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[185.219.167.24]) by smtp.gmail.com with ESMTPSA id z4sm12910440edb.97.2021.05.03.23.41.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 May 2021 23:41:48 -0700 (PDT) Subject: Re: linux-next failing build due to missing cubictcp_state symbol To: Jiri Olsa Cc: =?UTF-8?Q?Michal_Such=c3=a1nek?= , Yonghong Song , linux-kernel@vger.kernel.org, Martin KaFai Lau , "David S. Miller" , Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Song Liu , John Fastabend , KP Singh , netdev@vger.kernel.org, bpf@vger.kernel.org, Jiri Olsa , Jesper Dangaard Brouer , dwarves@vger.kernel.org, Arnaldo Carvalho de Melo References: <20210426121401.GO15381@kitsune.suse.cz> <49f84147-bf32-dc59-48e0-f89241cf6264@fb.com> <20210427121237.GK6564@kitsune.suse.cz> <20210430174723.GP15381@kitsune.suse.cz> <3d148516-0472-8f0a-085b-94d68c5cc0d5@suse.com> <6c14f3c8-7474-9f3f-b4a6-2966cb19e1ed@kernel.org> <4e051459-8532-7b61-c815-f3435767f8a0@kernel.org> From: Jiri Slaby Message-ID: <8c3cbd22-eb26-ea8b-c8bb-35a629d6d2d8@kernel.org> Date: Tue, 4 May 2021 08:41:47 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/mixed; boundary="------------2F0676AC09266ADBA754999C" Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a multi-part message in MIME format. --------------2F0676AC09266ADBA754999C Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Transfer-Encoding: 8bit On 03. 05. 21, 12:08, Jiri Olsa wrote: > On Mon, May 03, 2021 at 10:59:44AM +0200, Jiri Slaby wrote: >> CCing pahole people. >> >> On 03. 05. 21, 9:59, Jiri Slaby wrote: >>> On 03. 05. 21, 8:11, Jiri Slaby wrote: >>>>>>>>> looks like vfs_truncate did not get into BTF data, >>>>>>>>> I'll try to reproduce >>>>> >>>>> _None_ of the functions are generated by pahole -J from >>>>> debuginfo on ppc64. debuginfo appears to be correct. Neither >>>>> pahole -J fs/open.o works correctly. collect_functions in >>>>> dwarves seems to be defunct on ppc64... "functions" array is >>>>> bogus (so find_function -- the bsearch -- fails). >>>> >>>> It's not that bogus. I forgot an asterisk: >>>>> #0? find_function (btfe=0x100269f80, name=0x10024631c >>>>> "stream_open") at >>>>> /usr/src/debug/dwarves-1.21-1.1.ppc64/btf_encoder.c:350 >>>>> (gdb) p (*functions)@84 >>>>> $5 = {{name = 0x7ffff68e0922 ".__se_compat_sys_ftruncate", addr >>>>> = 75232, size = 72, sh_addr = 65536, generated = false}, { >>>>> ??? name = 0x7ffff68e019e ".__se_compat_sys_open", addr = 80592, >>>>> size = 216, sh_addr = 65536, generated = false}, { >>>>> ??? name = 0x7ffff68e0076 ".__se_compat_sys_openat", addr = >>>>> 80816, size = 232, sh_addr = 65536, generated = false}, { >>>>> ??? name = 0x7ffff68e0908 ".__se_compat_sys_truncate", addr = >>>>> 74304, size = 100, sh_addr = 65536, generated = false}, { >>>> ... >>>>> ??? name = 0x7ffff68e0808 ".stream_open", addr = 65824, size = >>>>> 72, sh_addr = 65536, generated = false}, { >>>> ... >>>>> ??? name = 0x7ffff68e0751 ".vfs_truncate", addr = 73392, size = >>>>> 544, sh_addr = 65536, generated = false}} >>>> >>>> The dot makes the difference, of course. The question is why is it >>>> there? I keep looking into it. Only if someone has an immediate >>>> idea... >>> >>> Well, .vfs_truncate is in .text (and contains an ._mcount call). And >>> vfs_truncate is in .opd (w/o an ._mcount call). Since setup_functions >>> excludes all functions without the ._mcount call, is_ftrace_func later >>> returns false for such functions and they are filtered before the BTF >>> processing. >>> >>> Technically, get_vmlinux_addrs looks at a list of functions between >>> __start_mcount_loc and __stop_mcount_loc and considers only the listed. >>> >>> I don't know what the correct fix is (exclude .opd functions from the >>> filter?). Neither why cross compiler doesn't fail, nor why ebi v2 avoids >>> this too. >> >> Attaching a patch for pahole which fixes the issue, but I have no idea >> whether it is the right fix at all. > > hi, > we're considering to disable ftrace filter completely, > I guess that would solve this issue for ppc as well > > https://lore.kernel.org/bpf/20210501001653.x3b4rk4vk4iqv3n7@kafai-mbp.dhcp.thefacebook.com/ Right, the attached patch fixes it for me too. -- js --------------2F0676AC09266ADBA754999C Content-Type: text/x-patch; charset=UTF-8; name="0001-remove-ftrace-filter.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="0001-remove-ftrace-filter.patch" From b0128f1ec6a234c5b40c40d73d55708d34f1a428 Mon Sep 17 00:00:00 2001 From: Jiri Slaby Date: Tue, 4 May 2021 08:09:50 +0200 Subject: [PATCH] remove ftrace filter Functions in the .opd section on ppc64 are currently ignored as they don't contain mcount calls -- they are excluded by the ftrace filter. Therefore, pahole cannot produce a .BTF section from vmlinux and kernel build fails on ppc64. Remove the ftrace filter completely as was discussed: https://lore.kernel.org/bpf/20210501001653.x3b4rk4vk4iqv3n7@kafai-mbp.dhcp.thefacebook.com/ https://lore.kernel.org/bpf/YI%2FLgjLxo9VCN%2Fd+@krava/ --- btf_encoder.c | 272 +------------------------------------------------- 1 file changed, 5 insertions(+), 267 deletions(-) diff --git a/btf_encoder.c b/btf_encoder.c index 80e896961d4e..ba83bb088efa 100644 --- a/btf_encoder.c +++ b/btf_encoder.c @@ -27,17 +27,8 @@ */ #define KSYM_NAME_LEN 128 -struct funcs_layout { - unsigned long mcount_start; - unsigned long mcount_stop; - unsigned long mcount_sec_idx; -}; - struct elf_function { const char *name; - unsigned long addr; - unsigned long size; - unsigned long sh_addr; bool generated; }; @@ -98,250 +89,11 @@ 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].size = elf_sym__size(sym); - functions[functions_cnt].sh_addr = sh.sh_addr; functions[functions_cnt].generated = false; functions_cnt++; return 0; } -static int addrs_cmp(const void *_a, const void *_b) -{ - const __u64 *a = _a; - const __u64 *b = _b; - - if (*a == *b) - return 0; - return *a < *b ? -1 : 1; -} - -static int get_vmlinux_addrs(struct btf_elf *btfe, struct funcs_layout *fl, - __u64 **paddrs, __u64 *pcount) -{ - __u64 *addrs, count, offset; - unsigned int addr_size, i; - Elf_Data *data; - GElf_Shdr shdr; - Elf_Scn *sec; - - /* Initialize for the sake of all error paths below. */ - *paddrs = NULL; - *pcount = 0; - - if (!fl->mcount_start || !fl->mcount_stop) - return 0; - - /* - * Find mcount addressed marked by __start_mcount_loc - * and __stop_mcount_loc symbols and load them into - * sorted array. - */ - sec = elf_getscn(btfe->elf, fl->mcount_sec_idx); - if (!sec || !gelf_getshdr(sec, &shdr)) { - fprintf(stderr, "Failed to get section(%lu) header.\n", - fl->mcount_sec_idx); - return -1; - } - - /* Get address size from processed file's ELF class. */ - addr_size = gelf_getclass(btfe->elf) == ELFCLASS32 ? 4 : 8; - - offset = fl->mcount_start - shdr.sh_addr; - count = (fl->mcount_stop - fl->mcount_start) / addr_size; - - data = elf_getdata(sec, 0); - if (!data) { - fprintf(stderr, "Failed to get section(%lu) data.\n", - fl->mcount_sec_idx); - return -1; - } - - addrs = malloc(count * sizeof(addrs[0])); - if (!addrs) { - fprintf(stderr, "Failed to allocate memory for ftrace addresses.\n"); - return -1; - } - - if (addr_size == sizeof(__u64)) { - memcpy(addrs, data->d_buf + offset, count * addr_size); - } else { - for (i = 0; i < count; i++) - addrs[i] = (__u64) *((__u32 *) (data->d_buf + offset + i * addr_size)); - } - - *paddrs = addrs; - *pcount = count; - return 0; -} - -static int -get_kmod_addrs(struct btf_elf *btfe, __u64 **paddrs, __u64 *pcount) -{ - __u64 *addrs, count; - unsigned int addr_size, i; - GElf_Shdr shdr_mcount; - Elf_Data *data; - Elf_Scn *sec; - - /* Initialize for the sake of all error paths below. */ - *paddrs = NULL; - *pcount = 0; - - /* get __mcount_loc */ - sec = elf_section_by_name(btfe->elf, &btfe->ehdr, &shdr_mcount, - "__mcount_loc", NULL); - if (!sec) { - if (btf_elf__verbose) { - printf("%s: '%s' doesn't have __mcount_loc section\n", __func__, - btfe->filename); - } - return 0; - } - - data = elf_getdata(sec, NULL); - if (!data) { - fprintf(stderr, "Failed to data for __mcount_loc section.\n"); - return -1; - } - - /* Get address size from processed file's ELF class. */ - addr_size = gelf_getclass(btfe->elf) == ELFCLASS32 ? 4 : 8; - - count = data->d_size / addr_size; - - addrs = malloc(count * sizeof(addrs[0])); - if (!addrs) { - fprintf(stderr, "Failed to allocate memory for ftrace addresses.\n"); - return -1; - } - - if (addr_size == sizeof(__u64)) { - memcpy(addrs, data->d_buf, count * addr_size); - } else { - for (i = 0; i < count; i++) - addrs[i] = (__u64) *((__u32 *) (data->d_buf + i * addr_size)); - } - - /* - * We get Elf object from dwfl_module_getelf function, - * which performs all possible relocations, including - * __mcount_loc section. - * - * So addrs array now contains relocated values, which - * we need take into account when we compare them to - * functions values, see comment in setup_functions - * function. - */ - *paddrs = addrs; - *pcount = count; - return 0; -} - -static int is_ftrace_func(struct elf_function *func, __u64 *addrs, __u64 count) -{ - __u64 start = func->addr; - __u64 addr, end = func->addr + func->size; - - /* - * The invariant here is addr[r] that is the smallest address - * that is >= than function start addr. Except the corner case - * where there is no such r, but for that we have a final check - * in the return. - */ - size_t l = 0, r = count - 1, m; - - /* make sure we don't use invalid r */ - if (count == 0) - return false; - - while (l < r) { - m = l + (r - l) / 2; - addr = addrs[m]; - - if (addr >= start) { - /* we satisfy invariant, so tighten r */ - r = m; - } else { - /* m is not good enough as l, maybe m + 1 will be */ - l = m + 1; - } - } - - return start <= addrs[r] && addrs[r] < end; -} - -static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) -{ - __u64 *addrs, count, i; - int functions_valid = 0; - bool kmod = false; - - /* - * Check if we are processing vmlinux image and - * get mcount data if it's detected. - */ - if (get_vmlinux_addrs(btfe, fl, &addrs, &count)) - return -1; - - /* - * Check if we are processing kernel module and - * get mcount data if it's detected. - */ - if (!addrs) { - if (get_kmod_addrs(btfe, &addrs, &count)) - return -1; - kmod = true; - } - - if (!addrs) { - if (btf_elf__verbose) - printf("ftrace symbols not detected, falling back to DWARF data\n"); - delete_functions(); - 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. - */ - 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. - */ - if (kmod) - func->addr += func->sh_addr; - - /* Make sure function is within ftrace addresses. */ - if (is_ftrace_func(func, addrs, count)) { - /* - * 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 != functions_valid) - functions[functions_valid] = functions[i]; - functions_valid++; - } - } - - functions_cnt = functions_valid; - free(addrs); - - if (btf_elf__verbose) - printf("Found %d functions!\n", functions_cnt); - return 0; -} - static struct elf_function *find_function(const struct btf_elf *btfe, const char *name) { @@ -620,23 +372,8 @@ static int collect_percpu_var(struct btf_elf *btfe, GElf_Sym *sym, return 0; } -static void collect_symbol(GElf_Sym *sym, struct funcs_layout *fl, - size_t sym_sec_idx) -{ - if (!fl->mcount_start && - !strcmp("__start_mcount_loc", elf_sym__name(sym, btfe->symtab))) { - fl->mcount_start = sym->st_value; - fl->mcount_sec_idx = sym_sec_idx; - } - - if (!fl->mcount_stop && - !strcmp("__stop_mcount_loc", elf_sym__name(sym, btfe->symtab))) - fl->mcount_stop = sym->st_value; -} - static int collect_symbols(struct btf_elf *btfe, bool collect_percpu_vars) { - struct funcs_layout fl = { }; Elf32_Word sym_sec_idx; uint32_t core_id; GElf_Sym sym; @@ -650,7 +387,6 @@ static int collect_symbols(struct btf_elf *btfe, bool collect_percpu_vars) return -1; if (collect_function(btfe, &sym, sym_sec_idx)) return -1; - collect_symbol(&sym, &fl, sym_sec_idx); } if (collect_percpu_vars) { @@ -661,9 +397,11 @@ static int collect_symbols(struct btf_elf *btfe, bool collect_percpu_vars) printf("Found %d per-CPU variables!\n", percpu_var_cnt); } - if (functions_cnt && setup_functions(btfe, &fl)) { - fprintf(stderr, "Failed to filter DWARF functions\n"); - return -1; + if (functions_cnt) { + qsort(functions, functions_cnt, sizeof(functions[0]), functions_cmp); + + if (btf_elf__verbose) + printf("Found %d functions!\n", functions_cnt); } return 0; -- 2.31.1 --------------2F0676AC09266ADBA754999C--