From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 530E0C433E0 for ; Wed, 10 Feb 2021 18:28:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 216D864E2E for ; Wed, 10 Feb 2021 18:28:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233770AbhBJS1m (ORCPT ); Wed, 10 Feb 2021 13:27:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35896 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232313AbhBJSZf (ORCPT ); Wed, 10 Feb 2021 13:25:35 -0500 Received: from mail-il1-x129.google.com (mail-il1-x129.google.com [IPv6:2607:f8b0:4864:20::129]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD507C06178B; Wed, 10 Feb 2021 10:24:52 -0800 (PST) Received: by mail-il1-x129.google.com with SMTP id q9so2767244ilo.1; Wed, 10 Feb 2021 10:24:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:reply-to:from:date:message-id :subject:to:cc; bh=oDJTdkdJJ7mBLZJmwXA5rlxyJMiuDx1sqSvJMOpL9yI=; b=axrnrRsMR6GPSnfE1ztyIKwtVIY/jj3CskFWDA4l68najWxv9DijoYPsqziWIr+7aZ FhWbujq/xWOuAlXkXxvve8mVhy6unBKaZVwsFeURNpqmChfoQzIzQMoEqQ4LRzr7OCKf MOn93VOyAGvqDJu9a6dvF+oEkdnDD37eQ7y4SJpuwjLstN3UKFp5oXRfYOzO8wZo+PzO rpBZRAzKCSCAAZ7rp195+/uJb3LDu853pYd/oXSry9YofHI7bvgelIpPgYgGszKOBaxH BdPyqH7ErVxYBQ75Sp0NFGHdA4QrMdluKgo42bDVh4mMiZa89buMJwvVy2gdIF0SsDR9 3E7A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:reply-to :from:date:message-id:subject:to:cc; bh=oDJTdkdJJ7mBLZJmwXA5rlxyJMiuDx1sqSvJMOpL9yI=; b=Fopqo6lIyaJzZdEmgNekw/MjUhIPqNmL8CTqWG8SexDdwt3NjQrhX65qjJvRxewjFv X9gyLVhsm78iestUhAIG8AH9Uid5cfCphCnJDeELkkJlmv9WrrC2JAWMt0YAWsR++Wd3 887twCBpZa3jHVK8YOkHEOuVs4QtkgxtnxfMI7ntAT/JGiq7VFUN6cRlMVOPMvg28k65 3Lcpd3GeUQbTd5JxiAIqYVouZVwkqs6v9hnEaloopZTynIcs48gBGT/Hy/Bn0zZy36kt 3kDXKFjcty8qw7nvCT7Nva17o/bwewiA9rq/S8ShVF0Xpgmej4/U+/uShLsV1Slm7ROg sF+A== X-Gm-Message-State: AOAM5311fuE2sC4vaindNFTVLmN+PtpJHNKJRE3PErwGkODFRBVsY6cq KhcF8WlenvljHwlfh4KEE+mvxqop4fyr7FW/1cz1rApkNXURxw== X-Google-Smtp-Source: ABdhPJwU0hdNaDARCTYv+SThcMpopiO5ZOh0LQfDZHUwO5jC6VuDOmw/1fJNm+GcZNcu3qQF9nTvSZQiJSjawdHJsnI= X-Received: by 2002:a05:6e02:4c9:: with SMTP id f9mr2221507ils.186.1612981492049; Wed, 10 Feb 2021 10:24:52 -0800 (PST) MIME-Version: 1.0 References: <20210209052311.GA125918@ubuntu-m3-large-x86> <20210209074904.GA286822@ubuntu-m3-large-x86> In-Reply-To: Reply-To: sedat.dilek@gmail.com From: Sedat Dilek Date: Wed, 10 Feb 2021 19:24:47 +0100 Message-ID: Subject: Re: FAILED unresolved symbol vfs_truncate on arm64 with LLVM To: Andrii Nakryiko Cc: Jiri Olsa , Nathan Chancellor , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Nick Desaulniers , Networking , bpf , clang-built-linux , Veronika Kabatova , Jiri Olsa Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Wed, Feb 10, 2021 at 7:20 PM Andrii Nakryiko wrote: > > On Wed, Feb 10, 2021 at 5:26 AM Jiri Olsa wrote: > > > > On Tue, Feb 09, 2021 at 02:00:29PM -0800, Andrii Nakryiko wrote: > > > > SNIP > > > > > > > > I'm still trying to build the kernel.. however ;-) > > > > > > > > > > > > patch below adds the ftrace check only for static functions > > > > > > and lets the externa go through.. but as you said, in this > > > > > > case we'll need to figure out the 'notrace' and other checks > > > > > > ftrace is doing > > > > > > > > > > > > jirka > > > > > > > > > > > > > > > > > > --- > > > > > > diff --git a/btf_encoder.c b/btf_encoder.c > > > > > > index b124ec20a689..4d147406cfa5 100644 > > > > > > --- a/btf_encoder.c > > > > > > +++ b/btf_encoder.c > > > > > > @@ -734,7 +734,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > > > > > continue; > > > > > > if (!has_arg_names(cu, &fn->proto)) > > > > > > continue; > > > > > > - if (functions_cnt) { > > > > > > + if (!fn->external && functions_cnt) { > > > > > > > > > > I wouldn't trust DWARF, honestly. Wouldn't checking GLOBAL vs LOCAL > > > > > FUNC ELF symbol be more reliable? > > > > > > > > that'd mean extra bsearch on each processed function, > > > > on the ther hand, we'are already slow ;-) I'll check > > > > how big the slowdown would be > > > > > > > > > > We currently record addresses and do binary search. Now we need to > > > record address + size and still do binary search with a slightly > > > different semantics (find closest entry >= addr). Then just check that > > > it overlaps, taking into account the length of the function code. It > > > shouldn't result in a noticeable slowdown. Might be actually faster, > > > because we might avoid callback function call costs. > > > > I'm still not sure how to handle the external check for function via elf, > > I might be missing something, but don't all functions have > corresponding ELF symbols? And then symbol can have LOCAL or GLOBAL > type. LOCALs are supposed to be not visible outside respective CUs (so > correspond to static functions), while GLOBALs are extern-able funcs. > So if func's symbol is GLOBAL, it should be ok to assume it's > attachable (not inlined, at least). > > > but below is change for checking that ftrace addrs are within elf functions > > > > seems to work in my tests, I'll run some more tests and send full patch > > It seems unnecessarily convoluted. I was thinking about something like > this (the diff will totally be screwed up by gmail, and I haven't even > compiled it): > Now, I know why vfs_truncate is so problematic. Let's split it: "vfs + trunc + ate". Eaten by Gmail :-). - Sedat - > diff --git a/btf_encoder.c b/btf_encoder.c > index b124ec20a689..8162b238bd43 100644 > --- a/btf_encoder.c > +++ b/btf_encoder.c > @@ -236,6 +236,23 @@ get_kmod_addrs(struct btf_elf *btfe, __u64 > **paddrs, __u64 *pcount) > return 0; > } > > +struct func_seg { __u64 start; __u64 end; }; > + > +static int func_exists(struct func_seg *segs, size_t len, __u64 addr) > +{ > + size_t l = 0, r = len - 1, m; > + > + while (l < r) { > + m = l + (r - l + 1) / 2; > + if (segs[m].start <= addr) > + l = m; > + else > + r = m - 1; > + } > + > + return segs[l].start <= addr && addr < segs[l].end; > +} > + > static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > { > __u64 *addrs, count, i; > @@ -286,7 +303,7 @@ static int setup_functions(struct btf_elf *btfe, > struct funcs_layout *fl) > __u64 addr = kmod ? func->addr + func->sh_addr : func->addr; > > /* Make sure function is within ftrace addresses. */ > - if (bsearch(&addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) { > + if (func_exists(addrs, count, addr)) > /* > * We iterate over sorted array, so we can easily skip > * not valid item and move following valid field into > > > So the idea is to use address segments and check whether there is a > segment that overlaps with a given address by first binary searching > for a segment with the largest starting address that is <= addr. And > then just confirming that segment does overlap with the requested > address. > > WDYT? > > > > > jirka > > > > > > --- > > diff --git a/btf_encoder.c b/btf_encoder.c > > index b124ec20a689..548a12847f99 100644 > > --- a/btf_encoder.c > > +++ b/btf_encoder.c > > @@ -36,6 +36,7 @@ struct funcs_layout { > > struct elf_function { > > const char *name; > > unsigned long addr; > > + unsigned long end; > > unsigned long sh_addr; > > bool generated; > > }; > > @@ -44,7 +45,7 @@ static struct elf_function *functions; > > static int functions_alloc; > > static int functions_cnt; > > > > -static int functions_cmp(const void *_a, const void *_b) > > +static int functions_cmp_name(const void *_a, const void *_b) > > { > > const struct elf_function *a = _a; > > const struct elf_function *b = _b; > > @@ -52,6 +53,16 @@ static int functions_cmp(const void *_a, const void *_b) > > return strcmp(a->name, b->name); > > } > > > > +static int functions_cmp_addr(const void *_a, const void *_b) > > +{ > > + const struct elf_function *a = _a; > > + const struct elf_function *b = _b; > > + > > + if (a->addr == b->addr) > > + return 0; > > + return a->addr < b->addr ? -1 : 1; > > +} > > + > > static void delete_functions(void) > > { > > free(functions); > > @@ -98,6 +109,7 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym, > > > > functions[functions_cnt].name = name; > > functions[functions_cnt].addr = elf_sym__value(sym); > > + functions[functions_cnt].end = (__u64) -1; > > functions[functions_cnt].sh_addr = sh.sh_addr; > > functions[functions_cnt].generated = false; > > functions_cnt++; > > @@ -236,9 +248,25 @@ get_kmod_addrs(struct btf_elf *btfe, __u64 **paddrs, __u64 *pcount) > > return 0; > > } > > > > +static bool is_addr_in_func(__u64 addr, struct elf_function *func, bool kmod) > > +{ > > + /* > > + * For vmlinux image both addrs[x] and functions[x]::addr > > + * values are final address and are comparable. > > + * > > + * For kernel module addrs[x] is final address, but > > + * functions[x]::addr is relative address within section > > + * and needs to be relocated by adding sh_addr. > > + */ > > + __u64 start = kmod ? func->addr + func->sh_addr : func->addr; > > + __u64 end = kmod ? func->end+ func->sh_addr : func->end; > > + > > + return start <= addr && addr < end; > > +} > > + > > static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > > { > > - __u64 *addrs, count, i; > > + __u64 *addrs, count, i_func, i_addr; > > int functions_valid = 0; > > bool kmod = false; > > > > @@ -266,43 +294,62 @@ static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) > > return 0; > > } > > > > - qsort(addrs, count, sizeof(addrs[0]), addrs_cmp); > > - qsort(functions, functions_cnt, sizeof(functions[0]), functions_cmp); > > - > > /* > > - * Let's got through all collected functions and filter > > - * out those that are not in ftrace. > > + * Sort both functions and addrs so we can iterate > > + * both of them simultaneously and found matching > > + * func/addr pairs. > > */ > > - for (i = 0; i < functions_cnt; i++) { > > - struct elf_function *func = &functions[i]; > > - /* > > - * For vmlinux image both addrs[x] and functions[x]::addr > > - * values are final address and are comparable. > > - * > > - * For kernel module addrs[x] is final address, but > > - * functions[x]::addr is relative address within section > > - * and needs to be relocated by adding sh_addr. > > - */ > > - __u64 addr = kmod ? func->addr + func->sh_addr : func->addr; > > + qsort(addrs, count, sizeof(addrs[0]), addrs_cmp); > > + qsort(functions, functions_cnt, sizeof(functions[0]), functions_cmp_addr); > > + > > + for (i_func = 0, i_addr = 0; i_func < functions_cnt; i_func++) { > > + struct elf_function *func = &functions[i_func]; > > + > > + if (i_func + 1 < functions_cnt) > > + func->end = functions[i_func + 1].addr; > > + > > + for (; i_addr < count; i_addr++) { > > + __u64 addr = addrs[i_addr]; > > + > > + /* Functions are ahead, catch up with addrs. */ > > + if (addr < func->addr) > > + continue; > > + > > + /* Addr is within function - mark function as valid. */ > > + if (is_addr_in_func(addr, func, kmod)) { > > + /* > > + * We iterate over sorted array, so we can easily skip > > + * not valid item and move following valid field into > > + * its place, and still keep the 'new' array sorted. > > + */ > > + if (i_func != functions_valid) > > + functions[functions_valid] = functions[i_func]; > > + functions_valid++; > > + i_addr++; > > + } > > > > - /* Make sure function is within ftrace addresses. */ > > - if (bsearch(&addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) { > > /* > > - * We iterate over sorted array, so we can easily skip > > - * not valid item and move following valid field into > > - * its place, and still keep the 'new' array sorted. > > + * Addrs are ahead, catch up with functions, or we just > > + * found valid function and want to move to another. > > */ > > - if (i != functions_valid) > > - functions[functions_valid] = functions[i]; > > - functions_valid++; > > + break; > > } > > } > > > > + if (btf_elf__verbose) { > > + printf("Found %d functions out of %d symbols and %llu ftrace addresses.\n", > > + functions_valid, functions_cnt, count); > > + } > > + > > functions_cnt = functions_valid; > > free(addrs); > > > > - if (btf_elf__verbose) > > - printf("Found %d functions!\n", functions_cnt); > > + /* > > + * And finaly sort 'valid' functions by name, > > + * so find_function can be used. > > + */ > > + qsort(functions, functions_cnt, sizeof(functions[0]), functions_cmp_name); > > + > > return 0; > > } > > > > @@ -312,7 +359,7 @@ static struct elf_function *find_function(const struct btf_elf *btfe, > > struct elf_function key = { .name = name }; > > > > return bsearch(&key, functions, functions_cnt, sizeof(functions[0]), > > - functions_cmp); > > + functions_cmp_name); > > } > > > > static bool btf_name_char_ok(char c, bool first) > > > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/CAEf4BzbzquqsA5%3D_UqDukScuoGLfDhZiiXs_sgYBuNUvTBuV6w%40mail.gmail.com.