Set cgp in boot.S

The common/boot.S is updated to reflect the improvements made to the
bootloader boot.S.

sw/cheri/boot/boot.S

@@ -23,10 +23,10 @@ start:
  cspecialw mtcc, ct0
 
  // No bounds on stack, grows down from the end of IRAM
- li sp, 0x00100ff0
+ li sp, 0x00101000
  csetaddr csp, cs0, sp
 
- // Clear the revocation bitmap before entering C code.
+ // Clear the revocation bitmap before entering C/C++ code.
  // The bitmap is not cleared upon reset so memset to return it to a
  // pristine state.
  li a0, 0x30000000
@@ -35,6 +35,11 @@ start:
  li a2, 4096
  ccall bl_memset
 
+ // Set cgp to correct location so globals can be used.
+.extern __global_pointer$
+ la_abs t0, __global_pointer$
+ csetaddr cgp, cs0, t0
+
  cmove ca0, cs0
  ccall rom_loader_entry
 

sw/cheri/checks/cheri_sanity.cc

@@ -21,6 +21,14 @@ extern "C" uint32_t entry_point(void *rwRoot)
 {
  Capability<void> root{rwRoot};
 
+ asm volatile(
+ // Store capability to stack
+ "csc cra, -4(csp)\n"
+ // Load capability from stack
+ "clc cra, -4(csp)\n"
+ // Clear capability from stack
+ "csc cnull, -4(csp)\n" ::
+ : "memory");
  // Capability to general purpose output
  Capability<volatile uint32_t> gpo = root.cast<volatile uint32_t>();
  gpo.address() = 0x80000000;

sw/cheri/common/boot.S

@@ -12,28 +12,67 @@
 start:
  // Enable the ICache
  csrsi 0x7c0, 1
- // ca0 (first argument) contains the read-write root
- cspecialr ca0, mtdc
+
+ // Upon reset mtdc contains the read-write root and pcc contains the execution root.
+ cspecialr cs0, mtdc
+ auipcc cs1, 0
 
  // No bounds on stack, grows down from the end of IRAM
- li sp, 0x0010E000
- csetaddr csp, ca0, sp
- auipcc cra, 0
- // Call the C++ entry point
- la_abs t0, entry_point
- csetaddr cra, cra, t0
- // Store capability to stack
- csc cra, 0(csp)
- // Load capability from stack
- clc cra, 0(csp)
- // Clear capability from stack
- csc cnull, 0(csp)
- cjalr cra
-
- // Jump to the newly loaded binary.
- // This could be a relative jump, but I'd need to get the relocations right
- // and we have 32 KiB of IROM so wasting a few bytes doesn't really matter.
- auipcc cra, 0
- li t0, 0x00140000
- csetaddr cra, cra, t0
- cjr cra
+ li sp, 0x00120000
+ csetaddr csp, cs0, sp
+
+ // Clear the revocation bitmap before entering C/C++ code.
+ // The bitmap is not cleared upon reset so memset to return it to a
+ // pristine state.
+ li a0, 0x30000000
+ csetaddr ca0, cs0, a0
+ li a1, 0
+ li a2, 4096
+ ccall bl_memset
+
+ // Set cgp to correct location so globals can be used.
+.extern __global_pointer$
+ la_abs t0, __global_pointer$
+ csetaddr cgp, cs0, t0
+
+ cmove ca0, cs0
+ ccall entry_point
+
+ // Infinite loop if the entry point ever returns
+1:
+ wfi
+ j 1b
+
+.section .text.bl_memset, "ax", @progbits
+.global bl_memset
+bl_memset:
+ // Check if everything is aligned, and if so use word fill.
+ andi a3, a0, 3
+ bnez a3, .Lbytes_fill
+ andi a3, a2, 3
+ bnez a3, .Lbytes_fill
+
+ // Broadcast a1 to all bytes.
+ andi a1, a1, 0xff
+ slli a3, a1, 8
+ or a1, a3, a1
+ slli a3, a1, 16
+ or a1, a3, a1
+
+0:
+ beqz a2, .Lret
+ csw a1, (ca0)
+ cincoffset ca0, ca0, 4
+ addi a2, a2, -4
+ j 0b
+
+.Lbytes_fill:
+0:
+ beqz a2, .Lret
+ csb a1, (ca0)
+ cincoffset ca0, ca0, 1
+ addi a2, a2, -1
+ j 0b
+
+.Lret:
+ cret