kexec: support for kexec on panic using new system call

This patch adds support for loading a kexec on panic (kdump) kernel usning
new system call.

It prepares ELF headers for memory areas to be dumped and for saved cpu
registers.  Also prepares the memory map for second kernel and limits its
boot to reserved areas only.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: WANG Chao <chaowang@redhat.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 45 insertions, 10 deletions

diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
index bcedd100192f..a8e646458a10 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -21,6 +21,9 @@
 
 #include <asm/bootparam.h>
 #include <asm/setup.h>
+#include <asm/crash.h>
+
+#define MAX_ELFCOREHDR_STR_LEN	30	/* elfcorehdr=0x<64bit-value> */
 
 /*
  * Defines lowest physical address for various segments. Not sure where
@@ -58,18 +61,24 @@ static int setup_initrd(struct boot_params *params,
 	return 0;
 }
 
-static int setup_cmdline(struct boot_params *params,
+static int setup_cmdline(struct kimage *image, struct boot_params *params,
 			 unsigned long bootparams_load_addr,
 			 unsigned long cmdline_offset, char *cmdline,
 			 unsigned long cmdline_len)
 {
 	char *cmdline_ptr = ((char *)params) + cmdline_offset;
-	unsigned long cmdline_ptr_phys;
+	unsigned long cmdline_ptr_phys, len;
 	uint32_t cmdline_low_32, cmdline_ext_32;
 
 	memcpy(cmdline_ptr, cmdline, cmdline_len);
+	if (image->type == KEXEC_TYPE_CRASH) {
+		len = sprintf(cmdline_ptr + cmdline_len - 1,
+			" elfcorehdr=0x%lx", image->arch.elf_load_addr);
+		cmdline_len += len;
+	}
 	cmdline_ptr[cmdline_len - 1] = '\0';
 
+	pr_debug("Final command line is: %s\n", cmdline_ptr);
 	cmdline_ptr_phys = bootparams_load_addr + cmdline_offset;
 	cmdline_low_32 = cmdline_ptr_phys & 0xffffffffUL;
 	cmdline_ext_32 = cmdline_ptr_phys >> 32;
@@ -98,11 +107,12 @@ static int setup_memory_map_entries(struct boot_params *params)
 	return 0;
 }
 
-static int setup_boot_parameters(struct boot_params *params)
+static int setup_boot_parameters(struct kimage *image,
+				 struct boot_params *params)
 {
 	unsigned int nr_e820_entries;
 	unsigned long long mem_k, start, end;
-	int i;
+	int i, ret = 0;
 
 	/* Get subarch from existing bootparams */
 	params->hdr.hardware_subarch = boot_params.hdr.hardware_subarch;
@@ -125,7 +135,13 @@ static int setup_boot_parameters(struct boot_params *params)
 	/* Default sysdesc table */
 	params->sys_desc_table.length = 0;
 
-	setup_memory_map_entries(params);
+	if (image->type == KEXEC_TYPE_CRASH) {
+		ret = crash_setup_memmap_entries(image, params);
+		if (ret)
+			return ret;
+	} else
+		setup_memory_map_entries(params);
+
 	nr_e820_entries = params->e820_entries;
 
 	for (i = 0; i < nr_e820_entries; i++) {
@@ -153,7 +169,7 @@ static int setup_boot_parameters(struct boot_params *params)
 	memcpy(params->edd_mbr_sig_buffer, boot_params.edd_mbr_sig_buffer,
 	       EDD_MBR_SIG_MAX * sizeof(unsigned int));
 
-	return 0;
+	return ret;
 }
 
 int bzImage64_probe(const char *buf, unsigned long len)
@@ -241,6 +257,22 @@ void *bzImage64_load(struct kimage *image, char *kernel,
 	}
 
 	/*
+	 * In case of crash dump, we will append elfcorehdr=<addr> to
+	 * command line. Make sure it does not overflow
+	 */
+	if (cmdline_len + MAX_ELFCOREHDR_STR_LEN > header->cmdline_size) {
+		pr_debug("Appending elfcorehdr=<addr> to command line exceeds maximum allowed length\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	/* Allocate and load backup region */
+	if (image->type == KEXEC_TYPE_CRASH) {
+		ret = crash_load_segments(image);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+
+	/*
 	 * Load purgatory. For 64bit entry point, purgatory  code can be
 	 * anywhere.
 	 */
@@ -254,7 +286,8 @@ void *bzImage64_load(struct kimage *image, char *kernel,
 	pr_debug("Loaded purgatory at 0x%lx\n", purgatory_load_addr);
 
 	/* Load Bootparams and cmdline */
-	params_cmdline_sz = sizeof(struct boot_params) + cmdline_len;
+	params_cmdline_sz = sizeof(struct boot_params) + cmdline_len +
+				MAX_ELFCOREHDR_STR_LEN;
 	params = kzalloc(params_cmdline_sz, GFP_KERNEL);
 	if (!params)
 		return ERR_PTR(-ENOMEM);
@@ -303,8 +336,8 @@ void *bzImage64_load(struct kimage *image, char *kernel,
 		setup_initrd(params, initrd_load_addr, initrd_len);
 	}
 
-	setup_cmdline(params, bootparam_load_addr, sizeof(struct boot_params),
-		      cmdline, cmdline_len);
+	setup_cmdline(image, params, bootparam_load_addr,
+		      sizeof(struct boot_params), cmdline, cmdline_len);
 
 	/* bootloader info. Do we need a separate ID for kexec kernel loader? */
 	params->hdr.type_of_loader = 0x0D << 4;
@@ -332,7 +365,9 @@ void *bzImage64_load(struct kimage *image, char *kernel,
 	if (ret)
 		goto out_free_params;
 
-	setup_boot_parameters(params);
+	ret = setup_boot_parameters(image, params);
+	if (ret)
+		goto out_free_params;
 
 	/* Allocate loader specific data */
 	ldata = kzalloc(sizeof(struct bzimage64_data), GFP_KERNEL);