shared: Add more dlopen() tests

Add dlopen_dw(), dlopen_elf() and dlopen_pcre2() to the dlopen test.
To enable adding dlopen_pcre2(), we move pcre2-dlopen.h/c from
src/journal to src/shared.

src/shared/elf-util.c

@@ -80,7 +80,7 @@ unsigned int (*sym_elf_version)(unsigned int);
 GElf_Phdr *(*sym_gelf_getphdr)(Elf *, int, GElf_Phdr *);
 size_t (*sym_gelf_getnote)(Elf_Data *, size_t, GElf_Nhdr *, size_t *, size_t *);
 
-static int dlopen_dw(void) {
+int dlopen_dw(void) {
         int r;
 
         r = dlopen_many_sym_or_warn(
@@ -123,7 +123,7 @@ static int dlopen_dw(void) {
         return 1;
 }
 
-static int dlopen_elf(void) {
+int dlopen_elf(void) {
         int r;
 
         r = dlopen_many_sym_or_warn(

src/shared/elf-util.h

@@ -4,6 +4,9 @@
 #include "json.h"
 
 #if HAVE_ELFUTILS
+int dlopen_dw(void);
+int dlopen_elf(void);
+
 /* Parse an ELF object in a forked process, so that errors while iterating over
  * untrusted and potentially malicious data do not propagate to the main caller's process.
  * If fork_disable_dump, the child process will not dump core if it crashes. */

src/shared/meson.build

@@ -243,6 +243,8 @@ shared_sources = files('''
         parse-argument.h
         parse-socket-bind-item.c
         parse-socket-bind-item.h
+        pcre2-dlopen.c
+        pcre2-dlopen.h
         pe-header.h
         pkcs11-util.c
         pkcs11-util.h

src/shared/pcre2-dlopen.c

@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "dlfcn-util.h"
+#include "log.h"
+#include "pcre2-dlopen.h"
+
+#if HAVE_PCRE2
+static void *pcre2_dl = NULL;
+
+pcre2_match_data* (*sym_pcre2_match_data_create)(uint32_t, pcre2_general_context *);
+void (*sym_pcre2_match_data_free)(pcre2_match_data *);
+void (*sym_pcre2_code_free)(pcre2_code *);
+pcre2_code* (*sym_pcre2_compile)(PCRE2_SPTR, PCRE2_SIZE, uint32_t, int *, PCRE2_SIZE *, pcre2_compile_context *);
+int (*sym_pcre2_get_error_message)(int, PCRE2_UCHAR *, PCRE2_SIZE);
+int (*sym_pcre2_match)(const pcre2_code *, PCRE2_SPTR, PCRE2_SIZE, PCRE2_SIZE, uint32_t, pcre2_match_data *, pcre2_match_context *);
+PCRE2_SIZE* (*sym_pcre2_get_ovector_pointer)(pcre2_match_data *);
+
+int dlopen_pcre2(void) {
+        /* So here's something weird: PCRE2 actually renames the symbols exported by the library via C
+         * macros, so that the exported symbols carry a suffix "_8" but when used from C the suffix is
+         * gone. In the argument list below we ignore this mangling. Surprisingly (at least to me), we
+         * actually get away with that. That's because DLSYM_ARG() useses STRINGIFY() to generate a string
+         * version of the symbol name, and that resolves the macro mapping implicitly already, so that the
+         * string actually contains the "_8" suffix already due to that and we don't have to append it
+         * manually anymore. C is weird. 🤯 */
+
+        return dlopen_many_sym_or_warn(
+                        &pcre2_dl, "libpcre2-8.so.0", LOG_ERR,
+                        DLSYM_ARG(pcre2_match_data_create),
+                        DLSYM_ARG(pcre2_match_data_free),
+                        DLSYM_ARG(pcre2_code_free),
+                        DLSYM_ARG(pcre2_compile),
+                        DLSYM_ARG(pcre2_get_error_message),
+                        DLSYM_ARG(pcre2_match),
+                        DLSYM_ARG(pcre2_get_ovector_pointer));
+}
+
+#else
+
+int dlopen_pcre2(void) {
+        return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                               "PCRE2 support is not compiled in.");
+}
+#endif

src/shared/pcre2-dlopen.h

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#if HAVE_PCRE2
+
+#define PCRE2_CODE_UNIT_WIDTH 8
+#include <pcre2.h>
+
+extern pcre2_match_data* (*sym_pcre2_match_data_create)(uint32_t, pcre2_general_context *);
+extern void (*sym_pcre2_match_data_free)(pcre2_match_data *);
+extern void (*sym_pcre2_code_free)(pcre2_code *);
+extern pcre2_code* (*sym_pcre2_compile)(PCRE2_SPTR, PCRE2_SIZE, uint32_t, int *, PCRE2_SIZE *, pcre2_compile_context *);
+extern int (*sym_pcre2_get_error_message)(int, PCRE2_UCHAR *, PCRE2_SIZE);
+extern int (*sym_pcre2_match)(const pcre2_code *, PCRE2_SPTR, PCRE2_SIZE, PCRE2_SIZE, uint32_t, pcre2_match_data *, pcre2_match_context *);
+extern PCRE2_SIZE* (*sym_pcre2_get_ovector_pointer)(pcre2_match_data *);
+#endif
+
+int dlopen_pcre2(void);