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Kernel and modules have "set_vnet" linker set, where virtualized

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global variables are placed. When a module is loaded by link_elf
linker its variables from "set_vnet" linker set are copied to the
kernel "set_vnet" ("modspace") and all references to these variables
inside the module are relocated accordingly.

The issue is when a module is loaded that has references to global
variables from another, previously loaded module: these references are
not relocated so an invalid address is used when the module tries to
access the variable. The example is V_layer3_chain, defined in ipfw
module and accessed from ipfw_nat.

The same issue is with DPCPU variables, which use "set_pcpu" linker
set.

Fix this making the link_elf linker on a module load recognize
"external" DPCPU/VNET variables defined in the previously loaded
modules and relocate them accordingly. For this set_pcpu_list and
set_vnet_list are used, where the addresses of modules' "set_pcpu" and
"set_vnet" linker sets are stored.

Note, archs that use link_elf_obj (amd64) were not affected by this
issue.

Reviewed by:	jhb, julian, zec (initial version)
MFC after:	1 month
This commit is contained in:
Mikolaj Golub 2012-09-27 14:55:15 +00:00
parent a0a6ff825b
commit 47813f5d94
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=240997
1 changed files with 98 additions and 1 deletions
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99
sys/kern/link_elf.c
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@ -123,6 +123,15 @@ typedef struct elf_file {
#endif
} *elf_file_t;
struct elf_set {
Elf_Addr es_start;
Elf_Addr es_stop;
Elf_Addr es_base;
TAILQ_ENTRY(elf_set) es_link;
};
TAILQ_HEAD(elf_set_head, elf_set);
#include <kern/kern_ctf.c>
static int link_elf_link_common_finish(linker_file_t);
@ -181,6 +190,75 @@ static int parse_dynamic(elf_file_t);
static int relocate_file(elf_file_t);
static int link_elf_preload_parse_symbols(elf_file_t);
static struct elf_set_head set_pcpu_list;
#ifdef VIMAGE
static struct elf_set_head set_vnet_list;
#endif
static void
elf_set_add(struct elf_set_head *list, Elf_Addr start, Elf_Addr stop, Elf_Addr base)
{
struct elf_set *set, *iter;
set = malloc(sizeof(*set), M_LINKER, M_WAITOK);
set->es_start = start;
set->es_stop = stop;
set->es_base = base;
TAILQ_FOREACH(iter, list, es_link) {
KASSERT((set->es_start < iter->es_start && set->es_stop < iter->es_stop) ||
(set->es_start > iter->es_start && set->es_stop > iter->es_stop),
("linker sets intersection: to insert: 0x%jx-0x%jx; inserted: 0x%jx-0x%jx",
(uintmax_t)set->es_start, (uintmax_t)set->es_stop,
(uintmax_t)iter->es_start, (uintmax_t)iter->es_stop));
if (iter->es_start > set->es_start) {
TAILQ_INSERT_BEFORE(iter, set, es_link);
break;
}
}
if (iter == NULL)
TAILQ_INSERT_TAIL(list, set, es_link);
}
static int
elf_set_find(struct elf_set_head *list, Elf_Addr addr, Elf_Addr *start, Elf_Addr *base)
{
struct elf_set *set;
TAILQ_FOREACH(set, list, es_link) {
if (addr < set->es_start)
return (0);
if (addr < set->es_stop) {
*start = set->es_start;
*base = set->es_base;
return (1);
}
}
return (0);
}
static void
elf_set_delete(struct elf_set_head *list, Elf_Addr start)
{
struct elf_set *set;
TAILQ_FOREACH(set, list, es_link) {
if (start < set->es_start)
break;
if (start == set->es_start) {
TAILQ_REMOVE(list, set, es_link);
free(set, M_LINKER);
return;
}
}
KASSERT(0, ("deleting unknown linker set (start = 0x%jx)",
(uintmax_t)start));
}
#ifdef GDB
static void r_debug_state(struct r_debug *, struct link_map *);
@ -345,6 +423,10 @@ link_elf_init(void* arg)
(void)link_elf_link_common_finish(linker_kernel_file);
linker_kernel_file->flags |= LINKER_FILE_LINKED;
TAILQ_INIT(&set_pcpu_list);
#ifdef VIMAGE
TAILQ_INIT(&set_vnet_list);
#endif
}
SYSINIT(link_elf, SI_SUB_KLD, SI_ORDER_THIRD, link_elf_init, 0);
@ -515,6 +597,8 @@ parse_dpcpu(elf_file_t ef)
return (ENOSPC);
memcpy((void *)ef->pcpu_base, (void *)ef->pcpu_start, count);
dpcpu_copy((void *)ef->pcpu_base, count);
elf_set_add(&set_pcpu_list, ef->pcpu_start, ef->pcpu_stop,
ef->pcpu_base);
return (0);
}
@ -544,6 +628,8 @@ parse_vnet(elf_file_t ef)
return (ENOSPC);
memcpy((void *)ef->vnet_base, (void *)ef->vnet_start, count);
vnet_data_copy((void *)ef->vnet_base, count);
elf_set_add(&set_vnet_list, ef->vnet_start, ef->vnet_stop,
ef->vnet_base);
return (0);
}
@ -996,11 +1082,13 @@ link_elf_unload_file(linker_file_t file)
if (ef->pcpu_base != 0) {
dpcpu_free((void *)ef->pcpu_base,
ef->pcpu_stop - ef->pcpu_start);
elf_set_delete(&set_pcpu_list, ef->pcpu_start);
}
#ifdef VIMAGE
if (ef->vnet_base != 0) {
vnet_data_free((void *)ef->vnet_base,
ef->vnet_stop - ef->vnet_start);
elf_set_delete(&set_vnet_list, ef->vnet_start);
}
#endif
#ifdef GDB
@ -1439,6 +1527,7 @@ elf_lookup(linker_file_t lf, Elf_Size symidx, int deps)
elf_file_t ef = (elf_file_t)lf;
const Elf_Sym *sym;
const char *symbol;
Elf_Addr addr, start, base;
/* Don't even try to lookup the symbol if the index is bogus. */
if (symidx >= ef->nchains)
@ -1470,7 +1559,15 @@ elf_lookup(linker_file_t lf, Elf_Size symidx, int deps)
if (*symbol == 0)
return (0);
return ((Elf_Addr)linker_file_lookup_symbol(lf, symbol, deps));
addr = ((Elf_Addr)linker_file_lookup_symbol(lf, symbol, deps));
if (elf_set_find(&set_pcpu_list, addr, &start, &base))
addr = addr - start + base;
#ifdef VIMAGE
else if (elf_set_find(&set_vnet_list, addr, &start, &base))
addr = addr - start + base;
#endif
return addr;
}
static void