This patch adds the kexec_file_load system call to s390 as well as the arch
specific functions common code requires to work. Loaders for the different
file types will be added later.

Signed-off-by: Philipp Rudo <pr...@linux.vnet.ibm.com>
---
 arch/s390/Kconfig                     |   4 +
 arch/s390/kernel/Makefile             |   1 +
 arch/s390/kernel/compat_wrapper.c     |   1 +
 arch/s390/kernel/machine_kexec_file.c | 174 ++++++++++++++++++++++++++++++++++
 arch/s390/kernel/syscalls/syscall.tbl |   1 +
 5 files changed, 181 insertions(+)
 create mode 100644 arch/s390/kernel/machine_kexec_file.c

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 0105ce28e246..baffd88109a5 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -51,6 +51,10 @@ config KEXEC
        def_bool y
        select KEXEC_CORE
 
+config KEXEC_FILE
+       def_bool y
+       select KEXEC_CORE
+
 config AUDIT_ARCH
        def_bool y
 
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 909bce65cb2b..496d4711c186 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -60,6 +60,7 @@ obj-y += debug.o irq.o ipl.o dis.o diag.o vdso.o als.o
 obj-y  += sysinfo.o jump_label.o lgr.o os_info.o machine_kexec.o pgm_check.o
 obj-y  += runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o
 obj-y  += entry.o reipl.o relocate_kernel.o kdebugfs.o alternative.o
+obj-y  += machine_kexec_file.o
 
 extra-y                                += head.o head64.o vmlinux.lds
 
diff --git a/arch/s390/kernel/compat_wrapper.c 
b/arch/s390/kernel/compat_wrapper.c
index 11e9d8b5c1b0..607c5e9fba3d 100644
--- a/arch/s390/kernel/compat_wrapper.c
+++ b/arch/s390/kernel/compat_wrapper.c
@@ -182,3 +182,4 @@ COMPAT_SYSCALL_WRAP6(copy_file_range, int, fd_in, loff_t 
__user *, off_in, int,
 COMPAT_SYSCALL_WRAP2(s390_guarded_storage, int, command, struct gs_cb *, 
gs_cb);
 COMPAT_SYSCALL_WRAP5(statx, int, dfd, const char __user *, path, unsigned, 
flags, unsigned, mask, struct statx __user *, buffer);
 COMPAT_SYSCALL_WRAP4(s390_sthyi, unsigned long, code, void __user *, info, u64 
__user *, rc, unsigned long, flags);
+COMPAT_SYSCALL_WRAP5(kexec_file_load, int, kernel_fd, int, initrd_fd, unsigned 
long, cmdline_len, const char __user *, cmdline_ptr, unsigned long, flags)
diff --git a/arch/s390/kernel/machine_kexec_file.c 
b/arch/s390/kernel/machine_kexec_file.c
new file mode 100644
index 000000000000..e6928cbed524
--- /dev/null
+++ b/arch/s390/kernel/machine_kexec_file.c
@@ -0,0 +1,174 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * s390 code for kexec_file_load system call
+ *
+ * Copyright IBM Corp. 2018
+ *
+ * Author(s): Philipp Rudo <pr...@linux.vnet.ibm.com>
+ */
+
+#include <linux/elf.h>
+#include <linux/kexec.h>
+#include <asm/setup.h>
+
+const struct kexec_file_ops * const kexec_file_loaders[] = {
+       NULL,
+};
+
+/*
+ * The kernel is loaded to a fixed location. Turn off kexec_locate_mem_hole
+ * and provide kbuf->mem by hand.
+ */
+int arch_kexec_walk_mem(struct kexec_buf *kbuf,
+                       int (*func)(struct resource *, void *))
+{
+       return 1;
+}
+
+int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
+                                    Elf_Shdr *section,
+                                    const Elf_Shdr *relsec,
+                                    const Elf_Shdr *symtab)
+{
+       Elf_Rela *relas;
+       int i;
+
+       relas = (void *)pi->ehdr + relsec->sh_offset;
+
+       for (i = 0; i < relsec->sh_size / sizeof(*relas); i++) {
+               const Elf_Sym *sym;     /* symbol to relocate */
+               unsigned long addr;     /* final location after relocation */
+               unsigned long val;      /* relocated symbol value */
+               void *loc;              /* tmp location to modify */
+
+               sym = (void *)pi->ehdr + symtab->sh_offset;
+               sym += ELF64_R_SYM(relas[i].r_info);
+
+               if (sym->st_shndx == SHN_UNDEF)
+                       return -ENOEXEC;
+
+               if (sym->st_shndx == SHN_COMMON)
+                       return -ENOEXEC;
+
+               if (sym->st_shndx >= pi->ehdr->e_shnum &&
+                   sym->st_shndx != SHN_ABS)
+                       return -ENOEXEC;
+
+               loc = pi->purgatory_buf;
+               loc += section->sh_offset;
+               loc += relas[i].r_offset;
+
+               val = sym->st_value;
+               if (sym->st_shndx != SHN_ABS)
+                       val += pi->sechdrs[sym->st_shndx].sh_addr;
+               val += relas[i].r_addend;
+
+               addr = section->sh_addr + relas[i].r_offset;
+
+               switch (ELF64_R_TYPE(relas[i].r_info)) {
+               case R_390_8:           /* Direct 8 bit.   */
+                       *(u8 *)loc = val;
+                       break;
+               case R_390_12:          /* Direct 12 bit.  */
+                       *(u16 *)loc &= 0xf000;
+                       *(u16 *)loc |= val & 0xfff;
+                       break;
+               case R_390_16:          /* Direct 16 bit.  */
+                       *(u16 *)loc = val;
+                       break;
+               case R_390_20:          /* Direct 20 bit.  */
+                       *(u32 *)loc &= 0xf00000ff;
+                       *(u32 *)loc |= (val & 0xfff) << 16;     /* DL */
+                       *(u32 *)loc |= (val & 0xff000) >> 4;    /* DH */
+                       break;
+               case R_390_32:          /* Direct 32 bit.  */
+                       *(u32 *)loc = val;
+                       break;
+               case R_390_64:          /* Direct 64 bit.  */
+                       *(u64 *)loc = val;
+                       break;
+               case R_390_PC16:        /* PC relative 16 bit.  */
+                       *(u16 *)loc = (val - addr);
+                       break;
+               case R_390_PC16DBL:     /* PC relative 16 bit shifted by 1.  */
+                       *(u16 *)loc = (val - addr) >> 1;
+                       break;
+               case R_390_PC32DBL:     /* PC relative 32 bit shifted by 1.  */
+                       *(u32 *)loc = (val - addr) >> 1;
+                       break;
+               case R_390_PC32:        /* PC relative 32 bit.  */
+                       *(u32 *)loc = (val - addr);
+                       break;
+               case R_390_PC64:        /* PC relative 64 bit.  */
+                       *(u64 *)loc = (val - addr);
+                       break;
+               default:
+                       break;
+               }
+       }
+       return 0;
+}
+
+int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
+                                 unsigned long buf_len)
+{
+       struct kexec_file_ops *fops;
+       int i, ret;
+
+       /* A kernel must be at least large enough to contain head.S. During
+        * load memory in head.S will be accessed, e.g. to register the next
+        * command line. If the next kernel were smaller the current kernel
+        * will panic at load.
+        *
+        * 0x11000 = sizeof(head.S)
+        */
+       if (buf_len < 0x11000)
+               return -ENOEXEC;
+
+       for (i = 0; i < ARRAY_SIZE(kexec_file_loaders); i++) {
+               fops = kexec_file_loaders[i];
+               if (!fops || !fops->probe)
+                       continue;
+
+               ret = fops->probe(buf, buf_len);
+               if (!ret) {
+                       image->fops = fops;
+                       return ret;
+               }
+       }
+
+       return -ENOEXEC;
+}
+
+void *arch_kexec_kernel_image_load(struct kimage *image)
+{
+       if (!image->fops || !image->fops->load)
+               return ERR_PTR(-ENOEXEC);
+
+       if (image->cmdline_buf_len >= ARCH_COMMAND_LINE_SIZE)
+               return ERR_PTR(-EINVAL);
+
+       return image->fops->load(image, image->kernel_buf,
+                                image->kernel_buf_len, image->initrd_buf,
+                                image->initrd_buf_len, image->cmdline_buf,
+                                image->cmdline_buf_len);
+}
+
+int arch_kimage_file_post_load_cleanup(struct kimage *image)
+{
+       if (!image->fops || !image->fops->cleanup)
+               return 0;
+
+       return image->fops->cleanup(image->image_loader_data);
+}
+
+#ifdef CONFIG_KEXEC_VERIFY_SIG
+int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel,
+                                unsigned long kernel_len)
+{
+       if (!image->fops || !image->fops->verify_sig)
+               return -EKEYREJECTED;
+
+       return image->fops->verify_sig(kernel, kernel_len);
+}
+#endif /* CONFIG_KEXEC_VERIFY_SIG */
diff --git a/arch/s390/kernel/syscalls/syscall.tbl 
b/arch/s390/kernel/syscalls/syscall.tbl
index b38d48464368..8b210ead7956 100644
--- a/arch/s390/kernel/syscalls/syscall.tbl
+++ b/arch/s390/kernel/syscalls/syscall.tbl
@@ -388,3 +388,4 @@
 378  common    s390_guarded_storage    sys_s390_guarded_storage        
compat_sys_s390_guarded_storage
 379  common    statx                   sys_statx                       
compat_sys_statx
 380  common    s390_sthyi              sys_s390_sthyi                  
compat_sys_s390_sthyi
+381  common    kexec_file_load         sys_kexec_file_load             
compat_sys_kexec_file_load
-- 
2.13.5


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