diff options
| author | Yonghong Song <yonghong.song@linux.dev> | 2023-07-27 18:11:56 -0700 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-07-27 18:52:33 -0700 |
| commit | 1f9a1ea821ff25353a0e80d971e7958cd55b47a3 (patch) | |
| tree | 3761503de2b1677a7d392b52710ee428d1a023d6 /arch/x86 | |
| parent | 10d78a66a5f29fbbde1b09b5139c17c436b08c6e (diff) | |
bpf: Support new sign-extension load insns
Add interpreter/jit support for new sign-extension load insns
which adds a new mode (BPF_MEMSX).
Also add verifier support to recognize these insns and to
do proper verification with new insns. In verifier, besides
to deduce proper bounds for the dst_reg, probed memory access
is also properly handled.
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20230728011156.3711870-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/net/bpf_jit_comp.c | 42 |
1 files changed, 39 insertions, 3 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 83c4b45dc65f..54478a9c93e1 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -779,6 +779,29 @@ static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off) *pprog = prog; } +/* LDSX: dst_reg = *(s8*)(src_reg + off) */ +static void emit_ldsx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off) +{ + u8 *prog = *pprog; + + switch (size) { + case BPF_B: + /* Emit 'movsx rax, byte ptr [rax + off]' */ + EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xBE); + break; + case BPF_H: + /* Emit 'movsx rax, word ptr [rax + off]' */ + EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xBF); + break; + case BPF_W: + /* Emit 'movsx rax, dword ptr [rax+0x14]' */ + EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x63); + break; + } + emit_insn_suffix(&prog, src_reg, dst_reg, off); + *pprog = prog; +} + /* STX: *(u8*)(dst_reg + off) = src_reg */ static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off) { @@ -1370,9 +1393,17 @@ st: if (is_imm8(insn->off)) case BPF_LDX | BPF_PROBE_MEM | BPF_W: case BPF_LDX | BPF_MEM | BPF_DW: case BPF_LDX | BPF_PROBE_MEM | BPF_DW: + /* LDXS: dst_reg = *(s8*)(src_reg + off) */ + case BPF_LDX | BPF_MEMSX | BPF_B: + case BPF_LDX | BPF_MEMSX | BPF_H: + case BPF_LDX | BPF_MEMSX | BPF_W: + case BPF_LDX | BPF_PROBE_MEMSX | BPF_B: + case BPF_LDX | BPF_PROBE_MEMSX | BPF_H: + case BPF_LDX | BPF_PROBE_MEMSX | BPF_W: insn_off = insn->off; - if (BPF_MODE(insn->code) == BPF_PROBE_MEM) { + if (BPF_MODE(insn->code) == BPF_PROBE_MEM || + BPF_MODE(insn->code) == BPF_PROBE_MEMSX) { /* Conservatively check that src_reg + insn->off is a kernel address: * src_reg + insn->off >= TASK_SIZE_MAX + PAGE_SIZE * src_reg is used as scratch for src_reg += insn->off and restored @@ -1415,8 +1446,13 @@ st: if (is_imm8(insn->off)) start_of_ldx = prog; end_of_jmp[-1] = start_of_ldx - end_of_jmp; } - emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off); - if (BPF_MODE(insn->code) == BPF_PROBE_MEM) { + if (BPF_MODE(insn->code) == BPF_PROBE_MEMSX || + BPF_MODE(insn->code) == BPF_MEMSX) + emit_ldsx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off); + else + emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off); + if (BPF_MODE(insn->code) == BPF_PROBE_MEM || + BPF_MODE(insn->code) == BPF_PROBE_MEMSX) { struct exception_table_entry *ex; u8 *_insn = image + proglen + (start_of_ldx - temp); s64 delta; |