machine.c

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// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/string.h>
#include <stdlib.h>

#include "../../util/machine.h"
#include "../../util/map.h"
#include "../../util/symbol.h"
#include "../../util/sane_ctype.h"

#include <symbol/kallsyms.h>

#if defined(__x86_64__)

struct extra_kernel_map_info {
    int cnt;
    int max_cnt;
    struct extra_kernel_map *maps;
    bool get_entry_trampolines;
    u64 entry_trampoline;
};

static int add_extra_kernel_map(struct extra_kernel_map_info *mi, u64 start,
                u64 end, u64 pgoff, const char *name)
{
    if (mi->cnt >= mi->max_cnt) {
        void *buf;
        size_t sz;

        mi->max_cnt = mi->max_cnt ? mi->max_cnt * 2 : 32;
        sz = sizeof(struct extra_kernel_map) * mi->max_cnt;
        buf = realloc(mi->maps, sz);
        if (!buf)
            return -1;
        mi->maps = buf;
    }

    mi->maps[mi->cnt].start = start;
    mi->maps[mi->cnt].end   = end;
    mi->maps[mi->cnt].pgoff = pgoff;
    strlcpy(mi->maps[mi->cnt].name, name, KMAP_NAME_LEN);

    mi->cnt += 1;

    return 0;
}

static int find_extra_kernel_maps(void *arg, const char *name, char type,
                  u64 start)
{
    struct extra_kernel_map_info *mi = arg;

    if (!mi->entry_trampoline && kallsyms2elf_binding(type) == STB_GLOBAL &&
        !strcmp(name, "_entry_trampoline")) {
        mi->entry_trampoline = start;
        return 0;
    }

    if (is_entry_trampoline(name)) {
        u64 end = start + page_size;

        return add_extra_kernel_map(mi, start, end, 0, name);
    }

    return 0;
}

int machine__create_extra_kernel_maps(struct machine *machine,
                      struct dso *kernel)
{
    struct extra_kernel_map_info mi = { .cnt = 0, };
    char filename[PATH_MAX];
    int ret;
    int i;

    machine__get_kallsyms_filename(machine, filename, PATH_MAX);

    if (symbol__restricted_filename(filename, "/proc/kallsyms"))
        return 0;

    ret = kallsyms__parse(filename, &mi, find_extra_kernel_maps);
    if (ret)
        goto out_free;

    if (!mi.entry_trampoline)
        goto out_free;

    for (i = 0; i < mi.cnt; i++) {
        struct extra_kernel_map *xm = &mi.maps[i];

        xm->pgoff = mi.entry_trampoline;
        ret = machine__create_extra_kernel_map(machine, kernel, xm);
        if (ret)
            goto out_free;
    }

    machine->trampolines_mapped = mi.cnt;
out_free:
    free(mi.maps);
    return ret;
}

#endif