San: Rename 'guard' to 'san'

This prepares the foundation for more sanitizer-related work in the
future.

src/san.c

@@ -0,0 +1,87 @@
+#include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
+
+#include "jemalloc/internal/assert.h"
+#include "jemalloc/internal/ehooks.h"
+#include "jemalloc/internal/san.h"
+#include "jemalloc/internal/tsd.h"
+
+/* The sanitizer options. */
+size_t opt_san_guard_large = SAN_GUARD_LARGE_EVERY_N_EXTENTS_DEFAULT;
+size_t opt_san_guard_small = SAN_GUARD_SMALL_EVERY_N_EXTENTS_DEFAULT;
+
+void
+san_guard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata, emap_t *emap) {
+	emap_deregister_boundary(tsdn, emap, edata);
+
+	size_t size_with_guards = edata_size_get(edata);
+	size_t usize = size_with_guards - PAGE_GUARDS_SIZE;
+
+	uintptr_t guard1 = (uintptr_t)edata_base_get(edata);
+	uintptr_t addr = guard1 + PAGE;
+	uintptr_t guard2 = addr + usize;
+
+	assert(edata_state_get(edata) == extent_state_active);
+	ehooks_guard(tsdn, ehooks, (void *)guard1, (void *)guard2);
+
+	/* Update the guarded addr and usable size of the edata. */
+	edata_size_set(edata, usize);
+	edata_addr_set(edata, (void *)addr);
+	edata_guarded_set(edata, true);
+
+	/* The new boundary will be registered on the pa_alloc path. */
+}
+
+static void
+san_unguard_pages_impl(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata,
+    emap_t *emap, bool reg_emap) {
+	/* Remove the inner boundary which no longer exists. */
+	if (reg_emap) {
+		assert(edata_state_get(edata) == extent_state_active);
+		emap_deregister_boundary(tsdn, emap, edata);
+	} else {
+		assert(edata_state_get(edata) == extent_state_retained);
+	}
+
+	size_t size = edata_size_get(edata);
+	size_t size_with_guards = size + PAGE_GUARDS_SIZE;
+
+	uintptr_t addr =  (uintptr_t)edata_base_get(edata);
+	uintptr_t guard1 = addr - PAGE;
+	uintptr_t guard2 = addr + size;
+
+	ehooks_unguard(tsdn, ehooks, (void *)guard1, (void *)guard2);
+
+	/* Update the true addr and usable size of the edata. */
+	edata_size_set(edata, size_with_guards);
+	edata_addr_set(edata, (void *)guard1);
+	edata_guarded_set(edata, false);
+
+	/*
+	 * Then re-register the outer boundary including the guards, if
+	 * requested.
+	 */
+	if (reg_emap) {
+		emap_register_boundary(tsdn, emap, edata, SC_NSIZES,
+		    /* slab */ false);
+	}
+}
+
+void
+san_unguard_pages(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata,
+    emap_t *emap) {
+	san_unguard_pages_impl(tsdn, ehooks, edata, emap, /* reg_emap */ true);
+}
+
+void
+san_unguard_pages_pre_destroy(tsdn_t *tsdn, ehooks_t *ehooks, edata_t *edata,
+    emap_t *emap) {
+	emap_assert_not_mapped(tsdn, emap, edata);
+	san_unguard_pages_impl(tsdn, ehooks, edata, emap, /* reg_emap */ false);
+}
+
+void
+tsd_san_init(tsd_t *tsd) {
+	*tsd_san_extents_until_guard_smallp_get(tsd) = opt_san_guard_small;
+	*tsd_san_extents_until_guard_largep_get(tsd) = opt_san_guard_large;
+}