From: Kees Cook <keescook@chromium.org> To: Thomas Gleixner <tglx@linutronix.de>, Will Deacon <will@kernel.org> Cc: "Kees Cook" <keescook@chromium.org>, "Nick Desaulniers" <ndesaulniers@google.com>, "Jian Cai" <jiancai@google.com>, "Fāng-ruì Sòng" <maskray@google.com>, "Luis Lozano" <llozano@google.com>, "Manoj Gupta" <manojgupta@google.com>, stable@vger.kernel.org, "Catalin Marinas" <catalin.marinas@arm.com>, "Mark Rutland" <mark.rutland@arm.com>, "Ard Biesheuvel" <ardb@kernel.org>, "Peter Collingbourne" <pcc@google.com>, "James Morse" <james.morse@arm.com>, "Borislav Petkov" <bp@suse.de>, "Ingo Molnar" <mingo@redhat.com>, "Russell King" <linux@armlinux.org.uk>, "Masahiro Yamada" <masahiroy@kernel.org>, "Arvind Sankar" <nivedita@alum.mit.edu>, "Nathan Chancellor" <natechancellor@gmail.com>, "Arnd Bergmann" <arnd@arndb.de>, x86@kernel.org, clang-built-linux@googlegroups.com, linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v5 13/36] vmlinux.lds.h: add PGO and AutoFDO input sections Date: Fri, 31 Jul 2020 16:07:57 -0700 Message-ID: <20200731230820.1742553-14-keescook@chromium.org> (raw) In-Reply-To: <20200731230820.1742553-1-keescook@chromium.org> From: Nick Desaulniers <ndesaulniers@google.com> Basically, consider .text.{hot|unlikely|unknown}.* part of .text, too. When compiling with profiling information (collected via PGO instrumentations or AutoFDO sampling), Clang will separate code into .text.hot, .text.unlikely, or .text.unknown sections based on profiling information. After D79600 (clang-11), these sections will have a trailing `.` suffix, ie. .text.hot., .text.unlikely., .text.unknown.. When using -ffunction-sections together with profiling infomation, either explicitly (FGKASLR) or implicitly (LTO), code may be placed in sections following the convention: .text.hot.<foo>, .text.unlikely.<bar>, .text.unknown.<baz> where <foo>, <bar>, and <baz> are functions. (This produces one section per function; we generally try to merge these all back via linker script so that we don't have 50k sections). For the above cases, we need to teach our linker scripts that such sections might exist and that we'd explicitly like them grouped together, otherwise we can wind up with code outside of the _stext/_etext boundaries that might not be mapped properly for some architectures, resulting in boot failures. If the linker script is not told about possible input sections, then where the section is placed as output is a heuristic-laiden mess that's non-portable between linkers (ie. BFD and LLD), and has resulted in many hard to debug bugs. Kees Cook is working on cleaning this up by adding --orphan-handling=warn linker flag used in ARCH=powerpc to additional architectures. In the case of linker scripts, borrowing from the Zen of Python: explicit is better than implicit. Also, ld.bfd's internal linker script considers .text.hot AND .text.hot.* to be part of .text, as well as .text.unlikely and .text.unlikely.*. I didn't see support for .text.unknown.*, and didn't see Clang producing such code in our kernel builds, but I see code in LLVM that can produce such section names if profiling information is missing. That may point to a larger issue with generating or collecting profiles, but I would much rather be safe and explicit than have to debug yet another issue related to orphan section placement. Reported-by: Jian Cai <jiancai@google.com> Suggested-by: Fāng-ruì Sòng <maskray@google.com> Tested-by: Luis Lozano <llozano@google.com> Tested-by: Manoj Gupta <manojgupta@google.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: stable@vger.kernel.org Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=add44f8d5c5c05e08b11e033127a744d61c26aee Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commitdiff;h=1de778ed23ce7492c523d5850c6c6dbb34152655 Link: https://reviews.llvm.org/D79600 Link: https://bugs.chromium.org/p/chromium/issues/detail?id=1084760 Debugged-by: Luis Lozano <llozano@google.com> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Kees Cook <keescook@chromium.org> --- include/asm-generic/vmlinux.lds.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 2593957f6e8b..af5211ca857c 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -561,7 +561,10 @@ */ #define TEXT_TEXT \ ALIGN_FUNCTION(); \ - *(.text.hot TEXT_MAIN .text.fixup .text.unlikely) \ + *(.text.hot .text.hot.*) \ + *(TEXT_MAIN .text.fixup) \ + *(.text.unlikely .text.unlikely.*) \ + *(.text.unknown .text.unknown.*) \ NOINSTR_TEXT \ *(.text..refcount) \ *(.ref.text) \ -- 2.25.1
next prev parent reply index Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-31 23:07 [PATCH v5 00/36] Warn on orphan section placement Kees Cook 2020-07-31 23:07 ` [PATCH v5 01/36] x86/boot/compressed: Move .got.plt entries out of the .got section Kees Cook 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Ard Biesheuvel 2020-07-31 23:07 ` [PATCH v5 02/36] x86/boot/compressed: Force hidden visibility for all symbol references Kees Cook 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Ard Biesheuvel 2020-07-31 23:07 ` [PATCH v5 03/36] x86/boot/compressed: Get rid of GOT fixup code Kees Cook 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Ard Biesheuvel 2020-07-31 23:07 ` [PATCH v5 04/36] x86/boot: Add .text.* to setup.ld Kees Cook 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar 2020-07-31 23:07 ` [PATCH v5 05/36] x86/boot: Remove run-time relocations from .head.text code Kees Cook 2020-07-31 23:42 ` Nick Desaulniers 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar 2020-07-31 23:07 ` [PATCH v5 06/36] x86/boot: Remove run-time relocations from head_{32,64}.S Kees Cook 2020-08-07 18:12 ` Nick Desaulniers 2020-08-07 20:20 ` Arvind Sankar 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar 2020-07-31 23:07 ` [PATCH v5 07/36] x86/boot: Check that there are no run-time relocations Kees Cook 2020-08-14 15:23 ` [tip: x86/boot] " tip-bot2 for Arvind Sankar 2020-07-31 23:07 ` [PATCH v5 08/36] vmlinux.lds.h: Create COMMON_DISCARDS Kees Cook 2020-07-31 23:07 ` [PATCH v5 09/36] vmlinux.lds.h: Add .gnu.version* to COMMON_DISCARDS Kees Cook 2020-07-31 23:07 ` [PATCH v5 10/36] vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections Kees Cook 2020-07-31 23:07 ` [PATCH v5 11/36] vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG Kees Cook 2020-07-31 23:07 ` [PATCH v5 12/36] vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS Kees Cook 2020-07-31 23:07 ` Kees Cook [this message] 2020-08-01 3:51 ` [PATCH v5 13/36] vmlinux.lds.h: add PGO and AutoFDO input sections Arvind Sankar 2020-08-01 6:18 ` Kees Cook 2020-08-01 17:27 ` Arvind Sankar 2020-08-03 19:05 ` Andi Kleen 2020-08-03 20:15 ` Arvind Sankar 2020-08-04 1:19 ` Fāng-ruì Sòng 2020-08-04 4:45 ` Andi Kleen 2020-08-04 5:32 ` Fāng-ruì Sòng 2020-08-04 16:06 ` Arvind Sankar 2020-08-21 19:18 ` Kees Cook 2020-07-31 23:07 ` [PATCH v5 14/36] efi/libstub: Disable -mbranch-protection Kees Cook 2020-07-31 23:07 ` [PATCH v5 15/36] arm64/mm: Remove needless section quotes Kees Cook 2020-07-31 23:08 ` [PATCH v5 16/36] arm64/kernel: Remove needless Call Frame Information annotations Kees Cook 2020-07-31 23:08 ` [PATCH v5 17/36] arm64/build: Remove .eh_frame* sections due to unwind tables Kees Cook 2020-07-31 23:08 ` [PATCH v5 18/36] arm64/build: Use common DISCARDS in linker script Kees Cook 2020-07-31 23:08 ` [PATCH v5 19/36] arm64/build: Add missing DWARF sections Kees Cook 2020-07-31 23:08 ` [PATCH v5 20/36] arm64/build: Assert for unwanted sections Kees Cook 2020-07-31 23:08 ` [PATCH v5 21/36] arm64/build: Warn on orphan section placement Kees Cook 2020-07-31 23:08 ` [PATCH v5 22/36] arm/build: Refactor linker script headers Kees Cook 2020-07-31 23:08 ` [PATCH v5 23/36] arm/build: Explicitly keep .ARM.attributes sections Kees Cook 2020-08-03 19:02 ` Nick Desaulniers 2020-08-17 22:06 ` Fangrui Song 2020-07-31 23:08 ` [PATCH v5 24/36] arm/build: Add missing sections Kees Cook 2020-07-31 23:08 ` [PATCH v5 25/36] arm/build: Warn on orphan section placement Kees Cook 2020-07-31 23:08 ` [PATCH v5 26/36] arm/boot: Handle all sections explicitly Kees Cook 2020-07-31 23:08 ` [PATCH v5 27/36] arm/boot: Warn on orphan section placement Kees Cook 2020-07-31 23:08 ` [PATCH v5 28/36] x86/asm: Avoid generating unused kprobe sections Kees Cook 2020-07-31 23:08 ` [PATCH v5 29/36] x86/build: Enforce an empty .got.plt section Kees Cook 2020-08-01 2:12 ` Arvind Sankar 2020-08-01 5:32 ` Kees Cook 2020-08-21 17:49 ` Kees Cook 2020-07-31 23:08 ` [PATCH v5 30/36] x86/build: Assert for unwanted sections Kees Cook 2020-07-31 23:08 ` [PATCH v5 31/36] x86/build: Warn on orphan section placement Kees Cook 2020-07-31 23:08 ` [PATCH v5 32/36] x86/boot/compressed: Reorganize zero-size section asserts Kees Cook 2020-08-01 1:47 ` Arvind Sankar 2020-08-01 2:53 ` Arvind Sankar 2020-08-01 5:36 ` Kees Cook 2020-08-01 17:12 ` Arvind Sankar 2020-08-21 18:24 ` Kees Cook 2020-08-01 5:35 ` Kees Cook 2020-08-01 17:00 ` Arvind Sankar 2020-08-21 18:19 ` Kees Cook 2020-07-31 23:08 ` [PATCH v5 33/36] x86/boot/compressed: Remove, discard, or assert for unwanted sections Kees Cook 2020-07-31 23:08 ` [PATCH v5 34/36] x86/boot/compressed: Add missing debugging sections to output Kees Cook 2020-07-31 23:08 ` [PATCH v5 35/36] x86/boot/compressed: Warn on orphan section placement Kees Cook 2020-07-31 23:08 ` [PATCH v5 36/36] arm/build: Assert for unwanted sections Kees Cook
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