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SubjectRe: [PATCH v9 07/11] arm64: kexec_file: add crash dump support
On Tue, May 15, 2018 at 06:12:59PM +0100, James Morse wrote:
> Hi guys,
>
> (CC: +RobH, devicetree list)

Thanks.

> On 25/04/18 07:26, AKASHI Takahiro wrote:
> > Enabling crash dump (kdump) includes
> > * prepare contents of ELF header of a core dump file, /proc/vmcore,
> > using crash_prepare_elf64_headers(), and
> > * add two device tree properties, "linux,usable-memory-range" and
> > "linux,elfcorehdr", which represent repsectively a memory range
> > to be used by crash dump kernel and the header's location

BTW, I intend to move existing parsing these out of the arch code.
Please don't add more DT handling to arch/ unless it is *really* arch
specific. I'd assume that the next arch to add kexec support will use
these bindings instead of the powerpc way.

> kexec_file_load() on arm64 needs to be able to create a prop encoded array to
> the FDT, but there doesn't appear to be a libfdt helper to do this.
>
> Akashi's code below adds fdt_setprop_range() to the arch code, and duplicates
> bits of libfdt_internal.h to do the work.
>
> How should this be done? I'm assuming this is something we need a new API in
> libfdt.h for. How do these come about, and is there an interim step we can use
> until then?

Submit patches to upstream dtc and then we can pull it in. Ahead of that
you can add it to drivers/of/fdt.c (or maybe fdt_address.c because
that's really what this is dealing with).

libfdt has only recently gained the beginnings of address handling.

>
> Thanks!
>
> James
>
> > diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> > index 37c0a9dc2e47..ec674f4d267c 100644
> > --- a/arch/arm64/kernel/machine_kexec_file.c
> > +++ b/arch/arm64/kernel/machine_kexec_file.c
> > @@ -76,6 +81,78 @@ int arch_kexec_walk_mem(struct kexec_buf *kbuf,
> > return ret;
> > }
> >
> > +static int __init arch_kexec_file_init(void)
> > +{
> > + /* Those values are used later on loading the kernel */
> > + __dt_root_addr_cells = dt_root_addr_cells;
> > + __dt_root_size_cells = dt_root_size_cells;

I intend to make dt_root_*_cells private, so don't add another user
outside of drivers/of/.

> > +
> > + return 0;
> > +}
> > +late_initcall(arch_kexec_file_init);
> > +
> > +#define FDT_ALIGN(x, a) (((x) + (a) - 1) & ~((a) - 1))
> > +#define FDT_TAGALIGN(x) (FDT_ALIGN((x), FDT_TAGSIZE))
> > +
> > +static int fdt_prop_len(const char *prop_name, int len)
> > +{
> > + return (strlen(prop_name) + 1) +
> > + sizeof(struct fdt_property) +
> > + FDT_TAGALIGN(len);
> > +}
> > +
> > +static bool cells_size_fitted(unsigned long base, unsigned long size)

I can't imagine this would happen. However, when this is moved to
drivers/of/ or dtc, these need to be u64 types to work on 32-bit.

> > +{
> > + /* if *_cells >= 2, cells can hold 64-bit values anyway */
> > + if ((__dt_root_addr_cells == 1) && (base >= (1ULL << 32)))
> > + return false;
> > +
> > + if ((__dt_root_size_cells == 1) && (size >= (1ULL << 32)))
> > + return false;
> > +
> > + return true;
> > +}
> > +
> > +static void fill_property(void *buf, u64 val64, int cells)
> > +{
> > + u32 val32;

This should be a __be32 or fdt32 type. So should buf.

> > +
> > + if (cells == 1) {
> > + val32 = cpu_to_fdt32((u32)val64);
> > + memcpy(buf, &val32, sizeof(val32));
> > + } else {
> > + memset(buf, 0, cells * sizeof(u32) - sizeof(u64));
> > + buf += cells * sizeof(u32) - sizeof(u64);
> > +
> > + val64 = cpu_to_fdt64(val64);
> > + memcpy(buf, &val64, sizeof(val64));

Look how of_read_number() is implemented. You should be able to do
something similar here looping and avoiding the if/else.

> > + }
> > +}
> > +
> > +static int fdt_setprop_range(void *fdt, int nodeoffset, const char *name,
> > + unsigned long addr, unsigned long size)

A very generic sounding function, but really only works on addresses in
children of the root node.

> > +{
> > + void *buf, *prop;
> > + size_t buf_size;
> > + int result;
> > +
> > + buf_size = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
> > + prop = buf = vmalloc(buf_size);

This can go on the stack instead (and would be required to to work in
libfdt).

> > + if (!buf)
> > + return -ENOMEM;
> > +
> > + fill_property(prop, addr, __dt_root_addr_cells);
> > + prop += __dt_root_addr_cells * sizeof(u32);
> > +
> > + fill_property(prop, size, __dt_root_size_cells);
> > +
> > + result = fdt_setprop(fdt, nodeoffset, name, buf, buf_size);
> > +
> > + vfree(buf);
> > +
> > + return result;
> > +}
> > +
> > static int setup_dtb(struct kimage *image,
> > unsigned long initrd_load_addr, unsigned long initrd_len,
> > char *cmdline, unsigned long cmdline_len,
> > @@ -88,10 +165,26 @@ static int setup_dtb(struct kimage *image,
> > int range_len;
> > int ret;
> >
> > + /* check ranges against root's #address-cells and #size-cells */
> > + if (image->type == KEXEC_TYPE_CRASH &&
> > + (!cells_size_fitted(image->arch.elf_load_addr,
> > + image->arch.elf_headers_sz) ||
> > + !cells_size_fitted(crashk_res.start,
> > + crashk_res.end - crashk_res.start + 1))) {
> > + pr_err("Crash memory region doesn't fit into DT's root cell sizes.\n");
> > + ret = -EINVAL;
> > + goto out_err;
> > + }
> > +
> > /* duplicate dt blob */
> > buf_size = fdt_totalsize(initial_boot_params);
> > range_len = (__dt_root_addr_cells + __dt_root_size_cells) * sizeof(u32);
> >
> > + if (image->type == KEXEC_TYPE_CRASH)
> > + buf_size += fdt_prop_len("linux,elfcorehdr", range_len)
> > + + fdt_prop_len("linux,usable-memory-range",
> > + range_len);
> > +
> > if (initrd_load_addr)
> > buf_size += fdt_prop_len("linux,initrd-start", sizeof(u64))
> > + fdt_prop_len("linux,initrd-end", sizeof(u64));
> > @@ -113,6 +206,23 @@ static int setup_dtb(struct kimage *image,
> > if (nodeoffset < 0)
> > goto out_err;
> >
> > + if (image->type == KEXEC_TYPE_CRASH) {
> > + /* add linux,elfcorehdr */
> > + ret = fdt_setprop_range(buf, nodeoffset, "linux,elfcorehdr",
> > + image->arch.elf_load_addr,
> > + image->arch.elf_headers_sz);
> > + if (ret)
> > + goto out_err;
> > +
> > + /* add linux,usable-memory-range */
> > + ret = fdt_setprop_range(buf, nodeoffset,
> > + "linux,usable-memory-range",
> > + crashk_res.start,
> > + crashk_res.end - crashk_res.start + 1);
> > + if (ret)
> > + goto out_err;
> > + }
> > +
> > /* add bootargs */
> > if (cmdline) {
> > ret = fdt_setprop(buf, nodeoffset, "bootargs",
>

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