Do not set a default ELF syscall ABI fallback.

If one runs an un-branded Linux static binary that calls Linux's fcntl
the machine will reboot when interupted by the FreeBSD syscall ABI.

2 files changed, 8 insertions, 6 deletions

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 553ef75..f35f864 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -438,9 +438,12 @@ fail:
 	return error;
 }
 
-static int fallback_elf_brand = ELFOSABI_FREEBSD;
+/*
+ * non static, as it can be overridden by start_init()
+ */
+int fallback_elf_brand = -1;
 SYSCTL_INT(_kern, OID_AUTO, fallback_elf_brand, CTLFLAG_RW,
-		&fallback_elf_brand, ELFOSABI_FREEBSD,
+		&fallback_elf_brand, -1,
 		"ELF brand of last resort");
 
 static int
@@ -612,10 +615,6 @@ exec_elf_imgact(struct image_params *imgp)
 		}
 	}
 
-	/* XXX - Assume FreeBSD after the branding method change. */
-	if (brand_info == NULL)
-		brand_info = &freebsd_brand_info;
-
 	if (brand_info == NULL) {
 		uprintf("ELF binary type \"%u\" not known.\n",
 		    hdr->e_ident[EI_OSABI]);
diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 021e813..8ef28a1 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -93,6 +93,7 @@ struct	proc *initproc;
 
 int cmask = CMASK;
 extern	struct user *proc0paddr;
+extern int fallback_elf_brand;
 
 struct	vnode *rootvp;
 int	boothowto = 0;		/* initialized so that it can be patched */
@@ -480,6 +481,8 @@ start_init(void *dummy)
 		strncpy(init_path, var, sizeof init_path);
 		init_path[sizeof init_path - 1] = 0;
 	}
+	if ((var = getenv("kern.fallback_elf_brand")) != NULL)
+		fallback_elf_brand = strtol(var, NULL, 0);
 	
 	for (path = init_path; *path != '\0'; path = next) {
 		while (*path == ':')