c18n: Fix various implementation bugs

bin/cheribsdtest/cheribsdtest.h

@@ -151,15 +151,6 @@ extern struct cheribsdtest_child_state *ccsp;
 #endif
 #endif
 
-#ifndef XFAIL_C18N_FPTR_CANON
-#ifdef CHERIBSD_C18N_TESTS
-#define	XFAIL_C18N_FPTR_CANON \
-    "function pointers are currently non-canonical with library-based compartmentalisation"
-#else
-#define	XFAIL_C18N_FPTR_CANON	NULL
-#endif
-#endif
-
 struct cheri_test {
 	const char	*ct_name;
 	const char	*ct_desc;

bin/cheribsdtest/cheribsdtest_fptr_canon.c

@@ -37,8 +37,7 @@
 #include "cheribsdtest.h"
 
 CHERIBSDTEST(fptr_canon_cross,
-    "Check that function pointers are canonical across objects",
-    .ct_xfail_reason = XFAIL_C18N_FPTR_CANON)
+    "Check that function pointers are canonical across objects")
 {
 	void (* volatile fptr_inside)(void);
 	void (* volatile fptr_outside)(void);
@@ -53,8 +52,7 @@ CHERIBSDTEST(fptr_canon_cross,
 }
 
 CHERIBSDTEST(fptr_canon_dlsym,
-    "Check that function pointers are canonical for dlsym",
-    .ct_xfail_reason = XFAIL_C18N_FPTR_CANON)
+    "Check that function pointers are canonical for dlsym")
 {
 	void (* volatile fptr_inside)(void);
 	void (* volatile fptr_dlsym)(void);
@@ -70,8 +68,7 @@ CHERIBSDTEST(fptr_canon_dlsym,
 }
 
 CHERIBSDTEST(fptr_canon_dlfunc,
-    "Check that function pointers are canonical for dlfunc",
-    .ct_xfail_reason = XFAIL_C18N_FPTR_CANON)
+    "Check that function pointers are canonical for dlfunc")
 {
 	void (* volatile fptr_inside)(void);
 	void (* volatile fptr_dlfunc)(void);

lib/libc/sys/sigaction.c

@@ -39,8 +39,10 @@ __weak_reference(sigaction, __libc_sigaction);
 /*
  * These weak symbols will always be resolved at runtime.
  */
-#pragma weak _rtld_sighandler
-void _rtld_sighandler(int, siginfo_t *, void *);
+/*
+ * XXX: Explicit function pointer used so that RTLD can wrap it in trampoline.
+ */
+extern void (*_rtld_sighandler)(int, siginfo_t *, void *);
 
 #pragma weak _rtld_sigaction_begin
 void *_rtld_sigaction_begin(int, struct sigaction *);

lib/libthr/thread/thr_sig.c

@@ -76,11 +76,15 @@ static void check_cancel(struct pthread *curthread, ucontext_t *ucp);
 /*
  * These weak symbols will always be resolved at runtime.
  */
-#pragma weak _rtld_sighandler
-void _rtld_sighandler(int, siginfo_t *, void *);
+/*
+ * XXX: Explicit function pointer used so that RTLD can wrap it in trampoline.
+ */
+extern void (*_rtld_sighandler)(int, siginfo_t *, void *);
 
-#pragma weak _rtld_dispatch_signal
-void _rtld_dispatch_signal(int, siginfo_t *, void *);
+/*
+ * XXX: Explicit function pointer used so that RTLD can wrap it in trampoline.
+ */
+extern void (*_rtld_dispatch_signal)(int, siginfo_t *, void *);
 
 #pragma weak _rtld_sigaction_begin
 void *_rtld_sigaction_begin(int, struct sigaction *);

libexec/rtld-elf/aarch64/rtld_c18n_asm.S

@@ -80,7 +80,7 @@ END(_rtld_thread_start)
  * is only ever invoked via a trampoline by the kernel when a signal is
  * delivered.
  */
-ENTRY(_rtld_sighandler)
+ENTRY(_rtld_sighandler_unsafe)
 #ifndef __ARM_MORELLO_PURECAP_BENCHMARK_ABI
 	/*
 	 * The sigframe is pushed onto the trusted stack, disrupting the linked-
@@ -116,7 +116,7 @@ ENTRY(_rtld_sighandler)
 	mov	c30, c19
 	b	sighandler_unfix_link
 #endif
-END(_rtld_sighandler)
+END(_rtld_sighandler_unsafe)
 
 /*
  * void _rtld_dispatch_signal(int, siginfo_t *, void *);
@@ -125,7 +125,7 @@ END(_rtld_sighandler)
  * is only ever invoked by either RTLD code that is aware of this behaviour or
  * external code via a trampoline.
  */
-ENTRY(_rtld_dispatch_signal)
+ENTRY(_rtld_dispatch_signal_unsafe)
 	mov	c24, c30
 	mov	w25, w0
 	mov	c26, c1
@@ -151,7 +151,7 @@ ENTRY(_rtld_dispatch_signal)
 	mov	c1, c27
 	mov	c30, c24
 	b	dispatch_signal_end
-END(_rtld_dispatch_signal)
+END(_rtld_dispatch_signal_unsafe)
 
 ENTRY(allocate_rstk)
 	/*

libexec/rtld-elf/cheri/cheri_reloc.h

@@ -119,14 +119,6 @@ process_r_cheri_capability(Obj_Entry *obj, Elf_Word r_symndx,
 		}
 		/* Remove write permissions and set bounds */
 		symval = make_function_cap_with_addend(def, defobj, addend);
-#if defined(__CHERI_PURE_CAPABILITY__) && defined(RTLD_SANDBOX)
-		symval = tramp_intern(obj, &(struct tramp_data) {
-			.target = __DECONST(void *, symval),
-			.defobj = defobj,
-			.def = def,
-			.sig = sigtab_get(obj, r_symndx)
-		});
-#endif
 		if (__predict_false(symval == NULL)) {
 			_rtld_error("Could not create function pointer for %s "
 				    "(in %s)\n",

libexec/rtld-elf/rtld.c

@@ -238,6 +238,9 @@ static bool ld_skip_init_funcs = false;	/* XXXAR: debug environment variable to
 static struct obj_entry_q obj_list;	/* Queue of all loaded objects */
 static Obj_Entry *obj_main;	/* The main program shared object */
 static Obj_Entry obj_rtld;	/* The dynamic linker shared object */
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(RTLD_SANDBOX)
+Obj_Entry *obj_rtld_p = &obj_rtld;
+#endif
 static unsigned int obj_count;	/* Number of objects in obj_list */
 static unsigned int obj_loads;	/* Number of loads of objects (gen count) */
 size_t ld_static_tls_extra =	/* Static TLS extra space (bytes) */
@@ -1228,12 +1231,21 @@ _rtld_bind(Obj_Entry *obj, Elf_Size reloff)
 	rtld_die();
     if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC)
 	target = (uintptr_t)rtld_resolve_ifunc(defobj, def);
-    else
+    else {
 #ifdef __CHERI_PURE_CAPABILITY__
 	target = (uintptr_t)make_function_pointer(def, defobj);
+#ifdef RTLD_SANDBOX
+	target = (uintptr_t)tramp_intern(obj, &(struct tramp_data) {
+	    .target = (void *)target,
+	    .defobj = defobj,
+	    .def = def,
+	    .sig = sigtab_get(obj, ELF_R_SYM(rel->r_info))
+	});
+#endif
 #else
 	target = (uintptr_t)(defobj->relocbase + def->st_value);
 #endif
+    }
 
     dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
       defobj->strtab + def->st_name,
@@ -1248,14 +1260,6 @@ _rtld_bind(Obj_Entry *obj, Elf_Size reloff)
      * address. The value returned from reloc_jmpslot() is the value
      * that the trampoline needs.
      */
-#if defined(__CHERI_PURE_CAPABILITY__) && defined(RTLD_SANDBOX)
-    target = (uintptr_t)tramp_intern(obj, &(struct tramp_data) {
-	.target = (void *)target,
-	.defobj = defobj,
-	.def = def,
-	.sig = sigtab_get(obj, ELF_R_SYM(rel->r_info))
-    });
-#endif
     target = reloc_jmpslot(where, target, defobj, obj, rel);
     lock_release(rtld_bind_lock, &lockstate);
     return (target);
@@ -3293,6 +3297,13 @@ Obj_Entry *
 obj_from_addr(const void *addr)
 {
     Obj_Entry *obj;
+#if defined(__CHERI_PURE_CAPABILITY__) && defined(RTLD_SANDBOX)
+    struct tramp_header *header;
+
+    header = tramp_reflect(__DECONST(void *, addr));
+    if (header != NULL)
+	return (__DECONST(Obj_Entry *, header->defobj));
+#endif
 
     TAILQ_FOREACH(obj, &obj_list, next) {
 	if (obj->marker)
@@ -4394,23 +4405,9 @@ do_dlsym(void *handle, const char *name, void *retaddr, const Ver_Entry *ve,
 	 */
 	if (ELF_ST_TYPE(def->st_info) == STT_FUNC) {
 	    sym = __DECONST(void*, make_function_pointer(def, defobj));
-#if defined(__CHERI_PURE_CAPABILITY__) && defined(RTLD_SANDBOX)
-	    sym = tramp_intern(obj, &(struct tramp_data) {
-		.target = sym,
-		.defobj = defobj,
-		.def = def
-	    });
-#endif
 	    dbg("dlsym(%s) is function: " PTR_FMT, name, sym);
 	} else if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
 	    sym = rtld_resolve_ifunc(defobj, def);
-#if defined(__CHERI_PURE_CAPABILITY__) && defined(RTLD_SANDBOX)
-	    sym = tramp_intern(obj, &(struct tramp_data) {
-		.target = sym,
-		.defobj = defobj,
-		.def = def
-	    });
-#endif
 	    dbg("dlsym(%s) is ifunc. Resolved to: " PTR_FMT, name, sym);
 	} else if (ELF_ST_TYPE(def->st_info) == STT_TLS) {
 	    ti.ti_module = defobj->tlsindex;