Make MINSIGSTKSZ machine dependent, and have the sigaltstack

syscall compare against a variable sv_minsigstksz in struct
sysentvec as to properly take the size of the machine- and
ABI dependent struct sigframe into account.

The SVR4 and iBCS2 modules continue to have a minsigstksz of
8192 to preserve behavior. The real values (if different) are
not known at this time. Other ABI modules use the real
values.

The native MINSIGSTKSZ is now defined as follows:

Arch		MINSIGSTKSZ
----		-----------
alpha		    4096
i386		    2048
ia64		   12288

Reviewed by: mjacob
Suggested by: bde

3 files changed, 7 insertions, 3 deletions

diff --git a/sys/kern/imgact_aout.c b/sys/kern/imgact_aout.c
index 80ecc0c..e27a80c 100644
--- a/sys/kern/imgact_aout.c
+++ b/sys/kern/imgact_aout.c
@@ -69,7 +69,9 @@ struct sysentvec aout_sysvec = {
 	&szsigcode,
 	0,
 	"FreeBSD a.out",
-	aout_coredump
+	aout_coredump,
+	NULL,
+	MINSIGSTKSZ
 };
 
 static int
diff --git a/sys/kern/imgact_elf.c b/sys/kern/imgact_elf.c
index 069bc9a..9706d67 100644
--- a/sys/kern/imgact_elf.c
+++ b/sys/kern/imgact_elf.c
@@ -99,7 +99,9 @@ struct sysentvec elf_freebsd_sysvec = {
         &szsigcode,
         0,
 	"FreeBSD ELF",
-	elf_coredump
+	elf_coredump,
+	NULL,
+	MINSIGSTKSZ
 };
 
 static Elf_Brandinfo freebsd_brand_info = {
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index 00624d4..af7a32f 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -830,7 +830,7 @@ sigaltstack(p, uap)
 		p->p_sigstk.ss_flags = ss.ss_flags;
 		return (0);
 	}
-	if (ss.ss_size < MINSIGSTKSZ)
+	if (ss.ss_size < p->p_sysent->sv_minsigstksz)
 		return (ENOMEM);
 	p->p_flag |= P_ALTSTACK;
 	p->p_sigstk = ss;