RISC-V: Add crash kernel support

This patch allows Linux to act as a crash kernel for use with
kdump. Userspace will let the crash kernel know about the
memory region it can use through linux,usable-memory property
on the /memory node (overriding its reg property), and about the
memory region where the elf core header of the previous kernel
is saved, through a reserved-memory node with a compatible string
of "linux,elfcorehdr". This approach is the least invasive and
re-uses functionality already present.

I tested this on riscv64 qemu and it works as expected, you
may test it by retrieving the dmesg of the previous kernel
through /proc/vmcore, using the vmcore-dmesg utility from
kexec-tools.

Signed-off-by: Nick Kossifidis <mick@ics.forth.gr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 0aa9f8340115..932ef73cf622 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -66,6 +66,9 @@ static struct resource code_res = { .name = "Kernel code", };
 static struct resource data_res = { .name = "Kernel data", };
 static struct resource rodata_res = { .name = "Kernel rodata", };
 static struct resource bss_res = { .name = "Kernel bss", };
+#ifdef CONFIG_CRASH_DUMP
+static struct resource elfcorehdr_res = { .name = "ELF Core hdr", };
+#endif
 
 static int __init add_resource(struct resource *parent,
 				struct resource *res)
@@ -169,6 +172,15 @@ static void __init init_resources(void)
 	}
 #endif
 
+#ifdef CONFIG_CRASH_DUMP
+	if (elfcorehdr_size > 0) {
+		elfcorehdr_res.start = elfcorehdr_addr;
+		elfcorehdr_res.end = elfcorehdr_addr + elfcorehdr_size - 1;
+		elfcorehdr_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
+		add_resource(&iomem_resource, &elfcorehdr_res);
+	}
+#endif
+
 	for_each_reserved_mem_region(region) {
 		res = &mem_res[res_idx--];