diff mbox series

[10/43] kmsan: pgtable: reduce vmalloc space

Message ID 20211214162050.660953-11-glider@google.com (mailing list archive)
State New
Headers show
Series Add KernelMemorySanitizer infrastructure | expand

Commit Message

Alexander Potapenko Dec. 14, 2021, 4:20 p.m. UTC 
KMSAN is going to use 3/4 of existing vmalloc space to hold the
metadata, therefore we lower VMALLOC_END to make sure vmalloc() doesn't
allocate past the first 1/4.

Signed-off-by: Alexander Potapenko <glider@google.com>
---
Link: https://linux-review.googlesource.com/id/I9d8b7f0a88a639f1263bc693cbd5c136626f7efd
---
 arch/x86/include/asm/pgtable_64_types.h | 41 ++++++++++++++++++++++++-
 arch/x86/mm/init_64.c                   |  2 +-
 2 files changed, 41 insertions(+), 2 deletions(-)

Comments

Mark Rutland Dec. 15, 2021, 1:36 p.m. UTC | #1 
On Tue, Dec 14, 2021 at 05:20:17PM +0100, Alexander Potapenko wrote:
> KMSAN is going to use 3/4 of existing vmalloc space to hold the
> metadata, therefore we lower VMALLOC_END to make sure vmalloc() doesn't
> allocate past the first 1/4.
> 
> Signed-off-by: Alexander Potapenko <glider@google.com>

It might be worth adding an 'x86: ' prefix to the commit title, since this
specifically affects x86 headers.

Mark.

> ---
> Link: https://linux-review.googlesource.com/id/I9d8b7f0a88a639f1263bc693cbd5c136626f7efd
> ---
>  arch/x86/include/asm/pgtable_64_types.h | 41 ++++++++++++++++++++++++-
>  arch/x86/mm/init_64.c                   |  2 +-
>  2 files changed, 41 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
> index 91ac106545703..7f15d43754a34 100644
> --- a/arch/x86/include/asm/pgtable_64_types.h
> +++ b/arch/x86/include/asm/pgtable_64_types.h
> @@ -139,7 +139,46 @@ extern unsigned int ptrs_per_p4d;
>  # define VMEMMAP_START		__VMEMMAP_BASE_L4
>  #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */
>  
> -#define VMALLOC_END		(VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)
> +#define VMEMORY_END		(VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)
> +
> +#ifndef CONFIG_KMSAN
> +#define VMALLOC_END		VMEMORY_END
> +#else
> +/*
> + * In KMSAN builds vmalloc area is four times smaller, and the remaining 3/4
> + * are used to keep the metadata for virtual pages. The memory formerly
> + * belonging to vmalloc area is now laid out as follows:
> + *
> + * 1st quarter: VMALLOC_START to VMALLOC_END - new vmalloc area
> + * 2nd quarter: KMSAN_VMALLOC_SHADOW_START to
> + *              VMALLOC_END+KMSAN_VMALLOC_SHADOW_OFFSET - vmalloc area shadow
> + * 3rd quarter: KMSAN_VMALLOC_ORIGIN_START to
> + *              VMALLOC_END+KMSAN_VMALLOC_ORIGIN_OFFSET - vmalloc area origins
> + * 4th quarter: KMSAN_MODULES_SHADOW_START to KMSAN_MODULES_ORIGIN_START
> + *              - shadow for modules,
> + *              KMSAN_MODULES_ORIGIN_START to
> + *              KMSAN_MODULES_ORIGIN_START + MODULES_LEN - origins for modules.
> + */
> +#define VMALLOC_QUARTER_SIZE	((VMALLOC_SIZE_TB << 40) >> 2)
> +#define VMALLOC_END		(VMALLOC_START + VMALLOC_QUARTER_SIZE - 1)
> +
> +/*
> + * vmalloc metadata addresses are calculated by adding shadow/origin offsets
> + * to vmalloc address.
> + */
> +#define KMSAN_VMALLOC_SHADOW_OFFSET	VMALLOC_QUARTER_SIZE
> +#define KMSAN_VMALLOC_ORIGIN_OFFSET	(VMALLOC_QUARTER_SIZE << 1)
> +
> +#define KMSAN_VMALLOC_SHADOW_START	(VMALLOC_START + KMSAN_VMALLOC_SHADOW_OFFSET)
> +#define KMSAN_VMALLOC_ORIGIN_START	(VMALLOC_START + KMSAN_VMALLOC_ORIGIN_OFFSET)
> +
> +/*
> + * The shadow/origin for modules are placed one by one in the last 1/4 of
> + * vmalloc space.
> + */
> +#define KMSAN_MODULES_SHADOW_START	(VMALLOC_END + KMSAN_VMALLOC_ORIGIN_OFFSET + 1)
> +#define KMSAN_MODULES_ORIGIN_START	(KMSAN_MODULES_SHADOW_START + MODULES_LEN)
> +#endif /* CONFIG_KMSAN */
>  
>  #define MODULES_VADDR		(__START_KERNEL_map + KERNEL_IMAGE_SIZE)
>  /* The module sections ends with the start of the fixmap */
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 36098226a9573..8e884e44a8d1e 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -1287,7 +1287,7 @@ static void __init preallocate_vmalloc_pages(void)
>  	unsigned long addr;
>  	const char *lvl;
>  
> -	for (addr = VMALLOC_START; addr <= VMALLOC_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
> +	for (addr = VMALLOC_START; addr <= VMEMORY_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
>  		pgd_t *pgd = pgd_offset_k(addr);
>  		p4d_t *p4d;
>  		pud_t *pud;
> -- 
> 2.34.1.173.g76aa8bc2d0-goog
>
Alexander Potapenko March 18, 2022, 2:14 p.m. UTC | #2 
On Wed, Dec 15, 2021 at 2:36 PM Mark Rutland <mark.rutland@arm.com> wrote:
>
> On Tue, Dec 14, 2021 at 05:20:17PM +0100, Alexander Potapenko wrote:
> > KMSAN is going to use 3/4 of existing vmalloc space to hold the
> > metadata, therefore we lower VMALLOC_END to make sure vmalloc() doesn't
> > allocate past the first 1/4.
> >
> > Signed-off-by: Alexander Potapenko <glider@google.com>
>
> It might be worth adding an 'x86: ' prefix to the commit title, since this
> specifically affects x86 headers.

Makes sense, will do!
diff mbox series

Patch

diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h
index 91ac106545703..7f15d43754a34 100644
--- a/arch/x86/include/asm/pgtable_64_types.h
+++ b/arch/x86/include/asm/pgtable_64_types.h
@@ -139,7 +139,46 @@  extern unsigned int ptrs_per_p4d;
 # define VMEMMAP_START		__VMEMMAP_BASE_L4
 #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */
 
-#define VMALLOC_END		(VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)
+#define VMEMORY_END		(VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1)
+
+#ifndef CONFIG_KMSAN
+#define VMALLOC_END		VMEMORY_END
+#else
+/*
+ * In KMSAN builds vmalloc area is four times smaller, and the remaining 3/4
+ * are used to keep the metadata for virtual pages. The memory formerly
+ * belonging to vmalloc area is now laid out as follows:
+ *
+ * 1st quarter: VMALLOC_START to VMALLOC_END - new vmalloc area
+ * 2nd quarter: KMSAN_VMALLOC_SHADOW_START to
+ *              VMALLOC_END+KMSAN_VMALLOC_SHADOW_OFFSET - vmalloc area shadow
+ * 3rd quarter: KMSAN_VMALLOC_ORIGIN_START to
+ *              VMALLOC_END+KMSAN_VMALLOC_ORIGIN_OFFSET - vmalloc area origins
+ * 4th quarter: KMSAN_MODULES_SHADOW_START to KMSAN_MODULES_ORIGIN_START
+ *              - shadow for modules,
+ *              KMSAN_MODULES_ORIGIN_START to
+ *              KMSAN_MODULES_ORIGIN_START + MODULES_LEN - origins for modules.
+ */
+#define VMALLOC_QUARTER_SIZE	((VMALLOC_SIZE_TB << 40) >> 2)
+#define VMALLOC_END		(VMALLOC_START + VMALLOC_QUARTER_SIZE - 1)
+
+/*
+ * vmalloc metadata addresses are calculated by adding shadow/origin offsets
+ * to vmalloc address.
+ */
+#define KMSAN_VMALLOC_SHADOW_OFFSET	VMALLOC_QUARTER_SIZE
+#define KMSAN_VMALLOC_ORIGIN_OFFSET	(VMALLOC_QUARTER_SIZE << 1)
+
+#define KMSAN_VMALLOC_SHADOW_START	(VMALLOC_START + KMSAN_VMALLOC_SHADOW_OFFSET)
+#define KMSAN_VMALLOC_ORIGIN_START	(VMALLOC_START + KMSAN_VMALLOC_ORIGIN_OFFSET)
+
+/*
+ * The shadow/origin for modules are placed one by one in the last 1/4 of
+ * vmalloc space.
+ */
+#define KMSAN_MODULES_SHADOW_START	(VMALLOC_END + KMSAN_VMALLOC_ORIGIN_OFFSET + 1)
+#define KMSAN_MODULES_ORIGIN_START	(KMSAN_MODULES_SHADOW_START + MODULES_LEN)
+#endif /* CONFIG_KMSAN */
 
 #define MODULES_VADDR		(__START_KERNEL_map + KERNEL_IMAGE_SIZE)
 /* The module sections ends with the start of the fixmap */
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 36098226a9573..8e884e44a8d1e 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1287,7 +1287,7 @@  static void __init preallocate_vmalloc_pages(void)
 	unsigned long addr;
 	const char *lvl;
 
-	for (addr = VMALLOC_START; addr <= VMALLOC_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
+	for (addr = VMALLOC_START; addr <= VMEMORY_END; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
 		pgd_t *pgd = pgd_offset_k(addr);
 		p4d_t *p4d;
 		pud_t *pud;