vmlinux-kallsyms.c

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// SPDX-License-Identifier: GPL-2.0
#include <linux/compiler.h>
#include <linux/rbtree.h>
#include <inttypes.h>
#include <string.h>
#include "map.h"
#include "symbol.h"
#include "util.h"
#include "tests.h"
#include "debug.h"
#include "machine.h"

#define UM(x) kallsyms_map->unmap_ip(kallsyms_map, (x))

int test__vmlinux_matches_kallsyms(struct test *test __maybe_unused, int subtest __maybe_unused)
{
    int err = -1;
    struct rb_node *nd;
    struct symbol *sym;
    struct map *kallsyms_map, *vmlinux_map, *map;
    struct machine kallsyms, vmlinux;
    struct maps *maps = machine__kernel_maps(&vmlinux);
    u64 mem_start, mem_end;
    bool header_printed;

    /*
     * Step 1:
     *
     * Init the machines that will hold kernel, modules obtained from
     * both vmlinux + .ko files and from /proc/kallsyms split by modules.
     */
    machine__init(&kallsyms, "", HOST_KERNEL_ID);
    machine__init(&vmlinux, "", HOST_KERNEL_ID);

    /*
     * Step 2:
     *
     * Create the kernel maps for kallsyms and the DSO where we will then
     * load /proc/kallsyms. Also create the modules maps from /proc/modules
     * and find the .ko files that match them in /lib/modules/`uname -r`/.
     */
    if (machine__create_kernel_maps(&kallsyms) < 0) {
        pr_debug("machine__create_kernel_maps ");
        goto out;
    }

    /*
     * Step 3:
     *
     * Load and split /proc/kallsyms into multiple maps, one per module.
     * Do not use kcore, as this test was designed before kcore support
     * and has parts that only make sense if using the non-kcore code.
     * XXX: extend it to stress the kcorre code as well, hint: the list
     * of modules extracted from /proc/kcore, in its current form, can't
     * be compacted against the list of modules found in the "vmlinux"
     * code and with the one got from /proc/modules from the "kallsyms" code.
     */
    if (machine__load_kallsyms(&kallsyms, "/proc/kallsyms") <= 0) {
        pr_debug("dso__load_kallsyms ");
        goto out;
    }

    /*
     * Step 4:
     *
     * kallsyms will be internally on demand sorted by name so that we can
     * find the reference relocation * symbol, i.e. the symbol we will use
     * to see if the running kernel was relocated by checking if it has the
     * same value in the vmlinux file we load.
     */
    kallsyms_map = machine__kernel_map(&kallsyms);

    /*
     * Step 5:
     *
     * Now repeat step 2, this time for the vmlinux file we'll auto-locate.
     */
    if (machine__create_kernel_maps(&vmlinux) < 0) {
        pr_debug("machine__create_kernel_maps ");
        goto out;
    }

    vmlinux_map = machine__kernel_map(&vmlinux);

    /*
     * Step 6:
     *
     * Locate a vmlinux file in the vmlinux path that has a buildid that
     * matches the one of the running kernel.
     *
     * While doing that look if we find the ref reloc symbol, if we find it
     * we'll have its ref_reloc_symbol.unrelocated_addr and then
     * maps__reloc_vmlinux will notice and set proper ->[un]map_ip routines
     * to fixup the symbols.
     */
    if (machine__load_vmlinux_path(&vmlinux) <= 0) {
        pr_debug("Couldn't find a vmlinux that matches the kernel running on this machine, skipping test\n");
        err = TEST_SKIP;
        goto out;
    }

    err = 0;
    /*
     * Step 7:
     *
     * Now look at the symbols in the vmlinux DSO and check if we find all of them
     * in the kallsyms dso. For the ones that are in both, check its names and
     * end addresses too.
     */
    map__for_each_symbol(vmlinux_map, sym, nd) {
        struct symbol *pair, *first_pair;

        sym  = rb_entry(nd, struct symbol, rb_node);

        if (sym->start == sym->end)
            continue;

        mem_start = vmlinux_map->unmap_ip(vmlinux_map, sym->start);
        mem_end = vmlinux_map->unmap_ip(vmlinux_map, sym->end);

        first_pair = machine__find_kernel_symbol(&kallsyms, mem_start, NULL);
        pair = first_pair;

        if (pair && UM(pair->start) == mem_start) {
next_pair:
            if (arch__compare_symbol_names(sym->name, pair->name) == 0) {
                /*
                 * kallsyms don't have the symbol end, so we
                 * set that by using the next symbol start - 1,
                 * in some cases we get this up to a page
                 * wrong, trace_kmalloc when I was developing
                 * this code was one such example, 2106 bytes
                 * off the real size. More than that and we
                 * _really_ have a problem.
                 */
                s64 skew = mem_end - UM(pair->end);
                if (llabs(skew) >= page_size)
                    pr_debug("WARN: %#" PRIx64 ": diff end addr for %s v: %#" PRIx64 " k: %#" PRIx64 "\n",
                         mem_start, sym->name, mem_end,
                         UM(pair->end));

                /*
                 * Do not count this as a failure, because we
                 * could really find a case where it's not
                 * possible to get proper function end from
                 * kallsyms.
                 */
                continue;
            } else {
                pair = machine__find_kernel_symbol_by_name(&kallsyms, sym->name, NULL);
                if (pair) {
                    if (UM(pair->start) == mem_start)
                        goto next_pair;

                    pr_debug("WARN: %#" PRIx64 ": diff name v: %s k: %s\n",
                         mem_start, sym->name, pair->name);
                } else {
                    pr_debug("WARN: %#" PRIx64 ": diff name v: %s k: %s\n",
                         mem_start, sym->name, first_pair->name);
                }

                continue;
            }
        } else
            pr_debug("ERR : %#" PRIx64 ": %s not on kallsyms\n",
                 mem_start, sym->name);

        err = -1;
    }

    if (verbose <= 0)
        goto out;

    header_printed = false;

    for (map = maps__first(maps); map; map = map__next(map)) {
        struct map *
        /*
         * If it is the kernel, kallsyms is always "[kernel.kallsyms]", while
         * the kernel will have the path for the vmlinux file being used,
         * so use the short name, less descriptive but the same ("[kernel]" in
         * both cases.
         */
        pair = map_groups__find_by_name(&kallsyms.kmaps,
                        (map->dso->kernel ?
                            map->dso->short_name :
                            map->dso->name));
        if (pair) {
            pair->priv = 1;
        } else {
            if (!header_printed) {
                pr_info("WARN: Maps only in vmlinux:\n");
                header_printed = true;
            }
            map__fprintf(map, stderr);
        }
    }

    header_printed = false;

    for (map = maps__first(maps); map; map = map__next(map)) {
        struct map *pair;

        mem_start = vmlinux_map->unmap_ip(vmlinux_map, map->start);
        mem_end = vmlinux_map->unmap_ip(vmlinux_map, map->end);

        pair = map_groups__find(&kallsyms.kmaps, mem_start);
        if (pair == NULL || pair->priv)
            continue;

        if (pair->start == mem_start) {
            if (!header_printed) {
                pr_info("WARN: Maps in vmlinux with a different name in kallsyms:\n");
                header_printed = true;
            }

            pr_info("WARN: %" PRIx64 "-%" PRIx64 " %" PRIx64 " %s in kallsyms as",
                map->start, map->end, map->pgoff, map->dso->name);
            if (mem_end != pair->end)
                pr_info(":\nWARN: *%" PRIx64 "-%" PRIx64 " %" PRIx64,
                    pair->start, pair->end, pair->pgoff);
            pr_info(" %s\n", pair->dso->name);
            pair->priv = 1;
        }
    }

    header_printed = false;

    maps = machine__kernel_maps(&kallsyms);

    for (map = maps__first(maps); map; map = map__next(map)) {
        if (!map->priv) {
            if (!header_printed) {
                pr_info("WARN: Maps only in kallsyms:\n");
                header_printed = true;
            }
            map__fprintf(map, stderr);
        }
    }
out:
    machine__exit(&kallsyms);
    machine__exit(&vmlinux);
    return err;
}