Summary:
llvm-objdump (via libObject) validates DYLD_INFO rebase and bind
entries against the basic structure found in the Mach-O file before
evaluating the contents of those entries. Certain malformed Mach-Os can
defeat the validation check and force llvm-objdump (libObject) to crash.
The previous logic verified a rebase or bind started in a valid Mach-O
section, but did not verify that the section wholely contained the
fixup. It also generally allows rebases or binds to start immediately
after a valid section even if that range is not itself part of a valid
section. Finally, bind and rebase opcodes that indicate more than one
fixup (apply N times...) are not completely validated: only the first
and final fixups are checked.
The previous logic also rejected certain binaries as false positives.
Some bind and rebase opcodes can modify the state machine such that the
next bind or rebase will fail. libObject will reject these opcodes as
invalid in order to be helpful and print an error message associated
with the instruction that caused the problem, even though the binary is
not actually illegal until it consumes the invalid state in the state
machine. In other words, libObject may reject a Mach-O binary that
Apple's dynamic linker may consider legal. The original version of
macho-rebase-add-addr-uleb-too-big is an example of such a binary.
I have replaced the existing checkSegAndOffset and checkCountAndSkip
functions with a single function, checkSegAndOffsets, which validates
all of the fixups realized by a DYLD_INFO opcode. checkSegAndOffsets
verifies that a Mach-O section fully contains each fixup. Every fixup
realized by an opcode is validated, and some (but not all!)
inconsistencies in the state machine are allowed until a fixup is
realized. This means that libObject may fail on an opcode that realizes
a fixup, not on the opcode that introduced the arithmetic error.
Existing test cases have been modified to reflect the changes in error
messages returned by libObject. What's more, the test case for
macho-rebase-add-addr-uleb-too-big has been modified so that it actually
triggers the error condition; the new code in libObject considers the
original test binary "legal".
rdar://47797757
Reviewers: lhames, pete, ab
Reviewed By: pete
Subscribers: rupprecht, jdoerfert, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D59574
llvm-svn: 356629
rebase entry errors and test cases for each of the error checks.
Also verified with Nick Kledzik that a BIND_OPCODE_SET_ADDEND_SLEB
opcode is legal in a lazy bind table, so code that had that as an error
check was removed.
With MachORebaseEntry and MachOBindEntry classes now returning
an llvm::Error in all cases for malformed input the variables Malformed
and logic to set use them is no longer needed and has been removed
from those classes.
Also in a few places, removed the redundant Done assignment to true
when also calling moveToEnd() as it does that assignment.
This only leaves the dyld compact export entries left to have
error handling yet to be added for the dyld compact info.
llvm-svn: 298883
Michael Trent