kexec_update_segment allows a given segment in kexec_image to have
its contents updated. This is useful if the current kernel wants to
send information to the next kernel that is up-to-date at the time of
reboot.
Signed-off-by: Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com>
---
include/linux/kexec.h | 2 ++
kernel/kexec_core.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 100 insertions(+)
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index edadff6c86ff..ff3aa93649e2 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -256,6 +256,8 @@ extern int kexec_purgatory_get_set_symbol(struct kimage *image,
unsigned int size, bool get_value);
extern void *kexec_purgatory_get_symbol_addr(struct kimage *image,
const char *name);
+int kexec_update_segment(const char *buffer, size_t bufsz,
+ unsigned long load_addr, size_t memsz);
extern void __crash_kexec(struct pt_regs *);
extern void crash_kexec(struct pt_regs *);
int kexec_should_crash(struct task_struct *);
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 561675589511..d3f1ebf66222 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -721,6 +721,104 @@ static struct page *kimage_alloc_page(struct kimage *image,
return page;
}
+/**
+ * kexec_update_segment - update the contents of a kimage segment
+ * @buffer: New contents of the segment.
+ * @bufsz: @buffer size.
+ * @load_addr: Segment's physical address in the next kernel.
+ * @memsz: Segment size.
+ *
+ * This function assumes kexec_mutex is held.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int kexec_update_segment(const char *buffer, size_t bufsz,
+ unsigned long load_addr, size_t memsz)
+{
+ int i;
+ unsigned long entry;
+ unsigned long *ptr = NULL;
+ void *dest = NULL;
+
+ if (kexec_image == NULL) {
+ pr_err("Can't update segment: no kexec image loaded.\n");
+ return -EINVAL;
+ }
+
+ /*
+ * kexec_add_buffer rounds up segment sizes to PAGE_SIZE, so
+ * we have to do it here as well.
+ */
+ memsz = ALIGN(memsz, PAGE_SIZE);
+
+ for (i = 0; i < kexec_image->nr_segments; i++)
+ /* We only support updating whole segments. */
+ if (load_addr == kexec_image->segment[i].mem &&
+ memsz == kexec_image->segment[i].memsz) {
+ if (!kexec_image->segment[i].skip_checksum) {
+ pr_err("Trying to update non-modifiable segment.\n");
+ return -EINVAL;
+ }
+
+ break;
+ }
+ if (i == kexec_image->nr_segments) {
+ pr_err("Couldn't find segment to update: 0x%lx, size 0x%zx\n",
+ load_addr, memsz);
+ return -EINVAL;
+ }
+
+ for (entry = kexec_image->head; !(entry & IND_DONE) && memsz;
+ entry = *ptr++) {
+ void *addr = (void *) (entry & PAGE_MASK);
+
+ switch (entry & IND_FLAGS) {
+ case IND_DESTINATION:
+ dest = addr;
+ break;
+ case IND_INDIRECTION:
+ ptr = __va(entry & PAGE_MASK);
+ break;
+ case IND_SOURCE:
+ /* Shouldn't happen, but verify just to be safe. */
+ if (dest == NULL) {
+ pr_err("Invalid kexec entries list.");
+ return -EINVAL;
+ }
+
+ if (dest == (void *) load_addr) {
+ void *page_addr;
+ unsigned long offset;
+ size_t uchunk, mchunk;
+
+ page_addr = kmap_atomic(kmap_to_page(addr));
+
+ offset = load_addr & ~PAGE_MASK;
+ mchunk = min_t(size_t, memsz,
+ PAGE_SIZE - offset);
+ uchunk = min(bufsz, mchunk);
+ memcpy(page_addr + offset, buffer, uchunk);
+
+ kunmap_atomic(page_addr);
+
+ bufsz -= uchunk;
+ load_addr += mchunk;
+ buffer += mchunk;
+ memsz -= mchunk;
+ }
+ dest += PAGE_SIZE;
+ }
+
+ /* Shouldn't happen, but verify just to be safe. */
+ if (ptr == NULL) {
+ pr_err("Invalid kexec entries list.");
+ return -EINVAL;
+ }
+ }
+
+ return 0;
+}
+
static int kimage_load_normal_segment(struct kimage *image,
struct kexec_segment *segment)
{
--
1.9.1
