s390/boot: Add startup debugging support

Add boot_debug() calls to log various memory layout decisions and
randomization details during early startup, improving debugging
capabilities.

Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

1 files changed, 26 insertions, 2 deletions

diff --git a/arch/s390/boot/startup.c b/arch/s390/boot/startup.c
index 89f1d12f1c10..807594cf246c 100644
--- a/arch/s390/boot/startup.c
+++ b/arch/s390/boot/startup.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#define boot_fmt(fmt) "startup: " fmt
 #include <linux/string.h>
 #include <linux/elf.h>
 #include <asm/page-states.h>
@@ -223,12 +224,16 @@ static void setup_ident_map_size(unsigned long max_physmem_end)
 	if (oldmem_data.start) {
 		__kaslr_enabled = 0;
 		ident_map_size = min(ident_map_size, oldmem_data.size);
+		boot_debug("kdump memory limit:  0x%016lx\n", oldmem_data.size);
 	} else if (ipl_block_valid && is_ipl_block_dump()) {
 		__kaslr_enabled = 0;
-		if (!sclp_early_get_hsa_size(&hsa_size) && hsa_size)
+		if (!sclp_early_get_hsa_size(&hsa_size) && hsa_size) {
 			ident_map_size = min(ident_map_size, hsa_size);
+			boot_debug("Stand-alone dump limit: 0x%016lx\n", hsa_size);
+		}
 	}
 #endif
+	boot_debug("Identity map size:   0x%016lx\n", ident_map_size);
 }
 
 #define FIXMAP_SIZE	round_up(MEMCPY_REAL_SIZE + ABS_LOWCORE_MAP_SIZE, sizeof(struct lowcore))
@@ -266,6 +271,7 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
 	BUILD_BUG_ON(!IS_ALIGNED(__NO_KASLR_START_KERNEL, THREAD_SIZE));
 	BUILD_BUG_ON(__NO_KASLR_END_KERNEL > _REGION1_SIZE);
 	vsize = get_vmem_size(ident_map_size, vmemmap_size, vmalloc_size, _REGION3_SIZE);
+	boot_debug("vmem size estimated: 0x%016lx\n", vsize);
 	if (IS_ENABLED(CONFIG_KASAN) || __NO_KASLR_END_KERNEL > _REGION2_SIZE ||
 	    (vsize > _REGION2_SIZE && kaslr_enabled())) {
 		asce_limit = _REGION1_SIZE;
@@ -289,8 +295,10 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
 	 * otherwise asce_limit and rte_size would have been adjusted.
 	 */
 	vmax = adjust_to_uv_max(asce_limit);
+	boot_debug("%d level paging       0x%016lx vmax\n", vmax == _REGION1_SIZE ? 4 : 3, vmax);
 #ifdef CONFIG_KASAN
 	BUILD_BUG_ON(__NO_KASLR_END_KERNEL > KASAN_SHADOW_START);
+	boot_debug("KASAN shadow area:   0x%016lx-0x%016lx\n", KASAN_SHADOW_START, KASAN_SHADOW_END);
 	/* force vmalloc and modules below kasan shadow */
 	vmax = min(vmax, KASAN_SHADOW_START);
 #endif
@@ -304,19 +312,27 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
 			pos = 0;
 		kernel_end = vmax - pos * THREAD_SIZE;
 		kernel_start = round_down(kernel_end - kernel_size, THREAD_SIZE);
+		boot_debug("Randomization range: 0x%016lx-0x%016lx\n", vmax - kaslr_len, vmax);
+		boot_debug("kernel image:        0x%016lx-0x%016lx (kaslr)\n", kernel_start,
+			   kernel_size + kernel_size);
 	} else if (vmax < __NO_KASLR_END_KERNEL || vsize > __NO_KASLR_END_KERNEL) {
 		kernel_start = round_down(vmax - kernel_size, THREAD_SIZE);
-		boot_debug("The kernel base address is forced to %lx\n", kernel_start);
+		boot_debug("kernel image:        0x%016lx-0x%016lx (constrained)\n", kernel_start,
+			   kernel_start + kernel_size);
 	} else {
 		kernel_start = __NO_KASLR_START_KERNEL;
+		boot_debug("kernel image:        0x%016lx-0x%016lx (nokaslr)\n", kernel_start,
+			   kernel_start + kernel_size);
 	}
 	__kaslr_offset = kernel_start;
+	boot_debug("__kaslr_offset:      0x%016lx\n", __kaslr_offset);
 
 	MODULES_END = round_down(kernel_start, _SEGMENT_SIZE);
 	MODULES_VADDR = MODULES_END - MODULES_LEN;
 	VMALLOC_END = MODULES_VADDR;
 	if (IS_ENABLED(CONFIG_KMSAN))
 		VMALLOC_END -= MODULES_LEN * 2;
+	boot_debug("modules area:        0x%016lx-0x%016lx\n", MODULES_VADDR, MODULES_END);
 
 	/* allow vmalloc area to occupy up to about 1/2 of the rest virtual space left */
 	vsize = (VMALLOC_END - FIXMAP_SIZE) / 2;
@@ -328,10 +344,15 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
 		VMALLOC_END -= vmalloc_size * 2;
 	}
 	VMALLOC_START = VMALLOC_END - vmalloc_size;
+	boot_debug("vmalloc area:        0x%016lx-0x%016lx\n", VMALLOC_START, VMALLOC_END);
 
 	__memcpy_real_area = round_down(VMALLOC_START - MEMCPY_REAL_SIZE, PAGE_SIZE);
+	boot_debug("memcpy real area:    0x%016lx-0x%016lx\n", __memcpy_real_area,
+		   __memcpy_real_area + MEMCPY_REAL_SIZE);
 	__abs_lowcore = round_down(__memcpy_real_area - ABS_LOWCORE_MAP_SIZE,
 				   sizeof(struct lowcore));
+	boot_debug("abs lowcore:         0x%016lx-0x%016lx\n", __abs_lowcore,
+		   __abs_lowcore + ABS_LOWCORE_MAP_SIZE);
 
 	/* split remaining virtual space between 1:1 mapping & vmemmap array */
 	pages = __abs_lowcore / (PAGE_SIZE + sizeof(struct page));
@@ -353,6 +374,8 @@ static unsigned long setup_kernel_memory_layout(unsigned long kernel_size)
 	max_mappable = min(max_mappable, vmemmap_start);
 	if (IS_ENABLED(CONFIG_RANDOMIZE_IDENTITY_BASE))
 		__identity_base = round_down(vmemmap_start - max_mappable, rte_size);
+	boot_debug("identity map:        0x%016lx-0x%016lx\n", __identity_base,
+		   __identity_base + ident_map_size);
 
 	return asce_limit;
 }
@@ -542,5 +565,6 @@ void startup_kernel(void)
 	 */
 	psw.addr = __kaslr_offset + vmlinux.entry;
 	psw.mask = PSW_KERNEL_BITS;
+	boot_debug("Starting kernel at:  0x%016lx\n", psw.addr);
 	__load_psw(psw);
 }