[RFC 2/4] kdump, x86: pass the LUKS master key to kdump kernel using a kernel command line parameter luksmasterkey

[Coiby Xu]

kdump will build up the kernel command parameter luksmasterkey as
similar to elfcorehdr to pass the memory address of the stored info of LUKS
master key to kdump kernel.

Signed-off-by: Coiby Xu <coxu@xxxxxxxxxx>
---
 arch/x86/include/asm/crash.h      |  1 +
 arch/x86/kernel/crash.c           | 42 ++++++++++++++++++++++++++++++-
 arch/x86/kernel/kexec-bzimage64.c |  7 ++++++
 include/linux/kexec.h             |  4 +++
 4 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/crash.h b/arch/x86/include/asm/crash.h
index 8b6bd63530dc..757374389296 100644
--- a/arch/x86/include/asm/crash.h
+++ b/arch/x86/include/asm/crash.h
@@ -4,6 +4,7 @@
 
 struct kimage;
 
+int crash_load_luks_key(struct kimage *image);
 int crash_load_segments(struct kimage *image);
 int crash_setup_memmap_entries(struct kimage *image,
 		struct boot_params *params);
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index e8326a8d1c5d..6d117da62da4 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -304,6 +304,7 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
 				 unsigned long long mend)
 {
 	unsigned long start, end;
+	int r;
 
 	cmem->ranges[0].start = mstart;
 	cmem->ranges[0].end = mend;
@@ -312,7 +313,19 @@ static int memmap_exclude_ranges(struct kimage *image, struct crash_mem *cmem,
 	/* Exclude elf header region */
 	start = image->elf_load_addr;
 	end = start + image->elf_headers_sz - 1;
-	return crash_exclude_mem_range(cmem, start, end);
+	r = crash_exclude_mem_range(cmem, start, end);
+
+	if (r)
+		return r;
+
+	/* Exclude LUKS master key region */
+	if (image->luks_master_key_addr) {
+		start = image->luks_master_key_addr;
+		end = start + image->luks_master_key_sz - 1;
+		return crash_exclude_mem_range(cmem, start, end);
+	}
+
+	return r;
 }
 
 /* Prepare memory map for crash dump kernel */
@@ -383,6 +396,33 @@ int crash_setup_memmap_entries(struct kimage *image, struct boot_params *params)
 	return ret;
 }
 
+int crash_load_luks_key(struct kimage *image)
+{
+	int ret;
+	struct kexec_buf kbuf = { .image = image, .buf_min = 0,
+				  .buf_max = ULONG_MAX, .top_down = false };
+
+	image->luks_master_key_addr = 0;
+	ret = kexec_pass_luks_master_key(&kbuf.buffer, &kbuf.bufsz);
+	if (ret)
+		return ret;
+
+	kbuf.memsz = kbuf.bufsz;
+	kbuf.buf_align = ELF_CORE_HEADER_ALIGN;
+	kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+	ret = kexec_add_buffer(&kbuf);
+	if (ret) {
+		vfree((void *)kbuf.buffer);
+		return ret;
+	}
+	image->luks_master_key_addr = kbuf.mem;
+	image->luks_master_key_sz = kbuf.bufsz;
+	pr_debug("Loaded LUKS master key at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
+		 image->luks_master_key_addr, kbuf.bufsz, kbuf.bufsz);
+
+	return ret;
+}
+
 int crash_load_segments(struct kimage *image)
 {
 	int ret;
diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index 170d0fd68b1f..64ea3b6a5768 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -76,6 +76,10 @@ static int setup_cmdline(struct kimage *image, struct boot_params *params,
 	if (image->type == KEXEC_TYPE_CRASH) {
 		len = sprintf(cmdline_ptr,
 			"elfcorehdr=0x%lx ", image->elf_load_addr);
+
+		if (image->luks_master_key_addr != 0)
+			len += sprintf(cmdline_ptr + len,
+					"luksmasterkey=0x%lx ", image->luks_master_key_addr);
 	}
 	memcpy(cmdline_ptr + len, cmdline, cmdline_len);
 	cmdline_len += len;
@@ -372,6 +376,9 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
 		ret = crash_load_segments(image);
 		if (ret)
 			return ERR_PTR(ret);
+		ret = crash_load_luks_key(image);
+		if (ret)
+			pr_debug("Either no LUKS master key or error to retrieve the LUKS master key\n");
 	}
 
 	/*
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 91507bc684e2..456a5bc28518 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -316,6 +316,10 @@ struct kimage {
 	void *elf_headers;
 	unsigned long elf_headers_sz;
 	unsigned long elf_load_addr;
+
+	/* LUKS master key buffer */
+	unsigned long luks_master_key_addr;
+	unsigned long luks_master_key_sz;
 };
 
 /* kexec interface functions */
-- 
2.34.1