Integrate compiler_builtins
#80
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Let me know what you think about this. I'm not 100% sure if this may bite us later on (e.g. if we end up having to add many builtins back later on for some reason), but it seems like a good choice at the moment. @alex was worried in #52 about the complexity for newcomers having to set this one up (apart from |
ojeda
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Are these really the only builtins we need? |
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Rewording of the comment to simplify and fix a typo too. |
These listed here are the ones we shouldn't need (from what I can tell, at least -- I added the ones using The ones that we currently/actually need are none, at least looking at the CI being successful. The ones that we may actually need in the future is not clear -- but we can add them as they come (either here or in the C side). In other words, in the future, if everything is customized for the kernel, this file would be empty (or with just the very subset actually needed and used in our code/compiler and not already defined by C). |
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I will leave this open for a couple days -- I'd like to give @nickdesaulniers & others involved with LLVM etc. the chance to tell us whether this looks like a sane enough approach. |
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@bjorn3 is probably interested in this, too, from the |
bjorn3
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Jan 21, 2021
This simplifies onboarding, it is smaller, faster to compile and it is one less dependency to worry about. It also simplifies the build system a tiny bit since now everything uses the 2018 edition. Fixes #69. Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
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This makes sense to me. I think this is unlikely to break in the near future. There isn't much that could change that would break it. |
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Thanks @bjorn3 for the analysis -- that is very good to hear and matches what I was expecting. |
ojeda
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Feb 15, 2023
As interrupts are Level-triggered,unless and until we deassert the register the interrupts are generated which causes spurious interrupts unhandled. Now we deasserted the interrupt at top half which solved the below "nobody cared" warning. warning reported in dmesg: irq 80: nobody cared (try booting with the "irqpoll" option) CPU: 5 PID: 2735 Comm: irq/80-AudioDSP Not tainted 5.15.86-15817-g4c19f3e06d49 #1 1bd3fd932cf58caacc95b0504d6ea1e3eab22289 Hardware name: Google Skyrim/Skyrim, BIOS Google_Skyrim.15303.0.0 01/03/2023 Call Trace: <IRQ> dump_stack_lvl+0x69/0x97 __report_bad_irq+0x3a/0xae note_interrupt+0x1a9/0x1e3 handle_irq_event_percpu+0x4b/0x6e handle_irq_event+0x36/0x5b handle_fasteoi_irq+0xae/0x171 __common_interrupt+0x48/0xc4 </IRQ> handlers: acp_irq_handler [snd_sof_amd_acp] threaded [<000000007e089f34>] acp_irq_thread [snd_sof_amd_acp] Disabling IRQ #80 Signed-off-by: V sujith kumar Reddy <Vsujithkumar.Reddy@amd.com> Link: https://lore.kernel.org/r/20230203123254.1898794-1-Vsujithkumar.Reddy@amd.com Signed-off-by: Mark Brown <broonie@kernel.org>
ojeda
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With latest clang18, I hit test_progs failures for the following test: #13/2 bpf_cookie/multi_kprobe_link_api:FAIL #13/3 bpf_cookie/multi_kprobe_attach_api:FAIL #13 bpf_cookie:FAIL #75 fentry_fexit:FAIL #76/1 fentry_test/fentry:FAIL #76 fentry_test:FAIL #80/1 fexit_test/fexit:FAIL #80 fexit_test:FAIL #110/1 kprobe_multi_test/skel_api:FAIL #110/2 kprobe_multi_test/link_api_addrs:FAIL #110/3 kprobe_multi_test/link_api_syms:FAIL #110/4 kprobe_multi_test/attach_api_pattern:FAIL #110/5 kprobe_multi_test/attach_api_addrs:FAIL #110/6 kprobe_multi_test/attach_api_syms:FAIL #110 kprobe_multi_test:FAIL For example, for #13/2, the error messages are: [...] kprobe_multi_test_run:FAIL:kprobe_test7_result unexpected kprobe_test7_result: actual 0 != expected 1 [...] kprobe_multi_test_run:FAIL:kretprobe_test7_result unexpected kretprobe_test7_result: actual 0 != expected 1 clang17 does not have this issue. Further investigation shows that kernel func bpf_fentry_test7(), used in the above tests, is inlined by the compiler although it is marked as noinline. int noinline bpf_fentry_test7(struct bpf_fentry_test_t *arg) { return (long)arg; } It is known that for simple functions like the above (e.g. just returning a constant or an input argument), the clang compiler may still do inlining for a noinline function. Adding 'asm volatile ("")' in the beginning of the bpf_fentry_test7() can prevent inlining. Signed-off-by: Yonghong Song <yonghong.song@linux.dev> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Tested-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/bpf/20230826200843.2210074-1-yonghong.song@linux.dev
ojeda
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Sep 12, 2023
In commit 0345691 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle") the new function report_idle_softirq() was created by breaking code out of the existing can_stop_idle_tick() for kernels v5.18 and newer. In doing so, the code essentially went from a one conditional: if (a && b && c) warn(); to a three conditional: if (!a) return; if (!b) return; if (!c) return; warn(); But that conversion got the condition for the RT specific local_bh_blocked() wrong. The original condition was: !local_bh_blocked() but the conversion failed to negate it so it ended up as: if (!local_bh_blocked()) return false; This issue lay dormant until another fixup for the same commit was added in commit a7e282c ("tick/rcu: Fix bogus ratelimit condition"). This commit realized the ratelimit was essentially set to zero instead of ten, and hence *no* softirq pending messages would ever be issued. Once this commit was backported via linux-stable, both the v6.1 and v6.4 preempt-rt kernels started printing out 10 instances of this at boot: NOHZ tick-stop error: local softirq work is pending, handler #80!!! Remove the negation and return when local_bh_blocked() evaluates to true to bring the correct behaviour back. Fixes: 0345691 ("tick/rcu: Stop allowing RCU_SOFTIRQ in idle") Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Ahmad Fatoum <a.fatoum@pengutronix.de> Reviewed-by: Wen Yang <wenyang.linux@foxmail.com> Acked-by: Frederic Weisbecker <frederic@kernel.org> Link: https://lore.kernel.org/r/20230818200757.1808398-1-paul.gortmaker@windriver.com
Darksonn
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Dec 5, 2023
When I perform the following test operations:
1.ip link add br0 type bridge
2.brctl addif br0 eth0
3.ip addr add 239.0.0.1/32 dev eth0
4.ip addr add 239.0.0.1/32 dev br0
5.ip addr add 224.0.0.1/32 dev br0
6.while ((1))
do
ifconfig br0 up
ifconfig br0 down
done
7.send IGMPv2 query packets to port eth0 continuously. For example,
./mausezahn ethX -c 0 "01 00 5e 00 00 01 00 72 19 88 aa 02 08 00 45 00 00
1c 00 01 00 00 01 02 0e 7f c0 a8 0a b7 e0 00 00 01 11 64 ee 9b 00 00 00 00"
The preceding tests may trigger the refcnt uaf issue of the mc list. The
stack is as follows:
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 21 PID: 144 at lib/refcount.c:25 refcount_warn_saturate (lib/refcount.c:25)
CPU: 21 PID: 144 Comm: ksoftirqd/21 Kdump: loaded Not tainted 6.7.0-rc1-next-20231117-dirty Rust-for-Linux#80
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
RIP: 0010:refcount_warn_saturate (lib/refcount.c:25)
RSP: 0018:ffffb68f00657910 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff8a00c3bf96c0 RCX: ffff8a07b6160908
RDX: 00000000ffffffd8 RSI: 0000000000000027 RDI: ffff8a07b6160900
RBP: ffff8a00cba36862 R08: 0000000000000000 R09: 00000000ffff7fff
R10: ffffb68f006577c0 R11: ffffffffb0fdcdc8 R12: ffff8a00c3bf9680
R13: ffff8a00c3bf96f0 R14: 0000000000000000 R15: ffff8a00d8766e00
FS: 0000000000000000(0000) GS:ffff8a07b6140000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055f10b520b28 CR3: 000000039741a000 CR4: 00000000000006f0
Call Trace:
<TASK>
igmp_heard_query (net/ipv4/igmp.c:1068)
igmp_rcv (net/ipv4/igmp.c:1132)
ip_protocol_deliver_rcu (net/ipv4/ip_input.c:205)
ip_local_deliver_finish (net/ipv4/ip_input.c:234)
__netif_receive_skb_one_core (net/core/dev.c:5529)
netif_receive_skb_internal (net/core/dev.c:5729)
netif_receive_skb (net/core/dev.c:5788)
br_handle_frame_finish (net/bridge/br_input.c:216)
nf_hook_bridge_pre (net/bridge/br_input.c:294)
__netif_receive_skb_core (net/core/dev.c:5423)
__netif_receive_skb_list_core (net/core/dev.c:5606)
__netif_receive_skb_list (net/core/dev.c:5674)
netif_receive_skb_list_internal (net/core/dev.c:5764)
napi_gro_receive (net/core/gro.c:609)
e1000_clean_rx_irq (drivers/net/ethernet/intel/e1000/e1000_main.c:4467)
e1000_clean (drivers/net/ethernet/intel/e1000/e1000_main.c:3805)
__napi_poll (net/core/dev.c:6533)
net_rx_action (net/core/dev.c:6735)
__do_softirq (kernel/softirq.c:554)
run_ksoftirqd (kernel/softirq.c:913)
smpboot_thread_fn (kernel/smpboot.c:164)
kthread (kernel/kthread.c:388)
ret_from_fork (arch/x86/kernel/process.c:153)
ret_from_fork_asm (arch/x86/entry/entry_64.S:250)
</TASK>
The root causes are as follows:
Thread A Thread B
... netif_receive_skb
br_dev_stop ...
br_multicast_leave_snoopers ...
__ip_mc_dec_group ...
__igmp_group_dropped igmp_rcv
igmp_stop_timer igmp_heard_query //ref = 1
ip_ma_put igmp_mod_timer
refcount_dec_and_test igmp_start_timer //ref = 0
... refcount_inc //ref increases from 0
When the device receives an IGMPv2 Query message, it starts the timer
immediately, regardless of whether the device is running. If the device is
down and has left the multicast group, it will cause the mc list refcount
uaf issue.
Fixes: 1da177e ("Linux-2.6.12-rc2")
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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This simplifies onboarding, it is smaller, faster to compile and it is one less dependency to worry about.
It also simplifies the build system a tiny bit since now everything uses the 2018 edition.
Fixes #69.