[ Upstream commit 2f1b0d3d73 ]
The RISC-V architecture does not expose sub-registers, and hold all
32-bit values in a sign-extended format [1] [2]:
| The compiler and calling convention maintain an invariant that all
| 32-bit values are held in a sign-extended format in 64-bit
| registers. Even 32-bit unsigned integers extend bit 31 into bits
| 63 through 32. Consequently, conversion between unsigned and
| signed 32-bit integers is a no-op, as is conversion from a signed
| 32-bit integer to a signed 64-bit integer.
While BPF, on the other hand, exposes sub-registers, and use
zero-extension (similar to arm64/x86).
This has led to some subtle bugs, where a BPF JITted program has not
sign-extended the a0 register (return value in RISC-V land), passed
the return value up the kernel, e.g.:
| int from_bpf(void);
|
| long foo(void)
| {
| return from_bpf();
| }
Here, a0 would be 0xffff_ffff, instead of the expected
0xffff_ffff_ffff_ffff.
Internally, the RISC-V JIT uses a5 as a dedicated register for BPF
return values.
Keep a5 zero-extended, but explicitly sign-extend a0 (which is used
outside BPF land). Now that a0 (RISC-V ABI) and a5 (BPF ABI) differs,
a0 is only moved to a5 for non-BPF native calls (BPF_PSEUDO_CALL).
Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://github.com/riscv/riscv-isa-manual/releases/download/riscv-isa-release-056b6ff-2023-10-02/unpriv-isa-asciidoc.pdf # [2]
Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/releases/download/draft-20230929-e5c800e661a53efe3c2678d71a306323b60eb13b/riscv-abi.pdf # [2]
Link: https://lore.kernel.org/bpf/20231004120706.52848-2-bjorn@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 0fd1fd0104 ]
The current emit_call function is not suitable for kernel function call as
it store return value to bpf R0 register. We can separate it out for common
use. Meanwhile, simplify judgment logic, that is, fixed function address
can use jal or auipc+jalr, while the unfixed can use only auipc+jalr.
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Acked-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/bpf/20230215135205.1411105-3-pulehui@huaweicloud.com
Stable-dep-of: 2f1b0d3d73 ("riscv, bpf: Sign-extend return values")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit c56fb2aab2 ]
In order to generate the prologue and epilogue, the BPF JIT needs to
know which registers that are clobbered. Therefore, the during
pre-final passes, the prologue is generated after the body of the
program body-prologue-epilogue. Then, in the final pass, a proper
prologue-body-epilogue JITted image is generated.
This scheme has worked most of the time. However, for some large
programs with many jumps, e.g. the test_kmod.sh BPF selftest with
hardening enabled (blinding constants), this has shown to be
incorrect. For the final pass, when the proper prologue-body-epilogue
is generated, the image has not converged. This will lead to that the
final image will have incorrect jump offsets. The following is an
excerpt from an incorrect image:
| ...
| 3b8: 00c50663 beq a0,a2,3c4 <.text+0x3c4>
| 3bc: 0020e317 auipc t1,0x20e
| 3c0: 49630067 jalr zero,1174(t1) # 20e852 <.text+0x20e852>
| ...
| 20e84c: 8796 c.mv a5,t0
| 20e84e: 6422 c.ldsp s0,8(sp) # Epilogue start
| 20e850: 6141 c.addi16sp sp,16
| 20e852: 853e c.mv a0,a5 # Incorrect jump target
| 20e854: 8082 c.jr ra
The image has shrunk, and the epilogue offset is incorrect in the
final pass.
Correct the problem by always generating proper prologue-body-epilogue
outputs, which means that the first pass will only generate the body
to track what registers that are touched.
Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20230710074131.19596-1-bjorn@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 3cb7041304 ]
Add support for riscv jit to provide bpf_line_info. We need to
consider the prologue offset in ctx->offset, but unlike x86 and
arm64, ctx->offset of riscv does not provide an extra slot for
the prologue, so here we just calculate the len of prologue and
add it to ctx->offset at the end. Both RV64 and RV32 have been
tested.
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220530092815.1112406-3-pulehui@huawei.com
Stable-dep-of: c56fb2aab2 ("riscv, bpf: Fix inconsistent JIT image generation")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit b54b600361 ]
For BPF_PSEUDO_FUNC instruction, verifier will refill imm with
correct addresses of bpf_calls and then run last pass of JIT.
Since the emit_imm of RV64 is variable-length, which will emit
appropriate length instructions accorroding to the imm, it may
broke ctx->offset, and lead to unpredictable problem, such as
inaccurate jump. So let's fix it with fixed-length instructions.
Fixes: 69c087ba62 ("bpf: Add bpf_for_each_map_elem() helper")
Suggested-by: Björn Töpel <bjorn@rivosinc.com>
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20221206091410.1584784-1-pulehui@huaweicloud.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
The bpf_jit_binary_free() function requires a non-NULL argument. When
the RISC-V BPF JIT fails to converge in NR_JIT_ITERATIONS steps,
jit_data->header will be NULL, which triggers a NULL
dereference. Avoid this by checking the argument, prior calling the
function.
Fixes: ca6cb5447c ("riscv, bpf: Factor common RISC-V JIT code")
Signed-off-by: Björn Töpel <bjorn@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20211028125115.514587-1-bjorn@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Expose the maximum amount of useable memory from the riscv JIT.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Luke Nelson <luke.r.nels@gmail.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/bpf/20211014142554.53120-2-lmb@cloudflare.com
In case of JITs, each of the JIT backends compiles the BPF nospec instruction
/either/ to a machine instruction which emits a speculation barrier /or/ to
/no/ machine instruction in case the underlying architecture is not affected
by Speculative Store Bypass or has different mitigations in place already.
This covers both x86 and (implicitly) arm64: In case of x86, we use 'lfence'
instruction for mitigation. In case of arm64, we rely on the firmware mitigation
as controlled via the ssbd kernel parameter. Whenever the mitigation is enabled,
it works for all of the kernel code with no need to provide any additional
instructions here (hence only comment in arm64 JIT). Other archs can follow
as needed. The BPF nospec instruction is specifically targeting Spectre v4
since i) we don't use a serialization barrier for the Spectre v1 case, and
ii) mitigation instructions for v1 and v4 might be different on some archs.
The BPF nospec is required for a future commit, where the BPF verifier does
annotate intermediate BPF programs with speculation barriers.
Co-developed-by: Piotr Krysiuk <piotras@gmail.com>
Co-developed-by: Benedict Schlueter <benedict.schlueter@rub.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Piotr Krysiuk <piotras@gmail.com>
Signed-off-by: Benedict Schlueter <benedict.schlueter@rub.de>
Acked-by: Alexei Starovoitov <ast@kernel.org>
We allocate Non-executable pages, then call bpf_jit_binary_lock_ro()
to enable executable permission after mapping them read-only. This is
to prepare for STRICT_MODULE_RWX in following patch.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
We will drop the executable permissions of the code pages from the
mapping at allocation time soon. Move bpf_jit_alloc_exec() and
bpf_jit_free_exec() to bpf_jit_core.c so that they can be shared by
both RV64I and RV32I.
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Acked-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
A subsequent patch will add additional atomic operations. These new
operations will use the same opcode field as the existing XADD, with
the immediate discriminating different operations.
In preparation, rename the instruction mode BPF_ATOMIC and start
calling the zero immediate BPF_ADD.
This is possible (doesn't break existing valid BPF progs) because the
immediate field is currently reserved MBZ and BPF_ADD is zero.
All uses are removed from the tree but the BPF_XADD definition is
kept around to avoid breaking builds for people including kernel
headers.
Signed-off-by: Brendan Jackman <jackmanb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20210114181751.768687-5-jackmanb@google.com
This patch uses the RVC support and encodings from bpf_jit.h to optimize
the rv64 jit.
The optimizations work by replacing emit(rv_X(...)) with a call to a
helper function emit_X, which will emit a compressed version of the
instruction when possible, and when RVC is enabled.
The JIT continues to pass all tests in lib/test_bpf.c, and introduces
no new failures to test_verifier; both with and without RVC being enabled.
Most changes are straightforward replacements of emit(rv_X(...), ctx)
with emit_X(..., ctx), with the following exceptions bearing mention;
* Change emit_imm to sign-extend the value in "lower", since the
checks for RVC (and the instructions themselves) treat the value as
signed. Otherwise, small negative immediates will not be recognized as
encodable using an RVC instruction. For example, without this change,
emit_imm(rd, -1, ctx) would cause lower to become 4095, which is not a
6b int even though a "c.li rd, -1" instruction suffices.
* For {BPF_MOV,BPF_ADD} BPF_X, drop using addiw,addw in the 32-bit
cases since the values are zero-extended into the upper 32 bits in
the following instructions anyways, and the addition commutes with
zero-extension. (BPF_SUB BPF_X must still use subw since subtraction
does not commute with zero-extension.)
This patch avoids optimizing branches and jumps to use RVC instructions
since surrounding code often makes assumptions about the sizes of
emitted instructions. Optimizing these will require changing these
functions (e.g., emit_branch) to dynamically compute jump offsets.
The following are examples of the JITed code for the verifier selftest
"direct packet read test#3 for CGROUP_SKB OK", without and with RVC
enabled, respectively. The former uses 178 bytes, and the latter uses 112,
for a ~37% reduction in code size for this example.
Without RVC:
0: 02000813 addi a6,zero,32
4: fd010113 addi sp,sp,-48
8: 02813423 sd s0,40(sp)
c: 02913023 sd s1,32(sp)
10: 01213c23 sd s2,24(sp)
14: 01313823 sd s3,16(sp)
18: 01413423 sd s4,8(sp)
1c: 03010413 addi s0,sp,48
20: 03056683 lwu a3,48(a0)
24: 02069693 slli a3,a3,0x20
28: 0206d693 srli a3,a3,0x20
2c: 03456703 lwu a4,52(a0)
30: 02071713 slli a4,a4,0x20
34: 02075713 srli a4,a4,0x20
38: 03856483 lwu s1,56(a0)
3c: 02049493 slli s1,s1,0x20
40: 0204d493 srli s1,s1,0x20
44: 03c56903 lwu s2,60(a0)
48: 02091913 slli s2,s2,0x20
4c: 02095913 srli s2,s2,0x20
50: 04056983 lwu s3,64(a0)
54: 02099993 slli s3,s3,0x20
58: 0209d993 srli s3,s3,0x20
5c: 09056a03 lwu s4,144(a0)
60: 020a1a13 slli s4,s4,0x20
64: 020a5a13 srli s4,s4,0x20
68: 00900313 addi t1,zero,9
6c: 006a7463 bgeu s4,t1,0x74
70: 00000a13 addi s4,zero,0
74: 02d52823 sw a3,48(a0)
78: 02e52a23 sw a4,52(a0)
7c: 02952c23 sw s1,56(a0)
80: 03252e23 sw s2,60(a0)
84: 05352023 sw s3,64(a0)
88: 00000793 addi a5,zero,0
8c: 02813403 ld s0,40(sp)
90: 02013483 ld s1,32(sp)
94: 01813903 ld s2,24(sp)
98: 01013983 ld s3,16(sp)
9c: 00813a03 ld s4,8(sp)
a0: 03010113 addi sp,sp,48
a4: 00078513 addi a0,a5,0
a8: 00008067 jalr zero,0(ra)
With RVC:
0: 02000813 addi a6,zero,32
4: 7179 c.addi16sp sp,-48
6: f422 c.sdsp s0,40(sp)
8: f026 c.sdsp s1,32(sp)
a: ec4a c.sdsp s2,24(sp)
c: e84e c.sdsp s3,16(sp)
e: e452 c.sdsp s4,8(sp)
10: 1800 c.addi4spn s0,sp,48
12: 03056683 lwu a3,48(a0)
16: 1682 c.slli a3,0x20
18: 9281 c.srli a3,0x20
1a: 03456703 lwu a4,52(a0)
1e: 1702 c.slli a4,0x20
20: 9301 c.srli a4,0x20
22: 03856483 lwu s1,56(a0)
26: 1482 c.slli s1,0x20
28: 9081 c.srli s1,0x20
2a: 03c56903 lwu s2,60(a0)
2e: 1902 c.slli s2,0x20
30: 02095913 srli s2,s2,0x20
34: 04056983 lwu s3,64(a0)
38: 1982 c.slli s3,0x20
3a: 0209d993 srli s3,s3,0x20
3e: 09056a03 lwu s4,144(a0)
42: 1a02 c.slli s4,0x20
44: 020a5a13 srli s4,s4,0x20
48: 4325 c.li t1,9
4a: 006a7363 bgeu s4,t1,0x50
4e: 4a01 c.li s4,0
50: d914 c.sw a3,48(a0)
52: d958 c.sw a4,52(a0)
54: dd04 c.sw s1,56(a0)
56: 03252e23 sw s2,60(a0)
5a: 05352023 sw s3,64(a0)
5e: 4781 c.li a5,0
60: 7422 c.ldsp s0,40(sp)
62: 7482 c.ldsp s1,32(sp)
64: 6962 c.ldsp s2,24(sp)
66: 69c2 c.ldsp s3,16(sp)
68: 6a22 c.ldsp s4,8(sp)
6a: 6145 c.addi16sp sp,48
6c: 853e c.mv a0,a5
6e: 8082 c.jr ra
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Cc: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200721025241.8077-4-luke.r.nels@gmail.com
This patch adds functions for encoding and emitting compressed riscv
(RVC) instructions to the BPF JIT.
Some regular riscv instructions can be compressed into an RVC instruction
if the instruction fields meet some requirements. For example, "add rd,
rs1, rs2" can be compressed into "c.add rd, rs2" when rd == rs1.
To make using RVC encodings simpler, this patch also adds helper
functions that selectively emit either a regular instruction or a
compressed instruction if possible.
For example, emit_add will produce a "c.add" if possible and regular
"add" otherwise.
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200721025241.8077-3-luke.r.nels@gmail.com
This patch makes the necessary changes to struct rv_jit_context and to
bpf_int_jit_compile to support compressed riscv (RVC) instructions in
the BPF JIT.
It changes the JIT image to be u16 instead of u32, since RVC instructions
are 2 bytes as opposed to 4.
It also changes ctx->offset and ctx->ninsns to refer to 2-byte
instructions rather than 4-byte ones. The riscv PC is required to be
16-bit aligned with or without RVC, so this is sufficient to refer to
any valid riscv offset.
The code for computing jump offsets in bytes is updated accordingly,
and factored into a new "ninsns_rvoff" function to simplify the code.
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200721025241.8077-2-luke.r.nels@gmail.com
This patch optimizes BPF_JSET BPF_K by using a RISC-V andi instruction
when the BPF immediate fits in 12 bits, instead of first loading the
immediate to a temporary register.
Examples of generated code with and without this optimization:
BPF_JMP_IMM(BPF_JSET, R1, 2, 1) without optimization:
20: li t1,2
24: and t1,a0,t1
28: bnez t1,0x30
BPF_JMP_IMM(BPF_JSET, R1, 2, 1) with optimization:
20: andi t1,a0,2
24: bnez t1,0x2c
BPF_JMP32_IMM(BPF_JSET, R1, 2, 1) without optimization:
20: li t1,2
24: mv t2,a0
28: slli t2,t2,0x20
2c: srli t2,t2,0x20
30: slli t1,t1,0x20
34: srli t1,t1,0x20
38: and t1,t2,t1
3c: bnez t1,0x44
BPF_JMP32_IMM(BPF_JSET, R1, 2, 1) with optimization:
20: andi t1,a0,2
24: bnez t1,0x2c
In these examples, because the upper 32 bits of the sign-extended
immediate are 0, BPF_JMP BPF_JSET and BPF_JMP32 BPF_JSET are equivalent
and therefore the JIT produces identical code for them.
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200506000320.28965-5-luke.r.nels@gmail.com
This patch adds an optimization to BPF_JMP (32- and 64-bit) BPF_K for
when the BPF immediate is zero.
When the immediate is zero, the code can directly use the RISC-V zero
register instead of loading a zero immediate to a temporary register
first.
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200506000320.28965-4-luke.r.nels@gmail.com
This patch adds two optimizations for BPF_ALU BPF_END BPF_FROM_LE in
the RV64 BPF JIT.
First, it enables the verifier zero-extension optimization to avoid zero
extension when imm == 32. Second, it avoids generating code for imm ==
64, since it is equivalent to a no-op.
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200506000320.28965-3-luke.r.nels@gmail.com
Commit 66d0d5a854 ("riscv: bpf: eliminate zero extension code-gen")
added support for the verifier zero-extension optimization on RV64 and
commit 46dd3d7d28 ("bpf, riscv: Enable zext optimization for more
RV64G ALU ops") enabled it for more instruction cases.
However, BPF_LSH BPF_X and BPF_{LSH,RSH,ARSH} BPF_K are still missing
the optimization.
This patch enables the zero-extension optimization for these remaining
cases.
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200506000320.28965-2-luke.r.nels@gmail.com
This patch fixes issues with stackframe unwinding and alignment in the
current stack layout for BPF programs on RV32.
In the current layout, RV32 fp points to the JIT scratch registers, rather
than to the callee-saved registers. This breaks stackframe unwinding,
which expects fp to point just above the saved ra and fp registers.
This patch fixes the issue by moving the callee-saved registers to be
stored on the top of the stack, pointed to by fp. This satisfies the
assumptions of stackframe unwinding.
This patch also fixes an issue with the old layout that the stack was
not aligned to 16 bytes.
Stacktrace from JITed code using the old stack layout:
[ 12.196249 ] [<c0402200>] walk_stackframe+0x0/0x96
Stacktrace using the new stack layout:
[ 13.062888 ] [<c0402200>] walk_stackframe+0x0/0x96
[ 13.063028 ] [<c04023c6>] show_stack+0x28/0x32
[ 13.063253 ] [<a403e778>] bpf_prog_82b916b2dfa00464+0x80/0x908
[ 13.063417 ] [<c09270b2>] bpf_test_run+0x124/0x39a
[ 13.063553 ] [<c09276c0>] bpf_prog_test_run_skb+0x234/0x448
[ 13.063704 ] [<c048510e>] __do_sys_bpf+0x766/0x13b4
[ 13.063840 ] [<c0485d82>] sys_bpf+0xc/0x14
[ 13.063961 ] [<c04010f0>] ret_from_syscall+0x0/0x2
The new code is also simpler to understand and includes an ASCII diagram
of the stack layout.
Tested on riscv32 QEMU virt machine.
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Xi Wang <xi.wang@gmail.com>
Link: https://lore.kernel.org/bpf/20200430005127.2205-1-luke.r.nels@gmail.com
This patch fixes an off by one error in the RV32 JIT handling for BPF
tail call. Currently, the code decrements TCC before checking if it
is less than zero. This limits the maximum number of tail calls to 32
instead of 33 as in other JITs. The fix is to instead check the old
value of TCC before decrementing.
Fixes: 5f316b65e9 ("riscv, bpf: Add RV32G eBPF JIT")
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Xi Wang <xi.wang@gmail.com>
Link: https://lore.kernel.org/bpf/20200421002804.5118-1-luke.r.nels@gmail.com
The existing code in emit_call on RV64 checks that the PC-relative offset
to the function fits in 32 bits before calling emit_jump_and_link to emit
an auipc+jalr pair. However, this check is incorrect because offsets in
the range [2^31 - 2^11, 2^31 - 1] cannot be encoded using auipc+jalr on
RV64 (see discussion [1]). The RISC-V spec has recently been updated
to reflect this fact [2, 3].
This patch fixes the problem by moving the check on the offset into
emit_jump_and_link and modifying it to the correct range of encodable
offsets, which is [-2^31 - 2^11, 2^31 - 2^11). This also enforces the
check on the offset to other uses of emit_jump_and_link (e.g., BPF_JA)
as well.
Currently, this bug is unlikely to be triggered, because the memory
region from which JITed images are allocated is close enough to kernel
text for the offsets to not become too large; and because the bounds on
BPF program size are small enough. This patch prevents this problem from
becoming an issue if either of these change.
[1]: https://groups.google.com/a/groups.riscv.org/forum/#!topic/isa-dev/bwWFhBnnZFQ
[2]: b1e42e09ac
[3]: 4c1b2066eb
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200406221604.18547-1-luke.r.nels@gmail.com
This is an eBPF JIT for RV32G, adapted from the JIT for RV64G and
the 32-bit ARM JIT.
There are two main changes required for this to work compared to
the RV64 JIT.
First, eBPF registers are 64-bit, while RV32G registers are 32-bit.
BPF registers either map directly to 2 RISC-V registers, or reside
in stack scratch space and are saved and restored when used.
Second, many 64-bit ALU operations do not trivially map to 32-bit
operations. Operations that move bits between high and low words,
such as ADD, LSH, MUL, and others must emulate the 64-bit behavior
in terms of 32-bit instructions.
This patch also makes related changes to bpf_jit.h, such
as adding RISC-V instructions required by the RV32 JIT.
Supported features:
The RV32 JIT supports the same features and instructions as the
RV64 JIT, with the following exceptions:
- ALU64 DIV/MOD: Requires loops to implement on 32-bit hardware.
- BPF_XADD | BPF_DW: There's no 8-byte atomic instruction in RV32.
These features are also unsupported on other BPF JITs for 32-bit
architectures.
Testing:
- lib/test_bpf.c
test_bpf: Summary: 378 PASSED, 0 FAILED, [349/366 JIT'ed]
test_bpf: test_skb_segment: Summary: 2 PASSED, 0 FAILED
The tests that are not JITed are all due to use of 64-bit div/mod
or 64-bit xadd.
- tools/testing/selftests/bpf/test_verifier.c
Summary: 1415 PASSED, 122 SKIPPED, 43 FAILED
Tested both with and without BPF JIT hardening.
This is the same set of tests that pass using the BPF interpreter
with the JIT disabled.
Verification and synthesis:
We developed the RV32 JIT using our automated verification tool,
Serval. We have used Serval in the past to verify patches to the
RV64 JIT. We also used Serval to superoptimize the resulting code
through program synthesis.
You can find the tool and a guide to the approach and results here:
https://github.com/uw-unsat/serval-bpf/tree/rv32-jit-v5
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200305050207.4159-3-luke.r.nels@gmail.com
This patch factors out code that can be used by both the RV64 and RV32
BPF JITs to a common bpf_jit.h and bpf_jit_core.c.
Move struct definitions and macro-like functions to header. Rename
rv_sb_insn/rv_uj_insn to rv_b_insn/rv_j_insn to match the RISC-V
specification.
Move reusable functions emit_body() and bpf_int_jit_compile() to
bpf_jit_core.c with minor simplifications. Rename emit_insn() and
build_{prologue,epilogue}() to be prefixed with "bpf_jit_" as they are
no longer static.
Rename bpf_jit_comp.c to bpf_jit_comp64.c to be more explicit.
Co-developed-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Link: https://lore.kernel.org/bpf/20200305050207.4159-2-luke.r.nels@gmail.com
Daniel Borkmann says:
====================
pull-request: bpf-next 2019-12-27
The following pull-request contains BPF updates for your *net-next* tree.
We've added 127 non-merge commits during the last 17 day(s) which contain
a total of 110 files changed, 6901 insertions(+), 2721 deletions(-).
There are three merge conflicts. Conflicts and resolution looks as follows:
1) Merge conflict in net/bpf/test_run.c:
There was a tree-wide cleanup c593642c8b ("treewide: Use sizeof_field() macro")
which gets in the way with b590cb5f80 ("bpf: Switch to offsetofend in
BPF_PROG_TEST_RUN"):
<<<<<<< HEAD
if (!range_is_zero(__skb, offsetof(struct __sk_buff, priority) +
sizeof_field(struct __sk_buff, priority),
=======
if (!range_is_zero(__skb, offsetofend(struct __sk_buff, priority),
>>>>>>> 7c8dce4b16
There are a few occasions that look similar to this. Always take the chunk with
offsetofend(). Note that there is one where the fields differ in here:
<<<<<<< HEAD
if (!range_is_zero(__skb, offsetof(struct __sk_buff, tstamp) +
sizeof_field(struct __sk_buff, tstamp),
=======
if (!range_is_zero(__skb, offsetofend(struct __sk_buff, gso_segs),
>>>>>>> 7c8dce4b16
Just take the one with offsetofend() /and/ gso_segs. Latter is correct due to
850a88cc40 ("bpf: Expose __sk_buff wire_len/gso_segs to BPF_PROG_TEST_RUN").
2) Merge conflict in arch/riscv/net/bpf_jit_comp.c:
(I'm keeping Bjorn in Cc here for a double-check in case I got it wrong.)
<<<<<<< HEAD
if (is_13b_check(off, insn))
return -1;
emit(rv_blt(tcc, RV_REG_ZERO, off >> 1), ctx);
=======
emit_branch(BPF_JSLT, RV_REG_T1, RV_REG_ZERO, off, ctx);
>>>>>>> 7c8dce4b16
Result should look like:
emit_branch(BPF_JSLT, tcc, RV_REG_ZERO, off, ctx);
3) Merge conflict in arch/riscv/include/asm/pgtable.h:
<<<<<<< HEAD
=======
#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
#define VMALLOC_END (PAGE_OFFSET - 1)
#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
#define BPF_JIT_REGION_SIZE (SZ_128M)
#define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
#define BPF_JIT_REGION_END (VMALLOC_END)
/*
* Roughly size the vmemmap space to be large enough to fit enough
* struct pages to map half the virtual address space. Then
* position vmemmap directly below the VMALLOC region.
*/
#define VMEMMAP_SHIFT \
(CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
#define VMEMMAP_SIZE BIT(VMEMMAP_SHIFT)
#define VMEMMAP_END (VMALLOC_START - 1)
#define VMEMMAP_START (VMALLOC_START - VMEMMAP_SIZE)
#define vmemmap ((struct page *)VMEMMAP_START)
>>>>>>> 7c8dce4b16
Only take the BPF_* defines from there and move them higher up in the
same file. Remove the rest from the chunk. The VMALLOC_* etc defines
got moved via 01f52e16b8 ("riscv: define vmemmap before pfn_to_page
calls"). Result:
[...]
#define __S101 PAGE_READ_EXEC
#define __S110 PAGE_SHARED_EXEC
#define __S111 PAGE_SHARED_EXEC
#define VMALLOC_SIZE (KERN_VIRT_SIZE >> 1)
#define VMALLOC_END (PAGE_OFFSET - 1)
#define VMALLOC_START (PAGE_OFFSET - VMALLOC_SIZE)
#define BPF_JIT_REGION_SIZE (SZ_128M)
#define BPF_JIT_REGION_START (PAGE_OFFSET - BPF_JIT_REGION_SIZE)
#define BPF_JIT_REGION_END (VMALLOC_END)
/*
* Roughly size the vmemmap space to be large enough to fit enough
* struct pages to map half the virtual address space. Then
* position vmemmap directly below the VMALLOC region.
*/
#define VMEMMAP_SHIFT \
(CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
#define VMEMMAP_SIZE BIT(VMEMMAP_SHIFT)
#define VMEMMAP_END (VMALLOC_START - 1)
#define VMEMMAP_START (VMALLOC_START - VMEMMAP_SIZE)
[...]
Let me know if there are any other issues.
Anyway, the main changes are:
1) Extend bpftool to produce a struct (aka "skeleton") tailored and specific
to a provided BPF object file. This provides an alternative, simplified API
compared to standard libbpf interaction. Also, add libbpf extern variable
resolution for .kconfig section to import Kconfig data, from Andrii Nakryiko.
2) Add BPF dispatcher for XDP which is a mechanism to avoid indirect calls by
generating a branch funnel as discussed back in bpfconf'19 at LSF/MM. Also,
add various BPF riscv JIT improvements, from Björn Töpel.
3) Extend bpftool to allow matching BPF programs and maps by name,
from Paul Chaignon.
4) Support for replacing cgroup BPF programs attached with BPF_F_ALLOW_MULTI
flag for allowing updates without service interruption, from Andrey Ignatov.
5) Cleanup and simplification of ring access functions for AF_XDP with a
bonus of 0-5% performance improvement, from Magnus Karlsson.
6) Enable BPF JITs for x86-64 and arm64 by default. Also, final version of
audit support for BPF, from Daniel Borkmann and latter with Jiri Olsa.
7) Move and extend test_select_reuseport into BPF program tests under
BPF selftests, from Jakub Sitnicki.
8) Various BPF sample improvements for xdpsock for customizing parameters
to set up and benchmark AF_XDP, from Jay Jayatheerthan.
9) Improve libbpf to provide a ulimit hint on permission denied errors.
Also change XDP sample programs to attach in driver mode by default,
from Toke Høiland-Jørgensen.
10) Extend BPF test infrastructure to allow changing skb mark from tc BPF
programs, from Nikita V. Shirokov.
11) Optimize prologue code sequence in BPF arm32 JIT, from Russell King.
12) Fix xdp_redirect_cpu BPF sample to manually attach to tracepoints after
libbpf conversion, from Jesper Dangaard Brouer.
13) Minor misc improvements from various others.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Instead of using emit_imm() and emit_jalr() which can expand to six
instructions, start using jal or auipc+jalr.
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216091343.23260-8-bjorn.topel@gmail.com
This commit makes sure that the JIT images is kept close to the kernel
text, so BPF calls can use relative calling with auipc/jalr or jal
instead of loading the full 64-bit address and jalr.
The BPF JIT image region is 128 MB before the kernel text.
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216091343.23260-7-bjorn.topel@gmail.com
This commit add support for far (offset > 21b) jumps and exits.
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Luke Nelson <lukenels@cs.washington.edu>
Link: https://lore.kernel.org/bpf/20191216091343.23260-5-bjorn.topel@gmail.com
This commit adds branch relaxation to the BPF JIT, and with that
support for far (offset greater than 12b) branching.
The branch relaxation requires more than two passes to converge. For
most programs it is three passes, but for larger programs it can be
more.
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Luke Nelson <lukenels@cs.washington.edu>
Link: https://lore.kernel.org/bpf/20191216091343.23260-3-bjorn.topel@gmail.com
The BPF JIT incorrectly clobbered the a0 register, and did not flag
usage of s5 register when BPF stack was being used.
Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191216091343.23260-2-bjorn.topel@gmail.com
All BPF JIT compilers except RISC-V's and MIPS' enforce a 33-tail calls
limit at runtime. In addition, a test was recently added, in tailcalls2,
to check this limit.
This patch updates the tail call limit in RISC-V's JIT compiler to allow
33 tail calls. I tested it using the above selftest on an emulated
RISCV64.
Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Reported-by: Mahshid Khezri <khezri.mahshid@gmail.com>
Signed-off-by: Paul Chaignon <paul.chaignon@orange.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/966fe384383bf23a0ee1efe8d7291c78a3fb832b.1575916815.git.paul.chaignon@gmail.com
Commit 66d0d5a854 ("riscv: bpf: eliminate zero extension code-gen")
added the new zero-extension optimization for some BPF ALU operations.
Since then, bugs in the JIT that have been fixed in the bpf tree require
this optimization to be added to other operations: commit 1e692f09e0
("bpf, riscv: clear high 32 bits for ALU32 add/sub/neg/lsh/rsh/arsh"),
and commit fe121ee531 ("bpf, riscv: clear target register high 32-bits
for and/or/xor on ALU32").
Now that these have been merged to bpf-next, the zext optimization can
be enabled for the fixed operations.
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Cc: Song Liu <liu.song.a23@gmail.com>
Cc: Jiong Wang <jiong.wang@netronome.com>
Cc: Xi Wang <xi.wang@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Daniel Borkmann says:
====================
pull-request: bpf 2019-06-07
The following pull-request contains BPF updates for your *net* tree.
The main changes are:
1) Fix several bugs in riscv64 JIT code emission which forgot to clear high
32-bits for alu32 ops, from Björn and Luke with selftests covering all
relevant BPF alu ops from Björn and Jiong.
2) Two fixes for UDP BPF reuseport that avoid calling the program in case of
__udp6_lib_err and UDP GRO which broke reuseport_select_sock() assumption
that skb->data is pointing to transport header, from Martin.
3) Two fixes for BPF sockmap: a use-after-free from sleep in psock's backlog
workqueue, and a missing restore of sk_write_space when psock gets dropped,
from Jakub and John.
4) Fix unconnected UDP sendmsg hook API which is insufficient as-is since it
breaks standard applications like DNS if reverse NAT is not performed upon
receive, from Daniel.
5) Fix an out-of-bounds read in __bpf_skc_lookup which in case of AF_INET6
fails to verify that the length of the tuple is long enough, from Lorenz.
6) Fix libbpf's libbpf__probe_raw_btf to return an fd instead of 0/1 (for
{un,}successful probe) as that is expected to be propagated as an fd to
load_sk_storage_btf() and thus closing the wrong descriptor otherwise,
from Michal.
7) Fix bpftool's JSON output for the case when a lookup fails, from Krzesimir.
8) Minor misc fixes in docs, samples and selftests, from various others.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
In BPF, 32-bit ALU operations should zero-extend their results into
the 64-bit registers.
The current BPF JIT on RISC-V emits incorrect instructions that perform
sign extension only (e.g., addw, subw) on 32-bit add, sub, lsh, rsh,
arsh, and neg. This behavior diverges from the interpreter and JITs
for other architectures.
This patch fixes the bugs by performing zero extension on the destination
register of 32-bit ALU operations.
Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Cc: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Luke Nelson <luke.r.nels@gmail.com>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Cc: Björn Töpel <bjorn.topel@gmail.com>
Acked-by: Björn Töpel <bjorn.topel@gmail.com>
Tested-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
When using 32-bit subregisters (ALU32), the RISC-V JIT would not clear
the high 32-bits of the target register and therefore generate
incorrect code.
E.g., in the following code:
$ cat test.c
unsigned int f(unsigned long long a,
unsigned int b)
{
return (unsigned int)a & b;
}
$ clang-9 -target bpf -O2 -emit-llvm -S test.c -o - | \
llc-9 -mattr=+alu32 -mcpu=v3
.text
.file "test.c"
.globl f
.p2align 3
.type f,@function
f:
r0 = r1
w0 &= w2
exit
.Lfunc_end0:
.size f, .Lfunc_end0-f
The JIT would not clear the high 32-bits of r0 after the
and-operation, which in this case might give an incorrect return
value.
After this patch, that is not the case, and the upper 32-bits are
cleared.
Reported-by: Jiong Wang <jiong.wang@netronome.com>
Fixes: 2353ecc6f9 ("bpf, riscv: add BPF JIT for RV64G")
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Add SPDX license identifiers to all Make/Kconfig files which:
- Have no license information of any form
These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:
GPL-2.0-only
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit adds a BPF JIT for RV64G.
The JIT is a two-pass JIT, and has a dynamic prolog/epilogue (similar
to the MIPS64 BPF JIT) instead of static ones (e.g. x86_64).
At the moment the RISC-V Linux port does not support
CONFIG_HAVE_KPROBES, which means that CONFIG_BPF_EVENTS is not
supported. Thus, no tests involving BPF_PROG_TYPE_TRACEPOINT,
BPF_PROG_TYPE_PERF_EVENT, BPF_PROG_TYPE_KPROBE and
BPF_PROG_TYPE_RAW_TRACEPOINT passes.
The implementation does not support "far branching" (>4KiB).
Test results:
# modprobe test_bpf
test_bpf: Summary: 378 PASSED, 0 FAILED, [366/366 JIT'ed]
# echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
# ./test_verifier
...
Summary: 761 PASSED, 507 SKIPPED, 2 FAILED
Note that "test_verifier" was run with one build with
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y and one without, otherwise
many of the the tests that require unaligned access were skipped.
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y:
# echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
# ./test_verifier | grep -c 'NOTE.*unknown align'
0
No CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS:
# echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
# ./test_verifier | grep -c 'NOTE.*unknown align'
59
The two failing test_verifier tests are:
"ld_abs: vlan + abs, test 1"
"ld_abs: jump around ld_abs"
This is due to that "far branching" involved in those tests.
All tests where done on QEMU (QEMU emulator version 3.1.50
(v3.1.0-688-g8ae951fbc106)).
Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Björn Töpel
Pu Lehui
Björn Töpel
Lorenz Bauer
Daniel Borkmann
Jisheng Zhang
Brendan Jackman
Gustavo A. R. Silva
Luke Nelson
David S. Miller
Björn Töpel
Paul Chaignon
Luke Nelson
Jiong Wang
Thomas Gleixner