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SubjectRe: [PATCH v9 05/11] arm64: kexec_file: load initrd and device-tree
James,

On Tue, May 15, 2018 at 05:20:00PM +0100, James Morse wrote:
> Hi Akashi,
>
> On 25/04/18 07:26, AKASHI Takahiro wrote:
> > load_other_segments() is expected to allocate and place all the necessary
> > memory segments other than kernel, including initrd and device-tree
> > blob (and elf core header for crash).
> > While most of the code was borrowed from kexec-tools' counterpart,
> > users may not be allowed to specify dtb explicitly, instead, the dtb
> > presented by a boot loader is reused.
>
> (Nit: "a boot loader" -> "the original boot loader")

OK

> > arch_kimage_kernel_post_load_cleanup() is responsible for freeing arm64-
> > specific data allocated in load_other_segments().
>
>
> > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> > index f9ebf54ca247..b3b9b1725d8a 100644
> > --- a/arch/arm64/kernel/machine_kexec_file.c
> > +++ b/arch/arm64/kernel/machine_kexec_file.c
> > @@ -13,7 +13,26 @@
> > #include <linux/ioport.h>
> > #include <linux/kernel.h>
> > #include <linux/kexec.h>
> > +#include <linux/libfdt.h>
> > #include <linux/memblock.h>
> > +#include <linux/of_fdt.h>
> > +#include <linux/types.h>
> > +#include <asm/byteorder.h>
> > +
> > +static int __dt_root_addr_cells;
> > +static int __dt_root_size_cells;
>
> > @@ -55,3 +74,144 @@ int arch_kexec_walk_mem(struct kexec_buf *kbuf,
> >
> > return ret;
> > }
> > +
> > +static int setup_dtb(struct kimage *image,
> > + unsigned long initrd_load_addr, unsigned long initrd_len,
> > + char *cmdline, unsigned long cmdline_len,
> > + char **dtb_buf, size_t *dtb_buf_len)
> > +{
> > + char *buf = NULL;
> > + size_t buf_size;
> > + int nodeoffset;
> > + u64 value;
> > + int range_len;
> > + int ret;
> > +
> > + /* duplicate dt blob */
> > + buf_size = fdt_totalsize(initial_boot_params);
> > + range_len = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
>
> These two cells values are 0 here. Did you want
> arch_kexec_file_init() in patch 7 in this patch?
>
> Ah, range_len isn't used, so, did you want the cells values and this range_len
> thing in in patch 7!?

Umm, this problem has long existed since my v1 :)
I might better re-think about patch order.

>
> > +
> > + if (initrd_load_addr)
> > + buf_size += fdt_prop_len("linux,initrd-start", sizeof(u64))
> > + + fdt_prop_len("linux,initrd-end", sizeof(u64));
> > +
> > + if (cmdline)
> > + buf_size += fdt_prop_len("bootargs", cmdline_len + 1);
>
> I can't find where fdt_prop_len() .... oh, patch 7. fdt_prop_len() doesn't look
> like the sort of thing that should be created here, but I agree there isn't an
> existing API to do this.

Will take care of it.


> (This must be why powerpc guesses that the fdt won't be more than double in size).
>
>
> > + buf = vmalloc(buf_size);
> > + if (!buf) {
> > + ret = -ENOMEM;
> > + goto out_err;
> > + }
> > +
> > + ret = fdt_open_into(initial_boot_params, buf, buf_size);
> > + if (ret)
> > + goto out_err;
> > +
> > + nodeoffset = fdt_path_offset(buf, "/chosen");
> > + if (nodeoffset < 0)
> > + goto out_err;
> > +
> > + /* add bootargs */
> > + if (cmdline) {
> > + ret = fdt_setprop(buf, nodeoffset, "bootargs",
> > + cmdline, cmdline_len + 1);
>
> fdt_setprop_string()?

OK

>
> > + if (ret)
> > + goto out_err;
> > + }
> > +
> > + /* add initrd-* */
> > + if (initrd_load_addr) {
> > + value = cpu_to_fdt64(initrd_load_addr);
> > + ret = fdt_setprop(buf, nodeoffset, "linux,initrd-start",
> > + &value, sizeof(value));
>
> sizeof(value) was assumed to be the same as sizeof(u64) earlier.
> fdt_setprop_u64()?

OK

>
> > + if (ret)
> > + goto out_err;
> > +
> > + value = cpu_to_fdt64(initrd_load_addr + initrd_len);
> > + ret = fdt_setprop(buf, nodeoffset, "linux,initrd-end",
> > + &value, sizeof(value));
> > + if (ret)
> > + goto out_err;
> > + }
> > +
> > + /* trim a buffer */
> > + fdt_pack(buf);
> > + *dtb_buf = buf;
> > + *dtb_buf_len = fdt_totalsize(buf);
> > +
> > + return 0;
> > +
> > +out_err:
> > + vfree(buf);
> > + return ret;
> > +}
>
> While powerpc has some similar code for updating the initrd and cmdline, it
> makes different assumptions about the size of the dt, and has different behavior
> for memreserve. (looks like we don't expect the initramfs to be memreserved).
> Lets leave unifying that stuff where possible for the future.

Sure

> > +int load_other_segments(struct kimage *image,
> > + char *initrd, unsigned long initrd_len,
> > + char *cmdline, unsigned long cmdline_len)
> > +{
> > + struct kexec_segment *kern_seg;
> > + struct kexec_buf kbuf;
> > + unsigned long initrd_load_addr = 0;
> > + char *dtb = NULL;
> > + unsigned long dtb_len = 0;
> > + int ret = 0;
> > +
> > + kern_seg = &image->segment[image->arch.kern_segment];
> > + kbuf.image = image;
> > + /* not allocate anything below the kernel */
> > + kbuf.buf_min = kern_seg->mem + kern_seg->memsz;
>
> > + /* load initrd */
> > + if (initrd) {
> > + kbuf.buffer = initrd;
> > + kbuf.bufsz = initrd_len;
> > + kbuf.memsz = initrd_len;
>
> > + kbuf.buf_align = 0;
>
> I'm surprised there initrd has no alignment requirement,

MeToo.

> but kexec_add_buffer()
> rounds this up to PAGE_SIZE.

It seems that kimage_load_segment() requires this, but I'm not sure.

>
> > + /* within 1GB-aligned window of up to 32GB in size */
> > + kbuf.buf_max = round_down(kern_seg->mem, SZ_1G)
> > + + (unsigned long)SZ_1G * 32;
> > + kbuf.top_down = false;
> > +
> > + ret = kexec_add_buffer(&kbuf);
> > + if (ret)
> > + goto out_err;
> > + initrd_load_addr = kbuf.mem;
> > +
> > + pr_debug("Loaded initrd at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
> > + initrd_load_addr, initrd_len, initrd_len);
> > + }
> > +
> > + /* load dtb blob */
> > + ret = setup_dtb(image, initrd_load_addr, initrd_len,
> > + cmdline, cmdline_len, &dtb, &dtb_len);
> > + if (ret) {
> > + pr_err("Preparing for new dtb failed\n");
> > + goto out_err;
> > + }
> > +
> > + kbuf.buffer = dtb;
> > + kbuf.bufsz = dtb_len;
> > + kbuf.memsz = dtb_len;
> > + /* not across 2MB boundary */
> > + kbuf.buf_align = SZ_2M;
> > + kbuf.buf_max = ULONG_MAX;
> > + kbuf.top_down = true;
> > +
> > + ret = kexec_add_buffer(&kbuf);
> > + if (ret)
> > + goto out_err;
> > + image->arch.dtb_mem = kbuf.mem;
> > + image->arch.dtb_buf = dtb;
> > +
> > + pr_debug("Loaded dtb at 0x%lx bufsz=0x%lx memsz=0x%lx\n",
> > + kbuf.mem, dtb_len, dtb_len);
> > +
> > + return 0;
> > +
> > +out_err:
> > + vfree(dtb);
> > + image->arch.dtb_buf = NULL;
>
> Won't kimage_file_post_load_cleanup() always be called if we return an error
> here? Why not leave the free()ing until then?

Right.
The reason why I left the code here was that we'd better locally clean up
all the stuff that were locally allocated if we trivially need to (and can)
do so.

As it's redundant, I will remove it.

Thanks,
-Takahiro AKASHI

>
> > + return ret;
> > +}
>
>
>
> Thanks,
>
> James

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