[PATCH v2] arm64: Make kpti command line options x86 compatible
From: Alexander Graf <hidden>
Date: 2018-11-13 15:29:14
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linux-doc, lkml
Subsystem:
arm64 port (aarch64 architecture), documentation, the rest · Maintainers:
Catalin Marinas, Will Deacon, Jonathan Corbet, Linus Torvalds
I've already stumbled over 2 cases where people got confused about how to disable kpti on AArch64. In both cases, they used existing x86_64 options and just applied that to an AArch64 system, expecting it to work. I think it makes a lot of sense to have compatible kernel command line parameters whenever we can have them be compatible. So this patch adds the pti= and no_pti kernel command line options, mapping them into the existing kpti= command line framework. It preserves the old syntax to maintain compatibility with older command lines. While at it, the patch also marks the respective options as dual-arch. Reported-by: Richard Brown <redacted> Signed-off-by: Alexander Graf <redacted> --- v1 -> v2: - Actually make it compile. Sorry for the sloppy v1. --- Documentation/admin-guide/kernel-parameters.txt | 6 +++--- arch/arm64/kernel/cpufeature.c | 20 +++++++++++++++++++- 2 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 81d1d5a74728..4a1c6bcfcdb5 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt@@ -3522,8 +3522,8 @@ pt. [PARIDE] See Documentation/blockdev/paride.txt. - pti= [X86_64] Control Page Table Isolation of user and - kernel address spaces. Disabling this feature + pti= [X86_64,ARM64] Control Page Table Isolation of user + and kernel address spaces. Disabling this feature removes hardening, but improves performance of system calls and interrupts.
@@ -3534,7 +3534,7 @@ Not specifying this option is equivalent to pti=auto. - nopti [X86_64] + nopti [X86_64,ARM64] Equivalent to pti=off pty.legacy_count=
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index af50064dea51..a67b4b563a7c 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c@@ -978,13 +978,31 @@ static int __init parse_kpti(char *str) bool enabled; int ret = strtobool(str, &enabled); - if (ret) + if (ret) { + if (!strncmp(str, "auto", 4)) { + __kpti_forced = 0; + return 0; + } return ret; + } __kpti_forced = enabled ? 1 : -1; return 0; } early_param("kpti", parse_kpti); + +static int __init parse_pti(char *str) +{ + return parse_kpti(str); +} +early_param("pti", parse_pti); + +static int __init parse_no_pti(char *p) +{ + __kpti_forced = -1; + return 0; +} +early_param("nopti", parse_no_pti); #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ #ifdef CONFIG_ARM64_HW_AFDBM
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