For networking-type bpf program, it often needs to access
packet data. A context data structure is provided to the bpf
programs with two fields:
u32 data;
u32 data_end;
User can access these two fields with ctx->data and ctx->data_end.
During program verification process, the kernel verifier modifies
the bpf program with loading of actual pointer value from kernel
data structure.
r = ctx->data ===> r = actual data start ptr
r = ctx->data_end ===> r = actual data end ptr
A typical program accessing ctx->data like
char *data_ptr = (char *)(long)ctx->data
will result in a 32-bit load followed by a zero extension.
Such an operation is combined into a single LDW in DAG combiner
as bpf LDW does zero extension automatically.
In cases like the below (which can be a result of global value numbering
and partial redundancy elimination before insn selection):
B1:
u32 a = load-32-bit &ctx->data
u64 pa = zext a
...
B2:
u32 b = load-32-bit &ctx->data
u64 pb = zext b
...
B3:
u32 m = PHI(a, b)
u64 pm = zext m
In B3, "pm = zext m" cannot be removed, which although is legal
from compiler perspective, will generate incorrect code after
kernel verification.
This patch recognizes this pattern and traces through PHI node
to see whether the operand of "zext m" is defined with LDWs or not.
If it is, the "zext m" itself can be removed.
The patch also recognizes the pattern where the load and use of
the load value not in the same basic block, where truncate operation
may be removed as well.
The patch handles 1-byte, 2-byte and 4-byte truncation.
Two test cases are added to verify the transformation happens properly
for the above code pattern.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 306685
processFixupValue is called on every relaxation iteration. applyFixup
is only called once at the very end. applyFixup is then the correct
place to do last minute changes and value checks.
While here, do proper range checks again for fixup_arm_thumb_bl. We
used to do it, but dropped because of thumb2. We now do it again, but
use the thumb2 range.
llvm-svn: 306177
Davide Italiano reported the following issue if llvm
is compiled with gcc -Wstrict-aliasing -Werror:
.....
lib/Target/BPF/CMakeFiles/LLVMBPFCodeGen.dir/BPFISelDAGToDAG.cpp.o
../lib/Target/BPF/BPFISelDAGToDAG.cpp: In member function ‘virtual
void {anonymous}::BPFDAGToDAGISel::PreprocessISelDAG()’:
../lib/Target/BPF/BPFISelDAGToDAG.cpp:264:26: warning: dereferencing
type-punned pointer will break strict-aliasing rules
[-Wstrict-aliasing]
val = *(uint16_t *)new_val;
.....
The error is caused by my previous commit (revision 305560).
This patch fixed the issue by introducing an union to avoid
type casting.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 305608
If users tried to have a structure decl/init code like below
struct test_t t = { .memeber1 = 45 };
It is very likely that compiler will generate a readonly section
to hold up the init values for variable t. Later load of t members,
e.g., t.member1 will result in a read from readonly section.
BPF program cannot handle relocation. This will force users to
write:
struct test_t t = {};
t.member1 = 45;
This is just inconvenient and unintuitive.
This patch addresses this issue by implementing BPF PreprocessISelDAG.
For any load from a global constant structure or an global array of
constant struct, it attempts to
translate it into a constant directly. The traversal of the
constant struct and other constant data structures are similar
to where the assembler emits read-only sections.
Four different unit test cases are also added to cover
different scenarios.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 305560
o This is discovered during my study of 32-bit subregister
support.
o This is no impact on current functionality since we
only support 64-bit registers.
o Searching the web, looks like the issue has been discovered
before, so fix it now.
Signed-off-by: Yonghong Song <yhs@fb.com>
llvm-svn: 305559
This creates a new library called BinaryFormat that has all of
the headers from llvm/Support containing structure and layout
definitions for various types of binary formats like dwarf, coff,
elf, etc as well as the code for identifying a file from its
magic.
Differential Revision: https://reviews.llvm.org/D33843
llvm-svn: 304864
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.
I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.
This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.
Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).
llvm-svn: 304787
TargetPassConfig is not useful for targets that do not use the CodeGen
library, so we may just as well store a pointer to an
LLVMTargetMachine instead of just to a TargetMachine.
While at it, also change the constructor to take a reference instead of a
pointer as the TM must not be nullptr.
llvm-svn: 304247
Wrong assembly code is generated for a simple program with
clang. If clang only produces IR and llc is used
for IR lowering and optimization, correct assembly
code is generated.
The main reason is that clang feeds default Reloc::Static
to llvm and llc feeds no RelocMode to llvm, where
for llc case, BPF backend picks up Reloc::PIC_ mode.
This leads different IR lowering behavior and clang
permits global_addr+off folding while llc doesn't.
This patch introduces isOffsetFoldingLegal function into
BPF backend and the function always return false.
This will make clang and llc behave the same for
the lowering.
Bug https://bugs.llvm.org//show_bug.cgi?id=33183
has more detailed explanation.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 304043
Using arguments with attribute inalloca creates problems for verification
of machine representation. This attribute instructs the backend that the
argument is prepared in stack prior to CALLSEQ_START..CALLSEQ_END
sequence (see http://llvm.org/docs/InAlloca.htm for details). Frame size
stored in CALLSEQ_START in this case does not count the size of this
argument. However CALLSEQ_END still keeps total frame size, as caller can
be responsible for cleanup of entire frame. So CALLSEQ_START and
CALLSEQ_END keep different frame size and the difference is treated by
MachineVerifier as stack error. Currently there is no way to distinguish
this case from actual errors.
This patch adds additional argument to CALLSEQ_START and its
target-specific counterparts to keep size of stack that is set up prior to
the call frame sequence. This argument allows MachineVerifier to calculate
actual frame size associated with frame setup instruction and correctly
process the case of inalloca arguments.
The changes made by the patch are:
- Frame setup instructions get the second mandatory argument. It
affects all targets that use frame pseudo instructions and touched many
files although the changes are uniform.
- Access to frame properties are implemented using special instructions
rather than calls getOperand(N).getImm(). For X86 and ARM such
replacement was made previously.
- Changes that reflect appearance of additional argument of frame setup
instruction. These involve proper instruction initialization and
methods that access instruction arguments.
- MachineVerifier retrieves frame size using method, which reports sum of
frame parts initialized inside frame instruction pair and outside it.
The patch implements approach proposed by Quentin Colombet in
https://bugs.llvm.org/show_bug.cgi?id=27481#c1.
It fixes 9 tests failed with machine verifier enabled and listed
in PR27481.
Differential Revision: https://reviews.llvm.org/D32394
llvm-svn: 302527
o Add bpfeb support in BPF dwarfdump unit test case
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@fb.com>
llvm-svn: 302265
. swap 4-bit register encoding, 16-bit offset and 32-bit imm to support big endian archs
. add a test
Reported-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 301653
If the offset cannot fit into the instruction, an addition to the
pointer is emitted before the actual access. However, BPF offsets are
16-bit but LLVM considers them to be, for the matter of this check,
to be 32-bit long.
This causes the following program:
int bpf_prog1(void *ign)
{
volatile unsigned long t = 0x8983984739ull;
return *(unsigned long *)((0xffffffff8fff0002ull) + t);
}
To generate the following (wrong) code:
0: 18 01 00 00 39 47 98 83 00 00 00 00 89 00 00 00
r1 = 590618314553ll
2: 7b 1a f8 ff 00 00 00 00 *(u64 *)(r10 - 8) = r1
3: 79 a1 f8 ff 00 00 00 00 r1 = *(u64 *)(r10 - 8)
4: 79 10 02 00 00 00 00 00 r0 = *(u64 *)(r1 + 2)
5: 95 00 00 00 00 00 00 00 exit
Fix it by changing the offset check to 16-bit.
Patch by Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Differential Revision: https://reviews.llvm.org/D32055
llvm-svn: 300269
A number of backends (AArch64, MIPS, ARM) have been using
MCContext::reportError to report issues such as out-of-range fixup values in
their TgtAsmBackend. This is great, but because MCContext couldn't easily be
threaded through to the adjustFixupValue helper function from its usual
callsite (applyFixup), these backends ended up adding an MCContext* argument
and adding another call to applyFixup to processFixupValue. Adding an
MCContext parameter to applyFixup makes this unnecessary, and even better -
applyFixup can take a reference to MCContext rather than a potentially null
pointer.
Differential Revision: https://reviews.llvm.org/D30264
llvm-svn: 299529
We had various variants of defining dump() functions in LLVM. Normalize
them (this should just consistently implement the things discussed in
http://lists.llvm.org/pipermail/cfe-dev/2014-January/034323.html
For reference:
- Public headers should just declare the dump() method but not use
LLVM_DUMP_METHOD or #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
- The definition of a dump method should look like this:
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
LLVM_DUMP_METHOD void MyClass::dump() {
// print stuff to dbgs()...
}
#endif
llvm-svn: 293359
Emit error when BPF backend sees a call to a global function or to an external symbol.
The kernel verifier only allows calls to predefined helpers from bpf.h
which are defined in 'enum bpf_func_id'. Such calls in assembler must
look like 'call [1-9]+' where number matches bpf_func_id.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 292204
- teach RelocVisitor to recognize bpf relocations
- fix AsmInfo->PointerSize to make sure dwarf is emitted correctly
- add a test for the above
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 287521
add BPF disassembler, so tools like llvm-objdump can be used:
$ llvm-objdump -d -no-show-raw-insn ./sockex1_kern.o
./sockex1_kern.o: file format ELF64-BPF
Disassembly of section socket1:
bpf_prog1:
0: r6 = r1
8: r0 = *(u8 *)skb[23]
10: *(u32 *)(r10 - 4) = r0
18: r1 = *(u32 *)(r6 + 4)
20: if r1 != 4 goto 8
28: r2 = r10
30: r2 += -4
ld_imm64 (the only 16-byte insn) and special ld_abs/ld_ind instructions
had to be treated in a special way. The decoders for the rest of the insns
are automatically generated.
Add tests to cover new functionality.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 287477
Summary:
* ARM is omitted from this patch because this check appears to expose bugs in this target.
* Mips is omitted from this patch because this check either detects bugs or deliberate
emission of instructions that don't satisfy their predicates. One deliberate
use is the SYNC instruction where the version with an operand is correctly
defined as requiring MIPS32 while the version without an operand is defined
as an alias of 'SYNC 0' and requires MIPS2.
* X86 is omitted from this patch because it doesn't use the tablegen-erated
MCCodeEmitter infrastructure.
Patches for ARM and Mips will follow.
Depends on D25617
Reviewers: tstellarAMD, jmolloy
Subscribers: wdng, jmolloy, aemerson, rengolin, arsenm, jyknight, nemanjai, nhaehnle, tstellarAMD, llvm-commits
Differential Revision: https://reviews.llvm.org/D25618
llvm-svn: 287439
since bpf instruction set was introduced people learned to
read and understand kernel verifier output whereas llvm asm
output stayed obscure and unknown. Convert llvm to emit
assembler text similar to kernel to avoid this discrepancy
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 287300
Some targets, notably AArch64 for ILP32, have different relocation encodings
based upon the ABI. This is an enabling change, so a future patch can use the
ABIName from MCTargetOptions to chose which relocations to use. Tested using
check-llvm.
The corresponding change to clang is in: http://reviews.llvm.org/D16538
Patch by: Joel Jones
Differential Revision: https://reviews.llvm.org/D16213
llvm-svn: 276654
The same value for EM_BPF is being propagated to glibc,
elfutils, and binutils.
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
llvm-svn: 275633
This is a mechanical change to make TargetLowering API take MachineInstr&
(instead of MachineInstr*), since the argument is expected to be a valid
MachineInstr. In one case, changed a parameter from MachineInstr* to
MachineBasicBlock::iterator, since it was used as an insertion point.
As a side effect, this removes a bunch of MachineInstr* to
MachineBasicBlock::iterator implicit conversions, a necessary step
toward fixing PR26753.
llvm-svn: 274287
MCSymbol.h shouldn't pull in MCAssembler.h, just MCFragment.h.
MCLinkerOptimizationHint.h shouldn't need MCMachObjectWriter.h. The
rest is fixing the fallout.
llvm-svn: 273507
This used to be free, copying and moving DebugLocs became expensive
after the metadata rewrite. Passing by reference eliminates a ton of
track/untrack operations. No functionality change intended.
llvm-svn: 272512
The exit-on-error flag is necessary to avoid some assertions/unreachables. We
can get past them by creating a few dummy nodes.
Fixes PR27768, PR27769.
Differential Revision: http://reviews.llvm.org/D20726
llvm-svn: 271200
The exit-on-error flag is needed to avoid an assert where
llvm::SelectionDAGISel::LowerArguments doesn't create enough arguments. Fill up
with zeroes to reach the right number of args.
Fixes PR27767.
Differential Revision: http://reviews.llvm.org/D20571
llvm-svn: 270855
The exit-on-error flag on the many_args1.ll test is needed to avoid an
unreachable in BPFTargetLowering::LowerCall. We can also avoid it by ignoring
any superfluous arguments to the call (i.e. any arguments after the first 5).
Fixes PR27766.
Differential Revision: http://reviews.llvm.org/D20471
v2 of r270419
llvm-svn: 270440
This patch reverts r270419 because it broke a lot of buildbots,
mostly Windows. We'd like help in investigating the issues, but
for now, it should stay out.
llvm-svn: 270433
The exit-on-error flag on the many_args1.ll test is needed to avoid an
unreachable in BPFTargetLowering::LowerCall. We can also avoid it by ignoring
any superfluous arguments to the call (i.e. any arguments after the first 5).
Fixes PR27766
llvm-svn: 270419
