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#include "Rts.h"
#include "RtsUtils.h"
#include "LinkerInternals.h"
#include "GetEnv.h"
#include "InitFini.h"
/*
* Note [Initializers and finalizers (PEi386/ELF)]
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Most ABIs allow an object to define initializers and finalizers to be run
* at load/unload time, respectively. These are represented in two ways:
*
* - a `.init`/`.fini` section which contains a function of type init_t which
* is to be executed during initialization/finalization.
*
* - `.ctors`/`.dtors` sections; these contain an array of pointers to
* `init_t`/`fini_t` functions, all of which should be executed at
* initialization/finalization time. The `.ctors` entries are run in reverse
* order. The list may end in a 0 or -1 sentinel value.
*
* - `.init_array`/`.fini_array` sections; these contain an array
* of pointers to `init_t`/`fini_t` functions.
*
* Objects may contain multiple `.ctors`/`.dtors` and
* `.init_array`/`.fini_array` sections, each optionally suffixed with an
* 16-bit integer priority (e.g. `.init_array.1234`). Confusingly, `.ctors`
* priorities and `.init_array` priorities have different orderings: `.ctors`
* sections are run from high to low priority whereas `.init_array` sections
* are run from low-to-high.
*
* Sections without a priority (e.g. `.ctors`) are assumed to run last (that
* is, are given a priority of 0xffff).
*
* In general, we run finalizers in the reverse order of the associated
* initializers. That is to say, e.g., .init_array entries are run from first
* to last entry and therefore .fini_array entries are run from last-to-first.
*
* To determine the ordering among the various section types, we follow glibc's
* model:
*
* - first run .ctors (last entry to first entry)
* - then run .init_arrays (first-to-last)
*
* and on unload we run in opposite order:
*
* - first run fini_arrays (first-to-last)
* - then run .dtors (last-to-first)
*
* For more about how the code generator emits initializers and finalizers see
* Note [Initializers and finalizers in Cmm] in GHC.Cmm.InitFini.
*/
// Priority follows the init_array definition: initializers are run
// lowest-to-highest, finalizers run highest-to-lowest.
void addInitFini(struct InitFiniList **head, Section *section, enum InitFiniKind kind, uint32_t priority)
{
struct InitFiniList *slist = stgMallocBytes(sizeof(struct InitFiniList), "addInitFini");
slist->section = section;
slist->kind = kind;
slist->priority = priority;
slist->next = *head;
*head = slist;
}
enum SortOrder { INCREASING, DECREASING };
// Sort a InitFiniList by priority.
static void sortInitFiniList(struct InitFiniList **slist, enum SortOrder order)
{
// Bubble sort
bool done = false;
while (!done) {
struct InitFiniList **last = slist;
done = true;
while (*last != NULL && (*last)->next != NULL) {
struct InitFiniList *s0 = *last;
struct InitFiniList *s1 = s0->next;
bool flip;
switch (order) {
case INCREASING: flip = s0->priority > s1->priority; break;
case DECREASING: flip = s0->priority < s1->priority; break;
}
if (flip) {
s0->next = s1->next;
s1->next = s0;
*last = s1;
done = false;
} else {
last = &s0->next;
}
}
}
}
void freeInitFiniList(struct InitFiniList *slist)
{
while (slist != NULL) {
struct InitFiniList *next = slist->next;
stgFree(slist);
slist = next;
}
}
static bool runInitFini(struct InitFiniList **head)
{
int argc, envc;
char **argv, **envv;
getProgArgv(&argc, &argv);
getProgEnvv(&envc, &envv);
for (struct InitFiniList *slist = *head;
slist != NULL;
slist = slist->next)
{
Section *section = slist->section;
switch (slist->kind) {
case INITFINI_INIT: {
init_t *init = (init_t*)section->start;
(*init)(argc, argv, envv);
break;
}
case INITFINI_FINI: {
fini_t *fini = (fini_t*)section->start;
(*fini)();
break;
}
case INITFINI_CTORS: {
uint8_t *init_startC = section->start;
init_t *init_start = (init_t*)init_startC;
init_t *init_end = (init_t*)(init_startC + section->size);
// ctors are run *backwards*!
for (init_t *init = init_end - 1; init >= init_start; init--) {
if ((intptr_t) *init == 0x0 || (intptr_t)*init == -1) {
continue;
}
(*init)(argc, argv, envv);
}
break;
}
case INITFINI_DTORS: {
char *fini_startC = section->start;
fini_t *fini_start = (fini_t*)fini_startC;
fini_t *fini_end = (fini_t*)(fini_startC + section->size);
for (fini_t *fini = fini_start; fini < fini_end; fini++) {
if ((intptr_t) *fini == 0x0 || (intptr_t) *fini == -1) {
continue;
}
(*fini)();
}
break;
}
case INITFINI_INIT_ARRAY: {
char *init_startC = section->start;
init_t *init_start = (init_t*)init_startC;
init_t *init_end = (init_t*)(init_startC + section->size);
for (init_t *init = init_start; init < init_end; init++) {
CHECK(0x0 != *init);
(*init)(argc, argv, envv);
}
break;
}
case INITFINI_FINI_ARRAY: {
char *fini_startC = section->start;
fini_t *fini_start = (fini_t*)fini_startC;
fini_t *fini_end = (fini_t*)(fini_startC + section->size);
// .fini_array finalizers are run backwards
for (fini_t *fini = fini_end - 1; fini >= fini_start; fini--) {
CHECK(0x0 != *fini);
(*fini)();
}
break;
}
default: barf("unknown InitFiniKind");
}
}
freeInitFiniList(*head);
*head = NULL;
freeProgEnvv(envc, envv);
return true;
}
// Run the constructors/initializers of an ObjectCode.
// Returns 1 on success.
// See Note [Initializers and finalizers (PEi386/ELF)].
bool runInit(struct InitFiniList **head)
{
sortInitFiniList(head, INCREASING);
return runInitFini(head);
}
// Run the finalizers of an ObjectCode.
// Returns 1 on success.
// See Note [Initializers and finalizers (PEi386/ELF)].
bool runFini(struct InitFiniList **head)
{
sortInitFiniList(head, DECREASING);
return runInitFini(head);
}
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