From b4924fbf83604538d55749f84455609e996af642 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Wed, 15 Apr 2015 08:13:53 +0000
Subject: [PATCH] Implement support for binary to requesting specific stack
 size for the initial thread.  It is read by the ELF image activator as the
 virtual size of the PT_GNU_STACK program header entry, and can be specified
 by the linker option -z stack-size in newer binutils.

The soft RLIMIT_STACK is auto-increased if possible, to satisfy the
binary' request.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
---
 sys/kern/imgact_elf.c    |  1 +
 sys/kern/kern_exec.c     | 17 +++++++++++++++--
 sys/kern/kern_resource.c |  7 ++++++-
 sys/sys/imgact.h         |  1 +
 4 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 0a8b79a4a927..39e4df3156d2 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -782,6 +782,7 @@ __CONCAT(exec_, __elfN(imgact))(struct image_params *imgp)
 			if (__elfN(nxstack))
 				imgp->stack_prot =
 				    __elfN(trans_prot)(phdr[i].p_flags);
+			imgp->stack_sz = phdr[i].p_memsz;
 			break;
 		}
 	}
diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index 388ed196bb69..ecc2651da32d 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -1009,6 +1009,7 @@ exec_new_vmspace(imgp, sv)
 	struct proc *p = imgp->proc;
 	struct vmspace *vmspace = p->p_vmspace;
 	vm_object_t obj;
+	struct rlimit rlim_stack;
 	vm_offset_t sv_minuser, stack_addr;
 	vm_map_t map;
 	u_long ssiz;
@@ -1058,10 +1059,22 @@ exec_new_vmspace(imgp, sv)
 	}
 
 	/* Allocate a new stack */
-	if (sv->sv_maxssiz != NULL)
+	if (imgp->stack_sz != 0) {
+		ssiz = imgp->stack_sz;
+		PROC_LOCK(p);
+		lim_rlimit(p, RLIMIT_STACK, &rlim_stack);
+		PROC_UNLOCK(p);
+		if (ssiz > rlim_stack.rlim_max)
+			ssiz = rlim_stack.rlim_max;
+		if (ssiz > rlim_stack.rlim_cur) {
+			rlim_stack.rlim_cur = ssiz;
+			kern_setrlimit(curthread, RLIMIT_STACK, &rlim_stack);
+		}
+	} else if (sv->sv_maxssiz != NULL) {
 		ssiz = *sv->sv_maxssiz;
-	else
+	} else {
 		ssiz = maxssiz;
+	}
 	stack_addr = sv->sv_usrstack - ssiz;
 	error = vm_map_stack(map, stack_addr, (vm_size_t)ssiz,
 	    obj != NULL && imgp->stack_prot != 0 ? imgp->stack_prot :
diff --git a/sys/kern/kern_resource.c b/sys/kern/kern_resource.c
index 56b598f4be18..dac49cd5fe3b 100644
--- a/sys/kern/kern_resource.c
+++ b/sys/kern/kern_resource.c
@@ -745,7 +745,12 @@ kern_proc_setrlimit(struct thread *td, struct proc *p, u_int which,
 	if (newlim != NULL)
 		lim_free(oldlim);
 
-	if (which == RLIMIT_STACK) {
+	if (which == RLIMIT_STACK &&
+	    /*
+	     * Skip calls from exec_new_vmspace(), done when stack is
+	     * not mapped yet.
+	     */
+	    (td != curthread || (p->p_flag & P_INEXEC) == 0)) {
 		/*
 		 * Stack is allocated to the max at exec time with only
 		 * "rlim_cur" bytes accessible.  If stack limit is going
diff --git a/sys/sys/imgact.h b/sys/sys/imgact.h
index 844093937352..ac88a149cb81 100644
--- a/sys/sys/imgact.h
+++ b/sys/sys/imgact.h
@@ -80,6 +80,7 @@ struct image_params {
 	unsigned long pagesizes;
 	int pagesizeslen;
 	vm_prot_t stack_prot;
+	u_long stack_sz;
 };
 
 #ifdef _KERNEL