Support CoVE local attestation by reserving memory in the kernel image for TVM Attestation

Payload (TAP). Pass the physical address of the TAP when requesting to be promoted to a
TVM.

Signed-off-by: Wojciech Ozga <woz@zurich.ibm.com>

Author: wojciechozga

arch/riscv/cove/core.c

@@ -13,6 +13,8 @@
 #include <asm/sbi.h>
 #include <asm/cove.h>
 
+extern char __cove_tap_start[];
+
 static bool is_tvm;
 
 bool is_cove_guest(void)

arch/riscv/kernel/head.S

@@ -205,6 +205,7 @@ ENTRY(_start_kernel)
 	li a7, COVE_PROMOTE_SBI_EXT_ID
 	li a6, COVE_PROMOTE_SBI_FID
 	mv a0, a1
+	la a1, __cove_tap_start
 	ecall
 	mv a0, s1
 	mv a1, s2

arch/riscv/kernel/vmlinux-xip.lds.S

@@ -58,6 +58,17 @@ SECTIONS
 	}
 	_exiprom = .;			/* End of XIP ROM area */
 
+#ifdef CONFIG_RISCV_COVE_GUEST
+	. = ALIGN(4096);
+	.cove_tvm_attestation_payload : {
+		__cove_tap_start =  .;
+		LONG(0xace0ace0)
+		SHORT(0x0FFA)
+		FILL(0x00)
+       . += 4090;
+		__cove_tap_end =  .;
+	}
+#endif
 
 /*
  * From this point, stuff is considered writable and will be copied to RAM

arch/riscv/kernel/vmlinux.lds.S

@@ -113,6 +113,18 @@ SECTIONS
 	}
 	__init_end = .;
 
+#ifdef CONFIG_RISCV_COVE_GUEST
+	. = ALIGN(4096);
+	.cove_tvm_attestation_payload : {
+		__cove_tap_start =  .;
+		LONG(0xace0ace0)
+		SHORT(0x0FFA)
+		FILL(0x00)
+       . += 4090;
+		__cove_tap_end =  .;
+	}
+#endif
+
 	/* Start of data section */
 	_sdata = .;
 	RO_DATA(SECTION_ALIGN)

drivers/of/fdt.c

@@ -1167,6 +1167,7 @@ int __init early_init_dt_scan_chosen(char *cmdline)
 	early_init_dt_check_for_initrd(node);
 	early_init_dt_check_for_elfcorehdr(node);
 
+#ifndef CONFIG_RISCV_COVE_GUEST
 	rng_seed = of_get_flat_dt_prop(node, "rng-seed", &l);
 	if (rng_seed && l > 0) {
 		add_bootloader_randomness(rng_seed, l);
@@ -1178,6 +1179,7 @@ int __init early_init_dt_scan_chosen(char *cmdline)
 		of_fdt_crc32 = crc32_be(~0, initial_boot_params,
 				fdt_totalsize(initial_boot_params));
 	}
+#endif
 
 	/* Retrieve command line */
 	p = of_get_flat_dt_prop(node, "bootargs", &l);