947e76cdc3
Impact: x86_64 percpu area layout change, irq_stack now at the beginning
Now that the PDA is empty except for the stack canary, it can be removed.
The irqstack is moved to the start of the per-cpu section. If the stack
protector is enabled, the canary overlaps the bottom 48 bytes of the irqstack.
tj: * updated subject
* dropped asm relocation of irq_stack_ptr
* updated comments a bit
* rebased on top of stack canary changes
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
38 lines
1,012 B
C
38 lines
1,012 B
C
#ifndef _ASM_STACKPROTECTOR_H
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#define _ASM_STACKPROTECTOR_H 1
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#include <asm/tsc.h>
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#include <asm/processor.h>
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/*
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* Initialize the stackprotector canary value.
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*
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* NOTE: this must only be called from functions that never return,
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* and it must always be inlined.
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*/
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static __always_inline void boot_init_stack_canary(void)
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{
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u64 canary;
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u64 tsc;
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/*
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* Build time only check to make sure the stack_canary is at
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* offset 40 in the pda; this is a gcc ABI requirement
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*/
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BUILD_BUG_ON(offsetof(union irq_stack_union, stack_canary) != 40);
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/*
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* We both use the random pool and the current TSC as a source
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* of randomness. The TSC only matters for very early init,
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* there it already has some randomness on most systems. Later
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* on during the bootup the random pool has true entropy too.
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*/
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get_random_bytes(&canary, sizeof(canary));
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tsc = __native_read_tsc();
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canary += tsc + (tsc << 32UL);
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current->stack_canary = canary;
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percpu_write(irq_stack_union.stack_canary, canary);
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}
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#endif
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