From: Song Liu <song@xxxxxxxxxx> [ Upstream commit 19c02415da2345d0dda2b5c4495bc17cc14b18b5 ] Allocate bpf_dispatcher with bpf_prog_pack_alloc so that bpf_dispatcher can share pages with bpf programs. arch_prepare_bpf_dispatcher() is updated to provide a RW buffer as working area for arch code to write to. This also fixes CPA W^X warnning like: CPA refuse W^X violation: 8000000000000163 -> 0000000000000163 range: ... Signed-off-by: Song Liu <song@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220926184739.3512547-2-song@xxxxxxxxxx Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- arch/x86/net/bpf_jit_comp.c | 16 ++++++++-------- include/linux/bpf.h | 3 ++- include/linux/filter.h | 5 +++++ kernel/bpf/core.c | 9 +++++++-- kernel/bpf/dispatcher.c | 27 +++++++++++++++++++++------ 5 files changed, 43 insertions(+), 17 deletions(-) diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 41d170653e8d..fc4d899f10f6 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -2216,7 +2216,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i return ret; } -static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs) +static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs, u8 *image, u8 *buf) { u8 *jg_reloc, *prog = *pprog; int pivot, err, jg_bytes = 1; @@ -2232,12 +2232,12 @@ static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs) EMIT2_off32(0x81, add_1reg(0xF8, BPF_REG_3), progs[a]); err = emit_cond_near_jump(&prog, /* je func */ - (void *)progs[a], prog, + (void *)progs[a], image + (prog - buf), X86_JE); if (err) return err; - emit_indirect_jump(&prog, 2 /* rdx */, prog); + emit_indirect_jump(&prog, 2 /* rdx */, image + (prog - buf)); *pprog = prog; return 0; @@ -2262,7 +2262,7 @@ static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs) jg_reloc = prog; err = emit_bpf_dispatcher(&prog, a, a + pivot, /* emit lower_part */ - progs); + progs, image, buf); if (err) return err; @@ -2276,7 +2276,7 @@ static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs) emit_code(jg_reloc - jg_bytes, jg_offset, jg_bytes); err = emit_bpf_dispatcher(&prog, a + pivot + 1, /* emit upper_part */ - b, progs); + b, progs, image, buf); if (err) return err; @@ -2296,12 +2296,12 @@ static int cmp_ips(const void *a, const void *b) return 0; } -int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs) +int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs) { - u8 *prog = image; + u8 *prog = buf; sort(funcs, num_funcs, sizeof(funcs[0]), cmp_ips, NULL); - return emit_bpf_dispatcher(&prog, 0, num_funcs - 1, funcs); + return emit_bpf_dispatcher(&prog, 0, num_funcs - 1, funcs, image, buf); } struct x64_jit_data { diff --git a/include/linux/bpf.h b/include/linux/bpf.h index ed352c00330c..df9cd469947a 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -869,6 +869,7 @@ struct bpf_dispatcher { struct bpf_dispatcher_prog progs[BPF_DISPATCHER_MAX]; int num_progs; void *image; + void *rw_image; u32 image_off; struct bpf_ksym ksym; }; @@ -888,7 +889,7 @@ int bpf_trampoline_unlink_prog(struct bpf_tramp_link *link, struct bpf_trampolin struct bpf_trampoline *bpf_trampoline_get(u64 key, struct bpf_attach_target_info *tgt_info); void bpf_trampoline_put(struct bpf_trampoline *tr); -int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs); +int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs); #define BPF_DISPATCHER_INIT(_name) { \ .mutex = __MUTEX_INITIALIZER(_name.mutex), \ .func = &_name##_func, \ diff --git a/include/linux/filter.h b/include/linux/filter.h index 8fd2e2f58eeb..e11335c70982 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1052,6 +1052,8 @@ extern long bpf_jit_limit_max; typedef void (*bpf_jit_fill_hole_t)(void *area, unsigned int size); +void bpf_jit_fill_hole_with_zero(void *area, unsigned int size); + struct bpf_binary_header * bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr, unsigned int alignment, @@ -1064,6 +1066,9 @@ void bpf_jit_free(struct bpf_prog *fp); struct bpf_binary_header * bpf_jit_binary_pack_hdr(const struct bpf_prog *fp); +void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns); +void bpf_prog_pack_free(struct bpf_binary_header *hdr); + static inline bool bpf_prog_kallsyms_verify_off(const struct bpf_prog *fp) { return list_empty(&fp->aux->ksym.lnode) || diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index cf44ff50b1f2..be736aa97927 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -822,6 +822,11 @@ struct bpf_prog_pack { unsigned long bitmap[]; }; +void bpf_jit_fill_hole_with_zero(void *area, unsigned int size) +{ + memset(area, 0, size); +} + #define BPF_PROG_SIZE_TO_NBITS(size) (round_up(size, BPF_PROG_CHUNK_SIZE) / BPF_PROG_CHUNK_SIZE) static size_t bpf_prog_pack_size = -1; @@ -892,7 +897,7 @@ static struct bpf_prog_pack *alloc_new_pack(bpf_jit_fill_hole_t bpf_fill_ill_ins return pack; } -static void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns) +void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insns) { unsigned int nbits = BPF_PROG_SIZE_TO_NBITS(size); struct bpf_prog_pack *pack; @@ -936,7 +941,7 @@ static void *bpf_prog_pack_alloc(u32 size, bpf_jit_fill_hole_t bpf_fill_ill_insn return ptr; } -static void bpf_prog_pack_free(struct bpf_binary_header *hdr) +void bpf_prog_pack_free(struct bpf_binary_header *hdr) { struct bpf_prog_pack *pack = NULL, *tmp; unsigned int nbits; diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c index 2444bd15cc2d..fa64b80b8bca 100644 --- a/kernel/bpf/dispatcher.c +++ b/kernel/bpf/dispatcher.c @@ -85,12 +85,12 @@ static bool bpf_dispatcher_remove_prog(struct bpf_dispatcher *d, return false; } -int __weak arch_prepare_bpf_dispatcher(void *image, s64 *funcs, int num_funcs) +int __weak arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs) { return -ENOTSUPP; } -static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image) +static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image, void *buf) { s64 ips[BPF_DISPATCHER_MAX] = {}, *ipsp = &ips[0]; int i; @@ -99,12 +99,12 @@ static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image) if (d->progs[i].prog) *ipsp++ = (s64)(uintptr_t)d->progs[i].prog->bpf_func; } - return arch_prepare_bpf_dispatcher(image, &ips[0], d->num_progs); + return arch_prepare_bpf_dispatcher(image, buf, &ips[0], d->num_progs); } static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) { - void *old, *new; + void *old, *new, *tmp; u32 noff; int err; @@ -117,8 +117,14 @@ static void bpf_dispatcher_update(struct bpf_dispatcher *d, int prev_num_progs) } new = d->num_progs ? d->image + noff : NULL; + tmp = d->num_progs ? d->rw_image + noff : NULL; if (new) { - if (bpf_dispatcher_prepare(d, new)) + /* Prepare the dispatcher in d->rw_image. Then use + * bpf_arch_text_copy to update d->image, which is RO+X. + */ + if (bpf_dispatcher_prepare(d, new, tmp)) + return; + if (IS_ERR(bpf_arch_text_copy(new, tmp, PAGE_SIZE / 2))) return; } @@ -140,9 +146,18 @@ void bpf_dispatcher_change_prog(struct bpf_dispatcher *d, struct bpf_prog *from, mutex_lock(&d->mutex); if (!d->image) { - d->image = bpf_jit_alloc_exec_page(); + d->image = bpf_prog_pack_alloc(PAGE_SIZE, bpf_jit_fill_hole_with_zero); if (!d->image) goto out; + d->rw_image = bpf_jit_alloc_exec(PAGE_SIZE); + if (!d->rw_image) { + u32 size = PAGE_SIZE; + + bpf_arch_text_copy(d->image, &size, sizeof(size)); + bpf_prog_pack_free((struct bpf_binary_header *)d->image); + d->image = NULL; + goto out; + } bpf_image_ksym_add(d->image, &d->ksym); } -- 2.35.1
