imgact_elf: Add helper macros for name of the ELF ABI (elf32 vs elf64)

Reviewed by:	brooks, kib
Obtained from:	CheriBSD
Sponsored by:	AFRL, DARPA
Differential Revision:	https://reviews.freebsd.org/D52032

sys/kern/imgact_elf.c

@@ -84,6 +84,13 @@
 #define ELF_NOTE_ROUNDSIZE	4
 #define OLD_EI_BRAND	8
 
+/*
+ * ELF_ABI_NAME is a string name of the ELF ABI.  ELF_ABI_ID is used
+ * to build variable names.
+ */
+#define	ELF_ABI_NAME	__XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
+#define	ELF_ABI_ID	__CONCAT(elf, __ELF_WORD_SIZE)
+
 static int __elfN(check_header)(const Elf_Ehdr *hdr);
 static Elf_Brandinfo *__elfN(get_brandinfo)(struct image_params *imgp,
     const char *interp, int32_t *osrel, uint32_t *fctl0);
@@ -104,14 +111,15 @@ static Elf_Word __elfN(untrans_prot)(vm_prot_t);
 static size_t __elfN(prepare_register_notes)(struct thread *td,
     struct note_info_list *list, struct thread *target_td);
 
-SYSCTL_NODE(_kern, OID_AUTO, __CONCAT(elf, __ELF_WORD_SIZE),
-    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
+SYSCTL_NODE(_kern, OID_AUTO, ELF_ABI_ID, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
     "");
 
+#define	ELF_NODE_OID	__CONCAT(_kern_, ELF_ABI_ID)
+
 int __elfN(fallback_brand) = -1;
-SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO,
+SYSCTL_INT(ELF_NODE_OID, OID_AUTO,
     fallback_brand, CTLFLAG_RWTUN, &__elfN(fallback_brand), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) " brand of last resort");
+    ELF_ABI_NAME " brand of last resort");
 
 static int elf_legacy_coredump = 0;
 SYSCTL_INT(_debug, OID_AUTO, __elfN(legacy_coredump), CTLFLAG_RW, 
@@ -126,22 +134,22 @@ int __elfN(nxstack) =
 #else
 	0;
 #endif
-SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO,
+SYSCTL_INT(ELF_NODE_OID, OID_AUTO,
     nxstack, CTLFLAG_RW, &__elfN(nxstack), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": support PT_GNU_STACK for non-executable stack control");
+    ELF_ABI_NAME ": support PT_GNU_STACK for non-executable stack control");
 
 #if defined(__amd64__)
 static int __elfN(vdso) = 1;
-SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO,
+SYSCTL_INT(ELF_NODE_OID, OID_AUTO,
     vdso, CTLFLAG_RWTUN, &__elfN(vdso), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": enable vdso preloading");
+    ELF_ABI_NAME ": enable vdso preloading");
 #else
 static int __elfN(vdso) = 0;
 #endif
 
 #if __ELF_WORD_SIZE == 32 && (defined(__amd64__) || defined(__i386__))
 int i386_read_exec = 0;
-SYSCTL_INT(_kern_elf32, OID_AUTO, read_exec, CTLFLAG_RW, &i386_read_exec, 0,
+SYSCTL_INT(ELF_NODE_OID, OID_AUTO, read_exec, CTLFLAG_RW, &i386_read_exec, 0,
     "enable execution from readable segments");
 #endif
 
@@ -161,15 +169,15 @@ sysctl_pie_base(SYSCTL_HANDLER_ARGS)
 	__elfN(pie_base) = val;
 	return (0);
 }
-SYSCTL_PROC(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, pie_base,
+SYSCTL_PROC(ELF_NODE_OID, OID_AUTO, pie_base,
     CTLTYPE_ULONG | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0,
     sysctl_pie_base, "LU",
     "PIE load base without randomization");
 
-SYSCTL_NODE(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, aslr,
+SYSCTL_NODE(ELF_NODE_OID, OID_AUTO, aslr,
     CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
     "");
-#define	ASLR_NODE_OID	__CONCAT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), _aslr)
+#define	ASLR_NODE_OID	__CONCAT(ELF_NODE_OID, _aslr)
 
 /*
  * Enable ASLR by default for 64-bit non-PIE binaries.  32-bit architectures
@@ -179,8 +187,7 @@ SYSCTL_NODE(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, aslr,
 static int __elfN(aslr_enabled) = __ELF_WORD_SIZE == 64;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, enable, CTLFLAG_RWTUN,
     &__elfN(aslr_enabled), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
-    ": enable address map randomization");
+    ELF_ABI_NAME ": enable address map randomization");
 
 /*
  * Enable ASLR by default for 64-bit PIE binaries.
@@ -188,8 +195,7 @@ SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, enable, CTLFLAG_RWTUN,
 static int __elfN(pie_aslr_enabled) = __ELF_WORD_SIZE == 64;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, pie_enable, CTLFLAG_RWTUN,
     &__elfN(pie_aslr_enabled), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
-    ": enable address map randomization for PIE binaries");
+    ELF_ABI_NAME ": enable address map randomization for PIE binaries");
 
 /*
  * Sbrk is deprecated and it can be assumed that in most cases it will not be
@@ -199,27 +205,25 @@ SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, pie_enable, CTLFLAG_RWTUN,
 static int __elfN(aslr_honor_sbrk) = 0;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, honor_sbrk, CTLFLAG_RW,
     &__elfN(aslr_honor_sbrk), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE)) ": assume sbrk is used");
+    ELF_ABI_NAME ": assume sbrk is used");
 
 static int __elfN(aslr_stack) = __ELF_WORD_SIZE == 64;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, stack, CTLFLAG_RWTUN,
     &__elfN(aslr_stack), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
-    ": enable stack address randomization");
+    ELF_ABI_NAME ": enable stack address randomization");
 
 static int __elfN(aslr_shared_page) = __ELF_WORD_SIZE == 64;
 SYSCTL_INT(ASLR_NODE_OID, OID_AUTO, shared_page, CTLFLAG_RWTUN,
     &__elfN(aslr_shared_page), 0,
-    __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
-    ": enable shared page address randomization");
+    ELF_ABI_NAME ": enable shared page address randomization");
 
 static int __elfN(sigfastblock) = 1;
-SYSCTL_INT(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, sigfastblock,
+SYSCTL_INT(ELF_NODE_OID, OID_AUTO, sigfastblock,
     CTLFLAG_RWTUN, &__elfN(sigfastblock), 0,
     "enable sigfastblock for new processes");
 
 static bool __elfN(allow_wx) = true;
-SYSCTL_BOOL(__CONCAT(_kern_elf, __ELF_WORD_SIZE), OID_AUTO, allow_wx,
+SYSCTL_BOOL(ELF_NODE_OID, OID_AUTO, allow_wx,
     CTLFLAG_RWTUN, &__elfN(allow_wx), 0,
     "Allow pages to be mapped simultaneously writable and executable");
 
@@ -2951,9 +2955,9 @@ __elfN(check_note)(struct image_params *imgp, Elf_Brandnote *brandnote,
  */
 static struct execsw __elfN(execsw) = {
 	.ex_imgact = __CONCAT(exec_, __elfN(imgact)),
-	.ex_name = __XSTRING(__CONCAT(ELF, __ELF_WORD_SIZE))
+	.ex_name = ELF_ABI_NAME
 };
-EXEC_SET(__CONCAT(elf, __ELF_WORD_SIZE), __elfN(execsw));
+EXEC_SET(ELF_ABI_ID, __elfN(execsw));
 
 static vm_prot_t
 __elfN(trans_prot)(Elf_Word flags)