Bhupesh,
On Mon, Apr 30, 2018 at 02:52:35AM +0530, Bhupesh Sharma 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 <[email protected]>
> ---
> kexec/dt-ops.c | 143
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> kexec/dt-ops.h | 1 +
> 2 files changed, 144 insertions(+)
>
> diff --git a/kexec/dt-ops.c b/kexec/dt-ops.c
> index 915dbf55afd2..cb95920e5c3e 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))))
Pointer doesn't always fit to unsigned long.
> +#define GET_CELL(p) (p += 4, *((const uint32_t *)(p-4)))
Tricky :) Inline function would be better.
> +
> static const char n_chosen[] = "/chosen";
>
> static const char p_bootargs[] = "bootargs";
> @@ -143,3 +147,142 @@ 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;
This (== '\0') can hit even if the data is numeric.
> +
> + ss = s;
> + while (*s)
> + s++;
You don't check for the length, so
> + /* Traverse till we hit a '\0' or reach 'len' */
> + if (*s != '\0')
> + return 0;
This will never hit.
> + if ((s + 1 - ss) < len) {
> + /* Handle special cases such as 'bootargs' properties
> + * in dtb which are actually strings, but they may have
> + * a format where (s + 1 - ss) < len remains true.
> + *
> + * We can catch such cases by checking if (s + 1 - ss)
> + * is greater than 1
What does this actually mean? Elaborate, please.
> + */
> + if ((s + 1 - ss) > 1)
> + return 1;
> +
> + 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;
I prefer more meaningful names.
> + 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;
't' is used only here, so
> +
> + p = PALIGN(p + sz, 4);
> +
> + dbgprintf("%*s%s", (int)(depth * shift), " ", s);
> + print_data(t, sz);
> + dbgprintf(";\n");
dbgprintf("%*s%s", (int)(depth * shift), " ", s);
print_data(p, sz);
dbgprintf(";\n");
p = PALIGN(p + sz, 4);
This will work.
Thanks,
-Takahiro AKASHI
> + }
> +}
> 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
>
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