From fd1e8a7c7fd796291204be26a78a3ef4a2ad12f1 Mon Sep 17 00:00:00 2001
From: clc5q <clc5q@git.zephyr-software.com>
Date: Mon, 21 Jan 2008 00:45:50 +0000
Subject: [PATCH] Avoid converting data region to code if it would be entirely
no-ops.
---
SMPStaticAnalyzer.cpp | 44 +++++++++++++++++++++++++++++++++++++++----
1 file changed, 40 insertions(+), 4 deletions(-)
diff --git a/SMPStaticAnalyzer.cpp b/SMPStaticAnalyzer.cpp
index 13313ce8..b123c540 100644
--- a/SMPStaticAnalyzer.cpp
+++ b/SMPStaticAnalyzer.cpp
@@ -968,7 +968,7 @@ bool MDPatchUnconvertedBytes(ea_t CurrDisasmAddr) {
return false;
}
PatchInstr.PrintOperands();
- op_t CallDest = PatchInstr.GetUse(0);
+ op_t CallDest = PatchInstr.GetUse(0).GetOp();
if ((o_near != CallDest.type) || (0 != CallDest.addr)) {
msg("Cannot patch call unless it is call near ptr 0 at %x",
CurrDisasmAddr);
@@ -993,7 +993,7 @@ bool MDPatchUnconvertedBytes(ea_t CurrDisasmAddr) {
return true;
} // end of MDPatchUnconvertedBytes()
-// Create lists of code addresses identified by IDA Pro (in IDAProLocs)
+// Use the lists of code addresses identified by IDA Pro (in IDAProLocs)
// and an external disassembler (in DisasmLocs). Compare the lists and
// try to convert addresses to code that are found in DisasmLocs but
// not in IDAProLocs. Emit warnings when IDAProLocs has a code address
@@ -1080,6 +1080,7 @@ void FixCodeIdentification(void) {
FixupRegion CurrRegion(ConvertRegion);
CodeReanalyzeList.push_back(CurrRegion);
bool AllConverted = true;
+ bool AllNops = true;
do {
flags_t InstrFlags = getFlags(CurrDisasmAddr);
if (!isUnknown(InstrFlags)) {
@@ -1090,6 +1091,8 @@ void FixCodeIdentification(void) {
if (InstrLen > 0) { // Successfully converted to code
SMPInstr NewInstr(CurrDisasmAddr);
NewInstr.Analyze();
+ if (!NewInstr.MDIsNop())
+ AllNops = false;
#if SMP_DEBUG_FIXUP_IDB
#if 0
msg("FixCodeID success at %x: len: %d %s\n", CurrDisasmAddr,
@@ -1117,6 +1120,21 @@ void FixCodeIdentification(void) {
++DisasmIndex; // skip cleanup loop
}
} while (CurrDisasmAddr < CurrAddr);
+ if (AllConverted && AllNops) {
+ // We want to convert the region back to unexplored bytes
+ // and take it off the work list. Regions that are all nops
+ // create data flow analysis problems sometimes. The region
+ // is often unreachable code and produces a basic block with
+ // no predecessors within a function. This often happens when
+ // an optimizing compiler uses nops as padding to align jump
+ // targets on cache line bounaries. With no fall through into
+ // the nops, they are unreachable and should be left as unknown.
+ msg("FixCodeID nops region from %x to %x\n", CurrRegion.GetStart(),
+ CurrRegion.GetEnd());
+ do_unknown_range(CurrRegion.GetStart(),
+ CurrRegion.GetEnd() - CurrRegion.GetStart(), DOUNK_SIMPLE);
+ CodeReanalyzeList.pop_back();
+ }
} // end if (SkipArea) ... else ...
} // end if (addr < CurrDisasmAddr) .. else if ... else ...
} // end while (DisasmIndex <= DisasmLocs.size()
@@ -1176,6 +1194,12 @@ int FixupNewCodeChunks(void) {
int changes = 0;
for (CurrRegion = CodeReanalyzeList.begin(); CurrRegion != CodeReanalyzeList.end(); ++CurrRegion) {
bool AllConverted = true;
+ bool AllNops = true;
+ bool NoFixups = (0 == CurrRegion->FixupInstrs.size());
+ if (NoFixups) {
+ CurrRegion->SetStart(BADADDR); // mark for removal
+ continue; // skip to next region
+ }
list<ea_t>::iterator CurrInstr;
for (CurrInstr = CurrRegion->FixupInstrs.begin(); CurrInstr != CurrRegion->FixupInstrs.end(); ++CurrInstr) {
int InstrLen = ua_code(*CurrInstr);
@@ -1185,7 +1209,10 @@ int FixupNewCodeChunks(void) {
#if SMP_DEBUG_FIXUP_IDB
msg("FixupNewCodeChunks success at %x: len: %d\n", *CurrInstr, InstrLen);
#endif
- *CurrInstr = BADADDR; // mark for removal
+ if (!NewInstr.MDIsNop()) {
+ AllNops = false;
+ *CurrInstr = BADADDR; // mark for removal
+ }
}
else {
AllConverted = false;
@@ -1194,13 +1221,22 @@ int FixupNewCodeChunks(void) {
#endif
}
} // end for all instrs in CurrRegion
- if (AllConverted) {
+ if (AllConverted && !AllNops) {
#if SMP_DEBUG_FIXUP_IDB
msg("FixupNewCodeChunks success for region from %x to %x\n",
CurrRegion->GetStart(), CurrRegion->GetEnd());
#endif
CurrRegion->SetStart(BADADDR); // mark for removal
}
+ else if (AllConverted && AllNops) {
+#if SMP_DEBUG_FIXUP_IDB
+ msg("FixupNewCodeChunks re-converting nops region from %x to %x\n",
+ CurrRegion->GetStart(), CurrRegion->GetEnd());
+#endif
+ do_unknown_range(CurrRegion->GetStart(),
+ CurrRegion->GetEnd() - CurrRegion->GetStart(), DOUNK_SIMPLE);
+ CurrRegion->SetStart(BADADDR); // mark for removal
+ }
else {
// Remove only the instructions that were fixed up.
CurrInstr = CurrRegion->FixupInstrs.begin();
--
GitLab