diff mbox series

[bpf-next,1/3] objtool: Move noreturns.h to a common location

Message ID 20250211023359.1570-2-laoar.shao@gmail.com (mailing list archive)
State Changes Requested
Delegated to: BPF
Headers show
Series bpf: Reject attaching fexit to __noreturn functions | expand

Checks

Context Check Description
bpf/vmtest-bpf-next-PR success PR summary
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/build_tools success Errors and warnings before: 26 (+1) this patch: 26 (+1)
netdev/cc_maintainers warning 2 maintainers not CCed: bp@alien8.de seanjc@google.com
netdev/build_clang success Errors and warnings before: 6688 this patch: 6688
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 3520 this patch: 3520
netdev/checkpatch warning WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-next-VM_Test-0 success Logs for Lint
bpf/vmtest-bpf-next-VM_Test-1 success Logs for ShellCheck
bpf/vmtest-bpf-next-VM_Test-3 success Logs for Validate matrix.py
bpf/vmtest-bpf-next-VM_Test-2 success Logs for Unittests
bpf/vmtest-bpf-next-VM_Test-4 success Logs for aarch64-gcc / GCC BPF
bpf/vmtest-bpf-next-VM_Test-5 success Logs for aarch64-gcc / build / build for aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-6 success Logs for aarch64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-11 success Logs for aarch64-gcc / veristat-kernel
bpf/vmtest-bpf-next-VM_Test-12 success Logs for aarch64-gcc / veristat-meta
bpf/vmtest-bpf-next-VM_Test-7 success Logs for aarch64-gcc / test (test_maps, false, 360) / test_maps on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-34 success Logs for x86_64-llvm-17 / build / build for x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-35 success Logs for x86_64-llvm-17 / build-release / build for x86_64 with llvm-17-O2
bpf/vmtest-bpf-next-VM_Test-40 success Logs for x86_64-llvm-17 / veristat-kernel
bpf/vmtest-bpf-next-VM_Test-41 success Logs for x86_64-llvm-17 / veristat-meta
bpf/vmtest-bpf-next-VM_Test-43 success Logs for x86_64-llvm-18 / build / build for x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-44 success Logs for x86_64-llvm-18 / build-release / build for x86_64 with llvm-18-O2
bpf/vmtest-bpf-next-VM_Test-14 success Logs for s390x-gcc / build / build for s390x with gcc
bpf/vmtest-bpf-next-VM_Test-10 success Logs for aarch64-gcc / test (test_verifier, false, 360) / test_verifier on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-13 success Logs for s390x-gcc / GCC BPF
bpf/vmtest-bpf-next-VM_Test-19 success Logs for s390x-gcc / veristat-kernel
bpf/vmtest-bpf-next-VM_Test-21 success Logs for set-matrix
bpf/vmtest-bpf-next-VM_Test-20 success Logs for s390x-gcc / veristat-meta
bpf/vmtest-bpf-next-VM_Test-18 success Logs for s390x-gcc / test (test_verifier, false, 360) / test_verifier on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-24 success Logs for x86_64-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-50 success Logs for x86_64-llvm-18 / veristat-kernel
bpf/vmtest-bpf-next-VM_Test-51 success Logs for x86_64-llvm-18 / veristat-meta
bpf/vmtest-bpf-next-VM_Test-23 success Logs for x86_64-gcc / build / build for x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-15 success Logs for s390x-gcc / build-release
bpf/vmtest-bpf-next-VM_Test-8 success Logs for aarch64-gcc / test (test_progs, false, 360) / test_progs on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-9 success Logs for aarch64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-next-VM_Test-17 success Logs for s390x-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-36 success Logs for x86_64-llvm-17 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-39 success Logs for x86_64-llvm-17 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-45 success Logs for x86_64-llvm-18 / test (test_maps, false, 360) / test_maps on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-49 success Logs for x86_64-llvm-18 / test (test_verifier, false, 360) / test_verifier on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-22 success Logs for x86_64-gcc / GCC BPF / GCC BPF
bpf/vmtest-bpf-next-VM_Test-25 success Logs for x86_64-gcc / test (test_maps, false, 360) / test_maps on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-32 success Logs for x86_64-gcc / veristat-meta / x86_64-gcc veristat_meta
bpf/vmtest-bpf-next-VM_Test-31 success Logs for x86_64-gcc / veristat-kernel / x86_64-gcc veristat_kernel
bpf/vmtest-bpf-next-VM_Test-30 success Logs for x86_64-gcc / test (test_verifier, false, 360) / test_verifier on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-16 success Logs for s390x-gcc / test (test_progs, false, 360) / test_progs on s390x with gcc
bpf/vmtest-bpf-next-VM_Test-33 success Logs for x86_64-llvm-17 / GCC BPF / GCC BPF
bpf/vmtest-bpf-next-VM_Test-27 success Logs for x86_64-gcc / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-28 success Logs for x86_64-gcc / test (test_progs_no_alu32_parallel, true, 30) / test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-29 success Logs for x86_64-gcc / test (test_progs_parallel, true, 30) / test_progs_parallel on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-26 success Logs for x86_64-gcc / test (test_progs, false, 360) / test_progs on x86_64 with gcc
bpf/vmtest-bpf-next-VM_Test-37 success Logs for x86_64-llvm-17 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-38 success Logs for x86_64-llvm-17 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-17
bpf/vmtest-bpf-next-VM_Test-42 success Logs for x86_64-llvm-18 / GCC BPF / GCC BPF
bpf/vmtest-bpf-next-VM_Test-46 success Logs for x86_64-llvm-18 / test (test_progs, false, 360) / test_progs on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-47 success Logs for x86_64-llvm-18 / test (test_progs_cpuv4, false, 360) / test_progs_cpuv4 on x86_64 with llvm-18
bpf/vmtest-bpf-next-VM_Test-48 success Logs for x86_64-llvm-18 / test (test_progs_no_alu32, false, 360) / test_progs_no_alu32 on x86_64 with llvm-18

Commit Message

Yafang Shao Feb. 11, 2025, 2:33 a.m. UTC 
It will used by bpf to reject attaching fexit prog to functions
annotated with __noreturn.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 {tools/objtool => include/linux}/noreturns.h |  0
 tools/include/linux/noreturns.h              | 52 ++++++++++++++++++++
 tools/objtool/Documentation/objtool.txt      |  3 +-
 tools/objtool/check.c                        |  2 +-
 4 files changed, 55 insertions(+), 2 deletions(-)
 rename {tools/objtool => include/linux}/noreturns.h (100%)
 create mode 100644 tools/include/linux/noreturns.h

Comments

Eduard Zingerman Feb. 11, 2025, 4:12 a.m. UTC | #1 
On Tue, 2025-02-11 at 10:33 +0800, Yafang Shao wrote:

[...]

> diff --git a/tools/include/linux/noreturns.h b/tools/include/linux/noreturns.h
> new file mode 100644
> index 000000000000..b2174894f9f7
> --- /dev/null
> +++ b/tools/include/linux/noreturns.h
> @@ -0,0 +1,52 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/*
> + * This is a (sorted!) list of all known __noreturn functions in the kernel.
> + * It's needed for objtool to properly reverse-engineer the control flow graph.
> + *
> + * Yes, this is unfortunate.  A better solution is in the works.
> + */

I'm probably out of context for this discussion, sorry if I'm raising
points already discussed.

The DW_AT_noreturn attribute is defined for DWARF. A simple script
like [1] could be used to find all functions with this attribute known
to DWARF. Using this script I see several functions present in my
kernel but not present in the NORETURN list from this patch:
- abort
- devtmpfs_work_loop
- play_dead
- rcu_gp_kthread
- rcu_tasks_kthread

All these are marked as FUNC symbols when doing 'readelf --symbols vmlinux'.

'pahole' could be modified to look for DW_AT_noreturn attributes and
add this information in BTF. E.g. by adding special btf_decl_tag to
corresponding FUNC definitions. This won't work if kernel is compiled
w/o BTF, of-course.

[1] https://gist.github.com/eddyz87/d8513a731dfe7e2be52b346aef1de353

> +NORETURN(__fortify_panic)
> +NORETURN(__ia32_sys_exit)
> +NORETURN(__ia32_sys_exit_group)
> +NORETURN(__kunit_abort)
> +NORETURN(__module_put_and_kthread_exit)
> +NORETURN(__stack_chk_fail)
> +NORETURN(__tdx_hypercall_failed)
> +NORETURN(__ubsan_handle_builtin_unreachable)
> +NORETURN(__x64_sys_exit)
> +NORETURN(__x64_sys_exit_group)
> +NORETURN(arch_cpu_idle_dead)
> +NORETURN(bch2_trans_in_restart_error)
> +NORETURN(bch2_trans_restart_error)
> +NORETURN(bch2_trans_unlocked_error)
> +NORETURN(cpu_bringup_and_idle)
> +NORETURN(cpu_startup_entry)
> +NORETURN(do_exit)
> +NORETURN(do_group_exit)
> +NORETURN(do_task_dead)
> +NORETURN(ex_handler_msr_mce)
> +NORETURN(hlt_play_dead)
> +NORETURN(hv_ghcb_terminate)
> +NORETURN(kthread_complete_and_exit)
> +NORETURN(kthread_exit)
> +NORETURN(kunit_try_catch_throw)
> +NORETURN(machine_real_restart)
> +NORETURN(make_task_dead)
> +NORETURN(mpt_halt_firmware)
> +NORETURN(nmi_panic_self_stop)
> +NORETURN(panic)
> +NORETURN(panic_smp_self_stop)
> +NORETURN(rest_init)
> +NORETURN(rewind_stack_and_make_dead)
> +NORETURN(rust_begin_unwind)
> +NORETURN(rust_helper_BUG)
> +NORETURN(sev_es_terminate)
> +NORETURN(snp_abort)
> +NORETURN(start_kernel)
> +NORETURN(stop_this_cpu)
> +NORETURN(usercopy_abort)
> +NORETURN(x86_64_start_kernel)
> +NORETURN(x86_64_start_reservations)
> +NORETURN(xen_cpu_bringup_again)
> +NORETURN(xen_start_kernel)

[...]
Yafang Shao Feb. 11, 2025, 6:12 a.m. UTC | #2 
On Tue, Feb 11, 2025 at 12:12 PM Eduard Zingerman <eddyz87@gmail.com> wrote:
>
> On Tue, 2025-02-11 at 10:33 +0800, Yafang Shao wrote:
>
> [...]
>
> > diff --git a/tools/include/linux/noreturns.h b/tools/include/linux/noreturns.h
> > new file mode 100644
> > index 000000000000..b2174894f9f7
> > --- /dev/null
> > +++ b/tools/include/linux/noreturns.h
> > @@ -0,0 +1,52 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +
> > +/*
> > + * This is a (sorted!) list of all known __noreturn functions in the kernel.
> > + * It's needed for objtool to properly reverse-engineer the control flow graph.
> > + *
> > + * Yes, this is unfortunate.  A better solution is in the works.
> > + */
>
> I'm probably out of context for this discussion, sorry if I'm raising
> points already discussed.

Please refer to the discussion at
https://lore.kernel.org/bpf/CAADnVQKXgPTQsjUDB3tjZ46aPWvoEcxBCnDXro8WPtNhkGNFyg@mail.gmail.com/
 for more details.

>
> The DW_AT_noreturn attribute is defined for DWARF. A simple script
> like [1] could be used to find all functions with this attribute known
> to DWARF. Using this script I see several functions present in my
> kernel but not present in the NORETURN list from this patch:
> - abort
> - devtmpfs_work_loop
> - play_dead
> - rcu_gp_kthread
> - rcu_tasks_kthread
>
> All these are marked as FUNC symbols when doing 'readelf --symbols vmlinux'.
>
> 'pahole' could be modified to look for DW_AT_noreturn attributes and
> add this information in BTF. E.g. by adding special btf_decl_tag to
> corresponding FUNC definitions. This won't work if kernel is compiled
> w/o BTF, of-course.
>
> [1] https://gist.github.com/eddyz87/d8513a731dfe7e2be52b346aef1de353

Thank you for your example—it’s been really helpful. Following
Alexei's suggestion, we’ll address this in the next step. We need to
apply the fix to the current kernel and backport it, so for now, the
simplest approach is to implement the current solution.

--
Regards
Yafang
Josh Poimboeuf Feb. 11, 2025, 3:50 p.m. UTC | #3 
On Tue, Feb 11, 2025 at 10:33:57AM +0800, Yafang Shao wrote:
> It will used by bpf to reject attaching fexit prog to functions
> annotated with __noreturn.
> 
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> Cc: Josh Poimboeuf <jpoimboe@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> ---
>  {tools/objtool => include/linux}/noreturns.h |  0
>  tools/include/linux/noreturns.h              | 52 ++++++++++++++++++++

Instead of moving the file, please make a copy and add it to
tools/objtool/sync-check.sh.
Josh Poimboeuf Feb. 11, 2025, 4:11 p.m. UTC | #4 
On Mon, Feb 10, 2025 at 08:12:32PM -0800, Eduard Zingerman wrote:
> I'm probably out of context for this discussion, sorry if I'm raising
> points already discussed.
> 
> The DW_AT_noreturn attribute is defined for DWARF. A simple script
> like [1] could be used to find all functions with this attribute known
> to DWARF. Using this script I see several functions present in my
> kernel but not present in the NORETURN list from this patch:
> - abort
> - devtmpfs_work_loop
> - play_dead
> - rcu_gp_kthread
> - rcu_tasks_kthread
> 
> All these are marked as FUNC symbols when doing 'readelf --symbols vmlinux'.
> 
> 'pahole' could be modified to look for DW_AT_noreturn attributes and
> add this information in BTF. E.g. by adding special btf_decl_tag to
> corresponding FUNC definitions. This won't work if kernel is compiled
> w/o BTF, of-course.
> 
> [1] https://gist.github.com/eddyz87/d8513a731dfe7e2be52b346aef1de353

I also suggested this, I agree this is a much better way to go.
noreturns.h is manually maintained based on objtool warnings and
I'm not surprised it has missing entries.

Alexei mentioned 30k+ noreturns, but when I eliminate dups and
__compiletime_assert_* it's a much smaller list:

$ ./noreturn_printer vmlinux |sort |uniq |grep -v compiletime_assert
arch_cpu_idle_dead               external idle.c
arch_cpu_idle_dead               external process.c
cpu_startup_entry                external cpu.h
cpu_startup_entry                external idle.c
do_exit                          external exit.c
do_exit                          external kernel.h
do_group_exit                    external exit.c
do_group_exit                    external task.h
do_task_dead                     external core.c
do_task_dead                     external task.h
doublefault_shim                 external doublefault_32.c
ex_handler_msr_mce               external core.c
ex_handler_msr_mce               external extable.h
__fortify_panic                  external fortify-string.h
__fortify_panic                  external string_helpers.c
i386_start_kernel                external head32.c
__ia32_sys_exit                  external syscalls_32.h
__ia32_sys_exit_group            external syscalls_32.h
kthread_complete_and_exit        external kthread.c
kthread_exit                     external kthread.c
kthread_exit                     external kthread.h
machine_real_restart             external reboot.c
make_task_dead                   external exit.c
__module_put_and_kthread_exit    external main.c
__module_put_and_kthread_exit    external module.h
nmi_panic_self_stop              external panic.c
panic                            external panic.c
panic                            external panic.h
panic_smp_self_stop              external panic.c
play_dead                                 process.c
rcu_gp_kthread                            tree.c
rcu_tasks_kthread                         tasks.h
rest_init                                 main.c
rewind_stack_and_make_dead       external dumpstack.c
start_kernel                     external main.c
start_kernel                     external start_kernel.h
stop_this_cpu                    external process.c
stop_this_cpu                    external processor.h

Also, for objtool we could use something based on your program to
autogenerate noreturns.h.  Only problem is, objtool doesn't currently
have a dependency on CONFIG_DEBUG_INFO.  Another option we've considered
is compiler annotations (or compiler plugins).
Yafang Shao Feb. 14, 2025, 7:26 a.m. UTC | #5 
On Tue, Feb 11, 2025 at 11:50 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> On Tue, Feb 11, 2025 at 10:33:57AM +0800, Yafang Shao wrote:
> > It will used by bpf to reject attaching fexit prog to functions
> > annotated with __noreturn.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > Cc: Josh Poimboeuf <jpoimboe@kernel.org>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > ---
> >  {tools/objtool => include/linux}/noreturns.h |  0
> >  tools/include/linux/noreturns.h              | 52 ++++++++++++++++++++
>
> Instead of moving the file, please make a copy

Are you suggesting we keep tools/objtool/noreturns.h as is and simply
copy it to include/linux/noreturns.h? In other words, the two files
would be tools/objtool/noreturns.h and include/linux/noreturns.h.

> and add it to
> tools/objtool/sync-check.sh.

Sure.
Yafang Shao Feb. 14, 2025, 7:29 a.m. UTC | #6 
On Wed, Feb 12, 2025 at 12:11 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
>
> On Mon, Feb 10, 2025 at 08:12:32PM -0800, Eduard Zingerman wrote:
> > I'm probably out of context for this discussion, sorry if I'm raising
> > points already discussed.
> >
> > The DW_AT_noreturn attribute is defined for DWARF. A simple script
> > like [1] could be used to find all functions with this attribute known
> > to DWARF. Using this script I see several functions present in my
> > kernel but not present in the NORETURN list from this patch:
> > - abort
> > - devtmpfs_work_loop
> > - play_dead
> > - rcu_gp_kthread
> > - rcu_tasks_kthread
> >
> > All these are marked as FUNC symbols when doing 'readelf --symbols vmlinux'.
> >
> > 'pahole' could be modified to look for DW_AT_noreturn attributes and
> > add this information in BTF. E.g. by adding special btf_decl_tag to
> > corresponding FUNC definitions. This won't work if kernel is compiled
> > w/o BTF, of-course.
> >
> > [1] https://gist.github.com/eddyz87/d8513a731dfe7e2be52b346aef1de353
>
> I also suggested this, I agree this is a much better way to go.
> noreturns.h is manually maintained based on objtool warnings and
> I'm not surprised it has missing entries.
>
> Alexei mentioned 30k+ noreturns, but when I eliminate dups and
> __compiletime_assert_* it's a much smaller list:
>
> $ ./noreturn_printer vmlinux |sort |uniq |grep -v compiletime_assert
> arch_cpu_idle_dead               external idle.c
> arch_cpu_idle_dead               external process.c
> cpu_startup_entry                external cpu.h
> cpu_startup_entry                external idle.c
> do_exit                          external exit.c
> do_exit                          external kernel.h
> do_group_exit                    external exit.c
> do_group_exit                    external task.h
> do_task_dead                     external core.c
> do_task_dead                     external task.h
> doublefault_shim                 external doublefault_32.c
> ex_handler_msr_mce               external core.c
> ex_handler_msr_mce               external extable.h
> __fortify_panic                  external fortify-string.h
> __fortify_panic                  external string_helpers.c
> i386_start_kernel                external head32.c
> __ia32_sys_exit                  external syscalls_32.h
> __ia32_sys_exit_group            external syscalls_32.h
> kthread_complete_and_exit        external kthread.c
> kthread_exit                     external kthread.c
> kthread_exit                     external kthread.h
> machine_real_restart             external reboot.c
> make_task_dead                   external exit.c
> __module_put_and_kthread_exit    external main.c
> __module_put_and_kthread_exit    external module.h
> nmi_panic_self_stop              external panic.c
> panic                            external panic.c
> panic                            external panic.h
> panic_smp_self_stop              external panic.c
> play_dead                                 process.c
> rcu_gp_kthread                            tree.c
> rcu_tasks_kthread                         tasks.h
> rest_init                                 main.c
> rewind_stack_and_make_dead       external dumpstack.c
> start_kernel                     external main.c
> start_kernel                     external start_kernel.h
> stop_this_cpu                    external process.c
> stop_this_cpu                    external processor.h
>
> Also, for objtool we could use something based on your program to
> autogenerate noreturns.h.

Automatically generating noreturns.h is a great idea, as it would make
the file accessible for use by others as well.

> Only problem is, objtool doesn't currently
> have a dependency on CONFIG_DEBUG_INFO.

Is there any reason we can't make it dependent on CONFIG_DEBUG_INFO?"

>  Another option we've considered
> is compiler annotations (or compiler plugins).
Josh Poimboeuf Feb. 14, 2025, 8:12 a.m. UTC | #7 
On Fri, Feb 14, 2025 at 03:26:40PM +0800, Yafang Shao wrote:
> On Tue, Feb 11, 2025 at 11:50 PM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> >
> > On Tue, Feb 11, 2025 at 10:33:57AM +0800, Yafang Shao wrote:
> > > It will used by bpf to reject attaching fexit prog to functions
> > > annotated with __noreturn.
> > >
> > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > > Cc: Josh Poimboeuf <jpoimboe@kernel.org>
> > > Cc: Peter Zijlstra <peterz@infradead.org>
> > > ---
> > >  {tools/objtool => include/linux}/noreturns.h |  0
> > >  tools/include/linux/noreturns.h              | 52 ++++++++++++++++++++
> >
> > Instead of moving the file, please make a copy
> 
> Are you suggesting we keep tools/objtool/noreturns.h as is and simply
> copy it to include/linux/noreturns.h? In other words, the two files
> would be tools/objtool/noreturns.h and include/linux/noreturns.h.

Right.
Josh Poimboeuf Feb. 14, 2025, 8:14 a.m. UTC | #8 
On Fri, Feb 14, 2025 at 03:29:43PM +0800, Yafang Shao wrote:
> On Wed, Feb 12, 2025 at 12:11 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> > Only problem is, objtool doesn't currently
> > have a dependency on CONFIG_DEBUG_INFO.
> 
> Is there any reason we can't make it dependent on CONFIG_DEBUG_INFO?"

Objtool is enabled by default on x86 and is pretty much required at this
point.  We definitely don't want to force enable CONFIG_DEBUG_INFO as
that will slow the build down considerably.
Peter Zijlstra Feb. 14, 2025, 10:48 a.m. UTC | #9 
On Tue, Feb 11, 2025 at 08:11:22AM -0800, Josh Poimboeuf wrote:

> Also, for objtool we could use something based on your program to
> autogenerate noreturns.h.  Only problem is, objtool doesn't currently
> have a dependency on CONFIG_DEBUG_INFO.  Another option we've considered
> is compiler annotations (or compiler plugins).

But we don't need to re-generate the file on every build, right? We can
have every DBUG_INFO build verify the file is still complete.
Peter Zijlstra Feb. 14, 2025, 10:52 a.m. UTC | #10 
On Fri, Feb 14, 2025 at 12:14:49AM -0800, Josh Poimboeuf wrote:
> On Fri, Feb 14, 2025 at 03:29:43PM +0800, Yafang Shao wrote:
> > On Wed, Feb 12, 2025 at 12:11 AM Josh Poimboeuf <jpoimboe@kernel.org> wrote:
> > > Only problem is, objtool doesn't currently
> > > have a dependency on CONFIG_DEBUG_INFO.
> > 
> > Is there any reason we can't make it dependent on CONFIG_DEBUG_INFO?"
> 
> Objtool is enabled by default on x86 and is pretty much required at this
> point.

x86_64, but yeah, disabling objtool for x86_64 is going to be *really*
hard.

i386 is still limping along without -- mostly because nobody cared
enough to make it work.

> We definitely don't want to force enable CONFIG_DEBUG_INFO as
> that will slow the build down considerably.

This, very much this. Same reason I hardly every use clang to build a
kernel -- just too slow.
Josh Poimboeuf Feb. 14, 2025, 6:19 p.m. UTC | #11 
On Fri, Feb 14, 2025 at 11:48:00AM +0100, Peter Zijlstra wrote:
> On Tue, Feb 11, 2025 at 08:11:22AM -0800, Josh Poimboeuf wrote:
> 
> > Also, for objtool we could use something based on your program to
> > autogenerate noreturns.h.  Only problem is, objtool doesn't currently
> > have a dependency on CONFIG_DEBUG_INFO.  Another option we've considered
> > is compiler annotations (or compiler plugins).
> 
> But we don't need to re-generate the file on every build, right? We can
> have every DBUG_INFO build verify the file is still complete.

Hm, yeah we could do that.  It's still not ideal, as a human now has to
go fix those warnings...

But it's probably better than the current situation.
diff mbox series

Patch

diff --git a/tools/objtool/noreturns.h b/include/linux/noreturns.h
similarity index 100%
rename from tools/objtool/noreturns.h
rename to include/linux/noreturns.h
diff --git a/tools/include/linux/noreturns.h b/tools/include/linux/noreturns.h
new file mode 100644
index 000000000000..b2174894f9f7
--- /dev/null
+++ b/tools/include/linux/noreturns.h
@@ -0,0 +1,52 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * This is a (sorted!) list of all known __noreturn functions in the kernel.
+ * It's needed for objtool to properly reverse-engineer the control flow graph.
+ *
+ * Yes, this is unfortunate.  A better solution is in the works.
+ */
+NORETURN(__fortify_panic)
+NORETURN(__ia32_sys_exit)
+NORETURN(__ia32_sys_exit_group)
+NORETURN(__kunit_abort)
+NORETURN(__module_put_and_kthread_exit)
+NORETURN(__stack_chk_fail)
+NORETURN(__tdx_hypercall_failed)
+NORETURN(__ubsan_handle_builtin_unreachable)
+NORETURN(__x64_sys_exit)
+NORETURN(__x64_sys_exit_group)
+NORETURN(arch_cpu_idle_dead)
+NORETURN(bch2_trans_in_restart_error)
+NORETURN(bch2_trans_restart_error)
+NORETURN(bch2_trans_unlocked_error)
+NORETURN(cpu_bringup_and_idle)
+NORETURN(cpu_startup_entry)
+NORETURN(do_exit)
+NORETURN(do_group_exit)
+NORETURN(do_task_dead)
+NORETURN(ex_handler_msr_mce)
+NORETURN(hlt_play_dead)
+NORETURN(hv_ghcb_terminate)
+NORETURN(kthread_complete_and_exit)
+NORETURN(kthread_exit)
+NORETURN(kunit_try_catch_throw)
+NORETURN(machine_real_restart)
+NORETURN(make_task_dead)
+NORETURN(mpt_halt_firmware)
+NORETURN(nmi_panic_self_stop)
+NORETURN(panic)
+NORETURN(panic_smp_self_stop)
+NORETURN(rest_init)
+NORETURN(rewind_stack_and_make_dead)
+NORETURN(rust_begin_unwind)
+NORETURN(rust_helper_BUG)
+NORETURN(sev_es_terminate)
+NORETURN(snp_abort)
+NORETURN(start_kernel)
+NORETURN(stop_this_cpu)
+NORETURN(usercopy_abort)
+NORETURN(x86_64_start_kernel)
+NORETURN(x86_64_start_reservations)
+NORETURN(xen_cpu_bringup_again)
+NORETURN(xen_start_kernel)
diff --git a/tools/objtool/Documentation/objtool.txt b/tools/objtool/Documentation/objtool.txt
index 7c3ee959b63c..726db5b2b1a5 100644
--- a/tools/objtool/Documentation/objtool.txt
+++ b/tools/objtool/Documentation/objtool.txt
@@ -326,7 +326,8 @@  the objtool maintainers.
 
    The call from foo() to bar() doesn't return, but bar() is missing the
    __noreturn annotation.  NOTE: In addition to annotating the function
-   with __noreturn, please also add it to tools/objtool/noreturns.h.
+   with __noreturn, please also add it to tools/include/linux/noreturns.h and
+   include/linux/noreturns.h.
 
 4. file.o: warning: objtool: func(): can't find starting instruction
    or
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 753dbc4f8198..2940ddc56b1a 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -250,7 +250,7 @@  static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 
 #define NORETURN(func) __stringify(func),
 	static const char * const global_noreturns[] = {
-#include "noreturns.h"
+#include <linux/noreturns.h>
 	};
 #undef NORETURN