From c282e7fdb4e4571d22d8fded9bcd5d6030e9a07a Mon Sep 17 00:00:00 2001
From: John Reiser <jreiser@BitWagon.com>
Date: Sat, 23 Apr 2005 04:17:57 +0000
Subject: [PATCH] PPC branch+call trick: filter first 4MB only 	filteri.cpp
 filter/ppcbxx.h stub/ppc_bxx.S

committer: jreiser <jreiser> 1114229877 +0000
---
 src/filter/ppcbxx.h | 11 ++++++-----
 src/filteri.cpp     | 10 ++++++++--
 src/stub/ppc_bxx.S  |  9 +++++++--
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/src/filter/ppcbxx.h b/src/filter/ppcbxx.h
index d27cdfe7..02879992 100644
--- a/src/filter/ppcbxx.h
+++ b/src/filter/ppcbxx.h
@@ -47,7 +47,8 @@ static int F(Filter *f)
     // scan
     const upx_byte *b = f->buf;
 #endif
-    const unsigned size = f->buf_len;
+    const unsigned size  = umin(f->buf_len, -(~0u<<(32 - (6+ W_CTO))));
+    const unsigned size4 = size -4;
 
     unsigned ic;
     unsigned calls = 0, noncalls = 0;
@@ -62,7 +63,7 @@ static int F(Filter *f)
         memset(buf     , 0,       WW);
         memset(buf + WW, 1, 256 - WW);
 
-        for (ic = 0; ic < size - 4; ic+=4) if (COND(b,ic)) {
+        for (ic = 0; ic<=size4; ic+=4) if (COND(b,ic)) {
             unsigned const off = (int)(get_be32(b+ic)<<6) >>6;
             if (size <= (off & (~0u<<2))+ic) {
                 buf[(~(~0u<<W_CTO)) & (off>>(26 - W_CTO))] |= 1;
@@ -81,7 +82,7 @@ static int F(Filter *f)
     const unsigned cto = (unsigned)f->cto << (24+2 - W_CTO);
 #endif
 
-    for (ic = 0; ic < size - 4; ic+=4) if (COND(b,ic)) {
+    for (ic = 0; ic<=size4; ic+=4) if (COND(b,ic)) {
         unsigned const word = get_be32(b+ic);
         unsigned const off = (int)(word<<6) >>6;
         unsigned const jc = (off & (~0u<<2))+ic;
@@ -121,12 +122,12 @@ static int F(Filter *f)
 static int U(Filter *f)
 {
     upx_byte *b = f->buf;
-    const unsigned size4 = f->buf_len - 4;
+    const unsigned size4 = umin(f->buf_len - 4, -(~0u<<(32 - (6+ W_CTO))));
     const unsigned addvalue = f->addvalue;
 
     unsigned ic;
 
-   for (ic = 0; ic < size4; ic+=4) if (COND(b,ic)) {
+   for (ic = 0; ic<=size4; ic+=4) if (COND(b,ic)) {
         unsigned const word = get_be32(b+ic);
         if ((~(~0u<<W_CTO) & (word>>(24+2 - W_CTO))) == f->cto) {
             unsigned const jc = word & (~(~0u<<(26 - W_CTO)) & (~0u<<2));
diff --git a/src/filteri.cpp b/src/filteri.cpp
index c98c4e75..10d19ff3 100644
--- a/src/filteri.cpp
+++ b/src/filteri.cpp
@@ -29,6 +29,12 @@
 #include "conf.h"
 #include "filter.h"
 
+static unsigned
+umin(unsigned const a, unsigned const b)
+{
+    return (a<=b) ? a : b;
+}
+
 
 #define set_dummy(p, v)     ((void)0)
 #define get_8(p)            (*(p))
@@ -244,8 +250,8 @@ const FilterImp::FilterEntry FilterImp::filters[] = {
     { 0xb2,99,          0, f_sub32_3, u_sub32_3, s_sub32_3 },
     { 0xb3,99,          0, f_sub32_4, u_sub32_4, s_sub32_4 },
 
-    // PowerPC call trick
-    { 0xd0, 8, 0x01000000, f_ppcbxx, u_ppcbxx, s_ppcbxx },
+    // PowerPC branch+call trick
+    { 0xd0, 8,          0, f_ppcbxx, u_ppcbxx, s_ppcbxx },
 };
 
 const int FilterImp::n_filters = TABLESIZE(filters);
diff --git a/src/stub/ppc_bxx.S b/src/stub/ppc_bxx.S
index 15dd395d..f24523ee 100644
--- a/src/stub/ppc_bxx.S
+++ b/src/stub/ppc_bxx.S
@@ -36,8 +36,13 @@ ppcbxx:  # (*f_unf)(xo->buf, out_len, h.b_cto8, h.b_ftid);
 
 #define ptr0 a4
 
-	cmpli cr0,ftid,0xd0;       bnelr- cr0  # if (0xd0!=ftid) return;
-	rlwinm. len,len,32-2,2,31; beqlr- cr0   # if (0==(len>>=2)) return;
+	cmpli cr0,ftid,0xd0;       bnelr- cr0  # if (0xd0!=ftid)   return;
+	rlwinm. len,len,32-2,2,31; beqlr- cr0  # if (0==(len>>=2)) return;
+	lis r0,-(~0<<(32-16- (2+6+ W_CTO)))  # limit in 32-bit words
+	cmpl cr0,len,r0
+	blt  cr0,L5
+	mr       len,r0
+L5:
 	addi cto8,cto8,18<<W_CTO  # cat(bxx_opcode, cto8)
 	movr ptr0,ptr  # save base address
 	addi ptr,ptr,-4  # prepare for 'lwzu'