[PATCH v2 3/3] ppc64: Add a flag to tell the kernel it's booting from kexec

[Scott Wood]

It needs to know this because the SMP release mechanism for Freescale
book3e is different from when booting with normal hardware.  In theory
we could simulate the normal spin table mechanism, but not (easily) at
the addresses U-Boot put in the device tree -- so there'd need to be
even more communication between the kernel and kexec to set that up.

Signed-off-by: Scott Wood <scottwood at freescale.com>
---
v2: Use a device tree property rather than setting a flag in the kernel
image, as requested by Michael Ellerman.
---
 kexec/arch/ppc64/Makefile           |  6 +++
 kexec/arch/ppc64/fdt.c              | 78 +++++++++++++++++++++++++++++++++++++
 kexec/arch/ppc64/include/arch/fdt.h |  9 +++++
 kexec/arch/ppc64/kexec-elf-ppc64.c  |  7 ++++
 4 files changed, 100 insertions(+)
 create mode 100644 kexec/arch/ppc64/fdt.c
 create mode 100644 kexec/arch/ppc64/include/arch/fdt.h

diff --git a/kexec/arch/ppc64/Makefile b/kexec/arch/ppc64/Makefile
index 9a6e475..37cd233 100644
--- a/kexec/arch/ppc64/Makefile
+++ b/kexec/arch/ppc64/Makefile
@@ -1,11 +1,15 @@
 #
 # kexec ppc64 (linux booting linux)
 #
+include $(srcdir)/kexec/libfdt/Makefile.libfdt
+
 ppc64_KEXEC_SRCS =  kexec/arch/ppc64/kexec-elf-rel-ppc64.c
 ppc64_KEXEC_SRCS += kexec/arch/ppc64/kexec-zImage-ppc64.c
 ppc64_KEXEC_SRCS += kexec/arch/ppc64/kexec-elf-ppc64.c
 ppc64_KEXEC_SRCS += kexec/arch/ppc64/kexec-ppc64.c
 ppc64_KEXEC_SRCS += kexec/arch/ppc64/crashdump-ppc64.c
+ppc64_KEXEC_SRCS += kexec/arch/ppc64/fdt.c
+ppc64_KEXEC_SRCS += $(LIBFDT_SRCS:%=kexec/libfdt/%)
 
 ppc64_ARCH_REUSE_INITRD =
 
@@ -13,6 +17,8 @@ ppc64_FS2DT	    = kexec/fs2dt.c
 ppc64_FS2DT_INCLUDE = -include $(srcdir)/kexec/arch/ppc64/crashdump-ppc64.h \
                       -include $(srcdir)/kexec/arch/ppc64/kexec-ppc64.h
 
+ppc64_CPPFLAGS = -I$(srcdir)/kexec/libfdt
+
 dist += kexec/arch/ppc64/Makefile $(ppc64_KEXEC_SRCS)			\
 	kexec/arch/ppc64/kexec-ppc64.h kexec/arch/ppc64/crashdump-ppc64.h \
 	kexec/arch/ppc64/include/arch/options.h
diff --git a/kexec/arch/ppc64/fdt.c b/kexec/arch/ppc64/fdt.c
new file mode 100644
index 0000000..8bc6d2d
--- /dev/null
+++ b/kexec/arch/ppc64/fdt.c
@@ -0,0 +1,78 @@
+/*
+ * ppc64 fdt fixups
+ *
+ * Copyright 2015 Freescale Semiconductor, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation (version 2 of the License).
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <arch/fdt.h>
+#include <libfdt.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+ * Let the kernel know it booted from kexec, as some things (e.g.
+ * secondary CPU release) may work differently.
+ */
+static int fixup_kexec_prop(void *fdt)
+{
+	int err, nodeoffset;
+
+	nodeoffset = fdt_subnode_offset(fdt, 0, "chosen");
+	if (nodeoffset < 0)
+		nodeoffset = fdt_add_subnode(fdt, 0, "chosen");
+	if (nodeoffset < 0) {
+		printf("%s: add /chosen %s\n", __func__,
+		       fdt_strerror(nodeoffset));
+		return -1;
+	}
+
+	err = fdt_setprop(fdt, nodeoffset, "linux,booted-from-kexec",
+			  NULL, 0);
+	if (err < 0) {
+		printf("%s: couldn't write linux,booted-from-kexec: %s\n",
+		       __func__, fdt_strerror(err));
+		return -1;
+	}
+
+	return 0;
+}
+
+
+/*
+ * For now, assume that the added content fits in the file.
+ * This should be the case when flattening from /proc/device-tree,
+ * and when passing in a dtb, dtc can be told to add padding.
+ */
+int fixup_dt(char **fdt, off_t *size)
+{
+	int ret;
+
+	*size += 4096;
+	*fdt = realloc(*fdt, *size);
+	if (!*fdt) {
+		fprintf(stderr, "%s: out of memory\n", __func__);
+		return -1;
+	}
+
+	ret = fdt_open_into(*fdt, *fdt, *size);
+	if (ret < 0) {
+		fprintf(stderr, "%s: fdt_open_into: %s\n", __func__,
+			fdt_strerror(ret));
+		return -1;
+	}
+
+	ret = fixup_kexec_prop(*fdt);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
diff --git a/kexec/arch/ppc64/include/arch/fdt.h b/kexec/arch/ppc64/include/arch/fdt.h
new file mode 100644
index 0000000..14f8be2
--- /dev/null
+++ b/kexec/arch/ppc64/include/arch/fdt.h
@@ -0,0 +1,9 @@
+#ifndef KEXEC_ARCH_PPC64_FDT
+#define KEXEC_ARCH_PPC64_FDT
+
+#include <sys/types.h>
+
+int fixup_dt(char **fdt, off_t *size);
+
+#endif
+
diff --git a/kexec/arch/ppc64/kexec-elf-ppc64.c b/kexec/arch/ppc64/kexec-elf-ppc64.c
index adcee4c..ddd3de8 100644
--- a/kexec/arch/ppc64/kexec-elf-ppc64.c
+++ b/kexec/arch/ppc64/kexec-elf-ppc64.c
@@ -37,6 +37,8 @@
 #include "kexec-ppc64.h"
 #include "../../fs2dt.h"
 #include "crashdump-ppc64.h"
+#include <libfdt.h>
+#include <arch/fdt.h>
 #include <arch/options.h>
 
 uint64_t initrd_base, initrd_size;
@@ -242,6 +244,11 @@ int elf_ppc64_load(int argc, char **argv, const char *buf, off_t len,
 		/* create from fs2dt */
 		create_flatten_tree(&seg_buf, &seg_size, cmdline);
 	}
+
+	result = fixup_dt(&seg_buf, &seg_size);
+	if (result < 0)
+		return result;
+
 	my_dt_offset = add_buffer(info, seg_buf, seg_size, seg_size,
 				0, 0, max_addr, -1);
 
-- 
2.1.4