[PATCH 1/2] dt-ops: Add helper API to dump fdt blob

[Bhupesh Sharma]

On Mon, Mar 19, 2018 at 3:55 PM, Bhupesh Sharma <bhsharma at redhat.com> wrote:
> At several occasions it would be useful to dump the fdt
> blob being passed to the second (kexec/kdump) kernel
> when '-d' flag is specified while invoking kexec/kdump.
>
> This allows one to look at the device-tree fields that
> is being passed to the secondary kernel and accordingly
> debug issues.
>
> This can be specially useful for the arm64 case, where
> kexec_load() or kdump passes important information like
> 'linux,usable-memory' ranges to the second kernel, and
> the correctness of the ranges can be verified by
> looking at the device-tree dump with '-d' flag specified.
>
> Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
> ---
>  kexec/dt-ops.c | 133 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  kexec/dt-ops.h |   1 +
>  2 files changed, 134 insertions(+)
>
> diff --git a/kexec/dt-ops.c b/kexec/dt-ops.c
> index 915dbf55afd2..caf6f8df6e6b 100644
> --- a/kexec/dt-ops.c
> +++ b/kexec/dt-ops.c
> @@ -8,6 +8,10 @@
>  #include "kexec.h"
>  #include "dt-ops.h"
>
> +#define ALIGN(x, a)    (((x) + ((a) - 1)) & ~((a) - 1))
> +#define PALIGN(p, a)   ((void *)(ALIGN((unsigned long)(p), (a))))
> +#define GET_CELL(p)    (p += 4, *((const uint32_t *)(p-4)))
> +
>  static const char n_chosen[] = "/chosen";
>
>  static const char p_bootargs[] = "bootargs";
> @@ -143,3 +147,132 @@ int dtb_delete_property(char *dtb, const char *node, const char *prop)
>
>         return result;
>  }
> +
> +static uint64_t is_printable_string(const void* data, uint64_t len)
> +{
> +       const char *s = data;
> +       const char *ss;
> +
> +       /* Check for zero length strings */
> +       if (len == 0) {
> +               return 0;
> +       }
> +
> +       /* String must be terminated with a '\0' */
> +       if (s[len - 1] != '\0') {
> +               return 0;
> +       }
> +
> +       ss = s;
> +       while (*s) {
> +               s++;
> +       }
> +
> +       /* Traverse till we hit a '\0' or reach 'len' */
> +       if (*s != '\0' || (s + 1 - ss) < len) {
> +               return 0;
> +       }
> +
> +       return 1;
> +}
> +
> +static void print_data(const char* data, uint64_t len)
> +{
> +       uint64_t i;
> +       const char *p = data;
> +
> +       /* Check for non-zero length */
> +       if (len == 0)
> +               return;
> +
> +       if (is_printable_string(data, len)) {
> +               dbgprintf(" = \"%s\"", (const char *)data);
> +       } else if ((len % 4) == 0) {
> +               dbgprintf(" = <");
> +               for (i = 0; i < len; i += 4) {
> +                       dbgprintf("0x%08x%s",
> +                                       fdt32_to_cpu(GET_CELL(p)),
> +                                       i < (len - 4) ? " " : "");
> +               }
> +               dbgprintf(">");
> +       } else {
> +               dbgprintf(" = [");
> +               for (i = 0; i < len; i++)
> +                       dbgprintf("%02x%s", *p++,
> +                                       i < len - 1 ? " " : "");
> +               dbgprintf("]");
> +       }
> +}
> +
> +void dump_fdt(void* fdt)
> +{
> +       struct fdt_header *bph;
> +       const char* p_struct;
> +       const char* p_strings;
> +       const char* p;
> +       const char* s;
> +       const char* t;
> +       uint32_t off_dt;
> +       uint32_t off_str;
> +       uint32_t tag;
> +       uint64_t sz;
> +       uint64_t depth;
> +       uint64_t shift;
> +       uint32_t version;
> +
> +       depth = 0;
> +       shift = 4;
> +
> +       bph = fdt;
> +       off_dt = fdt32_to_cpu(bph->off_dt_struct);
> +       off_str = fdt32_to_cpu(bph->off_dt_strings);
> +       p_struct = (const char*)fdt + off_dt;
> +       p_strings = (const char*)fdt + off_str;
> +       version = fdt32_to_cpu(bph->version);
> +
> +       p = p_struct;
> +       while ((tag = fdt32_to_cpu(GET_CELL(p))) != FDT_END) {
> +
> +               if (tag == FDT_BEGIN_NODE) {
> +                       s = p;
> +                       p = PALIGN(p + strlen(s) + 1, 4);
> +
> +                       if (*s == '\0')
> +                               s = "/";
> +
> +                       dbgprintf("%*s%s {\n", (int)(depth * shift), " ", s);
> +
> +                       depth++;
> +                       continue;
> +               }
> +
> +               if (tag == FDT_END_NODE) {
> +                       depth--;
> +
> +                       dbgprintf("%*s};\n", (int)(depth * shift), " ");
> +                       continue;
> +               }
> +
> +               if (tag == FDT_NOP) {
> +                       dbgprintf("%*s// [NOP]\n", (int)(depth * shift), " ");
> +                       continue;
> +               }
> +
> +               if (tag != FDT_PROP) {
> +                       dbgprintf("%*s ** Unknown tag 0x%08x\n",
> +                                       (int)(depth * shift), " ", tag);
> +                       break;
> +               }
> +               sz = fdt32_to_cpu(GET_CELL(p));
> +               s = p_strings + fdt32_to_cpu(GET_CELL(p));
> +               if (version < 16 && sz >= 8)
> +                       p = PALIGN(p, 8);
> +               t = p;
> +
> +               p = PALIGN(p + sz, 4);
> +
> +               dbgprintf("%*s%s", (int)(depth * shift), " ", s);
> +               print_data(t, sz);
> +               dbgprintf(";\n");
> +       }
> +}
> diff --git a/kexec/dt-ops.h b/kexec/dt-ops.h
> index e70d15d8ffbf..25b9b569f2b7 100644
> --- a/kexec/dt-ops.h
> +++ b/kexec/dt-ops.h
> @@ -9,5 +9,6 @@ int dtb_set_property(char **dtb, off_t *dtb_size, const char *node,
>         const char *prop, const void *value, int value_len);
>
>  int dtb_delete_property(char *dtb, const char *node, const char *prop);
> +void dump_fdt(void *fdt) ;
>
>  #endif
> --
> 2.7.4
>

Kindly ignore this version. It seems it had some issue before I sent
it out. I will send a revised version shortly.

regards,
Bhupesh