[PATCH v26 3/7] arm64: kdump: add kdump support

On Fri, Sep 16, 2016 at 03:50:24PM +0100, James Morse wrote:

On 07/09/16 05:29, AKASHI Takahiro wrote:

quoted

On crash dump kernel, all the information about primary kernel's system
memory (core image) is available in elf core header.
The primary kernel will set aside this header with reserve_elfcorehdr()
at boot time and inform crash dump kernel of its location via a new
device-tree property, "linux,elfcorehdr".

Please note that all other architectures use traditional "elfcorehdr="
kernel parameter for this purpose.

Then crash dump kernel will access the primary kernel's memory with
copy_oldmem_page(), which reads one page by ioremap'ing it since it does
not reside in linear mapping on crash dump kernel.

We also need our own elfcorehdr_read() here since the header is placed
within crash dump kernel's usable memory.

One nit below, looks good.

Fixed.

Thanks,
-Takahiro AKASHI

Reviewed-by: James Morse <james.morse@arm.com>


Thanks,

James

quoted

diff --git a/arch/arm64/kernel/crash_dump.c b/arch/arm64/kernel/crash_dump.c

quoted

+/**
+ * copy_oldmem_page() - copy one page from old kernel memory
+ * @pfn: page frame number to be copied
+ * @buf: buffer where the copied page is placed
+ * @csize: number of bytes to copy
+ * @offset: offset in bytes into the page
+ * @userbuf: if set, @buf is in a user address space
+ *
+ * This function copies one page from old kernel memory into buffer pointed by
+ * @buf. If @buf is in userspace, set @userbuf to %1. Returns number of bytes
+ * copied or negative error in case of failure.
+ */
+ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
+			 size_t csize, unsigned long offset,
+			 int userbuf)
+{
+	void *vaddr;
+
+	if (!csize)
+		return 0;
+
+	vaddr = memremap(__pfn_to_phys(pfn), PAGE_SIZE, MEMREMAP_WB);
+	if (!vaddr)
+		return -ENOMEM;
+
+	if (userbuf) {

quoted

+		if (copy_to_user(buf, vaddr + offset, csize)) {

If you re-cast buf with (char __user *), it should stop sparse complaining:

quoted

../arch/arm64/kernel/crash_dump.c:45:34: warning: incorrect type in argument 1

(different address spaces)

quoted

../arch/arm64/kernel/crash_dump.c:45:34:    expected void [noderef] <asn:1>*to
../arch/arm64/kernel/crash_dump.c:45:34:    got char *buf