linux-kernel - [PATCH 1/3] lib: Add a generic copy_oldmem

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Message-Id: <20200711035544.2832154-2-palmer@dabbelt.com>
Date:   Fri, 10 Jul 2020 20:55:42 -0700
From:   Palmer Dabbelt <palmer@...belt.com>
To:     mick@....forth.gr
Cc:     linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org,
        Arnd Bergmann <arnd@...db.de>, rppt@...ux.ibm.com,
        akpm@...ux-foundation.org, linus.walleij@...aro.org,
        mchehab+samsung@...nel.org, gregory.0xf0@...il.com,
        masahiroy@...nel.org, Nick Desaulniers <ndesaulniers@...gle.com>,
        bgolaszewski@...libre.com,
        Palmer Dabbelt <palmerdabbelt@...gle.com>, mingo@...nel.org,
        ben-linux@...ff.org, peterz@...radead.org, broonie@...nel.org,
        davem@...emloft.net, rdunlap@...radead.org, uwe@...ine-koenig.org,
        dan.j.williams@...el.com, mhiramat@...nel.org,
        matti.vaittinen@...rohmeurope.com, zaslonko@...ux.ibm.com,
        willy@...radead.org, krzk@...nel.org, paulmck@...nel.org,
        pmladek@...e.com, brendanhiggins@...gle.com, keescook@...omium.org,
        glider@...gle.com, elver@...gle.com, davidgow@...gle.com,
        mark.rutland@....com, ardb@...nel.org, takahiro.akashi@...aro.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: [PATCH 1/3] lib: Add a generic copy_oldmem_page()

From: Palmer Dabbelt <palmerdabbelt@...gle.com>

A version of this that is identical to the arm64 version was recently
copied into the RISC-V port while adding kexec() support.  Instead I'd
like to put a shared copy in lib/ and use it from the various ports.

Signed-off-by: Palmer Dabbelt <palmerdabbelt@...gle.com>
---
 lib/Kconfig            |  3 +++
 lib/Makefile           |  2 ++
 lib/copy_oldmem_page.c | 51 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 56 insertions(+)
 create mode 100644 lib/copy_oldmem_page.c

diff --git a/lib/Kconfig b/lib/Kconfig
index df3f3da95990..25544abc9547 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -676,3 +676,6 @@ config GENERIC_LIB_CMPDI2
 
 config GENERIC_LIB_UCMPDI2
 	bool
+
+config GENERIC_LIB_COPY_OLDMEM_PAGE
+	bool
diff --git a/lib/Makefile b/lib/Makefile
index b1c42c10073b..30d57d8b32b1 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -318,3 +318,5 @@ obj-$(CONFIG_OBJAGG) += objagg.o
 # KUnit tests
 obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
 obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
+
+obj-$(CONFIG_GENERIC_LIB_COPY_OLDMEM_PAGE) += copy_oldmem_page.o
diff --git a/lib/copy_oldmem_page.c b/lib/copy_oldmem_page.c
new file mode 100644
index 000000000000..f0090027218a
--- /dev/null
+++ b/lib/copy_oldmem_page.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Routines for doing kexec-based kdump
+ *
+ * Originally part of arch/arm64/kernel/crash_dump.c
+ * Copyright (C) 2017 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@...aro.org>
+ */
+
+#include <linux/io.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+
+/**
+ * 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) {
+		if (copy_to_user((char __user *)buf, vaddr + offset, csize)) {
+			memunmap(vaddr);
+			return -EFAULT;
+		}
+	} else {
+		memcpy(buf, vaddr + offset, csize);
+	}
+
+	memunmap(vaddr);
+
+	return csize;
+}
-- 
2.27.0.383.g050319c2ae-goog