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

[James Morse]

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")

> 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!?


> +
> +	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.

(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()?


> +		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()?


> +		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.


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


> +		/* 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?


> +	return ret;
> +}



Thanks,

James