s390/kexec_file: Load new kernel to absolute 0

The leading 64 kB of a kernel image doesn't contain any data needed to boot
the new kernel when it was loaded via kexec_file. Thus kexec_file currently
strips them off before loading the image. Keep the leading 64 kB in order
to be able to pass a ipl_report to the next kernel.
Signed-off-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/kexec.h

@@ -43,6 +43,9 @@
 /* The native architecture */
 #define KEXEC_ARCH KEXEC_ARCH_S390
 
+/* Allow kexec_file to load a segment to 0 */
+#define KEXEC_BUF_MEM_UNKNOWN -1
+
 /* Provide a dummy definition to avoid build failures. */
 static inline void crash_setup_regs(struct pt_regs *newregs,
 					struct pt_regs *oldregs) { }
@@ -52,6 +55,9 @@ struct s390_load_data {
 	/* Pointer to the kernel buffer. Used to register cmdline etc.. */
 	void *kernel_buf;
 
+	/* Load address of the kernel_buf. */
+	unsigned long kernel_mem;
+
 	/* Parmarea in the kernel buffer. */
 	struct parmarea *parm;
 

arch/s390/kernel/kexec_elf.c

@@ -39,28 +39,20 @@ static int kexec_file_add_kernel_elf(struct kimage *image,
 		buf.bufsz = phdr->p_filesz;
 
 		buf.mem = ALIGN(phdr->p_paddr, phdr->p_align);
+		if (image->type == KEXEC_TYPE_CRASH)
+			buf.mem += crashk_res.start;
 		buf.memsz = phdr->p_memsz;
+		data->memsz = ALIGN(data->memsz, phdr->p_align) + buf.memsz;
 
 		if (entry - phdr->p_paddr < phdr->p_memsz) {
 			data->kernel_buf = buf.buffer;
+			data->kernel_mem = buf.mem;
 			data->parm = buf.buffer + PARMAREA;
-			data->memsz += STARTUP_NORMAL_OFFSET;
-
-			buf.buffer += STARTUP_NORMAL_OFFSET;
-			buf.bufsz -= STARTUP_NORMAL_OFFSET;
-
-			buf.mem += STARTUP_NORMAL_OFFSET;
-			buf.memsz -= STARTUP_NORMAL_OFFSET;
 		}
 
-		if (image->type == KEXEC_TYPE_CRASH)
-			buf.mem += crashk_res.start;
-
 		ret = kexec_add_buffer(&buf);
 		if (ret)
 			return ret;
-
-		data->memsz = ALIGN(data->memsz, phdr->p_align) + buf.memsz;
 	}
 
 	return data->memsz ? 0 : -EINVAL;

arch/s390/kernel/kexec_image.c

@@ -19,17 +19,18 @@ static int kexec_file_add_kernel_image(struct kimage *image,
 
 	buf.image = image;
 
-	buf.buffer = image->kernel_buf + STARTUP_NORMAL_OFFSET;
-	buf.bufsz = image->kernel_buf_len - STARTUP_NORMAL_OFFSET;
+	buf.buffer = image->kernel_buf;
+	buf.bufsz = image->kernel_buf_len;
 
-	buf.mem = STARTUP_NORMAL_OFFSET;
+	buf.mem = 0;
 	if (image->type == KEXEC_TYPE_CRASH)
 		buf.mem += crashk_res.start;
 	buf.memsz = buf.bufsz;
 
 	data->kernel_buf = image->kernel_buf;
+	data->kernel_mem = buf.mem;
 	data->parm = image->kernel_buf + PARMAREA;
-	data->memsz += buf.memsz + STARTUP_NORMAL_OFFSET;
+	data->memsz += buf.memsz;
 
 	return kexec_add_buffer(&buf);
 }

arch/s390/kernel/machine_kexec_file.c

@@ -17,7 +17,8 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
 	NULL,
 };
 
-static int kexec_file_update_purgatory(struct kimage *image)
+static int kexec_file_update_purgatory(struct kimage *image,
+				       struct s390_load_data *data)
 {
 	u64 entry, type;
 	int ret;
@@ -76,7 +77,7 @@ static int kexec_file_add_purgatory(struct kimage *image,
 	if (ret)
 		return ret;
 
-	ret = kexec_file_update_purgatory(image);
+	ret = kexec_file_update_purgatory(image, data);
 	return ret;
 }
 
@@ -136,6 +137,13 @@ void *kexec_file_add_components(struct kimage *image,
 	if (ret)
 		return ERR_PTR(ret);
 
+	if (data.kernel_mem == 0) {
+		unsigned long restart_psw =  0x0008000080000000UL;
+		restart_psw += image->start;
+		memcpy(data.kernel_buf, &restart_psw, sizeof(restart_psw));
+		image->start = 0;
+	}
+
 	return NULL;
 }
 

arch/s390/kernel/relocate_kernel.S

@@ -58,10 +58,13 @@ ENTRY(relocate_kernel)
 		j	.base
 	.done:
 		sgr	%r0,%r0		# clear register r0
+		cghi	%r3,0
+		je	.diag
 		la	%r4,load_psw-.base(%r13)	# load psw-address into the register
 		o	%r3,4(%r4)	# or load address into psw
 		st	%r3,4(%r4)
 		mvc	0(8,%r0),0(%r4)	# copy psw to absolute address 0
+	.diag:
 		diag	%r0,%r0,0x308
 
 		.align	8