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Subject[PATCH 09/11] kexec: Provide a function to add a segment at fixed address
Date
kexec_add_buffer() can find a suitable range of memory for user buffer and
add it to list of segments. But ELF loader will require that a buffer can
be loaded at the address it has been compiled for (ET_EXEC type executables).
So we need a helper function which can see if requested memory is valid and
available and add a segment accordiingly. This patch provides that helper
function. It will be used by elf loader in later patch.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
include/linux/kexec.h | 3 +++
kernel/kexec.c | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 68 insertions(+)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index d391ed7..2fb052c 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -208,6 +208,9 @@ extern asmlinkage long sys_kexec_load(unsigned long entry,
struct kexec_segment __user *segments,
unsigned long flags);
extern int kernel_kexec(void);
+extern int kexec_add_segment(struct kimage *image, char *buffer,
+ unsigned long bufsz, unsigned long memsz,
+ unsigned long base);
extern int kexec_add_buffer(struct kimage *image, char *buffer,
unsigned long bufsz, unsigned long memsz,
unsigned long buf_align, unsigned long buf_min,
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 20169a4..9e4718b 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -2002,6 +2002,71 @@ static int __kexec_add_segment(struct kimage *image, char *buf,
return 0;
}

+static int validate_ram_range_callback(u64 start, u64 end, void *arg)
+{
+ struct kexec_segment *ksegment = arg;
+ u64 mstart = ksegment->mem;
+ u64 mend = ksegment->mem + ksegment->memsz - 1;
+
+ /* Found a valid range. Stop going through more ranges */
+ if (mstart >= start && mend <= end)
+ return 1;
+
+ /* Range did not match. Go to next one */
+ return 0;
+}
+
+/* Add a kexec segment at fixed address provided by caller */
+int kexec_add_segment(struct kimage *image, char *buffer, unsigned long bufsz,
+ unsigned long memsz, unsigned long base)
+{
+ struct kexec_segment ksegment;
+ int ret;
+
+ /* Currently adding segment this way is allowed only in file mode */
+ if (!image->file_mode)
+ return -EINVAL;
+
+ if (image->nr_segments >= KEXEC_SEGMENT_MAX)
+ return -EINVAL;
+
+ /*
+ * Make sure we are not trying to add segment after allocating
+ * control pages. All segments need to be placed first before
+ * any control pages are allocated. As control page allocation
+ * logic goes through list of segments to make sure there are
+ * no destination overlaps.
+ */
+ WARN_ONCE(!list_empty(&image->control_pages), "Adding kexec segment"
+ " after allocating control pages\n");
+
+ if (bufsz > memsz)
+ return -EINVAL;
+ if (memsz == 0)
+ return -EINVAL;
+
+ /* Align memsz to next page boundary */
+ memsz = ALIGN(memsz, PAGE_SIZE);
+
+ /* Make sure base is atleast page size aligned */
+ if (base & (PAGE_SIZE - 1))
+ return -EINVAL;
+
+ memset(&ksegment, 0, sizeof(struct kexec_segment));
+ ksegment.mem = base;
+ ksegment.memsz = memsz;
+
+ /* Validate memory range */
+ ret = walk_system_ram_res(base, base + memsz - 1, &ksegment,
+ validate_ram_range_callback);
+
+ /* If a valid range is found, 1 is returned */
+ if (ret != 1)
+ return -EINVAL;
+
+ return __kexec_add_segment(image, buffer, bufsz, base, memsz);
+}
+
static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
struct kexec_buf *kbuf)
{
--
1.8.4.2


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