| Message ID | 20210508034837.64585-17-alexei.starovoitov@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: syscall program, FD array, loader program, light skeleton. | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | fail | Series longer than 15 patches |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | warning | 6 maintainers not CCed: netdev@vger.kernel.org yhs@fb.com kpsingh@kernel.org kafai@fb.com ast@kernel.org songliubraving@fb.com |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | fail | ERROR: spaces required around that '+=' (ctx:VxW) WARNING: line length of 105 exceeds 80 columns WARNING: line length of 93 exceeds 80 columns |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
On Fri, May 7, 2021 at 8:49 PM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > From: Alexei Starovoitov <ast@kernel.org> > > Fix loader program to close temporary FDs when intermediate > sys_bpf command fails. > > Signed-off-by: Alexei Starovoitov <ast@kernel.org> > --- Looks good, but curious about 2 jumps vs 1 jump for cleanup Acked-by: Andrii Nakryiko <andrii@kernel.org> > tools/lib/bpf/bpf_gen_internal.h | 1 + > tools/lib/bpf/gen_loader.c | 38 ++++++++++++++++++++++++++++---- > 2 files changed, 35 insertions(+), 4 deletions(-) > > diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h > index f42a55efd559..da2c026a3f31 100644 > --- a/tools/lib/bpf/bpf_gen_internal.h > +++ b/tools/lib/bpf/bpf_gen_internal.h > @@ -15,6 +15,7 @@ struct bpf_gen { > void *data_cur; > void *insn_start; > void *insn_cur; > + size_t cleanup_label; > __u32 nr_progs; > __u32 nr_maps; > int log_level; > diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c > index 585c672cc53e..b1709421ba90 100644 > --- a/tools/lib/bpf/gen_loader.c > +++ b/tools/lib/bpf/gen_loader.c > @@ -97,8 +97,36 @@ static void bpf_gen__emit2(struct bpf_gen *gen, struct bpf_insn insn1, struct bp > > void bpf_gen__init(struct bpf_gen *gen, int log_level) > { > + size_t stack_sz = sizeof(struct loader_stack); > + int i; > + > gen->log_level = log_level; > + /* save ctx pointer into R6 */ > bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_6, BPF_REG_1)); > + > + /* bzero stack */ > + bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_1, BPF_REG_10)); > + bpf_gen__emit(gen, BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -stack_sz)); > + bpf_gen__emit(gen, BPF_MOV64_IMM(BPF_REG_2, stack_sz)); > + bpf_gen__emit(gen, BPF_MOV64_IMM(BPF_REG_3, 0)); > + bpf_gen__emit(gen, BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel)); > + > + /* jump over cleanup code */ > + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, > + /* size of cleanup code below */ > + (stack_sz / 4) * 3 + 2)); > + > + /* remember the label where all error branches will jump to */ > + gen->cleanup_label = gen->insn_cur - gen->insn_start; > + /* emit cleanup code: close all temp FDs */ > + for (i = 0; i < stack_sz; i+= 4) { nit: checkpatch complains about missing space before += > + bpf_gen__emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_10, -stack_sz + i)); > + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSLE, BPF_REG_1, 0, 1)); > + bpf_gen__emit(gen, BPF_EMIT_CALL(BPF_FUNC_sys_close)); > + } > + /* R7 contains the error code from sys_bpf. Copy it into R0 and exit. */ > + bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7)); > + bpf_gen__emit(gen, BPF_EXIT_INSN()); > } > > static int bpf_gen__add_data(struct bpf_gen *gen, const void *data, __u32 size) > @@ -179,10 +207,12 @@ static void bpf_gen__emit_sys_bpf(struct bpf_gen *gen, int cmd, int attr, int at > > static void bpf_gen__emit_check_err(struct bpf_gen *gen) > { > - bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 2)); > - bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7)); > - /* TODO: close intermediate FDs in case of error */ > - bpf_gen__emit(gen, BPF_EXIT_INSN()); > + /* R7 contains result of last sys_bpf command. > + * if (R7 < 0) goto cleanup; > + */ > + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 1)); > + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, > + -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 1)); Just curious, why not a single BPF_JSLT straight to the cleanup label? > } > > /* reg1 and reg2 should not be R1 - R5. They can be R0, R6 - R10 */ > -- > 2.30.2 >
On 5/11/21 4:34 PM, Andrii Nakryiko wrote: >> + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 1)); >> + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, >> + -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 1)); > Just curious, why not a single BPF_JSLT straight to the cleanup label? > ohh. I still didn't fix JA. I kept thinking to make it use imm32 to address long standing issue with large programs. It was on my mind for so long now that it became false reality :( So above I did to avoid doing simm16 check. That's what llvm will eventually generate. Once JA supports imm32, of course. Thanks for asking. Will fix.
diff --git a/tools/lib/bpf/bpf_gen_internal.h b/tools/lib/bpf/bpf_gen_internal.h index f42a55efd559..da2c026a3f31 100644 --- a/tools/lib/bpf/bpf_gen_internal.h +++ b/tools/lib/bpf/bpf_gen_internal.h @@ -15,6 +15,7 @@ struct bpf_gen { void *data_cur; void *insn_start; void *insn_cur; + size_t cleanup_label; __u32 nr_progs; __u32 nr_maps; int log_level; diff --git a/tools/lib/bpf/gen_loader.c b/tools/lib/bpf/gen_loader.c index 585c672cc53e..b1709421ba90 100644 --- a/tools/lib/bpf/gen_loader.c +++ b/tools/lib/bpf/gen_loader.c @@ -97,8 +97,36 @@ static void bpf_gen__emit2(struct bpf_gen *gen, struct bpf_insn insn1, struct bp void bpf_gen__init(struct bpf_gen *gen, int log_level) { + size_t stack_sz = sizeof(struct loader_stack); + int i; + gen->log_level = log_level; + /* save ctx pointer into R6 */ bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_6, BPF_REG_1)); + + /* bzero stack */ + bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_1, BPF_REG_10)); + bpf_gen__emit(gen, BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -stack_sz)); + bpf_gen__emit(gen, BPF_MOV64_IMM(BPF_REG_2, stack_sz)); + bpf_gen__emit(gen, BPF_MOV64_IMM(BPF_REG_3, 0)); + bpf_gen__emit(gen, BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel)); + + /* jump over cleanup code */ + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, + /* size of cleanup code below */ + (stack_sz / 4) * 3 + 2)); + + /* remember the label where all error branches will jump to */ + gen->cleanup_label = gen->insn_cur - gen->insn_start; + /* emit cleanup code: close all temp FDs */ + for (i = 0; i < stack_sz; i+= 4) { + bpf_gen__emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_10, -stack_sz + i)); + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSLE, BPF_REG_1, 0, 1)); + bpf_gen__emit(gen, BPF_EMIT_CALL(BPF_FUNC_sys_close)); + } + /* R7 contains the error code from sys_bpf. Copy it into R0 and exit. */ + bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7)); + bpf_gen__emit(gen, BPF_EXIT_INSN()); } static int bpf_gen__add_data(struct bpf_gen *gen, const void *data, __u32 size) @@ -179,10 +207,12 @@ static void bpf_gen__emit_sys_bpf(struct bpf_gen *gen, int cmd, int attr, int at static void bpf_gen__emit_check_err(struct bpf_gen *gen) { - bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 2)); - bpf_gen__emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7)); - /* TODO: close intermediate FDs in case of error */ - bpf_gen__emit(gen, BPF_EXIT_INSN()); + /* R7 contains result of last sys_bpf command. + * if (R7 < 0) goto cleanup; + */ + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 1)); + bpf_gen__emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, + -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 1)); } /* reg1 and reg2 should not be R1 - R5. They can be R0, R6 - R10 */