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<p>Compressing/decompressing can be used for any sections in theory, </p>
<p>but in practice <span style="font-size: 12pt;">use</span><span style="font-size: 12pt;">d for .debug_* ones only I think (not sure though). </span></p>
<p><span style="font-size: 12pt;"></span><span style="font-size: 12pt;">Afaik LLVM does not support DWARF64 now.</span></p>
<p><span style="font-size: 12pt;">Given above we probably can limit decompressed size to 4gb and it be reasonable limit ?</span></p>
<p><span style="font-size: 12pt;"><br>
</span></p>
<p><span style="font-size: 12pt;">Another point (already mentioned in different thread) is that</span></p>
<div class="gmail_extra">
<div class="gmail_quote">install_bad_alloc_error_handle<wbr>r API looks completely dead then ? </div>
<div class="gmail_quote">S<span style="font-size: 12pt;">ince it looks not possible to use it currently without breaking </span><span style="color: rgb(33, 33, 33); font-family: "Segoe UI", "Segoe WP", "Segoe UI WPC", Tahoma, Arial, sans-serif; font-size: 15px;">ASan</span><span style="font-size: 12pt;">.</span></div>
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<div class="PlainText">Best regards,<br>
George | Developer | <span style="background-color:rgb(255,255,255); color:rgb(33,33,33); font-family:Calibri,sans-serif; font-size:13.3333px">Access Softek, Inc</span></div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>От:</b> Kostya Serebryany <kcc@google.com><br>
<b>Отправлено:</b> 7 сентября 2017 г. 3:26<br>
<b>Кому:</b> Jonas Devlieghere<br>
<b>Копия:</b> Vedant Kumar; LLVM Commits; George Rimar<br>
<b>Тема:</b> Re: [llvm] r312582 - Revert "[Decompression] Fail gracefully when out of memory"</font>
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<div class="gmail_extra"><br>
<div class="gmail_quote">On Wed, Sep 6, 2017 at 2:38 PM, Jonas Devlieghere <span dir="ltr">
<<a href="mailto:jdevlieghere@apple.com" target="_blank">jdevlieghere@apple.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex; border-left:1px solid rgb(204,204,204); padding-left:1ex">
<div style="word-wrap:break-word">Hi Kostya,
<div><br>
</div>
<div>I completely agree with you that this is far from an optimal solution! However, I don’t really see an alternative here without a complete rewrite of how we currently do decompression. For this particular case, how would you decide whether the allocated
chuck is too big? </div>
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</div>
<div>It could be an arbitrary limit which can be redefined at compile-time or, better, with a run-time flag (and the default set to e.g. 1Gb?)</div>
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<div>Any limit would be arbitrary before doing the actual extraction. This is a pretty common problem with extraction
</div>
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</div>
<div>Oh yea. zip bombs they call it. </div>
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<div>and I *think* libz has some kind of work around for it, though I’d have to check to refresh my memory. We could probably do something similar in the decompressor, but that’d be a pretty big change and this seemed like a reasonable first step as opposed
to just crashing. <br>
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<div>This change doesn't really fix the problem though. </div>
<div>Yes, it might help if the requested allocation is e.g. 42Tb. </div>
<div>But what if the requested allocation is 3Gb? LibFuzzer will still die with OOM (default rss_limit_mb=2048). </div>
<div>What if the requested allocation is 1.99Gb? libFuzzer will dies due to OOM again, just because the process will consume 2Gb</div>
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<div>Here's the original differential <a href="https://reviews.llvm.org/D37447" target="_blank">
https://reviews.llvm.org/<wbr>D37447</a></div>
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<div><span class="gmail-HOEnZb"><font color="#888888">Jonas</font></span>
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<div class="gmail-h5"><br>
<div><br>
<blockquote type="cite">
<div>On Sep 6, 2017, at 9:37 PM, Kostya Serebryany <<a href="mailto:kcc@google.com" target="_blank">kcc@google.com</a>> wrote:</div>
<br class="gmail-m_9117679352079337087Apple-interchange-newline">
<div>
<div dir="ltr">I missed the original commit but I'm glad it's reverted.
<div>I think it's a really bad practice to allocate huge chunks of RAM (petabytes?) and rely on the new handler to bark. </div>
<div>Instead, we should simply not try to allocate large chunks. In most cases if the compiler-related too wants to allocate many Gb of RAM at once it's an indication of a logical bug. </div>
</div>
<div class="gmail_extra"><br>
<div class="gmail_quote">On Tue, Sep 5, 2017 at 3:04 PM, Vedant Kumar via llvm-commits
<span dir="ltr"><<a href="mailto:llvm-commits@lists.llvm.org" target="_blank">llvm-commits@lists.llvm.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex; border-left:1px solid rgb(204,204,204); padding-left:1ex">
Author: vedantk<br>
Date: Tue Sep 5 15:04:00 2017<br>
New Revision: 312582<br>
<br>
URL: <a href="http://llvm.org/viewvc/llvm-project?rev=312582&view=rev" rel="noreferrer" target="_blank">
http://llvm.org/viewvc/llvm-pr<wbr>oject?rev=312582&view=rev</a><br>
Log:<br>
Revert "[Decompression] Fail gracefully when out of memory"<br>
<br>
This reverts commit r312526.<br>
<br>
Revert "Fix test/DebugInfo/dwarfdump-decom<wbr>pression-invalid-size.test"<br>
<br>
This reverts commit r312527.<br>
<br>
It causes an ASan failure:<br>
<a href="http://lab.llvm.org:8080/green/job/clang-stage2-cmake-RgSan_check/4150" rel="noreferrer" target="_blank">http://lab.llvm.org:8080/green<wbr>/job/clang-stage2-cmake-RgSan_<wbr>check/4150</a><br>
<br>
Removed:<br>
llvm/trunk/test/DebugInfo/Inpu<wbr>ts/dwarfdump-decompression-<wbr>invalid-size.elf-x86-64<br>
llvm/trunk/test/DebugInfo/dwar<wbr>fdump-decompression-invalid-<wbr>size.test<br>
Modified:<br>
llvm/trunk/include/llvm/Object<wbr>/Decompressor.h<br>
llvm/trunk/lib/Object/Decompre<wbr>ssor.cpp<br>
<br>
Modified: llvm/trunk/include/llvm/Object<wbr>/Decompressor.h<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Object/Decompressor.h?rev=312582&r1=312581&r2=312582&view=diff" rel="noreferrer" target="_blank">
http://llvm.org/viewvc/llvm-pr<wbr>oject/llvm/trunk/include/llvm/<wbr>Object/Decompressor.h?rev=<wbr>312582&r1=312581&r2=312582&<wbr>view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/include/llvm/Object<wbr>/Decompressor.h (original)<br>
+++ llvm/trunk/include/llvm/Object<wbr>/Decompressor.h Tue Sep 5 15:04:00 2017<br>
@@ -13,7 +13,6 @@<br>
#include "llvm/ADT/SmallString.h"<br>
#include "llvm/ADT/StringRef.h"<br>
#include "llvm/Object/ObjectFile.h"<br>
-#include "llvm/Support/ErrorHandling.h"<br>
<br>
namespace llvm {<br>
namespace object {<br>
@@ -32,9 +31,7 @@ public:<br>
/// @brief Resize the buffer and uncompress section data into it.<br>
/// @param Out Destination buffer.<br>
template <class T> Error resizeAndDecompress(T &Out) {<br>
- install_bad_alloc_error_handle<wbr>r(outOfMemoryHandler, this);<br>
Out.resize(DecompressedSize);<br>
- remove_bad_alloc_error_handler<wbr>();<br>
return decompress({Out.data(), (size_t)DecompressedSize});<br>
}<br>
<br>
@@ -55,14 +52,11 @@ public:<br>
static bool isGnuStyle(StringRef Name);<br>
<br>
private:<br>
- static void outOfMemoryHandler(void *Data, const std::string &Message, bool);<br>
-<br>
- Decompressor(StringRef Name, StringRef Data);<br>
+ Decompressor(StringRef Data);<br>
<br>
Error consumeCompressedGnuHeader();<br>
Error consumeCompressedZLibHeader(bo<wbr>ol Is64Bit, bool IsLittleEndian);<br>
<br>
- StringRef SectionName;<br>
StringRef SectionData;<br>
uint64_t DecompressedSize;<br>
};<br>
<br>
Modified: llvm/trunk/lib/Object/Decompre<wbr>ssor.cpp<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/Decompressor.cpp?rev=312582&r1=312581&r2=312582&view=diff" rel="noreferrer" target="_blank">
http://llvm.org/viewvc/llvm-pr<wbr>oject/llvm/trunk/lib/Object/De<wbr>compressor.cpp?rev=312582&r1=<wbr>312581&r2=312582&view=diff</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/lib/Object/Decompre<wbr>ssor.cpp (original)<br>
+++ llvm/trunk/lib/Object/Decompre<wbr>ssor.cpp Tue Sep 5 15:04:00 2017<br>
@@ -23,7 +23,7 @@ Expected<Decompressor> Decompressor::cre<br>
if (!zlib::isAvailable())<br>
return createError("zlib is not available");<br>
<br>
- Decompressor D(Name, Data);<br>
+ Decompressor D(Data);<br>
Error Err = isGnuStyle(Name) ? D.consumeCompressedGnuHeader()<br>
: D.consumeCompressedZLibHeader(<wbr>Is64Bit, IsLE);<br>
if (Err)<br>
@@ -31,8 +31,8 @@ Expected<Decompressor> Decompressor::cre<br>
return D;<br>
}<br>
<br>
-Decompressor::Decompressor(St<wbr>ringRef Name, StringRef Data)<br>
- : SectionName(Name), SectionData(Data), DecompressedSize(0) {}<br>
+Decompressor::Decompressor(St<wbr>ringRef Data)<br>
+ : SectionData(Data), DecompressedSize(0) {}<br>
<br>
Error Decompressor::consumeCompresse<wbr>dGnuHeader() {<br>
if (!SectionData.startswith("ZLIB<wbr>"))<br>
@@ -92,11 +92,3 @@ Error Decompressor::decompress(Mutab<wbr>leAr<br>
size_t Size = Buffer.size();<br>
return zlib::uncompress(SectionData, Buffer.data(), Size);<br>
}<br>
-<br>
-void Decompressor::outOfMemoryHandl<wbr>er(void *Data, const std::string &Message,<br>
- bool) {<br>
- const auto *D = static_cast<const Decompressor *>(Data);<br>
- report_fatal_error("decompress<wbr>ion of '" + Twine(D->SectionName) +<br>
- "' failed: unable to allocate " +<br>
- Twine(D->DecompressedSize) + " bytes.");<br>
-}<br>
<br>
Removed: llvm/trunk/test/DebugInfo/Inpu<wbr>ts/dwarfdump-decompression-<wbr>invalid-size.elf-x86-64<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Inputs/dwarfdump-decompression-invalid-size.elf-x86-64?rev=312581&view=auto" rel="noreferrer" target="_blank">
http://llvm.org/viewvc/llvm-pr<wbr>oject/llvm/trunk/test/DebugInf<wbr>o/Inputs/dwarfdump-decompressi<wbr>on-invalid-size.elf-x86-64?<wbr>rev=312581&view=auto</a><br>
==============================<wbr>==============================<wbr>==================<br>
Binary files llvm/trunk/test/DebugInfo/Inpu<wbr>ts/dwarfdump-decompression-<wbr>invalid-size.elf-x86-64 (original) and llvm/trunk/test/DebugInfo/Inpu<wbr>ts/dwarfdump-decompression-<wbr>invalid-size.elf-x86-64 (removed) differ<br>
<br>
Removed: llvm/trunk/test/DebugInfo/dwar<wbr>fdump-decompression-invalid-<wbr>size.test<br>
URL: <a href="http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/dwarfdump-decompression-invalid-size.test?rev=312581&view=auto" rel="noreferrer" target="_blank">
http://llvm.org/viewvc/llvm-pr<wbr>oject/llvm/trunk/test/DebugInf<wbr>o/dwarfdump-decompression-<wbr>invalid-size.test?rev=312581&<wbr>view=auto</a><br>
==============================<wbr>==============================<wbr>==================<br>
--- llvm/trunk/test/DebugInfo/dwar<wbr>fdump-decompression-invalid-<wbr>size.test (original)<br>
+++ llvm/trunk/test/DebugInfo/dwar<wbr>fdump-decompression-invalid-<wbr>size.test (removed)<br>
@@ -1,15 +0,0 @@<br>
-REQUIRES: zlib<br>
-<br>
-// dwarfdump-decompression-invali<wbr>d-size.elf-x86-64 is prepared using following<br>
-// source code and invocation:<br>
-// test.cpp:<br>
-// int main() { return 0; }<br>
-//<br>
-// gcc test.cpp -o out -g -Wl,--compress-debug-sections,<wbr>zlib<br>
-//<br>
-// After that result object was modified manually. Decompressed size of<br>
-// .debug_frame section was changed to 0xffffffffffffffff in compression<br>
-// header.<br>
-RUN: not llvm-dwarfdump %p/Inputs/dwarfdump-decompress<wbr>ion-invalid-size.elf-x86-64 2>&1 | FileCheck %s<br>
-<br>
-CHECK: decompression of '.debug_frame' failed: unable to allocate 18446744073709551615 bytes.<br>
<br>
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