[PATCH v5 2/2] riscv: patch: skip fixmap mapping when kernel text is already writable
Xiaofeng Yuan <[email protected]>
| Newsgroups | org.infradead.lists.linux-riscv,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
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 <[email protected]> Closes: https://lore.kernel.org/all/[email protected]/ Reported-by: Lad Prabhakar <[email protected]> Closes: https://lore.kernel.org/all/CA+V-a8tQK8rih9SGGTyqrEBGpNkx4H0eX2YccCRrgkVAPr+EBg@mail.gmail.com/ --- v5: fix the fixmap gating for kernel text. The v4 early return on CONFIG_STRICT_MODULE_RWX wrongly skipped the fixmap for kernel text too, which panics on configs with CONFIG_MODULES=n where CONFIG_STRICT_MODULE_RWX is unavailable but CONFIG_STRICT_KERNEL_RWX is still enabled and kernel text is read-only. v3: early return when !CONFIG_STRICT_MODULE_RWX (per Nam Cao's suggestion) v2: add commit description Signed-off-by: Xiaofeng Yuan <[email protected]> --- arch/riscv/kernel/patch.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 16b243376f..2239c28981 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -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); -- 2.43.0 _______________________________________________ linux-riscv mailing list [email protected] http://lists.infradead.org/mailman/listinfo/linux-riscv