[PATCH v3 2/5] powerpc: kexec_file: Add buffer hand-over support for the next kernel

[Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>]

The buffer hand-over mechanism allows the currently running kernel to pass
data to kernel that will be kexec'd via a kexec segment. The second kernel
can check whether the previous kernel sent data and retrieve it.

This is the architecture-specific part.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/kexec.h       |  12 +++-
 arch/powerpc/kernel/kexec_elf_64.c     |   2 +-
 arch/powerpc/kernel/machine_kexec_64.c | 114 +++++++++++++++++++++++++++++++--
 3 files changed, 120 insertions(+), 8 deletions(-)

diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
index 09813f3ea3c2..cfc702f60726 100644
--- a/arch/powerpc/include/asm/kexec.h
+++ b/arch/powerpc/include/asm/kexec.h
@@ -92,12 +92,20 @@ static inline bool kdump_in_progress(void)
 }
 
 #ifdef CONFIG_KEXEC_FILE
+#define ARCH_HAS_KIMAGE_ARCH
+
+struct kimage_arch {
+	phys_addr_t handover_buffer_addr;
+	unsigned long handover_buffer_size;
+};
+
 int setup_purgatory(struct kimage *image, const void *slave_code,
 		    const void *fdt, unsigned long kernel_load_addr,
 		    unsigned long fdt_load_addr, unsigned long stack_top,
 		    int debug);
-int setup_new_fdt(void *fdt, unsigned long initrd_load_addr,
-		  unsigned long initrd_len, const char *cmdline);
+int setup_new_fdt(const struct kimage *image, void *fdt,
+		  unsigned long initrd_load_addr, unsigned long initrd_len,
+		  const char *cmdline);
 bool find_debug_console(const void *fdt);
 #endif /* CONFIG_KEXEC_FILE */
 
diff --git a/arch/powerpc/kernel/kexec_elf_64.c b/arch/powerpc/kernel/kexec_elf_64.c
index a2b8ddc44b74..6127a495a774 100644
--- a/arch/powerpc/kernel/kexec_elf_64.c
+++ b/arch/powerpc/kernel/kexec_elf_64.c
@@ -209,7 +209,7 @@ void *elf64_load(struct kimage *image, char *kernel_buf,
 		goto out;
 	}
 
-	ret = setup_new_fdt(fdt, initrd_load_addr, initrd_len, cmdline);
+	ret = setup_new_fdt(image, fdt, initrd_load_addr, initrd_len, cmdline);
 	if (ret)
 		goto out;
 
diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c
index 5d59ccdc39f5..59f1e5d4b6c4 100644
--- a/arch/powerpc/kernel/machine_kexec_64.c
+++ b/arch/powerpc/kernel/machine_kexec_64.c
@@ -489,6 +489,60 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
 	return image->fops->cleanup(image->image_loader_data);
 }
 
+bool kexec_can_hand_over_buffer(void)
+{
+	return true;
+}
+
+int arch_kexec_add_handover_buffer(struct kimage *image,
+				   unsigned long load_addr, unsigned long size)
+{
+	image->arch.handover_buffer_addr = load_addr;
+	image->arch.handover_buffer_size = size;
+
+	return 0;
+}
+
+int kexec_get_handover_buffer(void **addr, unsigned long *size)
+{
+	int ret;
+	u64 start_addr, end_addr;
+
+	ret = of_property_read_u64(of_chosen,
+				   "linux,kexec-handover-buffer-start",
+				   &start_addr);
+	if (ret == -EINVAL)
+		return -ENOENT;
+	else if (ret)
+		return -EINVAL;
+
+	ret = of_property_read_u64(of_chosen, "linux,kexec-handover-buffer-end",
+				   &end_addr);
+	if (ret == -EINVAL)
+		return -ENOENT;
+	else if (ret)
+		return -EINVAL;
+
+	*addr =  __va(start_addr);
+	/* -end is the first address after the buffer. */
+	*size = end_addr - start_addr;
+
+	return 0;
+}
+
+int kexec_free_handover_buffer(void)
+{
+	int ret;
+	void *addr;
+	unsigned long size;
+
+	ret = kexec_get_handover_buffer(&addr, &size);
+	if (ret)
+		return ret;
+
+	return memblock_free((phys_addr_t) addr, size);
+}
+
 /**
  * arch_kexec_walk_mem() - call func(data) for each unreserved memory block
  * @kbuf:	Context info for the search. Also passed to @func.
@@ -686,9 +740,52 @@ int setup_purgatory(struct kimage *image, const void *slave_code,
 	return 0;
 }
 
-/*
- * setup_new_fdt() - modify /chosen and memory reservation for the next kernel
- * @fdt:
+/**
+ * setup_handover_buffer() - add properties and reservation for the handover buffer
+ * @image:		kexec image being loaded.
+ * @fdt:		Flattened device tree for the next kernel.
+ * @chosen_node:	Offset to the chosen node.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+static int setup_handover_buffer(const struct kimage *image, void *fdt,
+				 int chosen_node)
+{
+	int ret;
+
+	if (image->arch.handover_buffer_addr == 0)
+		return 0;
+
+	ret = fdt_setprop_u64(fdt, chosen_node,
+			      "linux,kexec-handover-buffer-start",
+			      image->arch.handover_buffer_addr);
+	if (ret < 0)
+		return -EINVAL;
+
+	/* -end is the first address after the buffer. */
+	ret = fdt_setprop_u64(fdt, chosen_node,
+			      "linux,kexec-handover-buffer-end",
+			      image->arch.handover_buffer_addr +
+			      image->arch.handover_buffer_size);
+	if (ret < 0)
+		return -EINVAL;
+
+	ret = fdt_add_mem_rsv(fdt, image->arch.handover_buffer_addr,
+			      image->arch.handover_buffer_size);
+	if (ret)
+		return -EINVAL;
+
+	pr_debug("kexec handover buffer at 0x%llx, size = 0x%lx\n",
+		 image->arch.handover_buffer_addr,
+		 image->arch.handover_buffer_size);
+
+	return 0;
+}
+
+/**
+ * setup_new_fdt() - modify /chosen and memory reservations for the next kernel
+ * @image:		kexec image being loaded.
+ * @fdt:		Flattened device tree for the next kernel.
  * @initrd_load_addr:	Address where the next initrd will be loaded.
  * @initrd_len:		Size of the next initrd, or 0 if there will be none.
  * @cmdline:		Command line for the next kernel, or NULL if there will
@@ -696,8 +793,9 @@ int setup_purgatory(struct kimage *image, const void *slave_code,
  *
  * Return: 0 on success, or negative errno on error.
  */
-int setup_new_fdt(void *fdt, unsigned long initrd_load_addr,
-		  unsigned long initrd_len, const char *cmdline)
+int setup_new_fdt(const struct kimage *image, void *fdt,
+		  unsigned long initrd_load_addr, unsigned long initrd_len,
+		  const char *cmdline)
 {
 	uint64_t oldfdt_addr;
 	int i, ret, chosen_node;
@@ -839,6 +937,12 @@ int setup_new_fdt(void *fdt, unsigned long initrd_load_addr,
 		}
 	}
 
+	ret = setup_handover_buffer(image, fdt, chosen_node);
+	if (ret) {
+		pr_err("Error setting up the new device tree.\n");
+		return ret;
+	}
+
 	ret = fdt_setprop(fdt, chosen_node, "linux,booted-from-kexec", NULL, 0);
 	if (ret) {
 		pr_err("Error setting up the new device tree.\n");
-- 
1.9.1