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riscv: patch: skip fixmap mapping when kernel text is already writable

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patch_map() always creates a temporary writable mapping via fixmap for
kernel text addresses, even when CONFIG_STRICT_KERNEL_RWX is disabled
and the kernel text is already mapped with _PAGE_WRITE.

This is unnecessary overhead at best, and on minimal configurations
it can cause page faults.

Skip the fixmap path for kernel text when CONFIG_STRICT_KERNEL_RWX
is not enabled, since the text pages are already writable in that case.
The module text path is already gated on CONFIG_STRICT_MODULE_RWX and
is kept unchanged.

Reported-by: Klara Modin <klara@kasm.eu>
Closes: https://lore.kernel.org/all/ant_8TaBbov_GS4i@soda.int.kasm.eu/
Reported-by: Lad Prabhakar <prabhakar.csengg@gmail.com>
Closes: https://lore.kernel.org/all/CA+V-a8tQK8rih9SGGTyqrEBGpNkx4H0eX2YccCRrgkVAPr+EBg@mail.gmail.com/
Tested-by: Klara Modin <klarasmodin@gmail.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://patch.msgid.link/20260814082742.148403-3-xiaofengmian@163.com
Signed-off-by: Paul Walmsley <pjw@kernel.org>
This commit is contained in:
Xiaofeng Yuan 2026-08-31 19:11:23 -06:00 committed by Paul Walmsley
parent bdc46e507b
commit 8718e5a309
1 changed files with 2 additions and 0 deletions
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arch/riscv/kernel/patch.c
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@ -45,6 +45,8 @@ static __always_inline void *patch_map(void *addr, const unsigned int fixmap)
phys_addr_t phys;
if (core_kernel_text(uintaddr) || is_kernel_exittext(uintaddr)) {
if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
return addr;
phys = __pa_symbol(addr);
} else if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) {
struct page *page = vmalloc_to_page(addr);