Make the 'env' directive described in config(5) work on all architectures,

providing compiled-in static environment data that is used instead of any
data passed in from a boot loader.

Previously 'env' worked only on i386 and arm xscale systems, because it
required the MD startup code to examine the global envmode variable and
decide whether to use static_env or an environment obtained from the boot
loader, and set the global kern_envp accordingly.  Most startup code wasn't
doing so.  Making things even more complex, some mips startup code uses an
alternate scheme that involves calling init_static_kenv() to pass an empty
buffer and its size, then uses a series of kern_setenv() calls to populate
that buffer.

Now all MD startup code calls init_static_kenv(), and that routine provides
a single point where envmode is checked and the decision is made whether to
use the compiled-in static_kenv or the values provided by the MD code.

The routine also continues to serve its original purpose for mips; if a
non-zero buffer size is passed the routine installs the empty buffer ready
to accept kern_setenv() values.  Now if the size is zero, the provided buffer
full of existing env data is installed.  A NULL pointer can be passed if the
boot loader provides no env data; this allows the static env to be installed
if envmode is set to do so.

Most of the work here is a near-mechanical change to call the init function
instead of directly setting kern_envp.  A notable exception is in xen/pv.c;
that code was originally installing a buffer full of preformatted env data
along with its non-zero size (like mips code does), which would have allowed
kern_setenv() calls to wipe out the preformatted data.  Now it passes a zero
for the size so that the buffer of data it installs is treated as
non-writeable.

sys/amd64/amd64/machdep.c

@@ -1484,6 +1484,7 @@ static caddr_t
 native_parse_preload_data(u_int64_t modulep)
 {
 	caddr_t kmdp;
+	char *envp;
 #ifdef DDB
 	vm_offset_t ksym_start;
 	vm_offset_t ksym_end;
@@ -1495,7 +1496,10 @@ native_parse_preload_data(u_int64_t modulep)
 	if (kmdp == NULL)
 		kmdp = preload_search_by_type("elf64 kernel");
 	boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-	kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *) + KERNBASE;
+	envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+	if (envp != NULL)
+		envp += KERNBASE;
+	init_static_kenv(envp, 0);
 #ifdef DDB
 	ksym_start = MD_FETCH(kmdp, MODINFOMD_SSYM, uintptr_t);
 	ksym_end = MD_FETCH(kmdp, MODINFOMD_ESYM, uintptr_t);

sys/arm/arm/machdep.c

@@ -1002,6 +1002,8 @@ fake_preload_metadata(struct arm_boot_params *abp __unused)
 	fake_preload[i] = 0;
 	preload_metadata = (void *)fake_preload;
 
+	init_static_kenv(NULL, 0);
+
 	return (lastaddr);
 }
 
@@ -1074,6 +1076,8 @@ linux_parse_boot_param(struct arm_boot_params *abp)
 	bcopy(atag_list, atags,
 	    (char *)walker - (char *)atag_list + ATAG_SIZE(walker));
 
+	init_static_kenv(NULL, 0);
+
 	return fake_preload_metadata(abp);
 }
 #endif
@@ -1106,7 +1110,7 @@ freebsd_parse_boot_param(struct arm_boot_params *abp)
 		return 0;
 
 	boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-	kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+	init_static_kenv(MD_FETCH(kmdp, MODINFOMD_ENVP, char *), 0);
 	lastaddr = MD_FETCH(kmdp, MODINFOMD_KERNEND, vm_offset_t);
 #ifdef DDB
 	ksym_start = MD_FETCH(kmdp, MODINFOMD_SSYM, uintptr_t);

sys/arm/xscale/ixp425/avila_machdep.c

@@ -225,8 +225,8 @@ initarm(struct arm_boot_params *abp)
 	pcpu_init(pcpup, 0, sizeof(struct pcpu));
 	PCPU_SET(curthread, &thread0);
 
-	if (envmode == 1)
-		kern_envp = static_env;
+	init_static_kenv(NULL, 0);
+
 	/* Do basic tuning, hz etc */
       	init_param1();
 		
@@ -426,10 +426,6 @@ initarm(struct arm_boot_params *abp)
 	init_param2(physmem);
 	kdb_init();
 
-	/* use static kernel environment if so configured */
-	if (envmode == 1)
-		kern_envp = static_env;
-
 	return ((void *)(kernelstack.pv_va + USPACE_SVC_STACK_TOP -
 	    sizeof(struct pcb)));
 #undef next_page

sys/arm64/arm64/machdep.c

@@ -820,7 +820,7 @@ initarm(struct arm64_bootparams *abp)
 		kmdp = preload_search_by_type("elf64 kernel");
 
 	boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-	kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+	init_static_kenv(MD_FETCH(kmdp, MODINFOMD_ENVP, char *), 0);
 
 #ifdef FDT
 	try_load_dtb(kmdp);

sys/boot/Makefile.arm

@@ -5,3 +5,10 @@ SUBDIR+=		fdt
 .endif
 
 SUBDIR+=		efi uboot
+
+# Do not generate movt/movw, because the relocation fixup for them does not
+# translate to the -Bsymbolic -pie format required by self_reloc() in loader(8).
+# Also, the fpu is not available in a standalone environment.
+CFLAGS.clang+=	-mllvm -arm-use-movt=0
+CFLAGS.clang+=	-mfpu=none
+.export: CFLAGS.clang

sys/i386/i386/machdep.c

@@ -2462,10 +2462,11 @@ init386(first)
 	} else {
 		metadata_missing = 1;
 	}
-	if (envmode == 1)
-		kern_envp = static_env;
-	else if (bootinfo.bi_envp)
-		kern_envp = (caddr_t)bootinfo.bi_envp + KERNBASE;
+
+	if (bootinfo.bi_envp)
+		init_static_kenv((caddr_t)bootinfo.bi_envp + KERNBASE, 0);
+	else
+		init_static_kenv(NULL, 0);
 
 	/* Init basic tunables, hz etc */
 	init_param1();

sys/kern/kern_environment.c

@@ -210,12 +210,44 @@ sys_kenv(td, uap)
 	return (error);
 }
 
+/*
+ * Populate the initial kernel environment.
+ *
+ * This is called very early in MD startup, either to provide a copy of the
+ * environment obtained from a boot loader, or to provide an empty buffer into
+ * which MD code can store an initial environment using kern_setenv() calls.
+ *
+ * If the global envmode is 1, the environment is initialized from the global
+ * static_env[], regardless of the arguments passed.  This implements the env
+ * keyword described in config(5).  In this case env_pos is set to env_len,
+ * causing kern_setenv() to return -1 (if len > 0) or panic (if len == 0) until
+ * the dynamic environment is available.  The envmode and static_env variables
+ * are defined in env.c which is generated by config(8).
+ *
+ * If len is non-zero, the caller is providing an empty buffer.  The caller will
+ * subsequently use kern_setenv() to add up to len bytes of initial environment
+ * before the dynamic environment is available.
+ *
+ * If len is zero, the caller is providing a pre-loaded buffer containing
+ * environment strings.  Additional strings cannot be added until the dynamic
+ * environment is available.  The memory pointed to must remain stable at least
+ * until sysinit runs init_dynamic_kenv().  If no initial environment is
+ * available from the boot loader, passing a NULL pointer allows the static_env
+ * to be installed if it is configured.
+ */
 void
 init_static_kenv(char *buf, size_t len)
 {
-	kern_envp = buf;
-	env_len = len;
-	env_pos = 0;
+
+	if (envmode == 1) {
+		kern_envp = static_env;
+		env_len = len;
+		env_pos = len;
+	} else {
+		kern_envp = buf;
+		env_len = len;
+		env_pos = 0;
+	}
 }
 
 /*

sys/mips/beri/beri_machdep.c

@@ -273,7 +273,7 @@ platform_start(__register_t a0, __register_t a1,  __register_t a2,
 	 * Configure more boot-time parameters passed in by loader.
 	 */
 	boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-	kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+	init_static_kenv(MD_FETCH(kmdp, MODINFOMD_ENVP, char *), 0);
 
 	/*
 	 * Get bootargs from FDT if specified.

sys/powerpc/powerpc/machdep.c

@@ -261,7 +261,8 @@ powerpc_init(vm_offset_t fdt, vm_offset_t toc, vm_offset_t ofentry, void *mdp)
 		kmdp = preload_search_by_type("elf kernel");
 		if (kmdp != NULL) {
 			boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-			kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+			init_static_kenv(MD_FETCH(kmdp, MODINFOMD_ENVP, char *),
+			    0);
 			endkernel = ulmax(endkernel, MD_FETCH(kmdp,
 			    MODINFOMD_KERNEND, vm_offset_t));
 #ifdef DDB

sys/sparc64/sparc64/machdep.c

@@ -379,7 +379,8 @@ sparc64_init(caddr_t mdp, u_long o1, u_long o2, u_long o3, ofw_vec_t *vec)
 		kmdp = preload_search_by_type("elf kernel");
 		if (kmdp != NULL) {
 			boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-			kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+			init_static_kenv(MD_FETCH(kmdp, MODINFOMD_ENVP, char *),
+			    0);
 			end = MD_FETCH(kmdp, MODINFOMD_KERNEND, vm_offset_t);
 			kernel_tlb_slots = MD_FETCH(kmdp, MODINFOMD_DTLB_SLOTS,
 			    int);

sys/x86/xen/pv.c

@@ -296,7 +296,7 @@ xen_pv_set_env(void)
 	for (cmd_line_next = cmd_line; strsep(&cmd_line_next, ",") != NULL;)
 		;
 
-	init_static_kenv(cmd_line, env_size);
+	init_static_kenv(cmd_line, 0);
 }
 
 static void
@@ -382,6 +382,7 @@ xen_pv_parse_preload_data(u_int64_t modulep)
 	caddr_t		 kmdp;
 	vm_ooffset_t	 off;
 	vm_paddr_t	 metadata;
+	char             *envp;
 
 	if (HYPERVISOR_start_info->mod_start != 0) {
 		preload_metadata = (caddr_t)(HYPERVISOR_start_info->mod_start);
@@ -404,8 +405,10 @@ xen_pv_parse_preload_data(u_int64_t modulep)
 		preload_bootstrap_relocate(off);
 
 		boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
-		kern_envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
-		kern_envp += off;
+		envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
+		if (envp != NULL)
+			envp += off;
+		init_static_kenv(envp, 0);
 	} else {
 		/* Parse the extra boot information given by Xen */
 		xen_pv_set_env();