Commit 63289e7d authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc: align stack to 2 * THREAD_SIZE with VMAP_STACK 



In order to ease stack overflow detection, align
stack to 2 * THREAD_SIZE when using VMAP_STACK.
This allows overflow detection using a single bit check.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/60e9ae86b7d2cdcf21468787076d345663648f46.1576916812.git.christophe.leroy@c-s.fr
parent 02847487

arch/powerpc/include/asm/thread_info.h

+13 −0
Original line number Diff line number Diff line
@@ -22,6 +22,19 @@ 


#define THREAD_SIZE		(1 << THREAD_SHIFT)



/*

 * By aligning VMAP'd stacks to 2 * THREAD_SIZE, we can detect overflow by

 * checking sp & (1 << THREAD_SHIFT), which we can do cheaply in the entry

 * assembly.

 */

#ifdef CONFIG_VMAP_STACK

#define THREAD_ALIGN_SHIFT	(THREAD_SHIFT + 1)

#else

#define THREAD_ALIGN_SHIFT	THREAD_SHIFT

#endif



#define THREAD_ALIGN		(1 << THREAD_ALIGN_SHIFT)



#ifndef __ASSEMBLY__

#include <linux/cache.h>

#include <asm/processor.h>

arch/powerpc/kernel/setup_32.c

+1 −1
Original line number Diff line number Diff line
@@ -140,7 +140,7 @@ arch_initcall(ppc_init); 


static void *__init alloc_stack(void)

{

	void *ptr = memblock_alloc(THREAD_SIZE, THREAD_SIZE);

	void *ptr = memblock_alloc(THREAD_SIZE, THREAD_ALIGN);



	if (!ptr)

		panic("cannot allocate %d bytes for stack at %pS\n",

arch/powerpc/kernel/setup_64.c

+1 −1
Original line number Diff line number Diff line
@@ -633,7 +633,7 @@ static void *__init alloc_stack(unsigned long limit, int cpu) 


	BUILD_BUG_ON(STACK_INT_FRAME_SIZE % 16);



	ptr = memblock_alloc_try_nid(THREAD_SIZE, THREAD_SIZE,

	ptr = memblock_alloc_try_nid(THREAD_SIZE, THREAD_ALIGN,

				     MEMBLOCK_LOW_LIMIT, limit,

				     early_cpu_to_node(cpu));

	if (!ptr)

arch/powerpc/kernel/vmlinux.lds.S

+1 −1
Original line number Diff line number Diff line
@@ -323,7 +323,7 @@ SECTIONS 
#endif



	/* The initial task and kernel stack */

	INIT_TASK_DATA_SECTION(THREAD_SIZE)

	INIT_TASK_DATA_SECTION(THREAD_ALIGN)



	.data..page_aligned : AT(ADDR(.data..page_aligned) - LOAD_OFFSET) {

		PAGE_ALIGNED_DATA(PAGE_SIZE)

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