Create shared (readonly) page. Each ABI may specify the use of page by

setting SV_SHP flag and providing pointer to the vm object and mapping
address. Provide simple allocator to carve space in the page, tailored
to put the code with alignment restrictions.

Enable shared page use for amd64, both native and 32bit FreeBSD
binaries.  Page is private mapped at the top of the user address
space, moving a start of the stack one page down. Move signal
trampoline code from the top of the stack to the shared page.

Reviewed by:	 alc

1 files changed, 12 insertions, 0 deletions

diff --git a/sys/sys/sysent.h b/sys/sys/sysent.h
index e726fce..55cac2b 100644
--- a/sys/sys/sysent.h
+++ b/sys/sys/sysent.h
@@ -116,12 +116,17 @@ struct sysentvec {
 	int		(*sv_fetch_syscall_args)(struct thread *, struct
 			    syscall_args *);
 	const char	**sv_syscallnames;
+	vm_offset_t	sv_shared_page_base;
+	vm_offset_t	sv_shared_page_len;
+	vm_offset_t	sv_sigcode_base;
+	void		*sv_shared_page_obj;
 };
 
 #define	SV_ILP32	0x000100
 #define	SV_LP64		0x000200
 #define	SV_IA32		0x004000
 #define	SV_AOUT		0x008000
+#define	SV_SHP		0x010000
 
 #define	SV_ABI_MASK	0xff
 #define	SV_CURPROC_FLAG(x) (curproc->p_sysent->sv_flags & (x))
@@ -222,6 +227,13 @@ int	lkmressys(struct thread *, struct nosys_args *);
 int	syscall_thread_enter(struct thread *td, struct sysent *se);
 void	syscall_thread_exit(struct thread *td, struct sysent *se);
 
+int shared_page_fill(int size, int align, const char *data);
+void exec_sysvec_init(void *param);
+
+#define INIT_SYSENTVEC(name, sv)					\
+    SYSINIT(name, SI_SUB_EXEC, SI_ORDER_ANY,				\
+	(sysinit_cfunc_t)exec_sysvec_init, sv);
+
 #endif /* _KERNEL */
 
 #endif /* !_SYS_SYSENT_H_ */