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Unsupported value type with mcsema bitcode #220
Description
Trying to decompile the code for xz from the walkthrough:
F0206 08:52:46.518694 132263 IRToASTVisitor.cpp:379] Unsupported value type: @data_1ff0d023 = internal alias i8, getelementptr inbounds (<{ %seg_1ff00000_LOAD_2af8_type, [1288 x i8], %seg_1ff03000__init_1b_type, [923 x i8], %seg_1ff0d000__rodata_32f0_type, [5184 x i8], %seg_1ff13190__init_array_10_type }>, <{ %seg_1ff00000_LOAD_2af8_type, [1288 x i8], %seg_1ff03000__init_1b_type, [923 x i8], %seg_1ff0d000__rodata_32f0_type, [5184 x i8], %seg_1ff13190__init_array_10_type }>* @__mcsema_all_segments, i32 0, i32 4, i32 0, i32 35)
*** Check failure stack trace: ***
@ 0x5635a51727fc google::LogMessageFatal::~LogMessageFatal()
@ 0x5635a4fffbf9 rellic::IRToASTVisitor::GetOrCreateDecl()
@ 0x5635a4ffefbb rellic::IRToASTVisitor::GetOperandExpr()
@ 0x5635a5002393 rellic::IRToASTVisitor::CreateLiteralExpr()
@ 0x5635a4ffec00 rellic::IRToASTVisitor::GetOrCreateStmt()
@ 0x5635a4ffef75 rellic::IRToASTVisitor::GetOperandExpr()
@ 0x5635a5002393 rellic::IRToASTVisitor::CreateLiteralExpr()
@ 0x5635a4ffec00 rellic::IRToASTVisitor::GetOrCreateStmt()
@ 0x5635a4ffef75 rellic::IRToASTVisitor::GetOperandExpr()
@ 0x5635a4fff940 rellic::IRToASTVisitor::VisitGlobalVar()
@ 0x5635a4ff9f92 rellic::GenerateAST::runOnModule()
@ 0x5635a6b81cf9 llvm::legacy::PassManagerImpl::run()
@ 0x5635a4f3a6c2 main
@ 0x7ff593771b25 __libc_start_main
@ 0x5635a4f54bea _start
@ (nil) (unknown)
fish: Job 1, '/home/heath/rellic-test/usr/loc…' terminated by signal SIGABRT (Abort)
Happens at
https://github.com/lifting-bits/rellic/blob/master/lib/AST/IRToASTVisitor.cpp#L379
Activity
Heath123 commentedon Feb 6, 2022
Executable + bitcode:
files.zip
pgoodman commentedon Feb 7, 2022
Hrmm, this is a result of GlobalAliases. @frabert to handle these we'd probably need to lift the aliasee instead of the alias itself. We could probably lift to local variables accordingly initialized to retain the alias name. Then they wouldn't turn into global variables.
Heath123 commentedon Feb 7, 2022
Is Rellic designed to generate readable C code from mcsema output? At first I thought t would but mcsema bitcode doesn't seem to work like normal bitcode as it uses the State thing
pgoodman commentedon Feb 7, 2022
@Heath123 Rellic is designed more for anvill-produced bitcode or Clang-produced bitcode. McSerma-produced bitcode makes heavy use of global aliases for human readability of the bitcode, but those aliases can be disabled with
--disable_aliases.