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powerpc: align stack to 2 * THREAD_SIZE with VMAP_STACK

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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: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/60e9ae86b7d2cdcf21468787076d345663648f46.1576916812.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy 2019-12-21 08:32:28 +00:00 committed by Michael Ellerman
parent 028474876f
commit 63289e7d3a
4 changed files with 16 additions and 3 deletions
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13
arch/powerpc/include/asm/thread_info.h
View file

@ -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>

2
arch/powerpc/kernel/setup_32.c
View file

@ -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",

2
arch/powerpc/kernel/setup_64.c
View file

@ -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)

2
arch/powerpc/kernel/vmlinux.lds.S
View file

@ -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)