LoongArch: BPF: Make arch_protect_bpf_trampoline() return 0

Occasionally there exist "text_copy_cb: operation failed" when executing
the bpf selftests, the reason is copy_to_kernel_nofault() failed

LoongArch: BPF: Make arch_protect_bpf_trampoline() return 0

Occasionally there exist "text_copy_cb: operation failed" when executing
the bpf selftests, the reason is copy_to_kernel_nofault() failed and the
ecode of ESTAT register is 0x4 (PME: Page Modification Exception) due to
the pte is not writeable. The root cause is that there is another place
to set the pte entry as readonly which is in the generic weak version of
arch_protect_bpf_trampoline().

There are two ways to fix this race condition issue: the direct way is
to modify the generic weak arch_protect_bpf_trampoline() to add a mutex
lock for set_memory_rox(), but the other simple and proper way is to
just make arch_protect_bpf_trampoline() return 0 in the arch-specific
code because LoongArch has already use the BPF prog pack allocator for
trampoline.

Here are the trimmed kernel log messages:

copy_to_kernel_nofault: memory access failed, ecode 0x4
copy_to_kernel_nofault: the caller is text_copy_cb+0x50/0xa0
text_copy_cb: operation failed
------------[ cut here ]------------
bpf_prog_pack bug: missing bpf_arch_text_invalidate?
WARNING: kernel/bpf/core.c:1008 at bpf_prog_pack_free+0x200/0x228
...
Call Trace:
[<9000000000248914>] show_stack+0x64/0x188
[<9000000000241308>] dump_stack_lvl+0x6c/0x9c
[<90000000002705bc>] __warn+0x9c/0x200
[<9000000001c428c0>] __report_bug+0xa8/0x1c0
[<9000000001c42b5c>] report_bug+0x64/0x120
[<9000000001c7dcd0>] do_bp+0x270/0x3c0
[<9000000000246f40>] handle_bp+0x120/0x1c0
[<900000000047b030>] bpf_prog_pack_free+0x200/0x228
[<900000000047b2ec>] bpf_jit_binary_pack_free+0x24/0x60
[<900000000026989c>] bpf_jit_free+0x54/0xb0
[<900000000029e10c>] process_one_work+0x184/0x610
[<900000000029ef8c>] worker_thread+0x24c/0x388
[<90000000002a902c>] kthread+0x13c/0x170
[<9000000001c7dfe8>] ret_from_kernel_thread+0x28/0x1c0
[<9000000000246624>] ret_from_kernel_thread_asm+0xc/0x88

---[ end trace 0000000000000000 ]---

Here is a simple shell script to reproduce:

#!/bin/bash

for ((i=1; i<=1000; i++))
do
echo "Under testing $i ..."
dmesg -c > /dev/null
./test_progs -t fentry_attach_stress > /dev/null
dmesg -t | grep "text_copy_cb: operation failed"
if [ $? -eq 0 ]; then
break
fi
done

Cc: stable@vger.kernel.org
Fixes: 4ab17e762b34 ("LoongArch: BPF: Use BPF prog pack allocator")
Acked-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

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LoongArch: Fix calling smp_processor_id() in preemptible code

Fix the warning:

BUG: using smp_processor_id() in preemptible [00000000] code: systemd/1
caller is larch_insn_text_copy+0x40/0xf0

LoongArch: Fix calling smp_processor_id() in preemptible code

Fix the warning:

BUG: using smp_processor_id() in preemptible [00000000] code: systemd/1
caller is larch_insn_text_copy+0x40/0xf0

Simply changing it to raw_smp_processor_id() is not enough: if preempt
and CPU hotplug happens after raw_smp_processor_id() but before calling
stop_machine(), the CPU where raw_smp_processor_id() has run may become
offline when stop_machine() and no CPU will run copy_to_kernel_nofault()
in text_copy_cb(). Thus guard the larch_insn_text_copy() calls with
cpus_read_lock() and change stop_machine() to stop_machine_cpuslocked()
to prevent this.

I've considered moving the locks inside larch_insn_text_copy() but
doing so seems not an easy hack. In bpf_arch_text_poke() obviously the
memcpy() call must be guarded by text_mutex, so we have to leave the
acquire of text_mutex out of larch_insn_text_copy(). But in the entire
kernel the acquire of mutexes is always after cpus_read_lock(), so we
cannot put cpus_read_lock() into larch_insn_text_copy() while leaving
the text_mutex acquire out (or we risk a deadlock due to inconsistent
lock acquire order). So let's fix the bug first and leave the posssible
refactor as future work.

Fixes: 9fbd18cf4c69 ("LoongArch: BPF: Add dynamic code modification support")
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

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Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

This was done entirely with mindless brute force, using

git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs

Convert 'alloc_obj' family to use the new default GFP_KERNEL argument

This was done entirely with mindless brute force, using

git grep -l '\<k[vmz]*alloc_objs*(.*, GFP_KERNEL)' |
xargs sed -i 's/\(alloc_objs*(.*\), GFP_KERNEL)/\1)/'

to convert the new alloc_obj() users that had a simple GFP_KERNEL
argument to just drop that argument.

Note that due to the extreme simplicity of the scripting, any slightly
more complex cases spread over multiple lines would not be triggered:
they definitely exist, but this covers the vast bulk of the cases, and
the resulting diff is also then easier to check automatically.

For the same reason the 'flex' versions will be done as a separate
conversion.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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