On Tue, Oct 08, 2024 at 07:50:24PM -0700, John Hubbard wrote: > For clarity. It's increasingly hard to reason about the code, when KASLR > is moving around the boundaries. In this case where KASLR is randomizing > the location of the kernel image within physical memory, the maximum > number of address bits for physical memory has not changed. > > What has changed is the ending address of memory that is allowed to be > directly mapped by the kernel. > > Let's name the variable, and the associated macro accordingly. > > Also, enhance the comment above the direct_map_physmem_end definition, > to further clarify how this all works. > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Alistair Popple <apopple@xxxxxxxxxx> > Cc: Jordan Niethe <jniethe@xxxxxxxxxx> > Cc: David Hildenbrand <david@xxxxxxxxxx> > Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx> Reviewed-by: Mike Rapoport (Microsoft) <rppt@xxxxxxxxxx> > --- > > David Hildenbrand, I recall you had an unanswered question in this > vicinity [1] when tglx's recent kaslr fix was being reviewed. Maybe this > will help with that. To David's question, physmem_end (and now direct_map_physmem_end) is updated kernel_randomize_memory() via kaslr_regions[0].base > > [1] https://lore.kernel.org/linux-mm/ee205448-5fdd-495e-9d7c-c8a2b59f9c9e@xxxxxxxxxxxx/T/#mdf442f077c9023590e144dbed2b04a109793484d > > thanks, > John Hubbard > > > arch/arm64/include/asm/memory.h | 2 +- > arch/x86/include/asm/page_64.h | 2 +- > arch/x86/include/asm/pgtable_64_types.h | 2 +- > arch/x86/mm/init_64.c | 2 +- > arch/x86/mm/kaslr.c | 14 +++++++++----- > include/linux/mm.h | 6 +++--- > kernel/resource.c | 4 ++-- > mm/memory_hotplug.c | 2 +- > mm/sparse.c | 2 +- > 9 files changed, 20 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h > index 0480c61dbb4f..73eaa8c2536a 100644 > --- a/arch/arm64/include/asm/memory.h > +++ b/arch/arm64/include/asm/memory.h > @@ -110,7 +110,7 @@ > #define PAGE_END (_PAGE_END(VA_BITS_MIN)) > #endif /* CONFIG_KASAN */ > > -#define PHYSMEM_END __pa(PAGE_END - 1) > +#define DIRECT_MAP_PHYSMEM_END __pa(PAGE_END - 1) > > #define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT) > > diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h > index f3d257c45225..d63576608ce7 100644 > --- a/arch/x86/include/asm/page_64.h > +++ b/arch/x86/include/asm/page_64.h > @@ -17,7 +17,7 @@ extern unsigned long phys_base; > extern unsigned long page_offset_base; > extern unsigned long vmalloc_base; > extern unsigned long vmemmap_base; > -extern unsigned long physmem_end; > +extern unsigned long direct_map_physmem_end; > > static __always_inline unsigned long __phys_addr_nodebug(unsigned long x) > { > diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h > index a98e53491a4e..ec68f8369bdc 100644 > --- a/arch/x86/include/asm/pgtable_64_types.h > +++ b/arch/x86/include/asm/pgtable_64_types.h > @@ -141,7 +141,7 @@ extern unsigned int ptrs_per_p4d; > #endif /* CONFIG_DYNAMIC_MEMORY_LAYOUT */ > > #ifdef CONFIG_RANDOMIZE_MEMORY > -# define PHYSMEM_END physmem_end > +# define DIRECT_MAP_PHYSMEM_END direct_map_physmem_end > #endif > > /* > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index ff253648706f..5a564130b9d0 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -961,7 +961,7 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages, > unsigned long end = ((start_pfn + nr_pages) << PAGE_SHIFT) - 1; > int ret; > > - if (WARN_ON_ONCE(end > PHYSMEM_END)) > + if (WARN_ON_ONCE(end > DIRECT_MAP_PHYSMEM_END)) > return -ERANGE; > > ret = __add_pages(nid, start_pfn, nr_pages, params); > diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c > index 230f1dee4f09..70d3353c92fa 100644 > --- a/arch/x86/mm/kaslr.c > +++ b/arch/x86/mm/kaslr.c > @@ -52,7 +52,7 @@ static __initdata struct kaslr_memory_region { > } kaslr_regions[] = { > { > .base = &page_offset_base, > - .end = &physmem_end, > + .end = &direct_map_physmem_end, > }, > { > .base = &vmalloc_base, > @@ -62,8 +62,12 @@ static __initdata struct kaslr_memory_region { > }, > }; > > -/* The end of the possible address space for physical memory */ > -unsigned long physmem_end __ro_after_init; > +/* > + * The end of the physical address space that can be mapped directly by the > + * kernel. This starts out at (1<<MAX_PHYSMEM_BITS) - 1), but KASLR may reduce > + * that in order to increase the available entropy for mapping other regions. > + */ > +unsigned long direct_map_physmem_end __ro_after_init; > > /* Get size in bytes used by the memory region */ > static inline unsigned long get_padding(struct kaslr_memory_region *region) > @@ -94,7 +98,7 @@ void __init kernel_randomize_memory(void) > BUILD_BUG_ON(vaddr_end > __START_KERNEL_map); > > /* Preset the end of the possible address space for physical memory */ > - physmem_end = ((1ULL << MAX_PHYSMEM_BITS) - 1); > + direct_map_physmem_end = ((1ULL << MAX_PHYSMEM_BITS) - 1); > if (!kaslr_memory_enabled()) > return; > > @@ -145,7 +149,7 @@ void __init kernel_randomize_memory(void) > vaddr += get_padding(&kaslr_regions[i]); > /* > * KASLR trims the maximum possible size of the > - * direct-map. Update the physmem_end boundary. > + * direct-map. Update the direct_map_physmem_end boundary. > * No rounding required as the region starts > * PUD aligned and size is in units of TB. > */ > diff --git a/include/linux/mm.h b/include/linux/mm.h > index ecf63d2b0582..92c35fb60d18 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -97,11 +97,11 @@ extern const int mmap_rnd_compat_bits_max; > extern int mmap_rnd_compat_bits __read_mostly; > #endif > > -#ifndef PHYSMEM_END > +#ifndef DIRECT_MAP_PHYSMEM_END > # ifdef MAX_PHYSMEM_BITS > -# define PHYSMEM_END ((1ULL << MAX_PHYSMEM_BITS) - 1) > +# define DIRECT_MAP_PHYSMEM_END ((1ULL << MAX_PHYSMEM_BITS) - 1) > # else > -# define PHYSMEM_END (((phys_addr_t)-1)&~(1ULL<<63)) > +# define DIRECT_MAP_PHYSMEM_END (((phys_addr_t)-1)&~(1ULL<<63)) > # endif > #endif > > diff --git a/kernel/resource.c b/kernel/resource.c > index b730bd28b422..afa3ad09b834 100644 > --- a/kernel/resource.c > +++ b/kernel/resource.c > @@ -1871,7 +1871,7 @@ static resource_size_t gfr_start(struct resource *base, resource_size_t size, > if (flags & GFR_DESCENDING) { > resource_size_t end; > > - end = min_t(resource_size_t, base->end, PHYSMEM_END); > + end = min_t(resource_size_t, base->end, DIRECT_MAP_PHYSMEM_END); > return end - size + 1; > } > > @@ -1888,7 +1888,7 @@ static bool gfr_continue(struct resource *base, resource_size_t addr, > * @size did not wrap 0. > */ > return addr > addr - size && > - addr <= min_t(resource_size_t, base->end, PHYSMEM_END); > + addr <= min_t(resource_size_t, base->end, DIRECT_MAP_PHYSMEM_END); > } > > static resource_size_t gfr_next(resource_size_t addr, resource_size_t size, > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 621ae1015106..c43b4e7fb298 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1681,7 +1681,7 @@ struct range __weak arch_get_mappable_range(void) > > struct range mhp_get_pluggable_range(bool need_mapping) > { > - const u64 max_phys = PHYSMEM_END; > + const u64 max_phys = DIRECT_MAP_PHYSMEM_END; > struct range mhp_range; > > if (need_mapping) { > diff --git a/mm/sparse.c b/mm/sparse.c > index dc38539f8560..4cb9793f0b52 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -129,7 +129,7 @@ static inline int sparse_early_nid(struct mem_section *section) > static void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn, > unsigned long *end_pfn) > { > - unsigned long max_sparsemem_pfn = (PHYSMEM_END + 1) >> PAGE_SHIFT; > + unsigned long max_sparsemem_pfn = (DIRECT_MAP_PHYSMEM_END + 1) >> PAGE_SHIFT; > > /* > * Sanity checks - do not allow an architecture to pass > -- > 2.47.0 > > -- Sincerely yours, Mike.
