58 lines
1.5 KiB
Plaintext
58 lines
1.5 KiB
Plaintext
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From: Andrea Arcangeli <andrea@cpushare.com>
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Subject: [PATCH seccomp: make tsc disabling optional
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Patch-mainline: unknown
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References: 191123
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Make the TSC disable purely paranoid feature optional, so by default seccomp
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returns absolutely zerocost.
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Ported from 2.6.19 to 2.6.24-rc7 by Jeff Mahoney.
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Addition of x86-64 by Jan Beulich.
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Signed-off-by: Andrea Arcangeli <andrea@cpushare.com>
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Acked-by: Jeff Mahoney <jeffm@suse.com>
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---
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arch/x86/Kconfig | 12 ++++++++++++
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arch/x86/kernel/process.c | 2 ++
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2 files changed, 14 insertions(+)
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--- a/arch/x86/Kconfig
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+++ b/arch/x86/Kconfig
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@@ -1485,6 +1485,18 @@ config SECCOMP
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If unsure, say Y. Only embedded should say N here.
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+config SECCOMP_DISABLE_TSC
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+ bool "Disable the TSC for seccomp tasks"
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+ depends on SECCOMP
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+ default n
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+ help
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+ This feature mathematically prevents covert channels
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+ for tasks running under SECCOMP. This can generate
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+ a minuscule overhead in the scheduler.
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+
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+ If you care most about performance say N. Say Y only if you're
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+ paranoid about covert channels.
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+
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config CC_STACKPROTECTOR
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bool "Enable -fstack-protector buffer overflow detection (EXPERIMENTAL)"
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---help---
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--- a/arch/x86/kernel/process.c
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+++ b/arch/x86/kernel/process.c
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@@ -139,6 +139,7 @@ static void hard_disable_TSC(void)
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void disable_TSC(void)
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{
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+#ifdef CONFIG_SECCOMP_DISABLE_TSC
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preempt_disable();
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if (!test_and_set_thread_flag(TIF_NOTSC))
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/*
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@@ -147,6 +148,7 @@ void disable_TSC(void)
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*/
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hard_disable_TSC();
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preempt_enable();
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+#endif
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}
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static void hard_enable_TSC(void)
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