Messages in this thread Patch in this message | | | Subject | Re: linux-next failing build due to missing cubictcp_state symbol | From | Jiri Slaby <> | Date | Mon, 3 May 2021 10:59:44 +0200 |
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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.
> regards,-- js suse labs From: Jiri Slaby <jslaby@suse.cz> Subject: ppc64: .opd section fix Patch-mainline: submitted 2021/05/03
Functions in the .opd section should be considered valid too. Otherwise, pahole cannot produce a .BTF section from vmlinux and kernel build fails on ppc64. --- btf_encoder.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)
--- a/btf_encoder.c +++ b/btf_encoder.c @@ -31,6 +31,8 @@ struct funcs_layout { unsigned long mcount_start; unsigned long mcount_stop; unsigned long mcount_sec_idx; + unsigned long opd_start; + unsigned long opd_stop; }; struct elf_function { @@ -271,11 +273,24 @@ static int is_ftrace_func(struct elf_fun return start <= addrs[r] && addrs[r] < end; } +static int is_opd_func(struct elf_function *func, struct funcs_layout *fl) +{ + return fl->opd_start <= func->addr && func->addr < fl->opd_stop; +} + static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl) { __u64 *addrs, count, i; int functions_valid = 0; bool kmod = false; + GElf_Shdr shdr; + Elf_Scn *sec; + + sec = elf_section_by_name(btfe->elf, &btfe->ehdr, &shdr, ".opd", NULL); + if (sec) { + fl->opd_start = shdr.sh_addr; + fl->opd_stop = shdr.sh_addr + shdr.sh_size; + } /* * Check if we are processing vmlinux image and @@ -322,7 +337,8 @@ static int setup_functions(struct btf_el func->addr += func->sh_addr; /* Make sure function is within ftrace addresses. */ - if (is_ftrace_func(func, addrs, count)) { + if (is_opd_func(func, fl) || + 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 | |