Commit d9feb517 authored by Marc-André Lureau's avatar Marc-André Lureau Committed by Michael S. Tsirkin
Browse files

dump: update phys_base header field based on VMCOREINFO content 



If the guest note is VMCOREINFO, try to get phys_base from it.

Signed-off-by: default avatarMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 903ef734

docs/specs/vmcoreinfo.txt

+8 −0
Original line number Diff line number Diff line
@@ -39,3 +39,11 @@ qemu dumps. 


The note format/class must be of the target bitness and the size must

be less than 1Mb.



If the ELF note name is "VMCOREINFO", it is expected to be the Linux

vmcoreinfo note (see Documentation/ABI/testing/sysfs-kernel-vmcoreinfo

in Linux source). In this case, qemu dump code will read the content

as a key=value text file, looking for "NUMBER(phys_base)" key

value. The value is expected to be more accurate than architecture

guess of the value. This is useful for KASLR-enabled guest with

ancient tools not handling the VMCOREINFO note.

dump.c

+54 −2
Original line number Diff line number Diff line
@@ -779,6 +779,23 @@ static void get_note_sizes(DumpState *s, const void *note, 
    }

}



static bool note_name_equal(DumpState *s,

                            const uint8_t *note, const char *name)

{

    int len = strlen(name) + 1;

    uint64_t head_size, name_size;



    get_note_sizes(s, note, &head_size, &name_size, NULL);

    head_size = ROUND_UP(head_size, 4);



    if (name_size != len ||

        memcmp(note + head_size, "VMCOREINFO", len)) {

        return false;

    }



    return true;

}



/* write common header, sub header and elf note to vmcore */

static void create_header32(DumpState *s, Error **errp)

{
@@ -1553,6 +1570,39 @@ static int64_t dump_calculate_size(DumpState *s) 
    return total;

}



static void vmcoreinfo_update_phys_base(DumpState *s)

{

    uint64_t size, note_head_size, name_size, phys_base;

    char **lines;

    uint8_t *vmci;

    size_t i;



    if (!note_name_equal(s, s->guest_note, "VMCOREINFO")) {

        return;

    }



    get_note_sizes(s, s->guest_note, &note_head_size, &name_size, &size);

    note_head_size = ROUND_UP(note_head_size, 4);



    vmci = s->guest_note + note_head_size + ROUND_UP(name_size, 4);

    *(vmci + size) = '\0';



    lines = g_strsplit((char *)vmci, "\n", -1);

    for (i = 0; lines[i]; i++) {

        if (g_str_has_prefix(lines[i], "NUMBER(phys_base)=")) {

            if (qemu_strtou64(lines[i] + 18, NULL, 16,

                              &phys_base) < 0) {

                warn_report("Failed to read NUMBER(phys_base)=");

            } else {

                s->dump_info.phys_base = phys_base;

            }

            break;

        }

    }



    g_strfreev(lines);

}



static void dump_init(DumpState *s, int fd, bool has_format,

                      DumpGuestMemoryFormat format, bool paging, bool has_filter,

                      int64_t begin, int64_t length, Error **errp)
@@ -1636,8 +1686,9 @@ static void dump_init(DumpState *s, int fd, bool has_format, 
    }



    /*

     * The goal of this block is to copy the guest note out of

     * the guest.  Failure to do so is not fatal for dumping.

     * The goal of this block is to (a) update the previously guessed

     * phys_base, (b) copy the guest note out of the guest.

     * Failure to do so is not fatal for dumping.

     */

    if (vmci) {

        uint64_t addr, note_head_size, name_size, desc_size;
@@ -1670,6 +1721,7 @@ static void dump_init(DumpState *s, int fd, bool has_format, 
                g_free(s->guest_note);

                s->guest_note = NULL;

            } else {

                vmcoreinfo_update_phys_base(s);

                s->note_size += s->guest_note_size;

            }

        }