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, 37 insertions, 9 deletions

diff --git a/kernel/kexec.c b/kernel/kexec.c
index 0926f2a..f18c780 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -548,6 +548,7 @@ kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
 {
 	int ret;
 	struct kimage *image;
+	bool kexec_on_panic = flags & KEXEC_FILE_ON_CRASH;
 
 	image = do_kimage_alloc_init();
 	if (!image)
@@ -555,6 +556,12 @@ kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
 
 	image->file_mode = 1;
 
+	if (kexec_on_panic) {
+		/* Enable special crash kernel control page alloc policy. */
+		image->control_page = crashk_res.start;
+		image->type = KEXEC_TYPE_CRASH;
+	}
+
 	ret = kimage_file_prepare_segments(image, kernel_fd, initrd_fd,
 					   cmdline_ptr, cmdline_len, flags);
 	if (ret)
@@ -572,10 +579,12 @@ kimage_file_alloc_init(struct kimage **rimage, int kernel_fd,
 		goto out_free_post_load_bufs;
 	}
 
-	image->swap_page = kimage_alloc_control_pages(image, 0);
-	if (!image->swap_page) {
-		pr_err(KERN_ERR "Could not allocate swap buffer\n");
-		goto out_free_control_pages;
+	if (!kexec_on_panic) {
+		image->swap_page = kimage_alloc_control_pages(image, 0);
+		if (!image->swap_page) {
+			pr_err(KERN_ERR "Could not allocate swap buffer\n");
+			goto out_free_control_pages;
+		}
 	}
 
 	*rimage = image;
@@ -1113,10 +1122,14 @@ static int kimage_load_crash_segment(struct kimage *image,
 	unsigned long maddr;
 	size_t ubytes, mbytes;
 	int result;
-	unsigned char __user *buf;
+	unsigned char __user *buf = NULL;
+	unsigned char *kbuf = NULL;
 
 	result = 0;
-	buf = segment->buf;
+	if (image->file_mode)
+		kbuf = segment->kbuf;
+	else
+		buf = segment->buf;
 	ubytes = segment->bufsz;
 	mbytes = segment->memsz;
 	maddr = segment->mem;
@@ -1139,7 +1152,12 @@ static int kimage_load_crash_segment(struct kimage *image,
 			/* Zero the trailing part of the page */
 			memset(ptr + uchunk, 0, mchunk - uchunk);
 		}
-		result = copy_from_user(ptr, buf, uchunk);
+
+		/* For file based kexec, source pages are in kernel memory */
+		if (image->file_mode)
+			memcpy(ptr, kbuf, uchunk);
+		else
+			result = copy_from_user(ptr, buf, uchunk);
 		kexec_flush_icache_page(page);
 		kunmap(page);
 		if (result) {
@@ -1148,7 +1166,10 @@ static int kimage_load_crash_segment(struct kimage *image,
 		}
 		ubytes -= uchunk;
 		maddr  += mchunk;
-		buf += mchunk;
+		if (image->file_mode)
+			kbuf += mchunk;
+		else
+			buf += mchunk;
 		mbytes -= mchunk;
 	}
 out:
@@ -2127,7 +2148,14 @@ int kexec_add_buffer(struct kimage *image, char *buffer, unsigned long bufsz,
 	kbuf->top_down = top_down;
 
 	/* Walk the RAM ranges and allocate a suitable range for the buffer */
-	ret = walk_system_ram_res(0, -1, kbuf, locate_mem_hole_callback);
+	if (image->type == KEXEC_TYPE_CRASH)
+		ret = walk_iomem_res("Crash kernel",
+				     IORESOURCE_MEM | IORESOURCE_BUSY,
+				     crashk_res.start, crashk_res.end, kbuf,
+				     locate_mem_hole_callback);
+	else
+		ret = walk_system_ram_res(0, -1, kbuf,
+					  locate_mem_hole_callback);
 	if (ret != 1) {
 		/* A suitable memory range could not be found for buffer */
 		return -EADDRNOTAVAIL;