126 lines
4.5 KiB
Diff
126 lines
4.5 KiB
Diff
From 4631320e96f8a63c897fbbce4e87e3c47af40bc9 Mon Sep 17 00:00:00 2001
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From: Roman Bolshakov <r.bolshakov@yadro.com>
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Date: Thu, 17 Jun 2021 02:27:32 +0300
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Subject: [PATCH 02/27] diskdump: Fail readmem() early if dump is incomplete
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kdump format description [1] says:
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[...] zero page has its own offset not equal 0. So when reading page
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from incomplete core, only the page lost by ENOSPACE errors has 0 in its
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corresponding page descriptor's member offset.
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crash has special treatment for page descriptors with zero offset only if
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DUMP_DH_COMPRESSED_INCOMPLETE is set in dump header. However,
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makedumpfile places the flag after ENOSPC is hit and only if dump header
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modification went without errors.
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In case if crashkernel environment was terminated early (e.g. by BMC) or
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some other reason, DUMP_DH_COMPRESSED_INCOMPLETE won't be set on the
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dump header. Then cache_page() would be performed on pages with
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pd.offset == 0 and due to pd.size == 0 it'll skip read into
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compressed_page and then non related pre-existing contents of
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compressed_page will copied into page cache for the non-present page.
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Ultimately, it'll lead to a cryptic failure, like:
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crash: invalid kernel virtual address: 72288cacacf427f8 [...]
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The failure would be a bit cleaner if crash explicitly fails on the page
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that is an outcome of incomplete dump:
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crash: page incomplete: kernel virtual address: c000003fff9d17e8 [...]
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Debugging level 8 would also produce exact offset from data_offset to
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print descriptor value with ease:
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read_diskdump/cache_page: descriptor with zero offset found at paddr/pfn/pos: 3fff9d0000/3fff9d/743dd
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That helps in inspecting broken descriptor with hexdump or similar tools:
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hexdump -s (data_offset + pos * 0x18) -n 0x18
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[1] https://github.com/makedumpfile/makedumpfile/blob/master/IMPLEMENTATION
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Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
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---
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defs.h | 1 +
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diskdump.c | 16 +++++++++++-----
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memory.c | 7 +++++++
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3 files changed, 19 insertions(+), 5 deletions(-)
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diff --git a/defs.h b/defs.h
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index c91177a245fd..eb1c71b5333a 100644
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--- a/defs.h
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+++ b/defs.h
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@@ -361,6 +361,7 @@ struct number_option {
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#define READ_ERROR (-2)
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#define WRITE_ERROR (-3)
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#define PAGE_EXCLUDED (-4)
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+#define PAGE_INCOMPLETE (-5)
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#define RESTART() (longjmp(pc->main_loop_env, 1))
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#define RESUME_FOREACH() (longjmp(pc->foreach_loop_env, 1))
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diff --git a/diskdump.c b/diskdump.c
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index 668069585080..59b79e1bce95 100644
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--- a/diskdump.c
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+++ b/diskdump.c
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@@ -1146,10 +1146,9 @@ cache_page(physaddr_t paddr)
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if (FLAT_FORMAT()) {
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if (!read_flattened_format(dd->dfd, pd.offset, dd->compressed_page, pd.size))
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return READ_ERROR;
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- } else if (is_incomplete_dump() && (0 == pd.offset)) {
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+ } else if (0 == pd.offset) {
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/*
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- * If the incomplete flag has been set in the header,
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- * first check whether zero_excluded has been set.
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+ * First check whether zero_excluded has been set.
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*/
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if (*diskdump_flags & ZERO_EXCLUDED) {
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if (CRASHDEBUG(8))
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@@ -1158,8 +1157,15 @@ cache_page(physaddr_t paddr)
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"paddr/pfn: %llx/%lx\n",
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(ulonglong)paddr, pfn);
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memset(dd->compressed_page, 0, dd->block_size);
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- } else
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- return READ_ERROR;
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+ } else {
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+ if (CRASHDEBUG(8))
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+ fprintf(fp,
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+ "read_diskdump/cache_page: "
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+ "descriptor with zero offset found at "
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+ "paddr/pfn/pos: %llx/%lx/%lx\n",
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+ (ulonglong)paddr, pfn, desc_pos);
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+ return PAGE_INCOMPLETE;
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+ }
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} else {
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if (lseek(dd->dfd, pd.offset, SEEK_SET) == failed)
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return SEEK_ERROR;
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diff --git a/memory.c b/memory.c
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index ca4c633e5074..86c02c132890 100644
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--- a/memory.c
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+++ b/memory.c
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@@ -2213,6 +2213,7 @@ accessible(ulong kva)
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#define READ_ERRMSG "read error: %s address: %llx type: \"%s\"\n"
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#define WRITE_ERRMSG "write error: %s address: %llx type: \"%s\"\n"
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#define PAGE_EXCLUDED_ERRMSG "page excluded: %s address: %llx type: \"%s\"\n"
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+#define PAGE_INCOMPLETE_ERRMSG "page incomplete: %s address: %llx type: \"%s\"\n"
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#define RETURN_ON_PARTIAL_READ() \
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if ((error_handle & RETURN_PARTIAL) && (size < orig_size)) { \
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@@ -2378,6 +2379,12 @@ readmem(ulonglong addr, int memtype, void *buffer, long size,
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error(INFO, PAGE_EXCLUDED_ERRMSG, memtype_string(memtype, 0), addr, type);
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goto readmem_error;
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+ case PAGE_INCOMPLETE:
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+ RETURN_ON_PARTIAL_READ();
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+ if (PRINT_ERROR_MESSAGE)
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+ error(INFO, PAGE_INCOMPLETE_ERRMSG, memtype_string(memtype, 0), addr, type);
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+ goto readmem_error;
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+
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default:
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break;
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}
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--
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2.30.2
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