s390/kdump: virtio-mem kdump support (CONFIG_PROC_VMCORE_DEVICE_RAM)

JIRA: https://issues.redhat.com/browse/RHEL-72992

commit 212c3a8
Author: David Hildenbrand <david@redhat.com>
Date:   Wed Dec 4 13:54:43 2024 +0100

    s390/kdump: virtio-mem kdump support (CONFIG_PROC_VMCORE_DEVICE_RAM)

    Let's add support for including virtio-mem device RAM in the crash dump,
    setting NEED_PROC_VMCORE_DEVICE_RAM, and implementing
    elfcorehdr_fill_device_ram_ptload_elf64().

    To avoid code duplication, factor out the code to fill a PT_LOAD entry.

    Signed-off-by: David Hildenbrand <david@redhat.com>
    Message-Id: <20241204125444.1734652-13-david@redhat.com>
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Signed-off-by: Thomas Huth <thuth@redhat.com>

Author: huth

arch/s390/Kconfig

@@ -230,6 +230,7 @@ config S390
 	select MODULES_USE_ELF_RELA
 	select NEED_DMA_MAP_STATE	if PCI
 	select NEED_PER_CPU_EMBED_FIRST_CHUNK
+	select NEED_PROC_VMCORE_DEVICE_RAM if PROC_VMCORE
 	select NEED_SG_DMA_LENGTH	if PCI
 	select OLD_SIGACTION
 	select OLD_SIGSUSPEND3

arch/s390/kernel/crash_dump.c

@@ -497,6 +497,19 @@ static int get_mem_chunk_cnt(void)
 	return cnt;
 }
 
+static void fill_ptload(Elf64_Phdr *phdr, unsigned long paddr,
+		unsigned long vaddr, unsigned long size)
+{
+	phdr->p_type = PT_LOAD;
+	phdr->p_vaddr = vaddr;
+	phdr->p_offset = paddr;
+	phdr->p_paddr = paddr;
+	phdr->p_filesz = size;
+	phdr->p_memsz = size;
+	phdr->p_flags = PF_R | PF_W | PF_X;
+	phdr->p_align = PAGE_SIZE;
+}
+
 /*
  * Initialize ELF loads (new kernel)
  */
@@ -509,14 +522,8 @@ static void loads_init(Elf64_Phdr *phdr, bool os_info_has_vm)
 	if (os_info_has_vm)
 		old_identity_base = os_info_old_value(OS_INFO_IDENTITY_BASE);
 	for_each_physmem_range(idx, &oldmem_type, &start, &end) {
-		phdr->p_type = PT_LOAD;
-		phdr->p_vaddr = old_identity_base + start;
-		phdr->p_offset = start;
-		phdr->p_paddr = start;
-		phdr->p_filesz = end - start;
-		phdr->p_memsz = end - start;
-		phdr->p_flags = PF_R | PF_W | PF_X;
-		phdr->p_align = PAGE_SIZE;
+		fill_ptload(phdr, start, old_identity_base + start,
+			    end - start);
 		phdr++;
 	}
 }
@@ -526,6 +533,22 @@ static bool os_info_has_vm(void)
 	return os_info_old_value(OS_INFO_KASLR_OFFSET);
 }
 
+#ifdef CONFIG_PROC_VMCORE_DEVICE_RAM
+/*
+ * Fill PT_LOAD for a physical memory range owned by a device and detected by
+ * its device driver.
+ */
+void elfcorehdr_fill_device_ram_ptload_elf64(Elf64_Phdr *phdr,
+		unsigned long long paddr, unsigned long long size)
+{
+	unsigned long old_identity_base = 0;
+
+	if (os_info_has_vm())
+		old_identity_base = os_info_old_value(OS_INFO_IDENTITY_BASE);
+	fill_ptload(phdr, paddr, old_identity_base + paddr, size);
+}
+#endif
+
 /*
  * Prepare PT_LOAD type program header for kernel image region
  */