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@xxxxxxxxxx>
---
kexec/dt-ops.c | 141 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
kexec/dt-ops.h | 1 +
2 files changed, 142 insertions(+)
diff --git a/kexec/dt-ops.c b/kexec/dt-ops.c
index 915dbf55afd2..80ebfd31b4b6 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 +147,140 @@ 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')
+ return 0;
+
+ 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
+ */
+ 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 = 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_data)),
+ i < (len - 4) ? " " : "");
+ }
+ dbgprintf(">");
+ } else {
+ dbgprintf(" = [");
+ for (i = 0; i < len; i++)
+ dbgprintf("%02x%s", *p_data++,
+ i < len - 1 ? " " : "");
+ dbgprintf("]");
+ }
+}
+
+void dump_fdt(void* fdt)
+{
+ struct fdt_header *bph;
+ const char* p_struct;
+ const char* p_strings;
+ const char* p_data;
+ const char* s_data;
+ 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_data = p_struct;
+ while ((tag = fdt32_to_cpu(GET_CELL(p_data))) != FDT_END) {
+ if (tag == FDT_BEGIN_NODE) {
+ s_data = p_data;
+ p_data = PALIGN(p_data + strlen(s_data) + 1, 4);
+
+ if (*s_data == '\0')
+ s_data = "/";
+
+ dbgprintf("%*s%s {\n", (int)(depth * shift), " ", s_data);
+
+ 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_data));
+ s_data = p_strings + fdt32_to_cpu(GET_CELL(p_data));
+ if (version < 16 && sz >= 8)
+ p_data = PALIGN(p_data, 8);
+
+ dbgprintf("%*s%s", (int)(depth * shift), " ", s_data);
+ print_data(p_data, sz);
+ dbgprintf(";\n");
+
+ p_data = PALIGN(p_data + sz, 4);
+ }
+}
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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