From 0132e7fed0ee48dae66607fbccd7c0ab1acea45e Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Thu, 4 Apr 2019 15:21:25 +0200
Subject: [PATCH] pc64: get rid of TSTKTOP, USTKTOP is the end of user address
 space

the temporary stack segment used to be at a fixed address above or
below the user stack. these days, the temp stack is mapped dynamically
by sysexec so TSTKTOP is obsolete.
---
 sys/src/9/pc64/mem.h | 3 +--
 sys/src/9/pc64/mmu.c | 8 ++++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/sys/src/9/pc64/mem.h b/sys/src/9/pc64/mem.h
index e2d93cc4a..42a3a119a 100644
--- a/sys/src/9/pc64/mem.h
+++ b/sys/src/9/pc64/mem.h
@@ -44,9 +44,8 @@
  */
 #define UTZERO		(0x0000000000200000ull)		/* first address in user text */
 #define UADDRMASK	(0x00007fffffffffffull)		/* canonical address mask */
-#define TSTKTOP		(0x00007ffffffff000ull)
+#define USTKTOP		(0x00007ffffffff000ull)
 #define USTKSIZE	(16*MiB)			/* size of user stack */
-#define USTKTOP		(TSTKTOP-USTKSIZE)		/* end of new stack in sysexec */
 
 /*
  *  Address spaces. Kernel, sorted by address.
diff --git a/sys/src/9/pc64/mmu.c b/sys/src/9/pc64/mmu.c
index 02f96d55a..45bc76d40 100644
--- a/sys/src/9/pc64/mmu.c
+++ b/sys/src/9/pc64/mmu.c
@@ -221,12 +221,12 @@ mmucreate(uintptr *table, uintptr va, int level, int index)
 	flags = PTEWRITE|PTEVALID;
 	if(va < VMAP){
 		assert(up != nil);
-		assert((va < TSTKTOP) || (va >= KMAP && va < KMAP+KMAPSIZE));
+		assert((va < USTKTOP) || (va >= KMAP && va < KMAP+KMAPSIZE));
 
 		p = mmualloc();
 		p->index = index;
 		p->level = level;
-		if(va < TSTKTOP){
+		if(va < USTKTOP){
 			flags |= PTEUSER;
 			if(level == PML4E){
 				if((p->next = up->mmuhead) == nil)
@@ -341,9 +341,9 @@ mmuzap(void)
 
 	/* common case */
 	pte[PTLX(UTZERO, 3)] = 0;
-	pte[PTLX(TSTKTOP, 3)] = 0;
+	pte[PTLX(USTKTOP-1, 3)] = 0;
 	m->mmumap[PTLX(UTZERO, 3)/MAPBITS] &= ~(1ull<<(PTLX(UTZERO, 3)%MAPBITS));
-	m->mmumap[PTLX(TSTKTOP, 3)/MAPBITS] &= ~(1ull<<(PTLX(TSTKTOP, 3)%MAPBITS));
+	m->mmumap[PTLX(USTKTOP-1, 3)/MAPBITS] &= ~(1ull<<(PTLX(USTKTOP-1, 3)%MAPBITS));
 
 	for(i = 0; i < nelem(m->mmumap); pte += MAPBITS, i++){
 		if((w = m->mmumap[i]) == 0)