Hi Akashi, On Tue, Mar 20, 2018 at 12:36 AM, Bhupesh Sharma <bhsharma@xxxxxxxxxx> wrote: > On Mon, Mar 19, 2018 at 8:15 PM, AKASHI Takahiro > <takahiro.akashi@xxxxxxxxxx> wrote: >> On Mon, Mar 19, 2018 at 04:05:38PM +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. >> >> Why not just save binary data to a file and interpret it >> with dtc command? > > Well, there are a couple of reasons for that which can be understood > from a system which is in a production environment (for e.g. I have > worked on one arm64 system in the past which used a yocto based > distribution in which kexec -p was launched with a -d option as a part > of initial ramfs scriptware): > > - In a production environment, installing and executing tools like dtc > (which might not have been installed by default via 'yum' or 'apt-get > install' or other means is not only an additional step, but we might > not get a chance to run it even if it is installed if we have a early > crash in kdump itself (for e.g. consider the 'acpi table access' issue > in the arm64 crashkernel we discussed some time back > <https://www.spinics.net/lists/arm-kernel/msg616632.html>): > > a) In such a case the primary kernel has already crashed, so we had no > opportunity to run a dtc interpreter there and the kdump kernel itself > has crashed in a very early boot phase. So we didn't get a chance to > execute 'dtc' on the kdump kernel command prompt (if the kdump scripts > are configured not to reboot the primary again). > > b) Also when an early arm64 kdump crash is reported by a customer, we > usually only have access to the primary and secondary console log > which also might include the 'kexec -p -d' log messages, which can > point us to a discrepancy in dtc nodes like 'linux,usable-memory" > which might have caused a early crashkernel crash. > > Personally, so-far I have found this dtb dumping facility of use in > debugging atleast a couple of arm64 crashkernel crash/panic issues. > Till the arm64 kexec/kdump implementation matures further, I feel this > dumping facility is of good use to ease crashkernel panic debugs. Ping. Do you have any further comments on it? Regards, Bhupesh >>> 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 | 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 >>> _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
