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Message-Id: <1487498660-16600-1-git-send-email-hoeun.ryu@gmail.com> Date: Sun, 19 Feb 2017 19:04:04 +0900 From: Hoeun Ryu <hoeun.ryu@...il.com> To: kernel-hardening@...ts.openwall.com, linux-kernel@...r.kernel.org Cc: Hoeun Ryu <hoeun.ryu@...il.com>, Arnd Bergmann <arnd@...db.de>, Kees Cook <keescook@...omium.org>, Ingo Molnar <mingo@...nel.org>, linux-arch@...r.kernel.org Subject: [RFC 1/7] arch: add __ro_mostly_after_init section marker After `__ro_after_init` marker is included in kernel, many kernel data objects can be read-only-after-init. But there are many other places that would be good to read-only-after-init but `__ro_after_init` can not be simply applicable to them because they should be writable at some points, which are during module_init/exit or dynamic de/registration for a specific subsystem. `__ro_mostly_after_init` is basically the same to `__ro_after_init`. The section is mapped as read-only after kernel init. The different thing is this section is temporarily mapped as read-write during module_init/exit and de/registration of a subsystem using set_ro_mostly_after_init_rw/ro pair. Use `__ro_mostly_after_init` as a way to mark such memory instead when `__ro_after_init` is not applicable because the memory should be writable at the described points of time. They are read-only right after kernel init and writable temporarily only during module_init/exit and dynamic de/registration for a subsystem. Signed-off-by: Hoeun Ryu <hoeun.ryu@...il.com> --- include/asm-generic/sections.h | 1 + include/asm-generic/vmlinux.lds.h | 10 ++++++++++ include/linux/cache.h | 11 +++++++++++ 3 files changed, 22 insertions(+) diff --git a/include/asm-generic/sections.h b/include/asm-generic/sections.h index 4df64a1..16a6f21 100644 --- a/include/asm-generic/sections.h +++ b/include/asm-generic/sections.h @@ -34,6 +34,7 @@ extern char __bss_start[], __bss_stop[]; extern char __init_begin[], __init_end[]; extern char _sinittext[], _einittext[]; extern char __start_data_ro_after_init[], __end_data_ro_after_init[]; +extern char __start_data_ro_mostly_after_init[], __end_data_ro_mostly_after_init[]; extern char _end[]; extern char __per_cpu_load[], __per_cpu_start[], __per_cpu_end[]; extern char __kprobes_text_start[], __kprobes_text_end[]; diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 4e09b28..cc5f44e 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -265,6 +265,15 @@ __end_data_ro_after_init = .; #endif +#ifndef RO_MOSTLY_AFTER_INIT_DATA +#define RO_MOSTLY_AFTER_INIT_DATA(align) \ + . = ALIGN(align); \ + VMLINUX_SYMBOL(__start_data_ro_mostly_after_init) = .; \ + *(.data..ro_mostly_after_init) \ + . = ALIGN(align); \ + VMLINUX_SYMBOL(__end_data_ro_mostly_after_init) = .; +#endif + /* * Read only Data */ @@ -275,6 +284,7 @@ *(.rodata) *(.rodata.*) \ RO_AFTER_INIT_DATA /* Read only after init */ \ KEEP(*(__vermagic)) /* Kernel version magic */ \ + RO_MOSTLY_AFTER_INIT_DATA(align) \ . = ALIGN(8); \ VMLINUX_SYMBOL(__start___tracepoints_ptrs) = .; \ KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ diff --git a/include/linux/cache.h b/include/linux/cache.h index 1be04f8..fd1cb9b 100644 --- a/include/linux/cache.h +++ b/include/linux/cache.h @@ -30,6 +30,17 @@ #define __ro_after_init __attribute__((__section__(".data..ro_after_init"))) #endif +/* + * __ro_mostly_after_init is almost like __ro_after_init. + * but __ro_mostly_after_init section is temporarily writable only during + * module_init/exit or dynamic de/registeration of a subsystem using + * set_ro_mostly_after_init_rw/ro pair. + */ +#ifndef __ro_mostly_after_init +#define __ro_mostly_after_init \ + __attribute__((__section__(".data..ro_mostly_after_init"))) +#endif + #ifndef ____cacheline_aligned #define ____cacheline_aligned __attribute__((__aligned__(SMP_CACHE_BYTES))) #endif -- 2.7.4
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