[PATCH 5.9 120/255] arm64: kexec_file: try more regions if loading segments fails

Greg Kroah-Hartman
2020-11-17T13:36:12Z

From: Benjamin Gwin <bgwin@google.com>

[ Upstream commit 108aa503657ee2fe8aa071dc620d96372c252ecd ]

It's possible that the first region picked for the new kernel will make
it impossible to fit the other segments in the required 32GB window,
especially if we have a very large initrd.

Instead of giving up, we can keep testing other regions for the kernel
until we find one that works.

Suggested-by: Ryan O'Leary <ryanoleary@google.com>
Signed-off-by: Benjamin Gwin <bgwin@google.com>
Link: https://lore.kernel.org/r/20201103201106.2397844-1-bgwin@google.com
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/arm64/kernel/kexec_image.c | 41 +++++++++++++++++++-------
arch/arm64/kernel/machine_kexec_file.c | 9 +++++-
2 files changed, 39 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
index af9987c154cab..66adee8b5fc81 100644
--- a/arch/arm64/kernel/kexec_image.c
+++ b/arch/arm64/kernel/kexec_image.c
@@ -43,7 +43,7 @@ static void *image_load(struct kimage *image,
u64 flags, value;
bool be_image, be_kernel;
struct kexec_buf kbuf;
- unsigned long text_offset;
+ unsigned long text_offset, kernel_segment_number;
struct kexec_segment *kernel_segment;
int ret;

@@ -88,11 +88,37 @@ static void *image_load(struct kimage *image,
/* Adjust kernel segment with TEXT_OFFSET */
kbuf.memsz += text_offset;

- ret = kexec_add_buffer(&kbuf);
- if (ret)
+ kernel_segment_number = image->nr_segments;
+
+ /*
+ * The location of the kernel segment may make it impossible to satisfy
+ * the other segment requirements, so we try repeatedly to find a
+ * location that will work.
+ */
+ while ((ret = kexec_add_buffer(&kbuf)) == 0) {
+ /* Try to load additional data */
+ kernel_segment = &image->segment[kernel_segment_number];
+ ret = load_other_segments(image, kernel_segment->mem,
+ kernel_segment->memsz, initrd,
+ initrd_len, cmdline);
+ if (!ret)
+ break;
+
+ /*
+ * We couldn't find space for the other segments; erase the
+ * kernel segment and try the next available hole.
+ */
+ image->nr_segments -= 1;
+ kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz;
+ kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
+ }
+
+ if (ret) {
+ pr_err("Could not find any suitable kernel location!");
return ERR_PTR(ret);
+ }

- kernel_segment = &image->segment[image->nr_segments - 1];
+ kernel_segment = &image->segment[kernel_segment_number];
kernel_segment->mem += text_offset;
kernel_segment->memsz -= text_offset;
image->start = kernel_segment->mem;
@@ -101,12 +127,7 @@ static void *image_load(struct kimage *image,
kernel_segment->mem, kbuf.bufsz,
kernel_segment->memsz);

- /* Load additional data */
- ret = load_other_segments(image,
- kernel_segment->mem, kernel_segment->memsz,
- initrd, initrd_len, cmdline);
-
- return ERR_PTR(ret);
+ return 0;
}

#ifdef CONFIG_KEXEC_IMAGE_VERIFY_SIG
diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
index 361a1143e09ee..e443df8569881 100644
--- a/arch/arm64/kernel/machine_kexec_file.c
+++ b/arch/arm64/kernel/machine_kexec_file.c
@@ -242,6 +242,11 @@ static int prepare_elf_headers(void **addr, unsigned long *sz)
return ret;
}

+/*
+ * Tries to add the initrd and DTB to the image. If it is not possible to find
+ * valid locations, this function will undo changes to the image and return non
+ * zero.
+ */
int load_other_segments(struct kimage *image,
unsigned long kernel_load_addr,
unsigned long kernel_size,
@@ -250,7 +255,8 @@ int load_other_segments(struct kimage *image,
{
struct kexec_buf kbuf;
void *headers, *dtb = NULL;
- unsigned long headers_sz, initrd_load_addr = 0, dtb_len;
+ unsigned long headers_sz, initrd_load_addr = 0, dtb_len,
+ orig_segments = image->nr_segments;
int ret = 0;

kbuf.image = image;
@@ -336,6 +342,7 @@ int load_other_segments(struct kimage *image,
return 0;

out_err:
+ image->nr_segments = orig_segments;
vfree(dtb);
return ret;
}
--
2.27.0