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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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