Fix linker failure when building Opcache statically

We use linker relocations to fetch the TLS index and offset of _tsrm_ls_cache.
When building Opcache statically, linkers may attempt to optimize that into a
more efficient code sequence (relaxing from "General Dynamic" to "Local Exec"
model [1]). Unfortunately, linkers will fail, rather than ignore our
relocations, when they don't recognize the exact code sequence they are
expecting.

This results in errors as reported by GH-15074:

    TLS transition from R_X86_64_TLSGD to R_X86_64_GOTTPOFF against
    `_tsrm_ls_cache' at 0x12fc3 in section `.text' failed"

Here I take a different approach:

 * Emit the exact full code sequence expected by linkers
 * Extract the TLS index/offset by inspecting the linked ASM code, rather than
   executing it (execution would give us the thread-local address).
 * We detect when the code was relaxed, in which case we can extract the TCB
   offset instead.
 * This is done in a conservative way so that if the linker did something we
   didn't expect, we fallback to a safer (but slower) mechanism.

One additional benefit of that is we are now able to use the Local Exec model in
more cases, in JIT'ed code. This makes non-glibc builds faster in these cases.

Closes GH-18939.

Related RFC: https://wiki.php.net/rfc/make_opcache_required.

[1] https://www.akkadia.org/drepper/tls.pdf

Author: arnaud-lb

ext/opcache/config.m4

@@ -73,19 +73,23 @@ if test "$PHP_OPCACHE" != "no"; then
         IR_TARGET=IR_TARGET_X64
         DASM_FLAGS="-D X64APPLE=1 -D X64=1"
         DASM_ARCH="x86"
+        TLS_TARGET="darwin"
       ],
       [*x86_64*|amd64-*-freebsd*], [
         IR_TARGET=IR_TARGET_X64
         DASM_FLAGS="-D X64=1"
         DASM_ARCH="x86"
+        TLS_TARGET="x86_64"
       ],
       [[i[34567]86*|x86*]], [
         IR_TARGET=IR_TARGET_X86
         DASM_ARCH="x86"
+        TLS_TARGET="x86"
       ],
       [aarch64*], [
         IR_TARGET=IR_TARGET_AARCH64
         DASM_ARCH="aarch64"
+        TLS_TARGET="aarch64"
       ])
 
     AS_VAR_IF([PHP_CAPSTONE], [yes],
@@ -102,6 +106,10 @@ if test "$PHP_OPCACHE" != "no"; then
 
     JIT_CFLAGS="-I@ext_builddir@/jit/ir -D$IR_TARGET -DIR_PHP"
     AS_VAR_IF([ZEND_DEBUG], [yes], [JIT_CFLAGS="$JIT_CFLAGS -DIR_DEBUG"])
+
+    AS_VAR_IF([PHP_THREAD_SAFETY], [yes], [
+      ZEND_JIT_SRC="$ZEND_JIT_SRC jit/tls/zend_jit_tls_$TLS_TARGET.c"
+    ])
   ])
 
   AC_CHECK_FUNCS([mprotect shm_create_largepage])

ext/opcache/config.w32

@@ -33,6 +33,7 @@ if (PHP_OPCACHE != "no") {
 			DEFINE("IR_TARGET", ir_target);
 			DEFINE("DASM_FLAGS", dasm_flags);
 			DEFINE("DASM_ARCH", "x86");
+			DEFINE("TLS_TARGET", "win");
 
 			AC_DEFINE('HAVE_JIT', 1, 'Define to 1 to enable JIT.');
 
@@ -52,6 +53,11 @@ if (PHP_OPCACHE != "no") {
 			ADD_SOURCES(configure_module_dirname + "\\jit",
 				"zend_jit.c zend_jit_vm_helpers.c",
 				"opcache", "ext\\opcache\\jit");
+			if (PHP_ZTS == "yes") {
+				ADD_SOURCES(configure_module_dirname + "\\jit\\tls",
+					"zend_jit_tls_win.c",
+					"opcache", "ext\\opcache\\jit\\tls");
+			}
 			ADD_SOURCES(configure_module_dirname + "\\jit\\ir",
 				"ir.c", "opcache", "ext\\opcache\\jit\\ir");
 			ADD_SOURCES(configure_module_dirname + "\\jit\\ir",

ext/opcache/jit/tls/testing/.gitignore

@@ -0,0 +1,4 @@
+*.so
+*.o
+main
+main.dSYM