| Message ID | 20210929111855.50254-8-hbathini@linux.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf powerpc: Add BPF_PROBE_MEM support in powerpc JIT compiler | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
| bpf/vmtest-bpf-next-PR | success | PR summary |
| bpf/vmtest-bpf-PR | success | PR summary |
| bpf/vmtest-bpf | success | VM_Test |
| bpf/vmtest-bpf-next | success | VM_Test |
Le 29/09/2021 à 13:18, Hari Bathini a écrit : > BPF load instruction with BPF_PROBE_MEM mode can cause a fault > inside kernel. Append exception table for such instructions > within BPF program. > > Unlike other archs which uses extable 'fixup' field to pass dest_reg > and nip, BPF exception table on PowerPC follows the generic PowerPC > exception table design, where it populates both fixup and extable > sections within BPF program. fixup section contains 3 instructions, > first 2 instructions clear dest_reg (lower & higher 32-bit registers) > and last instruction jumps to next instruction in the BPF code. > extable 'insn' field contains relative offset of the instruction and > 'fixup' field contains relative offset of the fixup entry. Example > layout of BPF program with extable present: > > +------------------+ > | | > | | > 0x4020 -->| lwz r28,4(r4) | > | | > | | > 0x40ac -->| lwz r3,0(r24) | > | lwz r4,4(r24) | > | | > | | > |------------------| > 0x4278 -->| li r28,0 | \ > | li r27,0 | | fixup entry > | b 0x4024 | / > 0x4284 -->| li r4,0 | > | li r3,0 | > | b 0x40b4 | > |------------------| > 0x4290 -->| insn=0xfffffd90 | \ extable entry > | fixup=0xffffffe4 | / > 0x4298 -->| insn=0xfffffe14 | > | fixup=0xffffffe8 | > +------------------+ > > (Addresses shown here are chosen random, not real) > > Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> > --- > > Changes in v4: > * Dropped explicit fallthrough statement for empty switch cases. > > > arch/powerpc/net/bpf_jit.h | 4 ++++ > arch/powerpc/net/bpf_jit_comp.c | 2 ++ > arch/powerpc/net/bpf_jit_comp32.c | 30 ++++++++++++++++++++++++++++++ > 3 files changed, 36 insertions(+) > > diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h > index 561689a2abdf..800734056200 100644 > --- a/arch/powerpc/net/bpf_jit.h > +++ b/arch/powerpc/net/bpf_jit.h > @@ -144,7 +144,11 @@ struct codegen_context { > unsigned int exentry_idx; > }; > > +#ifdef CONFIG_PPC32 > +#define BPF_FIXUP_LEN 3 /* Three instructions => 12 bytes */ > +#else > #define BPF_FIXUP_LEN 2 /* Two instructions => 8 bytes */ > +#endif > > static inline void bpf_flush_icache(void *start, void *end) > { > diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c > index f02457c6b54f..1a0041997050 100644 > --- a/arch/powerpc/net/bpf_jit_comp.c > +++ b/arch/powerpc/net/bpf_jit_comp.c > @@ -297,6 +297,8 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code > (ctx->exentry_idx * BPF_FIXUP_LEN * 4); > > fixup[0] = PPC_RAW_LI(dst_reg, 0); > + if (IS_ENABLED(CONFIG_PPC32)) > + fixup[1] = PPC_RAW_LI(dst_reg - 1, 0); /* clear higher 32-bit register too */ > > fixup[BPF_FIXUP_LEN - 1] = > PPC_RAW_BRANCH((long)(pc + jmp_off) - (long)&fixup[BPF_FIXUP_LEN - 1]); > diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c > index c04291517a7e..6ee13a09c70d 100644 > --- a/arch/powerpc/net/bpf_jit_comp32.c > +++ b/arch/powerpc/net/bpf_jit_comp32.c > @@ -811,9 +811,13 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * > * BPF_LDX > */ > case BPF_LDX | BPF_MEM | BPF_B: /* dst = *(u8 *)(ul) (src + off) */ > + case BPF_LDX | BPF_PROBE_MEM | BPF_B: > case BPF_LDX | BPF_MEM | BPF_H: /* dst = *(u16 *)(ul) (src + off) */ > + case BPF_LDX | BPF_PROBE_MEM | BPF_H: > case BPF_LDX | BPF_MEM | BPF_W: /* dst = *(u32 *)(ul) (src + off) */ > + case BPF_LDX | BPF_PROBE_MEM | BPF_W: > case BPF_LDX | BPF_MEM | BPF_DW: /* dst = *(u64 *)(ul) (src + off) */ > + case BPF_LDX | BPF_PROBE_MEM | BPF_DW: > switch (size) { > case BPF_B: > EMIT(PPC_RAW_LBZ(dst_reg, src_reg, off)); > @@ -832,6 +836,32 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * > > if (size != BPF_DW && !fp->aux->verifier_zext) > EMIT(PPC_RAW_LI(dst_reg_h, 0)); > + > + if (BPF_MODE(code) == BPF_PROBE_MEM) { > + int insn_idx = ctx->idx - 1; > + int jmp_off = 4; > + > + /* > + * In case of BPF_DW, two lwz instructions are emitted, one > + * for higher 32-bit and another for lower 32-bit. So, set > + * ex->insn to the first of the two and jump over both > + * instructions in fixup. > + * > + * Similarly, with !verifier_zext, two instructions are > + * emitted for BPF_B/H/W case. So, set ex->insn to the > + * instruction that could fault and skip over both > + * instructions. > + */ > + if (size == BPF_DW || !fp->aux->verifier_zext) { > + insn_idx -= 1; > + jmp_off += 4; > + } > + > + ret = bpf_add_extable_entry(fp, image, pass, ctx, insn_idx, > + jmp_off, dst_reg); > + if (ret) > + return ret; > + } > break; > > /* >
diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 561689a2abdf..800734056200 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -144,7 +144,11 @@ struct codegen_context { unsigned int exentry_idx; }; +#ifdef CONFIG_PPC32 +#define BPF_FIXUP_LEN 3 /* Three instructions => 12 bytes */ +#else #define BPF_FIXUP_LEN 2 /* Two instructions => 8 bytes */ +#endif static inline void bpf_flush_icache(void *start, void *end) { diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index f02457c6b54f..1a0041997050 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -297,6 +297,8 @@ int bpf_add_extable_entry(struct bpf_prog *fp, u32 *image, int pass, struct code (ctx->exentry_idx * BPF_FIXUP_LEN * 4); fixup[0] = PPC_RAW_LI(dst_reg, 0); + if (IS_ENABLED(CONFIG_PPC32)) + fixup[1] = PPC_RAW_LI(dst_reg - 1, 0); /* clear higher 32-bit register too */ fixup[BPF_FIXUP_LEN - 1] = PPC_RAW_BRANCH((long)(pc + jmp_off) - (long)&fixup[BPF_FIXUP_LEN - 1]); diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index c04291517a7e..6ee13a09c70d 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -811,9 +811,13 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * * BPF_LDX */ case BPF_LDX | BPF_MEM | BPF_B: /* dst = *(u8 *)(ul) (src + off) */ + case BPF_LDX | BPF_PROBE_MEM | BPF_B: case BPF_LDX | BPF_MEM | BPF_H: /* dst = *(u16 *)(ul) (src + off) */ + case BPF_LDX | BPF_PROBE_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_W: /* dst = *(u32 *)(ul) (src + off) */ + case BPF_LDX | BPF_PROBE_MEM | BPF_W: case BPF_LDX | BPF_MEM | BPF_DW: /* dst = *(u64 *)(ul) (src + off) */ + case BPF_LDX | BPF_PROBE_MEM | BPF_DW: switch (size) { case BPF_B: EMIT(PPC_RAW_LBZ(dst_reg, src_reg, off)); @@ -832,6 +836,32 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * if (size != BPF_DW && !fp->aux->verifier_zext) EMIT(PPC_RAW_LI(dst_reg_h, 0)); + + if (BPF_MODE(code) == BPF_PROBE_MEM) { + int insn_idx = ctx->idx - 1; + int jmp_off = 4; + + /* + * In case of BPF_DW, two lwz instructions are emitted, one + * for higher 32-bit and another for lower 32-bit. So, set + * ex->insn to the first of the two and jump over both + * instructions in fixup. + * + * Similarly, with !verifier_zext, two instructions are + * emitted for BPF_B/H/W case. So, set ex->insn to the + * instruction that could fault and skip over both + * instructions. + */ + if (size == BPF_DW || !fp->aux->verifier_zext) { + insn_idx -= 1; + jmp_off += 4; + } + + ret = bpf_add_extable_entry(fp, image, pass, ctx, insn_idx, + jmp_off, dst_reg); + if (ret) + return ret; + } break; /*
BPF load instruction with BPF_PROBE_MEM mode can cause a fault inside kernel. Append exception table for such instructions within BPF program. Unlike other archs which uses extable 'fixup' field to pass dest_reg and nip, BPF exception table on PowerPC follows the generic PowerPC exception table design, where it populates both fixup and extable sections within BPF program. fixup section contains 3 instructions, first 2 instructions clear dest_reg (lower & higher 32-bit registers) and last instruction jumps to next instruction in the BPF code. extable 'insn' field contains relative offset of the instruction and 'fixup' field contains relative offset of the fixup entry. Example layout of BPF program with extable present: +------------------+ | | | | 0x4020 -->| lwz r28,4(r4) | | | | | 0x40ac -->| lwz r3,0(r24) | | lwz r4,4(r24) | | | | | |------------------| 0x4278 -->| li r28,0 | \ | li r27,0 | | fixup entry | b 0x4024 | / 0x4284 -->| li r4,0 | | li r3,0 | | b 0x40b4 | |------------------| 0x4290 -->| insn=0xfffffd90 | \ extable entry | fixup=0xffffffe4 | / 0x4298 -->| insn=0xfffffe14 | | fixup=0xffffffe8 | +------------------+ (Addresses shown here are chosen random, not real) Signed-off-by: Hari Bathini <hbathini@linux.ibm.com> --- Changes in v4: * Dropped explicit fallthrough statement for empty switch cases. arch/powerpc/net/bpf_jit.h | 4 ++++ arch/powerpc/net/bpf_jit_comp.c | 2 ++ arch/powerpc/net/bpf_jit_comp32.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 36 insertions(+)