From 451c3cab9a65e656c3b3d106831fc02d56b8c34a Mon Sep 17 00:00:00 2001 From: Puranjay Mohan Date: Wed, 28 Feb 2024 14:18:23 +0000 Subject: [PATCH 1/2] arm64: patching: implement text_poke API The text_poke API is used to implement functions like memcpy() and memset() for instruction memory (RO+X). The implementation is similar to the x86 version. This will be used by the BPF JIT to write and modify BPF programs. There could be more users of this in the future. Signed-off-by: Puranjay Mohan Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/20240228141824.119877-2-puranjay12@gmail.com Signed-off-by: Alexei Starovoitov --- arch/arm64/include/asm/patching.h | 2 + arch/arm64/kernel/patching.c | 75 +++++++++++++++++++++++++++++++ 2 files changed, 77 insertions(+) diff --git a/arch/arm64/include/asm/patching.h b/arch/arm64/include/asm/patching.h index 68908b82b168..587bdb91ab7a 100644 --- a/arch/arm64/include/asm/patching.h +++ b/arch/arm64/include/asm/patching.h @@ -8,6 +8,8 @@ int aarch64_insn_read(void *addr, u32 *insnp); int aarch64_insn_write(void *addr, u32 insn); int aarch64_insn_write_literal_u64(void *addr, u64 val); +void *aarch64_insn_set(void *dst, u32 insn, size_t len); +void *aarch64_insn_copy(void *dst, void *src, size_t len); int aarch64_insn_patch_text_nosync(void *addr, u32 insn); int aarch64_insn_patch_text(void *addrs[], u32 insns[], int cnt); diff --git a/arch/arm64/kernel/patching.c b/arch/arm64/kernel/patching.c index b4835f6d594b..255534930368 100644 --- a/arch/arm64/kernel/patching.c +++ b/arch/arm64/kernel/patching.c @@ -105,6 +105,81 @@ noinstr int aarch64_insn_write_literal_u64(void *addr, u64 val) return ret; } +typedef void text_poke_f(void *dst, void *src, size_t patched, size_t len); + +static void *__text_poke(text_poke_f func, void *addr, void *src, size_t len) +{ + unsigned long flags; + size_t patched = 0; + size_t size; + void *waddr; + void *ptr; + + raw_spin_lock_irqsave(&patch_lock, flags); + + while (patched < len) { + ptr = addr + patched; + size = min_t(size_t, PAGE_SIZE - offset_in_page(ptr), + len - patched); + + waddr = patch_map(ptr, FIX_TEXT_POKE0); + func(waddr, src, patched, size); + patch_unmap(FIX_TEXT_POKE0); + + patched += size; + } + raw_spin_unlock_irqrestore(&patch_lock, flags); + + flush_icache_range((uintptr_t)addr, (uintptr_t)addr + len); + + return addr; +} + +static void text_poke_memcpy(void *dst, void *src, size_t patched, size_t len) +{ + copy_to_kernel_nofault(dst, src + patched, len); +} + +static void text_poke_memset(void *dst, void *src, size_t patched, size_t len) +{ + u32 c = *(u32 *)src; + + memset32(dst, c, len / 4); +} + +/** + * aarch64_insn_copy - Copy instructions into (an unused part of) RX memory + * @dst: address to modify + * @src: source of the copy + * @len: length to copy + * + * Useful for JITs to dump new code blocks into unused regions of RX memory. + */ +noinstr void *aarch64_insn_copy(void *dst, void *src, size_t len) +{ + /* A64 instructions must be word aligned */ + if ((uintptr_t)dst & 0x3) + return NULL; + + return __text_poke(text_poke_memcpy, dst, src, len); +} + +/** + * aarch64_insn_set - memset for RX memory regions. + * @dst: address to modify + * @insn: value to set + * @len: length of memory region. + * + * Useful for JITs to fill regions of RX memory with illegal instructions. + */ +noinstr void *aarch64_insn_set(void *dst, u32 insn, size_t len) +{ + if ((uintptr_t)dst & 0x3) + return NULL; + + return __text_poke(text_poke_memset, dst, &insn, len); +} + int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn) { u32 *tp = addr; From 1dad391daef129e01e28206b8d586608ff026548 Mon Sep 17 00:00:00 2001 From: Puranjay Mohan Date: Wed, 28 Feb 2024 14:18:24 +0000 Subject: [PATCH 2/2] bpf, arm64: use bpf_prog_pack for memory management Use bpf_jit_binary_pack_alloc for memory management of JIT binaries in ARM64 BPF JIT. The bpf_jit_binary_pack_alloc creates a pair of RW and RX buffers. The JIT writes the program into the RW buffer. When the JIT is done, the program is copied to the final RX buffer with bpf_jit_binary_pack_finalize. Implement bpf_arch_text_copy() and bpf_arch_text_invalidate() for ARM64 JIT as these functions are required by bpf_jit_binary_pack allocator. Signed-off-by: Puranjay Mohan Acked-by: Song Liu Acked-by: Catalin Marinas Link: https://lore.kernel.org/r/20240228141824.119877-3-puranjay12@gmail.com Signed-off-by: Alexei Starovoitov --- arch/arm64/net/bpf_jit_comp.c | 139 ++++++++++++++++++++++++++++------ 1 file changed, 115 insertions(+), 24 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 20720ec346b8..5afc7a525eca 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -76,6 +76,7 @@ struct jit_ctx { int *offset; int exentry_idx; __le32 *image; + __le32 *ro_image; u32 stack_size; int fpb_offset; }; @@ -205,6 +206,14 @@ static void jit_fill_hole(void *area, unsigned int size) *ptr++ = cpu_to_le32(AARCH64_BREAK_FAULT); } +int bpf_arch_text_invalidate(void *dst, size_t len) +{ + if (!aarch64_insn_set(dst, AARCH64_BREAK_FAULT, len)) + return -EINVAL; + + return 0; +} + static inline int epilogue_offset(const struct jit_ctx *ctx) { int to = ctx->epilogue_offset; @@ -746,7 +755,8 @@ static int add_exception_handler(const struct bpf_insn *insn, struct jit_ctx *ctx, int dst_reg) { - off_t offset; + off_t ins_offset; + off_t fixup_offset; unsigned long pc; struct exception_table_entry *ex; @@ -763,12 +773,17 @@ static int add_exception_handler(const struct bpf_insn *insn, return -EINVAL; ex = &ctx->prog->aux->extable[ctx->exentry_idx]; - pc = (unsigned long)&ctx->image[ctx->idx - 1]; + pc = (unsigned long)&ctx->ro_image[ctx->idx - 1]; - offset = pc - (long)&ex->insn; - if (WARN_ON_ONCE(offset >= 0 || offset < INT_MIN)) + /* + * This is the relative offset of the instruction that may fault from + * the exception table itself. This will be written to the exception + * table and if this instruction faults, the destination register will + * be set to '0' and the execution will jump to the next instruction. + */ + ins_offset = pc - (long)&ex->insn; + if (WARN_ON_ONCE(ins_offset >= 0 || ins_offset < INT_MIN)) return -ERANGE; - ex->insn = offset; /* * Since the extable follows the program, the fixup offset is always @@ -777,12 +792,25 @@ static int add_exception_handler(const struct bpf_insn *insn, * bits. We don't need to worry about buildtime or runtime sort * modifying the upper bits because the table is already sorted, and * isn't part of the main exception table. + * + * The fixup_offset is set to the next instruction from the instruction + * that may fault. The execution will jump to this after handling the + * fault. */ - offset = (long)&ex->fixup - (pc + AARCH64_INSN_SIZE); - if (!FIELD_FIT(BPF_FIXUP_OFFSET_MASK, offset)) + fixup_offset = (long)&ex->fixup - (pc + AARCH64_INSN_SIZE); + if (!FIELD_FIT(BPF_FIXUP_OFFSET_MASK, fixup_offset)) return -ERANGE; - ex->fixup = FIELD_PREP(BPF_FIXUP_OFFSET_MASK, offset) | + /* + * The offsets above have been calculated using the RO buffer but we + * need to use the R/W buffer for writes. + * switch ex to rw buffer for writing. + */ + ex = (void *)ctx->image + ((void *)ex - (void *)ctx->ro_image); + + ex->insn = ins_offset; + + ex->fixup = FIELD_PREP(BPF_FIXUP_OFFSET_MASK, fixup_offset) | FIELD_PREP(BPF_FIXUP_REG_MASK, dst_reg); ex->type = EX_TYPE_BPF; @@ -1550,7 +1578,8 @@ static inline void bpf_flush_icache(void *start, void *end) struct arm64_jit_data { struct bpf_binary_header *header; - u8 *image; + u8 *ro_image; + struct bpf_binary_header *ro_header; struct jit_ctx ctx; }; @@ -1559,12 +1588,14 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) int image_size, prog_size, extable_size, extable_align, extable_offset; struct bpf_prog *tmp, *orig_prog = prog; struct bpf_binary_header *header; + struct bpf_binary_header *ro_header; struct arm64_jit_data *jit_data; bool was_classic = bpf_prog_was_classic(prog); bool tmp_blinded = false; bool extra_pass = false; struct jit_ctx ctx; u8 *image_ptr; + u8 *ro_image_ptr; if (!prog->jit_requested) return orig_prog; @@ -1591,8 +1622,11 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) } if (jit_data->ctx.offset) { ctx = jit_data->ctx; - image_ptr = jit_data->image; + ro_image_ptr = jit_data->ro_image; + ro_header = jit_data->ro_header; header = jit_data->header; + image_ptr = (void *)header + ((void *)ro_image_ptr + - (void *)ro_header); extra_pass = true; prog_size = sizeof(u32) * ctx.idx; goto skip_init_ctx; @@ -1637,18 +1671,27 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) /* also allocate space for plt target */ extable_offset = round_up(prog_size + PLT_TARGET_SIZE, extable_align); image_size = extable_offset + extable_size; - header = bpf_jit_binary_alloc(image_size, &image_ptr, - sizeof(u32), jit_fill_hole); - if (header == NULL) { + ro_header = bpf_jit_binary_pack_alloc(image_size, &ro_image_ptr, + sizeof(u32), &header, &image_ptr, + jit_fill_hole); + if (!ro_header) { prog = orig_prog; goto out_off; } /* 2. Now, the actual pass. */ + /* + * Use the image(RW) for writing the JITed instructions. But also save + * the ro_image(RX) for calculating the offsets in the image. The RW + * image will be later copied to the RX image from where the program + * will run. The bpf_jit_binary_pack_finalize() will do this copy in the + * final step. + */ ctx.image = (__le32 *)image_ptr; + ctx.ro_image = (__le32 *)ro_image_ptr; if (extable_size) - prog->aux->extable = (void *)image_ptr + extable_offset; + prog->aux->extable = (void *)ro_image_ptr + extable_offset; skip_init_ctx: ctx.idx = 0; ctx.exentry_idx = 0; @@ -1656,9 +1699,8 @@ skip_init_ctx: build_prologue(&ctx, was_classic, prog->aux->exception_cb); if (build_body(&ctx, extra_pass)) { - bpf_jit_binary_free(header); prog = orig_prog; - goto out_off; + goto out_free_hdr; } build_epilogue(&ctx, prog->aux->exception_cb); @@ -1666,34 +1708,44 @@ skip_init_ctx: /* 3. Extra pass to validate JITed code. */ if (validate_ctx(&ctx)) { - bpf_jit_binary_free(header); prog = orig_prog; - goto out_off; + goto out_free_hdr; } /* And we're done. */ if (bpf_jit_enable > 1) bpf_jit_dump(prog->len, prog_size, 2, ctx.image); - bpf_flush_icache(header, ctx.image + ctx.idx); - if (!prog->is_func || extra_pass) { if (extra_pass && ctx.idx != jit_data->ctx.idx) { pr_err_once("multi-func JIT bug %d != %d\n", ctx.idx, jit_data->ctx.idx); - bpf_jit_binary_free(header); prog->bpf_func = NULL; prog->jited = 0; prog->jited_len = 0; + goto out_free_hdr; + } + if (WARN_ON(bpf_jit_binary_pack_finalize(prog, ro_header, + header))) { + /* ro_header has been freed */ + ro_header = NULL; + prog = orig_prog; goto out_off; } - bpf_jit_binary_lock_ro(header); + /* + * The instructions have now been copied to the ROX region from + * where they will execute. Now the data cache has to be cleaned to + * the PoU and the I-cache has to be invalidated for the VAs. + */ + bpf_flush_icache(ro_header, ctx.ro_image + ctx.idx); } else { jit_data->ctx = ctx; - jit_data->image = image_ptr; + jit_data->ro_image = ro_image_ptr; jit_data->header = header; + jit_data->ro_header = ro_header; } - prog->bpf_func = (void *)ctx.image; + + prog->bpf_func = (void *)ctx.ro_image; prog->jited = 1; prog->jited_len = prog_size; @@ -1714,6 +1766,14 @@ out: bpf_jit_prog_release_other(prog, prog == orig_prog ? tmp : orig_prog); return prog; + +out_free_hdr: + if (header) { + bpf_arch_text_copy(&ro_header->size, &header->size, + sizeof(header->size)); + bpf_jit_binary_pack_free(ro_header, header); + } + goto out_off; } bool bpf_jit_supports_kfunc_call(void) @@ -1721,6 +1781,13 @@ bool bpf_jit_supports_kfunc_call(void) return true; } +void *bpf_arch_text_copy(void *dst, void *src, size_t len) +{ + if (!aarch64_insn_copy(dst, src, len)) + return ERR_PTR(-EINVAL); + return dst; +} + u64 bpf_jit_alloc_exec_limit(void) { return VMALLOC_END - VMALLOC_START; @@ -2359,3 +2426,27 @@ bool bpf_jit_supports_exceptions(void) */ return true; } + +void bpf_jit_free(struct bpf_prog *prog) +{ + if (prog->jited) { + struct arm64_jit_data *jit_data = prog->aux->jit_data; + struct bpf_binary_header *hdr; + + /* + * If we fail the final pass of JIT (from jit_subprogs), + * the program may not be finalized yet. Call finalize here + * before freeing it. + */ + if (jit_data) { + bpf_arch_text_copy(&jit_data->ro_header->size, &jit_data->header->size, + sizeof(jit_data->header->size)); + kfree(jit_data); + } + hdr = bpf_jit_binary_pack_hdr(prog); + bpf_jit_binary_pack_free(hdr, NULL); + WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); + } + + bpf_prog_unlock_free(prog); +}