s390: setup kernel memory layout early

Currently there are two separate places where kernel memory layout has
to be known and adjusted:
1. early kasan setup.
2. paging setup later.

Those 2 places had to be kept in sync and adjusted to reflect peculiar
technical details of one another. With additional factors which influence
kernel memory layout like ultravisor secure storage limit, complexity
of keeping two things in sync grew up even more.

Besides that if we look forward towards creating identity mapping and
enabling DAT before jumping into uncompressed kernel - that would also
require full knowledge of and control over kernel memory layout.

So, de-duplicate and move kernel memory layout setup logic into
the decompressor.

Reviewed-by: Alexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index 61a8ac4067e5..bbe4df6c2f8b 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -5,6 +5,7 @@
 #include <asm/sections.h>
 #include <asm/cpu_mf.h>
 #include <asm/setup.h>
+#include <asm/kasan.h>
 #include <asm/kexec.h>
 #include <asm/sclp.h>
 #include <asm/diag.h>
@@ -15,6 +16,12 @@
 extern char __boot_data_start[], __boot_data_end[];
 extern char __boot_data_preserved_start[], __boot_data_preserved_end[];
 unsigned long __bootdata_preserved(__kaslr_offset);
+unsigned long __bootdata_preserved(VMALLOC_START);
+unsigned long __bootdata_preserved(VMALLOC_END);
+struct page *__bootdata_preserved(vmemmap);
+unsigned long __bootdata_preserved(vmemmap_size);
+unsigned long __bootdata_preserved(MODULES_VADDR);
+unsigned long __bootdata_preserved(MODULES_END);
 unsigned long __bootdata(ident_map_size);
 
 u64 __bootdata_preserved(stfle_fac_list[16]);
@@ -172,6 +179,86 @@ static void setup_ident_map_size(unsigned long max_physmem_end)
 #endif
 }
 
+static void setup_kernel_memory_layout(void)
+{
+	bool vmalloc_size_verified = false;
+	unsigned long vmemmap_off;
+	unsigned long vspace_left;
+	unsigned long rte_size;
+	unsigned long pages;
+	unsigned long vmax;
+
+	pages = ident_map_size / PAGE_SIZE;
+	/* vmemmap contains a multiple of PAGES_PER_SECTION struct pages */
+	vmemmap_size = SECTION_ALIGN_UP(pages) * sizeof(struct page);
+
+	/* choose kernel address space layout: 4 or 3 levels. */
+	vmemmap_off = round_up(ident_map_size, _REGION3_SIZE);
+	if (IS_ENABLED(CONFIG_KASAN) ||
+	    vmalloc_size > _REGION2_SIZE ||
+	    vmemmap_off + vmemmap_size + vmalloc_size + MODULES_LEN > _REGION2_SIZE)
+		vmax = _REGION1_SIZE;
+	else
+		vmax = _REGION2_SIZE;
+
+	/* keep vmemmap_off aligned to a top level region table entry */
+	rte_size = vmax == _REGION1_SIZE ? _REGION2_SIZE : _REGION3_SIZE;
+	MODULES_END = vmax;
+	if (is_prot_virt_host()) {
+		/*
+		 * forcing modules and vmalloc area under the ultravisor
+		 * secure storage limit, so that any vmalloc allocation
+		 * we do could be used to back secure guest storage.
+		 */
+		adjust_to_uv_max(&MODULES_END);
+	}
+
+#ifdef CONFIG_KASAN
+	if (MODULES_END < vmax) {
+		/* force vmalloc and modules below kasan shadow */
+		MODULES_END = min(MODULES_END, KASAN_SHADOW_START);
+	} else {
+		/*
+		 * leave vmalloc and modules above kasan shadow but make
+		 * sure they don't overlap with it
+		 */
+		vmalloc_size = min(vmalloc_size, vmax - KASAN_SHADOW_END - MODULES_LEN);
+		vmalloc_size_verified = true;
+		vspace_left = KASAN_SHADOW_START;
+	}
+#endif
+	MODULES_VADDR = MODULES_END - MODULES_LEN;
+	VMALLOC_END = MODULES_VADDR;
+
+	if (vmalloc_size_verified) {
+		VMALLOC_START = VMALLOC_END - vmalloc_size;
+	} else {
+		vmemmap_off = round_up(ident_map_size, rte_size);
+
+		if (vmemmap_off + vmemmap_size > VMALLOC_END ||
+		    vmalloc_size > VMALLOC_END - vmemmap_off - vmemmap_size) {
+			/*
+			 * allow vmalloc area to occupy up to 1/2 of
+			 * the rest virtual space left.
+			 */
+			vmalloc_size = min(vmalloc_size, VMALLOC_END / 2);
+		}
+		VMALLOC_START = VMALLOC_END - vmalloc_size;
+		vspace_left = VMALLOC_START;
+	}
+
+	pages = vspace_left / (PAGE_SIZE + sizeof(struct page));
+	pages = SECTION_ALIGN_UP(pages);
+	vmemmap_off = round_up(vspace_left - pages * sizeof(struct page), rte_size);
+	/* keep vmemmap left most starting from a fresh region table entry */
+	vmemmap_off = min(vmemmap_off, round_up(ident_map_size, rte_size));
+	/* take care that identity map is lower then vmemmap */
+	ident_map_size = min(ident_map_size, vmemmap_off);
+	vmemmap_size = SECTION_ALIGN_UP(ident_map_size / PAGE_SIZE) * sizeof(struct page);
+	VMALLOC_START = max(vmemmap_off + vmemmap_size, VMALLOC_START);
+	vmemmap = (struct page *)vmemmap_off;
+}
+
 /*
  * This function clears the BSS section of the decompressed Linux kernel and NOT the decompressor's.
  */
@@ -211,6 +298,7 @@ void startup_kernel(void)
 	parse_boot_command_line();
 	setup_ident_map_size(detect_memory());
 	setup_vmalloc_size();
+	setup_kernel_memory_layout();
 
 	random_lma = __kaslr_offset = 0;
 	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_enabled) {