attack the biggest stack users:

-mkfs_minix_main [busybox_unstripped]:                  4288
-mkfs_minix_main [busybox_unstripped]:                  4276
-grave [busybox_unstripped]:                            4260
(bzip2 users too - not listed)

price we pay in code size increase:
mainSort                                            2458    2515     +57
grave                                               1005    1058     +53
sendMTFValues                                       2177    2195     +18
BZ2_blockSort                                        122     125      +3
mkfs_minix_main                                     3070    3022     -48
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/1 up/down: 131/-48)            Total: 83 bytes

Makefile.custom

@@ -90,7 +90,7 @@ objsizes: busybox_unstripped
 
 .PHONY: stksizes
 stksizes: busybox_unstripped
-	$(CROSS_COMPILE)objdump -d busybox_unstripped | $(srctree)/scripts/checkstack.pl $(ARCH)
+	$(CROSS_COMPILE)objdump -d busybox_unstripped | $(srctree)/scripts/checkstack.pl $(ARCH) | uniq
 
 .PHONY: bigdata
 bigdata: busybox_unstripped

archival/bz/blocksort.c

@@ -721,7 +721,8 @@ void mainQSort3(uint32_t* ptr,
 #define CLEARMASK (~(SETMASK))
 
 static NOINLINE
-void mainSort(uint32_t*   ptr,
+void mainSort(EState* state,
+		uint32_t* ptr,
 		uint8_t*  block,
 		uint16_t* quadrant,
 		uint32_t* ftab,
@@ -729,13 +730,18 @@ void mainSort(uint32_t*   ptr,
 		int32_t*  budget)
 {
 	int32_t  i, j, k, ss, sb;
-	int32_t  runningOrder[256];
-	Bool     bigDone[256];
-	int32_t  copyStart[256];
-	int32_t  copyEnd  [256];
 	uint8_t  c1;
 	int32_t  numQSorted;
 	uint16_t s;
+	Bool     bigDone[256];
+	/* bbox: moved to EState to save stack
+	int32_t  runningOrder[256];
+	int32_t  copyStart[256];
+	int32_t  copyEnd  [256];
+	*/
+#define runningOrder (state->mainSort__runningOrder)
+#define copyStart    (state->mainSort__copyStart)
+#define copyEnd      (state->mainSort__copyEnd)
 
 	/*-- set up the 2-byte frequency table --*/
 	/* was: for (i = 65536; i >= 0; i--) ftab[i] = 0; */
@@ -985,6 +991,9 @@ void mainSort(uint32_t*   ptr,
 			AssertH(((bbSize-1) >> shifts) <= 65535, 1002);
 		}
 	}
+#undef runningOrder
+#undef copyStart
+#undef copyEnd
 }
 
 #undef BIGFREQ
@@ -1041,7 +1050,7 @@ void BZ2_blockSort(EState* s)
 		 */
 		budget = nblock * ((wfact-1) / 3);
 
-		mainSort(ptr, block, quadrant, ftab, nblock, &budget);
+		mainSort(s, ptr, block, quadrant, ftab, nblock, &budget);
 		if (budget < 0) {
 			fallbackSort(s->arr1, s->arr2, ftab, nblock);
 		}

archival/bz/bzlib_private.h

@@ -178,13 +178,22 @@ typedef struct EState {
 	uint8_t  selector   [BZ_MAX_SELECTORS];
 	uint8_t  selectorMtf[BZ_MAX_SELECTORS];
 
-	uint8_t  len  [BZ_N_GROUPS][BZ_MAX_ALPHA_SIZE];
+	uint8_t  len[BZ_N_GROUPS][BZ_MAX_ALPHA_SIZE];
-	int32_t  code [BZ_N_GROUPS][BZ_MAX_ALPHA_SIZE];
+
-	int32_t  rfreq[BZ_N_GROUPS][BZ_MAX_ALPHA_SIZE];
+	/* stack-saving measures: these can be local, but they are too big */
+	int32_t  sendMTFValues__code [BZ_N_GROUPS][BZ_MAX_ALPHA_SIZE];
+	int32_t  sendMTFValues__rfreq[BZ_N_GROUPS][BZ_MAX_ALPHA_SIZE];
 #if CONFIG_BZIP2_FEATURE_SPEED >= 5
 	/* second dimension: only 3 needed; 4 makes index calculations faster */
-	uint32_t len_pack[BZ_MAX_ALPHA_SIZE][4];
+	uint32_t sendMTFValues__len_pack[BZ_MAX_ALPHA_SIZE][4];
 #endif
+	int32_t  BZ2_hbMakeCodeLengths__heap  [BZ_MAX_ALPHA_SIZE + 2];
+	int32_t  BZ2_hbMakeCodeLengths__weight[BZ_MAX_ALPHA_SIZE * 2];
+	int32_t  BZ2_hbMakeCodeLengths__parent[BZ_MAX_ALPHA_SIZE * 2];
+
+	int32_t  mainSort__runningOrder[256];
+	int32_t  mainSort__copyStart[256];
+	int32_t  mainSort__copyEnd[256];
 } EState;
 
 
@@ -203,7 +212,7 @@ static void
 BZ2_hbAssignCodes(int32_t*, uint8_t*, int32_t, int32_t, int32_t);
 
 static void
-BZ2_hbMakeCodeLengths(uint8_t*, int32_t*, int32_t, int32_t);
+BZ2_hbMakeCodeLengths(EState*, uint8_t*, int32_t*, int32_t, int32_t);
 
 /*-------------------------------------------------------------*/
 /*--- end                                   bzlib_private.h ---*/

archival/bz/compress.c

@@ -264,13 +264,16 @@ void sendMTFValues(EState* s)
 	 * are also globals only used in this proc.
 	 * Made global to keep stack frame size small.
 	 */
+#define code     sendMTFValues__code
+#define rfreq    sendMTFValues__rfreq
+#define len_pack sendMTFValues__len_pack
 
 	uint16_t cost[BZ_N_GROUPS];
 	int32_t  fave[BZ_N_GROUPS];
 
 	uint16_t* mtfv = s->mtfv;
 
-	alphaSize = s->nInUse+2;
+	alphaSize = s->nInUse + 2;
 	for (t = 0; t < BZ_N_GROUPS; t++)
 		for (v = 0; v < alphaSize; v++)
 			s->len[t][v] = BZ_GREATER_ICOST;
@@ -453,7 +456,7 @@ void sendMTFValues(EState* s)
 		/* maxLen was changed from 20 to 17 in bzip2-1.0.3.  See
 		 * comment in huffman.c for details. */
 		for (t = 0; t < nGroups; t++)
-			BZ2_hbMakeCodeLengths(&(s->len[t][0]), &(s->rfreq[t][0]), alphaSize, 17 /*20*/);
+			BZ2_hbMakeCodeLengths(s, &(s->len[t][0]), &(s->rfreq[t][0]), alphaSize, 17 /*20*/);
 	}
 
 	AssertH(nGroups < 8, 3002);
@@ -602,6 +605,9 @@ void sendMTFValues(EState* s)
 		selCtr++;
 	}
 	AssertH(selCtr == nSelectors, 3007);
+#undef code
+#undef rfreq
+#undef len_pack
 }
 
 

archival/bz/huffman.c

@@ -98,7 +98,8 @@ void DOWNHEAP1(int32_t *heap, int32_t *weight, int32_t nHeap)
 
 /*---------------------------------------------------*/
 static
-void BZ2_hbMakeCodeLengths(uint8_t *len,
+void BZ2_hbMakeCodeLengths(EState *s,
+		uint8_t *len,
 		int32_t *freq,
 		int32_t alphaSize,
 		int32_t maxLen)
@@ -110,9 +111,14 @@ void BZ2_hbMakeCodeLengths(uint8_t *len,
 	int32_t nNodes, nHeap, n1, n2, i, j, k;
 	Bool  tooLong;
 
+	/* bbox: moved to EState to save stack
 	int32_t heap  [BZ_MAX_ALPHA_SIZE + 2];
 	int32_t weight[BZ_MAX_ALPHA_SIZE * 2];
 	int32_t parent[BZ_MAX_ALPHA_SIZE * 2];
+	*/
+#define heap   (s->BZ2_hbMakeCodeLengths__heap)
+#define weight (s->BZ2_hbMakeCodeLengths__weight)
+#define parent (s->BZ2_hbMakeCodeLengths__parent)
 
 	for (i = 0; i < alphaSize; i++)
 		weight[i+1] = (freq[i] == 0 ? 1 : freq[i]) << 8;
@@ -189,6 +195,9 @@ void BZ2_hbMakeCodeLengths(uint8_t *len,
 			weight[i] = j << 8;
 		}
 	}
+#undef heap
+#undef weight
+#undef parent
 }
 
 

scripts/checkstack.pl

@@ -126,7 +126,8 @@ while (my $line = <STDIN>) {
 		$addr =~ s/ /0/g;
 		$addr = "0x$addr";
 
-		my $intro = "$addr $func [$file]:";
+		# bbox: was: my $intro = "$addr $func [$file]:";
+		my $intro = "$func [$file]:";
 		my $padlen = 56 - length($intro);
 		while ($padlen > 0) {
 			$intro .= '	';

shell/msh.c

@@ -735,6 +735,9 @@ struct globals {
 	char filechar_cmdbuf[BUFSIZ];
 	char line[LINELIM];
 	char child_cmd[LINELIM];
+
+	char grave__var_name[LINELIM];
+	char grave__alt_value[LINELIM];
 };
 
 #define G (*ptr_to_globals)
@@ -746,6 +749,9 @@ struct globals {
 #define filechar_cmdbuf (G.filechar_cmdbuf)
 #define line            (G.line           )
 #define child_cmd       (G.child_cmd      )
+#define INIT_G() do { \
+	PTR_TO_GLOBALS = xzalloc(sizeof(G)); \
+} while (0)
 
 
 #ifdef MSHDEBUG
@@ -4042,8 +4048,12 @@ static int grave(int quoted)
 			ignore_once = 1;
 		if (*src == '$' && !ignore && !ignore_once) {
 			struct var *vp;
+			/* moved to G to reduce stack usage
 			char var_name[LINELIM];
 			char alt_value[LINELIM];
+			*/
+#define var_name (G.grave__var_name)
+#define alt_value (G.grave__alt_value)
 			int var_index = 0;
 			int alt_index = 0;
 			char operator = 0;
@@ -4131,6 +4141,8 @@ static int grave(int quoted)
 					count++;
 				}
 			}
+#undef var_name
+#undef alt_value
 		} else {
 			*dest++ = *src++;
 			count++;
@@ -5173,7 +5185,8 @@ int msh_main(int argc, char **argv)
 	char *name, **ap;
 	int (*iof) (struct ioarg *);
 
-	PTR_TO_GLOBALS = xzalloc(sizeof(G));
+	INIT_G();
+
 	sharedbuf.id = AFID_NOBUF;
 	mainbuf.id = AFID_NOBUF;
 	e.linep = line;

util-linux/mkfs_minix.c

@@ -109,16 +109,22 @@ struct globals {
 	unsigned long req_nr_inodes;
 	unsigned currently_testing;
 
-
 	char root_block[BLOCK_SIZE];
 	char super_block_buffer[BLOCK_SIZE];
 	char boot_block_buffer[512];
 	unsigned short good_blocks_table[MAX_GOOD_BLOCKS];
 	/* check_blocks(): buffer[] was the biggest static in entire bbox */
 	char check_blocks_buffer[BLOCK_SIZE * TEST_BUFFER_BLOCKS];
-};
 
+	unsigned short ind_block1[BLOCK_SIZE >> 1];
+	unsigned short dind_block1[BLOCK_SIZE >> 1];
+	unsigned long ind_block2[BLOCK_SIZE >> 2];
+	unsigned long dind_block2[BLOCK_SIZE >> 2];
+};
 #define G (*ptr_to_globals)
+#define INIT_G() do { \
+	PTR_TO_GLOBALS = xzalloc(sizeof(G)); \
+} while (0)
 
 static ALWAYS_INLINE unsigned div_roundup(unsigned size, unsigned n)
 {
@@ -306,8 +312,12 @@ static void make_bad_inode(void)
 	struct minix1_inode *inode = &INODE_BUF1[MINIX_BAD_INO];
 	int i, j, zone;
 	int ind = 0, dind = 0;
+	/* moved to globals to reduce stack usage
 	unsigned short ind_block[BLOCK_SIZE >> 1];
 	unsigned short dind_block[BLOCK_SIZE >> 1];
+	*/
+#define ind_block (G.ind_block1)
+#define dind_block (G.dind_block1)
 
 #define NEXT_BAD (zone = next(zone))
 
@@ -351,6 +361,8 @@ static void make_bad_inode(void)
 		write_block(ind, (char *) ind_block);
 	if (dind)
 		write_block(dind, (char *) dind_block);
+#undef ind_block
+#undef dind_block
 }
 
 #if ENABLE_FEATURE_MINIX2
@@ -359,8 +371,12 @@ static void make_bad_inode2(void)
 	struct minix2_inode *inode = &INODE_BUF2[MINIX_BAD_INO];
 	int i, j, zone;
 	int ind = 0, dind = 0;
+	/* moved to globals to reduce stack usage
 	unsigned long ind_block[BLOCK_SIZE >> 2];
 	unsigned long dind_block[BLOCK_SIZE >> 2];
+	*/
+#define ind_block (G.ind_block2)
+#define dind_block (G.dind_block2)
 
 	if (!G.badblocks)
 		return;
@@ -401,6 +417,8 @@ static void make_bad_inode2(void)
 		write_block(ind, (char *) ind_block);
 	if (dind)
 		write_block(dind, (char *) dind_block);
+#undef ind_block
+#undef dind_block
 }
 #else
 void make_bad_inode2(void);
@@ -613,7 +631,7 @@ int mkfs_minix_main(int argc, char **argv)
 	char *str_i, *str_n;
 	char *listfile = NULL;
 
-	PTR_TO_GLOBALS = xzalloc(sizeof(G));
+	INIT_G();
 /* default (changed to 30, per Linus's suggestion, Sun Nov 21 08:05:07 1993) */
 	G.namelen = 30;
 	G.dirsize = 32;