From 1d44643a7c7cf650efd1093d22cd5bf859fdcb51 Mon Sep 17 00:00:00 2001
From: Shawn Anastasio <shawnanastasio@yahoo.com>
Date: Thu, 9 Aug 2018 20:52:13 -0500
Subject: [PATCH] sandbox/linux/seccomp-bpf: Add ppc64 syscall stub

---
 sandbox/linux/seccomp-bpf/syscall.cc | 53 ++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

Index: chromium-127.0.6533.72/sandbox/linux/seccomp-bpf/syscall.cc
===================================================================
--- chromium-127.0.6533.72.orig/sandbox/linux/seccomp-bpf/syscall.cc
+++ chromium-127.0.6533.72/sandbox/linux/seccomp-bpf/syscall.cc
@@ -18,7 +18,7 @@ namespace sandbox {
 namespace {
 
 #if defined(ARCH_CPU_X86_FAMILY) || defined(ARCH_CPU_ARM_FAMILY) || \
-    defined(ARCH_CPU_MIPS_FAMILY)
+    defined(ARCH_CPU_MIPS_FAMILY) || defined (ARCH_CPU_PPC64_FAMILY)
 // Number that's not currently used by any Linux kernel ABIs.
 const int kInvalidSyscallNumber = 0x351d3;
 #else
@@ -308,10 +308,54 @@ asm(// We need to be able to tell the ke
     "2:ret\n"
     ".cfi_endproc\n"
     ".size SyscallAsm, .-SyscallAsm\n"
+#elif defined(__powerpc64__)
+    ".text\n"
+    ".align 4\n"
+    ".type SyscallAsm @function\n"
+    "SyscallAsm:\n"
+    ".cfi_startproc\n"
+
+    // Check if r3 is negative
+    "cmpdi 3, 0\n"
+    "bgt 2f\n"
+
+    // Load address of 3f into r3 and return
+    "mflr 10\n"
+    "bl 1f\n"
+    "1: mflr 3\n"
+    "mtlr 10\n"
+    "addi 3, 3, 4*13\n"
+    "blr\n"
+
+    // Load arguments from array into r3-8
+    // save param 3 in r10
+    "2:\n"
+    "mr 0, 3\n"
+    "ld 3, 0(4)\n"
+    "ld 5, 16(4)\n"
+    "ld 6, 24(4)\n"
+    "ld 7, 32(4)\n"
+    "ld 8, 40(4)\n"
+    "ld 4, 8(4)\n"
+    "li 9, 0\n"
+
+    // Enter kernel
+    "sc\n"
+
+    // Magic return address
+    "3:\n"
+    // Like MIPS, ppc64 return values are always positive.
+    // Check for error in cr0.SO and negate upon error
+    "bc 4, 3, 4f\n"
+    "neg 3, 3\n"
+    "4: blr\n"
+
+    ".cfi_endproc\n"
+    ".size SyscallAsm, .-SyscallAsm\n"
 #endif
     );  // asm
 
-#if defined(__x86_64__)
+#if defined(__x86_64__) || defined(__powerpc64__)
 extern "C" {
 intptr_t SyscallAsm(intptr_t nr, const intptr_t args[6]);
 }
@@ -425,6 +469,8 @@ intptr_t Syscall::Call(int nr,
     ret = inout;
   }
 
+#elif defined(__powerpc64__)
+  intptr_t ret = SyscallAsm(nr, args);
 #else
 #error "Unimplemented architecture"
 #endif
@@ -441,8 +487,18 @@ void Syscall::PutValueInUcontext(intptr_
     // needs to be changed back.
     ret_val = -ret_val;
     SECCOMP_PARM4(ctx) = 1;
-  } else
+  } else {
     SECCOMP_PARM4(ctx) = 0;
+  }
+#endif
+#if defined(__powerpc64__)
+  // Same as MIPS, need to invert ret and set error register (cr0.SO)
+  if (ret_val <= -1 && ret_val >= -4095) {
+    ret_val = -ret_val;
+    ctx->uc_mcontext.regs->ccr |= (1 << 28);
+  } else {
+    ctx->uc_mcontext.regs->ccr &= ~(1 << 28);
+  }
 #endif
   SECCOMP_RESULT(ctx) = static_cast<greg_t>(ret_val);
 }