On Mon, Mar 30, 2020 at 3:49 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > On Wed, Mar 25, 2020 at 5:13 PM <glider@xxxxxxxxxx> 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@xxxxxxxxxx> > > To: Alexander Potapenko <glider@xxxxxxxxxx> > > Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx> > > Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > > Cc: Marco Elver <elver@xxxxxxxxxx> > > Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx> > > Cc: linux-mm@xxxxxxxxx > > > > --- > > > > Change-Id: Iaa5e8e0fc2aa66c956f937f5a1de6e5ef40d57cc > > --- > > arch/x86/include/asm/pgtable_64_types.h | 15 +++++++++++++++ > > 1 file changed, 15 insertions(+) > > > > diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h > > index 52e5f5f2240d9..586629e204366 100644 > > --- a/arch/x86/include/asm/pgtable_64_types.h > > +++ b/arch/x86/include/asm/pgtable_64_types.h > > @@ -139,7 +139,22 @@ extern unsigned int ptrs_per_p4d; > > # define VMEMMAP_START __VMEMMAP_BASE_L4 > > #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */ > > > > +#ifndef CONFIG_KMSAN > > #define VMALLOC_END (VMALLOC_START + (VMALLOC_SIZE_TB << 40) - 1) > > +#else > > +/* > > + * In KMSAN builds vmalloc area is four times smaller, and the remaining 3/4 > > + * are used to keep the metadata for virtual pages. > > + */ > > +#define VMALLOC_QUARTER_SIZE ((VMALLOC_SIZE_TB << 40) >> 2) > > +#define VMALLOC_END (VMALLOC_START + VMALLOC_QUARTER_SIZE - 1) > > +#define VMALLOC_SHADOW_OFFSET VMALLOC_QUARTER_SIZE > > +#define VMALLOC_ORIGIN_OFFSET (VMALLOC_QUARTER_SIZE * 2) > > "<< 1" instead of "* 2" for consistency (since we're using ">> 2" just above")? Done, thanks! > > +#define VMALLOC_META_END (VMALLOC_END + VMALLOC_ORIGIN_OFFSET) > > +#define MODULES_SHADOW_START (VMALLOC_META_END + 1) > > +#define MODULES_ORIGIN_START (MODULES_SHADOW_START + MODULES_LEN) > > +#define MODULES_ORIGIN_END (MODULES_ORIGIN_START + MODULES_LEN) > > +#endif > > These macros are a bit hard to understand. VMALLOC_SHADOW_OFFSET and > VMALLOC_ORIGIN_OFFSET are offsets from VMALLOC_END and denote where > shadow and origin areas start? What is stored in (VMALLOC_END, > VMALLOC_END + VMALLOC_SHADOW_OFFSET] then? Maybe sorting these > constants in some logical order would help, or adding a comment on how > exactly those 3/4th of vmalloc space are split. Added an extensive comment describing this in v6.
