In rtld, read the initial stack access mode from AT_STACKPROT as set

by kernel, and parse PT_GNU_STACK phdr from linked and loaded dsos.

If the loaded dso requires executable stack, as specified by PF_X bit
of p_flags of PT_GNU_STACK phdr, but current stack protection does not
permit execution, the __pthread_map_stacks_exec symbol is looked up
and called. It should be implemented in libc or threading library and
change the protection mode of all thread stacks to be executable.

Provide a private interface _rtld_get_stack_prot() to export the stack
access mode as calculated by rtld.

Reviewed by:	   kan

1 files changed, 1 insertions, 0 deletions

diff --git a/libexec/rtld-elf/Symbol.map b/libexec/rtld-elf/Symbol.map
index 7a8273f..6a416a7 100644
--- a/libexec/rtld-elf/Symbol.map
+++ b/libexec/rtld-elf/Symbol.map
@@ -28,4 +28,5 @@ FBSDprivate_1.0 {
     _rtld_atfork_pre;
     _rtld_atfork_post;
     _rtld_addr_phdr;
+    _rtld_get_stack_prot;
 };