powerpc/kexec_file: Enable early kernel OPAL calls

Kernels built with CONFIG_PPC_EARLY_DEBUG_OPAL enabled expects r8 & r9
to be filled with OPAL base & entry addresses respectively. Setting
these registers allows the kernel to perform OPAL calls before the
device tree is parsed.
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/159602303975.575379.5032301944162937479.stgit@hbathini

arch/powerpc/kexec/file_load_64.c

@@ -876,6 +876,7 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
 			  const void *fdt, unsigned long kernel_load_addr,
 			  unsigned long fdt_load_addr)
 {
+	struct device_node *dn = NULL;
 	int ret;
 
 	ret = setup_purgatory(image, slave_code, fdt, kernel_load_addr,
@@ -903,9 +904,28 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
 					     &image->arch.backup_start,
 					     sizeof(image->arch.backup_start),
 					     false);
+	if (ret)
+		goto out;
+
+	/* Setup OPAL base & entry values */
+	dn = of_find_node_by_path("/ibm,opal");
+	if (dn) {
+		u64 val;
+
+		of_property_read_u64(dn, "opal-base-address", &val);
+		ret = kexec_purgatory_get_set_symbol(image, "opal_base", &val,
+						     sizeof(val), false);
+		if (ret)
+			goto out;
+
+		of_property_read_u64(dn, "opal-entry-address", &val);
+		ret = kexec_purgatory_get_set_symbol(image, "opal_entry", &val,
+						     sizeof(val), false);
+	}
 out:
 	if (ret)
 		pr_err("Failed to setup purgatory symbols");
+	of_node_put(dn);
 	return ret;
 }
 

arch/powerpc/purgatory/trampoline_64.S

@@ -87,6 +87,10 @@ master:
 	li	%r4,28
 	STWX_BE	%r17,%r3,%r4	/* Store my cpu as __be32 at byte 28 */
 1:
+	/* Load opal base and entry values in r8 & r9 respectively */
+	ld	%r8,(opal_base - 0b)(%r18)
+	ld	%r9,(opal_entry - 0b)(%r18)
+
 	/* load the kernel address */
 	ld	%r4,(kernel - 0b)(%r18)
 
@@ -133,6 +137,18 @@ backup_start:
 	.8byte  0x0
 	.size backup_start, . - backup_start
 
+	.balign 8
+	.globl opal_base
+opal_base:
+	.8byte  0x0
+	.size opal_base, . - opal_base
+
+	.balign 8
+	.globl opal_entry
+opal_entry:
+	.8byte  0x0
+	.size opal_entry, . - opal_entry
+
 	.data
 	.balign 8
 .globl purgatory_sha256_digest