s390/kasan: use noexec and large pages

To lower memory footprint and speed up kasan initialisation detect
EDAT availability and use large pages if possible. As we know how
much memory is needed for initialisation, another simplistic large
page allocator is introduced to avoid memory fragmentation.

Since facilities list is retrieved anyhow, detect noexec support and
adjust pages attributes. Handle noexec kernel option to avoid inconsistent
kasan shadow memory pages flags.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 62 insertions, 4 deletions

diff --git a/arch/s390/mm/kasan_init.c b/arch/s390/mm/kasan_init.c
index 714ac41e3ee5..e4697900e884 100644
--- a/arch/s390/mm/kasan_init.c
+++ b/arch/s390/mm/kasan_init.c
@@ -7,11 +7,16 @@
 #include <asm/kasan.h>
 #include <asm/processor.h>
 #include <asm/sclp.h>
+#include <asm/facility.h>
 #include <asm/sections.h>
 #include <asm/setup.h>
 
+static unsigned long segment_pos __initdata;
+static unsigned long segment_low __initdata;
 static unsigned long pgalloc_pos __initdata;
 static unsigned long pgalloc_low __initdata;
+static bool has_edat __initdata;
+static bool has_nx __initdata;
 
 #define __sha(x) ((unsigned long)kasan_mem_to_shadow((void *)x))
 
@@ -24,6 +29,16 @@ static void __init kasan_early_panic(const char *reason)
 	disabled_wait(0);
 }
 
+static void * __init kasan_early_alloc_segment(void)
+{
+	segment_pos -= _SEGMENT_SIZE;
+
+	if (segment_pos < segment_low)
+		kasan_early_panic("out of memory during initialisation\n");
+
+	return (void *)segment_pos;
+}
+
 static void * __init kasan_early_alloc_pages(unsigned int order)
 {
 	pgalloc_pos -= (PAGE_SIZE << order);
@@ -71,7 +86,7 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 						unsigned long end,
 						enum populate_mode mode)
 {
-	unsigned long pgt_prot_zero, pgt_prot;
+	unsigned long pgt_prot_zero, pgt_prot, sgt_prot;
 	pgd_t *pg_dir;
 	p4d_t *p4_dir;
 	pud_t *pu_dir;
@@ -79,8 +94,10 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 	pte_t *pt_dir;
 
 	pgt_prot_zero = pgprot_val(PAGE_KERNEL_RO);
-	pgt_prot_zero &= ~_PAGE_NOEXEC;
+	if (!has_nx)
+		pgt_prot_zero &= ~_PAGE_NOEXEC;
 	pgt_prot = pgprot_val(PAGE_KERNEL_EXEC);
+	sgt_prot = pgprot_val(SEGMENT_KERNEL_EXEC);
 
 	while (address < end) {
 		pg_dir = pgd_offset_k(address);
@@ -131,8 +148,27 @@ static void __init kasan_early_vmemmap_populate(unsigned long address,
 				address = (address + PMD_SIZE) & PMD_MASK;
 				continue;
 			}
+			/* the first megabyte of 1:1 is mapped with 4k pages */
+			if (has_edat && address && end - address >= PMD_SIZE &&
+			    mode != POPULATE_ZERO_SHADOW) {
+				void *page;
+
+				if (mode == POPULATE_ONE2ONE) {
+					page = (void *)address;
+				} else {
+					page = kasan_early_alloc_segment();
+					memset(page, 0, _SEGMENT_SIZE);
+				}
+				pmd_val(*pm_dir) = __pa(page) | sgt_prot;
+				address = (address + PMD_SIZE) & PMD_MASK;
+				continue;
+			}
+
 			pt_dir = kasan_early_pte_alloc();
 			pmd_populate(&init_mm, pm_dir, pt_dir);
+		} else if (pmd_large(*pm_dir)) {
+			address = (address + PMD_SIZE) & PMD_MASK;
+			continue;
 		}
 
 		pt_dir = pte_offset_kernel(pm_dir, address);
@@ -182,6 +218,20 @@ static void __init kasan_enable_dat(void)
 	__load_psw_mask(psw.mask);
 }
 
+static void __init kasan_early_detect_facilities(void)
+{
+	stfle(S390_lowcore.stfle_fac_list,
+	      ARRAY_SIZE(S390_lowcore.stfle_fac_list));
+	if (test_facility(8)) {
+		has_edat = true;
+		__ctl_set_bit(0, 23);
+	}
+	if (!noexec_disabled && test_facility(130)) {
+		has_nx = true;
+		__ctl_set_bit(0, 20);
+	}
+}
+
 void __init kasan_early_init(void)
 {
 	unsigned long untracked_mem_end;
@@ -196,7 +246,9 @@ void __init kasan_early_init(void)
 	pud_t pud_z = __pud(__pa(kasan_zero_pmd) | _REGION3_ENTRY);
 	p4d_t p4d_z = __p4d(__pa(kasan_zero_pud) | _REGION2_ENTRY);
 
-	pgt_prot &= ~_PAGE_NOEXEC;
+	kasan_early_detect_facilities();
+	if (!has_nx)
+		pgt_prot &= ~_PAGE_NOEXEC;
 	pte_z = __pte(__pa(kasan_zero_page) | pgt_prot);
 
 	/* 3 level paging */
@@ -224,7 +276,13 @@ void __init kasan_early_init(void)
 	if (pgalloc_low + shadow_alloc_size > memsize)
 		kasan_early_panic("out of memory during initialisation\n");
 
-	pgalloc_pos = memsize;
+	if (has_edat) {
+		segment_pos = round_down(memsize, _SEGMENT_SIZE);
+		segment_low = segment_pos - shadow_alloc_size;
+		pgalloc_pos = segment_low;
+	} else {
+		pgalloc_pos = memsize;
+	}
 	init_mm.pgd = early_pg_dir;
 	/*
 	 * Current memory layout: