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Date: Fri, 02 Sep 2022 15:06:32 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Thomas Gleixner <tglx@...utronix.de> Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, x86@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>, Tim Chen <tim.c.chen@...ux.intel.com>, Josh Poimboeuf <jpoimboe@...nel.org>, Andrew Cooper <Andrew.Cooper3@...rix.com>, Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Johannes Wikner <kwikner@...z.ch>, Alyssa Milburn <alyssa.milburn@...ux.intel.com>, Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>, Joao Moreira <joao.moreira@...el.com>, Joseph Nuzman <joseph.nuzman@...el.com>, Steven Rostedt <rostedt@...dmis.org>, Juergen Gross <jgross@...e.com>, Masami Hiramatsu <mhiramat@...nel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, K Prateek Nayak <kprateek.nayak@....com>, Eric Dumazet <edumazet@...gle.com> Subject: [PATCH v2 07/59] x86: Sanitize linker script From: Thomas Gleixner <tglx@...utronix.de> The section ordering in the text section is more than suboptimal: ALIGN_ENTRY_TEXT_BEGIN ENTRY_TEXT ALIGN_ENTRY_TEXT_END SOFTIRQENTRY_TEXT STATIC_CALL_TEXT INDIRECT_THUNK_TEXT ENTRY_TEXT is in a seperate PMD so it can be mapped into the cpu entry area when KPTI is enabled. That means the sections after it are also in a seperate PMD. That's wasteful especially as the indirect thunk text is a hotpath on retpoline enabled systems and the static call text is fairly hot on 32bit. Move the entry text section last so that the other sections share a PMD with the text before it. This is obviously just best effort and not guaranteed when the previous text is just at a PMD boundary. The text section placement needs an overhaul in general. There is e.g. no point to have debugfs, sysfs, cpuhotplug and other rarely used functions next to hot path text. Signed-off-by: Thomas Gleixner <tglx@...utronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> --- arch/x86/kernel/vmlinux.lds.S | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -132,18 +132,19 @@ SECTIONS CPUIDLE_TEXT LOCK_TEXT KPROBES_TEXT - ALIGN_ENTRY_TEXT_BEGIN - ENTRY_TEXT - ALIGN_ENTRY_TEXT_END SOFTIRQENTRY_TEXT - STATIC_CALL_TEXT - *(.gnu.warning) - #ifdef CONFIG_RETPOLINE __indirect_thunk_start = .; *(.text.__x86.*) __indirect_thunk_end = .; #endif + STATIC_CALL_TEXT + + ALIGN_ENTRY_TEXT_BEGIN + ENTRY_TEXT + ALIGN_ENTRY_TEXT_END + *(.gnu.warning) + } :text =0xcccc /* End of text section, which should occupy whole number of pages */
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