git a/sandbox/linux/seccomp-bpf/syscall.cc b/sandbox/linux/seccomp-bpf/syscall.cc |
index fd599e893b2b7d3b3fdefe81dfcfeb8dd17717d4..40882fffe26e79b0b0fd58bf8f5a303e27e7d344 100644 |
--- a/sandbox/linux/seccomp-bpf/syscall.cc |
+++ b/sandbox/linux/seccomp-bpf/syscall.cc |
@@ -168,6 +168,54 @@ namespace sandbox { |
#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, 32, $ra\n" |
+ ".set push\n" |
+ ".set noreorder\n" |
+ "addiu $sp, $sp, -32\n" |
+ "sw $ra, 28($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" |
+ " addiu $v0, -12\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 $t0, 20($a0)\n" |
+ "sw $t0, 20($sp)\n" |
+ "lw $t0, 16($a0)\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" |
+ // Return value is in v0 instead of syscall number. |
+ "beqz $a3, 2f\n" |
+ " nop\n" |
+ // On error, MIPS returns errno from syscall instead of -errno. |
+ // The purpose of this negation is for SyscallAsm to behave |
+ // more like it would on other architectures. |
+ "subu $v0, $zero, $v0\n" |
jln (very slow on Chromium)
2014/05/28 00:06:57
How about doing this negation in C, later.
We cou
nedeljko
2014/05/29 14:06:45
I created SandboxSyscallRaw() as you suggested, bu
nedeljko
2014/05/29 14:06:45
Done.
|
+ // This is our "magic" return address that the BPF filter sees. |
+ // Restore the return address from the stack. |
+ "2:lw $ra, 28($sp)\n" |
+ "jr $ra\n" |
+ " addiu $sp, $sp, 32\n" |
+ ".set pop\n" |
+ ".end SyscallAsm\n" |
+ ".size SyscallAsm,.-SyscallAsm\n" |
#endif |
); // asm |
@@ -233,6 +281,21 @@ intptr_t SandboxSyscall(int nr, |
); |
ret = inout; |
} |
+#elif defined(__mips__) |
+ // In register v0 is syscall number before the call and |
+ // return value from SyscallAsm after the call |
+ register intptr_t ret __asm__("v0") = nr; |
+ { |
+ register const intptr_t *data __asm__("a0") = args; |
+ asm volatile( |
+ "la $t9, SyscallAsm\n" |
+ "jalr $t9\n" |
+ " nop\n" |
+ : "=r"(ret) |
+ : "0"(ret), "r"(data) |
+ : "memory", "ra", "t9" |
+ ); |
+ } |
#else |
errno = ENOSYS; |
intptr_t ret = -1; |