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

4 files changed, 10 insertions, 6 deletions

diff --git a/sys/amd64/amd64/elf_machdep.c b/sys/amd64/amd64/elf_machdep.c
index 6472d55..4344731 100644
--- a/sys/amd64/amd64/elf_machdep.c
+++ b/sys/amd64/amd64/elf_machdep.c
@@ -75,11 +75,14 @@ struct sysentvec elf64_freebsd_sysvec = {
 	.sv_setregs	= exec_setregs,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_FREEBSD | SV_LP64,
+	.sv_flags	= SV_ABI_FREEBSD | SV_LP64 | SV_SHP,
 	.sv_set_syscall_retval = cpu_set_syscall_retval,
 	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
 	.sv_syscallnames = syscallnames,
+	.sv_shared_page_base = SHAREDPAGE,
+	.sv_shared_page_len = PAGE_SIZE,
 };
+INIT_SYSENTVEC(elf64_sysvec, &elf64_freebsd_sysvec);
 
 static Elf64_Brandinfo freebsd_brand_info = {
 	.brand		= ELFOSABI_FREEBSD,
@@ -129,7 +132,6 @@ SYSINIT(kelf64, SI_SUB_EXEC, SI_ORDER_ANY,
 	(sysinit_cfunc_t) elf64_insert_brand_entry,
 	&kfreebsd_brand_info);
 
-
 void
 elf64_dump_thread(struct thread *td __unused, void *dst __unused,
     size_t *off __unused)
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 6c946e6..72e0fd7 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -386,7 +386,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 	}
 
 	regs->tf_rsp = (long)sfp;
-	regs->tf_rip = PS_STRINGS - *(p->p_sysent->sv_szsigcode);
+	regs->tf_rip = p->p_sysent->sv_sigcode_base;
 	regs->tf_rflags &= ~(PSL_T | PSL_D);
 	regs->tf_cs = _ucodesel;
 	regs->tf_ds = _udatasel;
diff --git a/sys/amd64/ia32/ia32_signal.c b/sys/amd64/ia32/ia32_signal.c
index 808790b..91884d2 100644
--- a/sys/amd64/ia32/ia32_signal.c
+++ b/sys/amd64/ia32/ia32_signal.c
@@ -393,7 +393,8 @@ freebsd4_ia32_sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 	}
 
 	regs->tf_rsp = (uintptr_t)sfp;
-	regs->tf_rip = p->p_sysent->sv_psstrings - sz_freebsd4_ia32_sigcode;
+	regs->tf_rip = p->p_sysent->sv_sigcode_base + sz_ia32_sigcode -
+	    sz_freebsd4_ia32_sigcode;
 	regs->tf_rflags &= ~(PSL_T | PSL_D);
 	regs->tf_cs = _ucode32sel;
 	regs->tf_ss = _udatasel;
@@ -514,7 +515,7 @@ ia32_sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 	}
 
 	regs->tf_rsp = (uintptr_t)sfp;
-	regs->tf_rip = p->p_sysent->sv_psstrings - *(p->p_sysent->sv_szsigcode);
+	regs->tf_rip = p->p_sysent->sv_sigcode_base;
 	regs->tf_rflags &= ~(PSL_T | PSL_D);
 	regs->tf_cs = _ucode32sel;
 	regs->tf_ss = _udatasel;
diff --git a/sys/amd64/include/vmparam.h b/sys/amd64/include/vmparam.h
index 7a50c59..88d68b9 100644
--- a/sys/amd64/include/vmparam.h
+++ b/sys/amd64/include/vmparam.h
@@ -186,7 +186,8 @@
 
 #define	VM_MAXUSER_ADDRESS	UVADDR(NUPML4E, 0, 0, 0)
 
-#define	USRSTACK		VM_MAXUSER_ADDRESS
+#define	SHAREDPAGE		(VM_MAXUSER_ADDRESS - PAGE_SIZE)
+#define	USRSTACK		SHAREDPAGE
 
 #define	VM_MAX_ADDRESS		UPT_MAX_ADDRESS
 #define	VM_MIN_ADDRESS		(0)