| Message ID | 1431063591-16668-1-git-send-email-xi.wang@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, May 08, 2015 at 06:39:51AM +0100, Xi Wang wrote: > Consider "(u64)insn1.imm << 32 | imm" in the arm64 JIT. Since imm is > signed 32-bit, it is sign-extended to 64-bit, losing the high 32 bits. > The fix is to convert imm to u32 first and zero-extend it to u64. > > Also extend test_bpf to catch this JIT bug; the interpreter is correct. > > Before: > test_bpf: #58 load 64-bit immediate ret -1 != 1 FAIL (1 times) > > After: > test_bpf: #58 load 64-bit immediate 74 PASS > > Fixes: 30d3d94cc3d5 ("arm64: bpf: add 'load 64-bit immediate' instruction") > Cc: Zi Shen Lim <zlim.lnx@gmail.com> > Cc: Alexei Starovoitov <ast@plumgrid.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Signed-off-by: Xi Wang <xi.wang@gmail.com> > --- > arch/arm64/net/bpf_jit_comp.c | 2 +- > lib/test_bpf.c | 3 ++- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > index edba042b2325..14cdc099fda0 100644 > --- a/arch/arm64/net/bpf_jit_comp.c > +++ b/arch/arm64/net/bpf_jit_comp.c > @@ -487,7 +487,7 @@ emit_cond_jmp: > return -EINVAL; > } > > - imm64 = (u64)insn1.imm << 32 | imm; > + imm64 = ((u64)(u32)insn1.imm) << 32 | (u64)(u32)imm; This seems a bit convoluted to me. Don't you just need to add a (u32) cast to imm and that's it? The (u64)(u32) looks redundant. > emit_a64_mov_i64(dst, imm64, ctx); > > return 1; > diff --git a/lib/test_bpf.c b/lib/test_bpf.c > index 80d78c51f65f..9f6849891b5f 100644 > --- a/lib/test_bpf.c > +++ b/lib/test_bpf.c > @@ -1755,7 +1755,8 @@ static struct bpf_test tests[] = { > BPF_EXIT_INSN(), > BPF_JMP_IMM(BPF_JEQ, R3, 0x1234, 1), > BPF_EXIT_INSN(), > - BPF_ALU64_IMM(BPF_MOV, R0, 1), > + BPF_LD_IMM64(R0, 0x1ffffffffLL), > + BPF_ALU64_IMM(BPF_RSH, R0, 32), /* R0 = 1 */ > BPF_EXIT_INSN(), This hunk should probably be a separate patch, unless you get Alexei's ack for me to take it via the arm64 tree too. Will
On Fri, May 8, 2015 at 1:38 AM, Will Deacon <will.deacon@arm.com> wrote: >> - imm64 = (u64)insn1.imm << 32 | imm; >> + imm64 = ((u64)(u32)insn1.imm) << 32 | (u64)(u32)imm; > > This seems a bit convoluted to me. Don't you just need to add a (u32) > cast to imm and that's it? The (u64)(u32) looks redundant. You're right - the second (u64) is redundant; the hope was to make the code easier to understand. It's from the interpreter code in kernel/core/bpf.c, which uses (u64)(u32) as well. >> - BPF_ALU64_IMM(BPF_MOV, R0, 1), >> + BPF_LD_IMM64(R0, 0x1ffffffffLL), >> + BPF_ALU64_IMM(BPF_RSH, R0, 32), /* R0 = 1 */ >> BPF_EXIT_INSN(), > > This hunk should probably be a separate patch, unless you get Alexei's ack > for me to take it via the arm64 tree too. I would be happy to split this into a separate patch if that works better, or simply drop this part. - xi
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index edba042b2325..14cdc099fda0 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -487,7 +487,7 @@ emit_cond_jmp: return -EINVAL; } - imm64 = (u64)insn1.imm << 32 | imm; + imm64 = ((u64)(u32)insn1.imm) << 32 | (u64)(u32)imm; emit_a64_mov_i64(dst, imm64, ctx); return 1; diff --git a/lib/test_bpf.c b/lib/test_bpf.c index 80d78c51f65f..9f6849891b5f 100644 --- a/lib/test_bpf.c +++ b/lib/test_bpf.c @@ -1755,7 +1755,8 @@ static struct bpf_test tests[] = { BPF_EXIT_INSN(), BPF_JMP_IMM(BPF_JEQ, R3, 0x1234, 1), BPF_EXIT_INSN(), - BPF_ALU64_IMM(BPF_MOV, R0, 1), + BPF_LD_IMM64(R0, 0x1ffffffffLL), + BPF_ALU64_IMM(BPF_RSH, R0, 32), /* R0 = 1 */ BPF_EXIT_INSN(), }, INTERNAL,
Consider "(u64)insn1.imm << 32 | imm" in the arm64 JIT. Since imm is signed 32-bit, it is sign-extended to 64-bit, losing the high 32 bits. The fix is to convert imm to u32 first and zero-extend it to u64. Also extend test_bpf to catch this JIT bug; the interpreter is correct. Before: test_bpf: #58 load 64-bit immediate ret -1 != 1 FAIL (1 times) After: test_bpf: #58 load 64-bit immediate 74 PASS Fixes: 30d3d94cc3d5 ("arm64: bpf: add 'load 64-bit immediate' instruction") Cc: Zi Shen Lim <zlim.lnx@gmail.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Xi Wang <xi.wang@gmail.com> --- arch/arm64/net/bpf_jit_comp.c | 2 +- lib/test_bpf.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-)