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From 9a2ab369a3685f85dfa7449c31a2267333cb1468 Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
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Date: Wed, 13 Dec 2017 13:39:02 +0100
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Subject: [PATCH 31/41] dump: update phys_base header field based on VMCOREINFO
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 content
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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RH-Author: Marc-André Lureau <marcandre.lureau@redhat.com>
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Message-id: <20171213133912.26176-32-marcandre.lureau@redhat.com>
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Patchwork-id: 78380
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O-Subject: [RHEL-7.5 qemu-kvm PATCH v3 31/41] dump: update phys_base header field based on VMCOREINFO content
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Bugzilla: 1411490
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RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
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RH-Acked-by: Michael S. Tsirkin <mst@redhat.com>
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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If the guest note is VMCOREINFO, try to get phys_base from it.
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry picked from commit d9feb51772b4ade9700c7fa54529327a6c8183a7)
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RHEL: replace qemu_strotu64() usage, warn_report()->error_report()
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Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 docs/specs/vmcoreinfo.txt |  8 +++++++
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 dump.c                    | 57 +++++++++++++++++++++++++++++++++++++++++++++--
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 2 files changed, 63 insertions(+), 2 deletions(-)
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diff --git a/docs/specs/vmcoreinfo.txt b/docs/specs/vmcoreinfo.txt
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index 2868a77..8212610 100644
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--- a/docs/specs/vmcoreinfo.txt
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+++ b/docs/specs/vmcoreinfo.txt
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@@ -39,3 +39,11 @@ qemu dumps.
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 The note format/class must be of the target bitness and the size must
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 be less than 1Mb.
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+
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+If the ELF note name is "VMCOREINFO", it is expected to be the Linux
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+vmcoreinfo note (see Documentation/ABI/testing/sysfs-kernel-vmcoreinfo
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+in Linux source). In this case, qemu dump code will read the content
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+as a key=value text file, looking for "NUMBER(phys_base)" key
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+value. The value is expected to be more accurate than architecture
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+guess of the value. This is useful for KASLR-enabled guest with
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+ancient tools not handling the VMCOREINFO note.
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diff --git a/dump.c b/dump.c
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index 823d1ad..3bce730 100644
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--- a/dump.c
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+++ b/dump.c
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@@ -777,6 +777,23 @@ static void get_note_sizes(DumpState *s, const void *note,
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     }
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 }
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+static bool note_name_equal(DumpState *s,
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+                            const uint8_t *note, const char *name)
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+{
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+    int len = strlen(name) + 1;
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+    uint64_t head_size, name_size;
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+
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+    get_note_sizes(s, note, &head_size, &name_size, NULL);
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+    head_size = ROUND_UP(head_size, 4);
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+
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+    if (name_size != len ||
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+        memcmp(note + head_size, "VMCOREINFO", len)) {
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+        return false;
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+    }
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+
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+    return true;
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+}
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+
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 /* write common header, sub header and elf note to vmcore */
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 static void create_header32(DumpState *s, Error **errp)
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 {
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@@ -1553,6 +1570,40 @@ static int64_t dump_calculate_size(DumpState *s)
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     return total;
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 }
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+static void vmcoreinfo_update_phys_base(DumpState *s)
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+{
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+    uint64_t size, note_head_size, name_size, phys_base;
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+    char **lines;
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+    uint8_t *vmci;
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+    size_t i;
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+
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+    if (!note_name_equal(s, s->guest_note, "VMCOREINFO")) {
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+        return;
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+    }
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+
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+    get_note_sizes(s, s->guest_note, &note_head_size, &name_size, &size);
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+    note_head_size = ROUND_UP(note_head_size, 4);
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+
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+    vmci = s->guest_note + note_head_size + ROUND_UP(name_size, 4);
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+    *(vmci + size) = '\0';
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+
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+    lines = g_strsplit((char *)vmci, "\n", -1);
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+    for (i = 0; lines[i]; i++) {
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+        if (g_str_has_prefix(lines[i], "NUMBER(phys_base)=")) {
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+            errno = 0;
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+            phys_base = strtoull(lines[i] + 18, NULL, 16);
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+            if (errno == ERANGE) {
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+                error_report("Failed to read NUMBER(phys_base)=");
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+            } else {
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+                s->dump_info.phys_base = phys_base;
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+            }
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+            break;
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+        }
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+    }
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+
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+    g_strfreev(lines);
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+}
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+
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 static void dump_init(DumpState *s, int fd, bool has_format,
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                       DumpGuestMemoryFormat format, bool paging, bool has_filter,
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                       int64_t begin, int64_t length, Error **errp)
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@@ -1636,8 +1687,9 @@ static void dump_init(DumpState *s, int fd, bool has_format,
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     }
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     /*
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-     * The goal of this block is to copy the guest note out of
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-     * the guest.  Failure to do so is not fatal for dumping.
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+     * The goal of this block is to (a) update the previously guessed
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+     * phys_base, (b) copy the guest note out of the guest.
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+     * Failure to do so is not fatal for dumping.
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      */
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     if (vmci) {
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         uint64_t addr, note_head_size, name_size, desc_size;
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@@ -1670,6 +1722,7 @@ static void dump_init(DumpState *s, int fd, bool has_format,
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                 g_free(s->guest_note);
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                 s->guest_note = NULL;
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             } else {
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+                vmcoreinfo_update_phys_base(s);
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                 s->note_size += s->guest_note_size;
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             }
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         }
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-- 
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1.8.3.1
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