ash: [MEMALLOC] Add pushstackmark

Upstream commit:

    Author: Herbert Xu <herbert@gondor.apana.org.au>
    Date:   Sat Oct 6 00:45:52 2007 +0800

    [MEMALLOC] Add pushstackmark

    This patch gets rid of the stack mark tracking hack by allocating a little
    bit of stack memory if we're at risk of planting a stack mark which may be
    grown later.  To do this a new function pushstackmark is added which lets
    the user pick a bigger amount to allocate since some users do that anyway
    after setting a stack mark.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 19 insertions, 34 deletions

diff --git a/shell/ash.c b/shell/ash.c
index 97f8d9377..f7ce698a3 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -1371,13 +1371,11 @@ struct stackmark {
         struct stack_block *stackp;
         char *stacknxt;
         size_t stacknleft;
-        struct stackmark *marknext;
 };
 
 
 struct globals_memstack {
         struct stack_block *g_stackp; // = &stackbase;
-        struct stackmark *markp;
         char *g_stacknxt; // = stackbase.space;
         char *sstrend; // = stackbase.space + MINSIZE;
         size_t g_stacknleft; // = MINSIZE;
@@ -1387,7 +1385,6 @@ struct globals_memstack {
 extern struct globals_memstack *const ash_ptr_to_globals_memstack;
 #define G_memstack (*ash_ptr_to_globals_memstack)
 #define g_stackp     (G_memstack.g_stackp    )
-#define markp        (G_memstack.markp       )
 #define g_stacknxt   (G_memstack.g_stacknxt  )
 #define sstrend      (G_memstack.sstrend     )
 #define g_stacknleft (G_memstack.g_stacknleft)
@@ -1478,13 +1475,26 @@ sstrdup(const char *p)
 }
 
 static void
-setstackmark(struct stackmark *mark)
+grabstackblock(size_t len)
+{
+        len = SHELL_ALIGN(len);
+        g_stacknxt += len;
+        g_stacknleft -= len;
+}
+
+static void
+pushstackmark(struct stackmark *mark, size_t len)
 {
         mark->stackp = g_stackp;
         mark->stacknxt = g_stacknxt;
         mark->stacknleft = g_stacknleft;
-        mark->marknext = markp;
-        markp = mark;
+        grabstackblock(len);
+}
+
+static void
+setstackmark(struct stackmark *mark)
+{
+        pushstackmark(mark, g_stacknxt == g_stackp->space && g_stackp != &stackbase);
 }
 
 static void
@@ -1496,7 +1506,6 @@ popstackmark(struct stackmark *mark)
                 return;
 
         INT_OFF;
-        markp = mark->marknext;
         while (g_stackp != mark->stackp) {
                 sp = g_stackp;
                 g_stackp = sp->prev;
@@ -1530,7 +1539,6 @@ growstackblock(void)
 
         if (g_stacknxt == g_stackp->space && g_stackp != &stackbase) {
                 struct stack_block *oldstackp;
-                struct stackmark *xmark;
                 struct stack_block *sp;
                 struct stack_block *prevstackp;
                 size_t grosslen;
@@ -1546,18 +1554,6 @@ growstackblock(void)
                 g_stacknxt = sp->space;
                 g_stacknleft = newlen;
                 sstrend = sp->space + newlen;
-
-                /*
-                 * Stack marks pointing to the start of the old block
-                 * must be relocated to point to the new block
-                 */
-                xmark = markp;
-                while (xmark != NULL && xmark->stackp == oldstackp) {
-                        xmark->stackp = g_stackp;
-                        xmark->stacknxt = g_stacknxt;
-                        xmark->stacknleft = g_stacknleft;
-                        xmark = xmark->marknext;
-                }
                 INT_ON;
         } else {
                 char *oldspace = g_stacknxt;
@@ -1570,14 +1566,6 @@ growstackblock(void)
         }
 }
 
-static void
-grabstackblock(size_t len)
-{
-        len = SHELL_ALIGN(len);
-        g_stacknxt += len;
-        g_stacknleft -= len;
-}
-
 /*
  * The following routines are somewhat easier to use than the above.
  * The user declares a variable of type STACKSTR, which may be declared
@@ -2482,8 +2470,7 @@ setprompt_if(smallint do_set, int whichprompt)
                 prompt = nullstr;
         }
 #if ENABLE_ASH_EXPAND_PRMT
-        setstackmark(&smark);
-        stalloc(stackblocksize());
+        pushstackmark(&smark, stackblocksize());
 #endif
         putprompt(expandstr(prompt));
 #if ENABLE_ASH_EXPAND_PRMT
@@ -5938,10 +5925,8 @@ expbackq(union node *cmd, int flag)
         struct stackmark smark;
 
         INT_OFF;
-        setstackmark(&smark);
-        dest = expdest;
-        startloc = dest - (char *)stackblock();
-        grabstackstr(dest);
+        startloc = expdest - (char *)stackblock();
+        pushstackmark(&smark, startloc);
         evalbackcmd(cmd, &in);
         popstackmark(&smark);