From: "Björn Töpel" <bjorn@kernel.org>
To: Karl Mehltretter <kmehltretter@gmail.com>,
Paul Walmsley <pjw@kernel.org>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>
Cc: Karl Mehltretter <kmehltretter@gmail.com>,
Alexandre Ghiti <alex@ghiti.fr>, Mike Rapoport <rppt@kernel.org>,
Luis Chamberlain <mcgrof@kernel.org>,
linux-riscv@lists.infradead.org, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] riscv: mm: Pre-allocate module page tables for execmem
Date: Thu, 15 Oct 2026 18:19:24 +0200 [thread overview]
Message-ID: <87a4of5437.fsf@all.your.base.are.belong.to.us> (raw)
In-Reply-To: <20261015033643.84972-1-kmehltretter@gmail.com>
Karl Mehltretter <kmehltretter@gmail.com> writes:
> RV64 pre-allocates page-table levels for late kernel mappings. The module
> range is guarded by CONFIG_MODULES, although execmem can use it without
> modules.
>
> With CONFIG_BPF_JIT=y and CONFIG_MODULES=n, execmem adds a mapping to
> init_mm while the current process retains an empty PGD entry. Initializing
> a BPF program pack then faults:
>
> Unable to handle kernel paging request ...
> [ffffffff78000000] pgd=0000000000000000
> ...
> bpf_jit_fill_hole_with_zero
> bpf_prog_pack_alloc
>
> Use CONFIG_EXECMEM for the module-range pre-allocation, as powerpc does
> for its execmem page-table setup. Both CONFIG_MODULES and CONFIG_BPF_JIT
> select it.
>
> Fixes: 2c9e5d4a0082 ("bpf: remove CONFIG_BPF_JIT dependency on CONFIG_MODULES of")
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Karl Mehltretter <kmehltretter@gmail.com>
TY!
Acked-by: Björn Töpel <bjorn@kernel.org>
prev parent reply other threads:[~2026-10-15 16:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 3:36 Karl Mehltretter
2026-10-15 8:16 ` Mike Rapoport
2026-10-15 16:19 ` Björn Töpel [this message]
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