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rtld: load preloaded vdso

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Reviewed by:	emaste
Discussed with:	jrtc27
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
Differential revision:	https://reviews.freebsd.org/D32960
This commit is contained in:
Konstantin Belousov 2021-11-11 20:07:44 +02:00
parent 63fc4e820c
commit c210ef1347
1 changed files with 79 additions and 0 deletions
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79
libexec/rtld-elf/rtld.c
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@ -125,6 +125,7 @@ static void load_filtees(Obj_Entry *, int flags, RtldLockState *);
static void unload_filtees(Obj_Entry *, RtldLockState *);
static int load_needed_objects(Obj_Entry *, int);
static int load_preload_objects(const char *, bool);
static int load_kpreload(const void *addr);
static Obj_Entry *load_object(const char *, int fd, const Obj_Entry *, int);
static void map_stacks_exec(RtldLockState *);
static int obj_disable_relro(Obj_Entry *);
@ -828,6 +829,13 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
if (!libmap_disable)
libmap_disable = (bool)lm_init(libmap_override);
if (aux_info[AT_KPRELOAD] != NULL &&
aux_info[AT_KPRELOAD]->a_un.a_ptr != NULL) {
dbg("loading kernel vdso");
if (load_kpreload(aux_info[AT_KPRELOAD]->a_un.a_ptr) == -1)
rtld_die();
}
dbg("loading LD_PRELOAD_FDS libraries");
if (load_preload_objects(ld_preload_fds, true) == -1)
rtld_die();
@ -2842,6 +2850,77 @@ do_load_object(int fd, const char *name, char *path, struct stat *sbp,
return (NULL);
}
static int
load_kpreload(const void *addr)
{
Obj_Entry *obj;
const Elf_Ehdr *ehdr;
const Elf_Phdr *phdr, *phlimit, *phdyn, *seg0, *segn;
static const char kname[] = "[vdso]";
ehdr = addr;
if (!check_elf_headers(ehdr, "kpreload"))
return (-1);
obj = obj_new();
phdr = (const Elf_Phdr *)((const char *)addr + ehdr->e_phoff);
obj->phdr = phdr;
obj->phsize = ehdr->e_phnum * sizeof(*phdr);
phlimit = phdr + ehdr->e_phnum;
seg0 = segn = NULL;
for (; phdr < phlimit; phdr++) {
switch (phdr->p_type) {
case PT_DYNAMIC:
phdyn = phdr;
break;
case PT_GNU_STACK:
/* Absense of PT_GNU_STACK implies stack_flags == 0. */
obj->stack_flags = phdr->p_flags;
break;
case PT_LOAD:
if (seg0 == NULL || seg0->p_vaddr > phdr->p_vaddr)
seg0 = phdr;
if (segn == NULL || segn->p_vaddr + segn->p_memsz <
phdr->p_vaddr + phdr->p_memsz)
segn = phdr;
break;
}
}
obj->mapbase = __DECONST(caddr_t, addr);
obj->mapsize = segn->p_vaddr + segn->p_memsz - (Elf_Addr)addr;
obj->vaddrbase = 0;
obj->relocbase = obj->mapbase;
object_add_name(obj, kname);
obj->path = xstrdup(kname);
obj->dynamic = (const Elf_Dyn *)(obj->relocbase + phdyn->p_vaddr);
if (!digest_dynamic(obj, 0)) {
obj_free(obj);
return (-1);
}
/*
* We assume that kernel-preloaded object does not need
* relocation. It is currently written into read-only page,
* handling relocations would mean we need to allocate at
* least one additional page per AS.
*/
dbg("%s mapbase %p phdrs %p PT_LOAD phdr %p vaddr %p dynamic %p",
obj->path, obj->mapbase, obj->phdr, seg0,
obj->relocbase + seg0->p_vaddr, obj->dynamic);
TAILQ_INSERT_TAIL(&obj_list, obj, next);
obj_count++;
obj_loads++;
linkmap_add(obj); /* for GDB & dlinfo() */
max_stack_flags |= obj->stack_flags;
LD_UTRACE(UTRACE_LOAD_OBJECT, obj, obj->mapbase, 0, 0, obj->path);
return (0);
}
Obj_Entry *
obj_from_addr(const void *addr)
{