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Subject: [PATCH 01/11] kexec_file: allow archs to handle special regions
 while locating memory hole
From:   Hari Bathini <hbathini@linux.ibm.com>
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Pingfan Liu <piliu@redhat.com>,
        Kexec-ml <kexec@lists.infradead.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Petr Tesarik <ptesarik@suse.cz>,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        Sourabh Jain <sourabhjain@linux.ibm.com>,
        lkml <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@ozlabs.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Dave Young <dyoung@redhat.com>, Vivek Goyal <vgoyal@redhat.com>
Date:   Sat, 27 Jun 2020 00:34:43 +0530
Message-ID: <159319828304.16351.6990340111766605842.stgit@hbathini.in.ibm.com>
In-Reply-To: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com>
References: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com>
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Some archs can have special memory regions, within the given memory
range, which can't be used for the buffer in a kexec segment. As
kexec_add_buffer() function is being called from generic code as well,
add weak arch_kexec_add_buffer definition for archs to override & take
care of special regions before trying to locate a memory hole.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
---
 include/linux/kexec.h |    5 +++++
 kernel/kexec_file.c   |   37 +++++++++++++++++++++++++++++++++----
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 1776eb2..1237682 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -195,6 +195,11 @@ int __weak arch_kexec_apply_relocations(struct purgatory_info *pi,
 					const Elf_Shdr *relsec,
 					const Elf_Shdr *symtab);
 
+extern int arch_kexec_add_buffer(struct kexec_buf *kbuf);
+
+/* arch_kexec_add_buffer calls this when it is ready */
+extern int __kexec_add_buffer(struct kexec_buf *kbuf);
+
 extern int kexec_add_buffer(struct kexec_buf *kbuf);
 int kexec_locate_mem_hole(struct kexec_buf *kbuf);
 
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index bb05fd5..a0b4f7f 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -669,10 +669,6 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
  */
 int kexec_add_buffer(struct kexec_buf *kbuf)
 {
-
-	struct kexec_segment *ksegment;
-	int ret;
-
 	/* Currently adding segment this way is allowed only in file mode */
 	if (!kbuf->image->file_mode)
 		return -EINVAL;
@@ -696,6 +692,25 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
 	kbuf->memsz = ALIGN(kbuf->memsz, PAGE_SIZE);
 	kbuf->buf_align = max(kbuf->buf_align, PAGE_SIZE);
 
+	return arch_kexec_add_buffer(kbuf);
+}
+
+/**
+ * __kexec_add_buffer - arch_kexec_add_buffer would call this function after
+ *                      updating kbuf, to place a buffer in a kexec segment.
+ * @kbuf:               Buffer contents and memory parameters.
+ *
+ * This function assumes that kexec_mutex is held.
+ * On successful return, @kbuf->mem will have the physical address of
+ * the buffer in memory.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int __kexec_add_buffer(struct kexec_buf *kbuf)
+{
+	struct kexec_segment *ksegment;
+	int ret;
+
 	/* Walk the RAM ranges and allocate a suitable range for the buffer */
 	ret = kexec_locate_mem_hole(kbuf);
 	if (ret)
@@ -711,6 +726,20 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
 	return 0;
 }
 
+/**
+ * arch_kexec_add_buffer - Some archs have memory regions within the given
+ *                         range that can't be used to place a kexec segment.
+ *                         Such archs can override this function to take care
+ *                         of them before trying to locate the memory hole.
+ * @kbuf:                  Buffer contents and memory parameters.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int __weak arch_kexec_add_buffer(struct kexec_buf *kbuf)
+{
+	return __kexec_add_buffer(kbuf);
+}
+
 /* Calculate and store the digest of segments */
 static int kexec_calculate_store_digests(struct kimage *image)
 {