When building current linux-5.10 (or master) with gcc-11/binutins-2.36 gas complains about incorrect (used) section flags. Minimal reproducer: $ cat bug.c static const int _note_55 __attribute__((__used__)) __attribute__((section(".note.Linux"))) = 42; $ gcc-11.0.0 -c bug.c -o bug-11.o -fno-ident /tmp/ccJ9p7TD.s: Assembler messages: /tmp/ccJ9p7TD.s:3: Warning: setting incorrect section attributes for .note.Linux $ gcc-10.2.0 -c bug.c -o bug-11.o -fno-ident <ok> gcc-11 generates the following code: $ gcc-11.0.0 -S bug.c -o bug-11.s -fno-ident && cat bug-11.s .file "bug.c" .text .section .note.Linux,"aR" .align 4 .type _note_55, @object .size _note_55, 4 _note_55: .long 42 .section .note.GNU-stack,"",@progbits gcc-10 for completeness: $ gcc-10.2.0 -S bug.c -o bug-11.s -fno-ident && cat bug-11.s .file "bug.c" .text .section .note.Linux,"a" .align 4 .type _note_55, @object .size _note_55, 4 _note_55: .long 42 .section .note.GNU-stack,"",@progbits Original code comes from: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/elfnote.h#n71 Is it a real problem or a false positive warning? Currently gcc-11/binutils-2.36 generates kernels that can't load some modules and complain about a bunch of orphan sections. I wonder if this warhing is related and somehow affects future linking.
(In reply to Sergei Trofimovich from comment #0) > When building current linux-5.10 (or master) with gcc-11/binutins-2.36 gas > complains about incorrect (used) section flags. Minimal reproducer: > > $ cat bug.c > static const int _note_55 __attribute__((__used__)) > __attribute__((section(".note.Linux"))) = 42; > > $ gcc-11.0.0 -c bug.c -o bug-11.o -fno-ident > /tmp/ccJ9p7TD.s: Assembler messages: > /tmp/ccJ9p7TD.s:3: Warning: setting incorrect section attributes for > .note.Linux This is an assembler bug. > > Is it a real problem or a false positive warning? Currently > gcc-11/binutils-2.36 generates kernels that can't load some modules and > complain about a bunch of orphan sections. I wonder if this warhing is > related and somehow affects future linking. Please try: https://github.com/hjl-tools/linux/commit/d97c4aeb041b756861bb16ee895e2616f4b4061a
(In reply to H.J. Lu from comment #1) > (In reply to Sergei Trofimovich from comment #0) > > When building current linux-5.10 (or master) with gcc-11/binutins-2.36 gas > > complains about incorrect (used) section flags. Minimal reproducer: > > > > $ cat bug.c > > static const int _note_55 __attribute__((__used__)) > > __attribute__((section(".note.Linux"))) = 42; > > > > $ gcc-11.0.0 -c bug.c -o bug-11.o -fno-ident > > /tmp/ccJ9p7TD.s: Assembler messages: > > /tmp/ccJ9p7TD.s:3: Warning: setting incorrect section attributes for > > .note.Linux > > This is an assembler bug. Aha. I'll ignore the warning for now then. > > Is it a real problem or a false positive warning? Currently > > gcc-11/binutils-2.36 generates kernels that can't load some modules and > > complain about a bunch of orphan sections. I wonder if this warhing is > > related and somehow affects future linking. > Please try: > > https://github.com/hjl-tools/linux/commit/ > d97c4aeb041b756861bb16ee895e2616f4b4061a Did not help. More details of what I see: When I try to load mei-me.ko kernel crashes in jump_labels init as if there are no certain sections (maybe data sections?): $ modprobe mei-me $ dmesg BUG: unable to handle page fault for address: ffffffffc006eb90 #PF: supervisor write access in kernel mode #PF: error_code(0x0003) - permissions violation PGD 12840b067 P4D 12840b067 PUD 12840d067 PMD 100323067 PTE 800000010178e161 Oops: 0003 [#1] PREEMPT SMP CPU: 1 PID: 116 Comm: modprobe Not tainted 5.11.0-rc7-00091-g34add6d4b676 #209 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190711_202441-buildvm-armv7-10.arm.fedoraproject.org-2.fc31 04/01/2014 RIP: 0010:jump_label_add_module+0x1b4/0x280 Code: 00 48 8b 43 08 a8 02 0f 85 a7 00 00 00 48 83 e0 fc 48 c7 02 00 00 00 00 48 89 42 08 48 8b 43 08 83 e0 03 48 09 c2 48 83 ca 02 <48> 89 53 08 4d 89 6e 10 49 89 6e 08 48 8b 43 08 a8 02 74 6b 48 83 RSP: 0018:ffffb48e001b7d88 EFLAGS: 00010282 RAX: 0000000000000000 RBX: ffffffffc006eb88 RCX: 0000000000000000 RDX: ffffa43a802f53c2 RSI: ffffffffa41d2cc8 RDI: ffffffffa41d2cc8 RBP: ffffffffc004d1f0 R08: 0000000000000001 R09: 0000000000000012 R10: 0000000000001000 R11: ffffa43a816d9001 R12: ffffffffc004d5b0 R13: ffffffffc004ea00 R14: ffffa43a802f53a0 R15: ffffffffc004d1f8 FS: 00000000019f53c0(0000) GS:ffffa43abbc80000(0000) knl GS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffc006eb90 CR3: 00000001016fe003 CR4: 0000000000060ee0 Call Trace: jump_label_module_notify+0x53/0x90 blocking_notifier_call_chain_robust+0x6c/0xd0 load_module+0x58e/0x810 __do_sys_init_module+0x115/0x160 do_syscall_64+0x2d/0x70 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x55ce39 Code: 0c 00 b8 ca 00 00 00 0f 05 eb a5 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffc3a5e37c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000af RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 000000000055ce39 RDX: 00000000006042ca RSI: 0000000000042078 RDI: 00007fb66fff7010 RBP: 00007fb66fff7010 R08: 0000000001a0b890 R09: 0000000000042078 R10: 0000000000000007 R11: 0000000000000246 R12: 00000000006042ca R13: 0000000000000000 R14: 0000000001a08054 R15: 00007fb66ffd6ad0 Modules linked in: mei_me(+) mei CR2: ffffffffc006eb90 ---[ end trace d7a0c94b086625bf ]--- Seemingly related linker warnings are in form of: ... x86_64-pc-linux-gnu-ld: warning: orphan section `.data.event_kfree_skb' from `net/core/net-traces.o' being placed in section `.data.event_kfree_skb' x86_64-pc-linux-gnu-ld: warning: orphan section `.data.event_bpf_test_finish' from `net/bpf/test_run.o' being placed in section `.data.event_bpf_test_finish' x86_64-pc-linux-gnu-ld: warning: orphan section `.data.event_fib6_table_lookup' from `net/ipv6/route.o' being placed in section `.data.event_fib6_table_lookup' ... These appeared after gcc-10 switch. gcc-10 seems to be very eager at placing things to their own sections: Minimal example: $ cat net-traces.c struct s { void *print_fmt; }; struct s print_fmt_napi_poll[1]; __attribute__((__used__)) struct s event_napi_poll = {print_fmt_napi_poll}; Note the .section .data.event_napi_poll,"awR" vs .data in: $ gcc-11.0.0 -fno-PIE -S net-traces.c -fno-ident && cat net-traces.s .file "net-traces.c" .text .globl print_fmt_napi_poll .bss .align 8 .type print_fmt_napi_poll, @object .size print_fmt_napi_poll, 8 print_fmt_napi_poll: .zero 8 .globl event_napi_poll .section .data.event_napi_poll,"awR" .align 8 .type event_napi_poll, @object .size event_napi_poll, 8 event_napi_poll: .quad print_fmt_napi_poll .section .note.GNU-stack,"",@progbits $ gcc-10.2.0 -fno-PIE -S net-traces.c -fno-ident && cat net-traces.s .file "net-traces.c" .text .globl print_fmt_napi_poll .bss .align 8 .type print_fmt_napi_poll, @object .size print_fmt_napi_poll, 8 print_fmt_napi_poll: .zero 8 .globl event_napi_poll .data .align 8 .type event_napi_poll, @object .size event_napi_poll, 8 event_napi_poll: .quad print_fmt_napi_poll .section .note.GNU-stack,"",@progbits
A patch is posted at https://sourceware.org/pipermail/binutils/2021-February/115343.html
(In reply to H.J. Lu from comment #3) > A patch is posted at > > https://sourceware.org/pipermail/binutils/2021-February/115343.html Works for me. Thank you!
The master branch has been updated by H.J. Lu <hjl@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ca1289b9f3b6c9854386d1373918978412a59f94 commit ca1289b9f3b6c9854386d1373918978412a59f94 Author: H.J. Lu <hjl.tools@gmail.com> Date: Tue Feb 16 04:55:42 2021 -0800 gas: Allow SHF_GNU_RETAIN on all sections Since SHF_GNU_RETAIN is allowed on all sections, strip SHF_GNU_RETAIN when checking incorrect section attributes. PR gas/27412 * config/obj-elf.c (obj_elf_change_section): Strip SHF_GNU_RETAIN when checking incorrect section attributes. * testsuite/gas/elf/elf.exp: Run section28 and section29. * testsuite/gas/elf/section28.d: New file. * testsuite/gas/elf/section28.s: Likewise. * testsuite/gas/elf/section29.d: Likewise. * testsuite/gas/elf/section29.s: Likewise.
Fixed for 2.37.