From 8b4421bacba28f97da2ddeb6a6fba9e184e91bee Mon Sep 17 00:00:00 2001
From: "Wesley W. Terpstra" <wesley@sifive.com>
Date: Wed, 5 Apr 2017 16:27:19 -0700
Subject: bbl: prevent named cores from booting

---
 bbl/bbl.c        |  2 +-
 machine/mentry.S | 14 +++++++++++++-
 machine/minit.c  |  2 +-
 machine/mtrap.c  |  1 +
 machine/mtrap.h  |  3 +++
 5 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/bbl/bbl.c b/bbl/bbl.c
index 44802c1..f64b2e7 100644
--- a/bbl/bbl.c
+++ b/bbl/bbl.c
@@ -23,7 +23,7 @@ static void filter_dtb(uintptr_t source)
   memcpy((void*)dest, (void*)source, size);
 
   // Remove information from the chained FDT
-  // filter_harts(dest, 0x2);
+  filter_harts(dest, HART_MASK);
   filter_plic(dest);
   filter_compat(dest, "riscv,clint0");
   filter_compat(dest, "riscv,debug-013");
diff --git a/machine/mentry.S b/machine/mentry.S
index 9575dc9..62a850d 100644
--- a/machine/mentry.S
+++ b/machine/mentry.S
@@ -257,7 +257,11 @@ do_reset:
   slli a2, a3, RISCV_PGSHIFT
   add sp, sp, a2
 
-  beqz a3, init_first_hart
+  # Boot on the first unmasked hart
+  li a4, (~HART_MASK & (HART_MASK+1))
+  srl a4, a4, a3
+  andi a4, a4, 1
+  bnez a4, init_first_hart
 
   # set MSIE bit to receive IPI
   li a2, MIP_MSIP
@@ -267,6 +271,14 @@ do_reset:
 #if MAX_HARTS > 1
   # wait for an IPI to signal that it's safe to boot
   wfi
+
+  # masked harts never start
+  li a4, HART_MASK
+  srl a4, a4, a3
+  andi a4, a4, 1
+  bnez a4, .LmultiHart
+
+  # only start if mip is set
   csrr a2, mip
   andi a2, a2, MIP_MSIP
   beqz a2, .LmultiHart
diff --git a/machine/minit.c b/machine/minit.c
index baf45a5..94a1491 100644
--- a/machine/minit.c
+++ b/machine/minit.c
@@ -124,7 +124,7 @@ static void hart_plic_init()
 static void wake_harts()
 {
   for (int hart = 0; hart < MAX_HARTS; ++hart)
-    if (((hart_mask >> hart) & 1))
+    if ((((~HART_MASK & hart_mask) >> hart) & 1))
       *OTHER_HLS(hart)->ipi = 1; // wakeup the hart
 }
 
diff --git a/machine/mtrap.c b/machine/mtrap.c
index d7def4c..be264f3 100644
--- a/machine/mtrap.c
+++ b/machine/mtrap.c
@@ -50,6 +50,7 @@ void printm(const char* s, ...)
 
 static void send_ipi(uintptr_t recipient, int event)
 {
+  if (((HART_MASK >> recipient) & 1)) return;
   atomic_or(&OTHER_HLS(recipient)->mipi_pending, event);
   mb();
   *OTHER_HLS(recipient)->ipi = 1;
diff --git a/machine/mtrap.h b/machine/mtrap.h
index e8dfc49..1437b11 100644
--- a/machine/mtrap.h
+++ b/machine/mtrap.h
@@ -9,6 +9,9 @@
 # define MAX_HARTS 1
 #endif
 
+// These harts will be prevented from booting beyond bbl
+#define HART_MASK	0x0UL
+
 #ifndef __ASSEMBLER__
 
 #include <stdint.h>
-- 
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