kernel/kexec_file.c: allow archs to set purgatory load address

For s390 new kernels are loaded to fixed addresses in memory before they
are booted.  With the current code this is a problem as it assumes the
kernel will be loaded to an 'arbitrary' address.  In particular,
kexec_locate_mem_hole searches for a large enough memory region and sets
the load address (kexec_bufer->mem) to it.

Luckily there is a simple workaround for this problem.  By returning 1
in arch_kexec_walk_mem, kexec_locate_mem_hole is turned off.  This
allows the architecture to set kbuf->mem by hand.  While the trick works
fine for the kernel it does not for the purgatory as here the
architectures don't have access to its kexec_buffer.

Give architectures access to the purgatories kexec_buffer by changing
kexec_load_purgatory to take a pointer to it.  With this change
architectures have access to the buffer and can edit it as they need.

A nice side effect of this change is that we can get rid of the
purgatory_info->purgatory_load_address field.  As now the information
stored there can directly be accessed from kbuf->mem.

Link: http://lkml.kernel.org/r/20180321112751.22196-11-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo <prudo@linux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Acked-by: Dave Young <dyoung@redhat.com>
Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 13 deletions

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 269116fd932c..75d8e7cf040e 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -730,8 +730,8 @@ static int kexec_purgatory_setup_kbuf(struct purgatory_info *pi,
         int i, ret;
 
         sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;
-        bss_align = 1;
-        bss_sz = 0;
+        kbuf->buf_align = bss_align = 1;
+        kbuf->bufsz = bss_sz = 0;
 
         for (i = 0; i < pi->ehdr->e_shnum; i++) {
                 if (!(sechdrs[i].sh_flags & SHF_ALLOC))
@@ -763,7 +763,6 @@ static int kexec_purgatory_setup_kbuf(struct purgatory_info *pi,
         ret = kexec_add_buffer(kbuf);
         if (ret)
                 goto out;
-        pi->purgatory_load_addr = kbuf->mem;
 
         return 0;
 out:
@@ -901,27 +900,32 @@ static int kexec_apply_relocations(struct kimage *image)
         return 0;
 }
 
-/* Load relocatable purgatory object and relocate it appropriately */
-int kexec_load_purgatory(struct kimage *image, unsigned long min,
-                         unsigned long max, int top_down,
-                         unsigned long *load_addr)
+/*
+ * kexec_load_purgatory - Load and relocate the purgatory object.
+ * @image:      Image to add the purgatory to.
+ * @kbuf:       Memory parameters to use.
+ *
+ * Allocates the memory needed for image->purgatory_info.sechdrs and
+ * image->purgatory_info.purgatory_buf/kbuf->buffer. Caller is responsible
+ * to free the memory after use.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf)
 {
         struct purgatory_info *pi = &image->purgatory_info;
         int ret;
-        struct kexec_buf kbuf = { .image = image, .bufsz = 0, .buf_align = 1,
-                                  .buf_min = min, .buf_max = max,
-                                  .top_down = top_down };
 
         if (kexec_purgatory_size <= 0)
                 return -EINVAL;
 
         pi->ehdr = (const Elf_Ehdr *)kexec_purgatory;
 
-        ret = kexec_purgatory_setup_kbuf(pi, &kbuf);
+        ret = kexec_purgatory_setup_kbuf(pi, kbuf);
         if (ret)
                 return ret;
 
-        ret = kexec_purgatory_setup_sechdrs(pi, &kbuf);
+        ret = kexec_purgatory_setup_sechdrs(pi, kbuf);
         if (ret)
                 goto out_free_kbuf;
 
@@ -929,7 +933,6 @@ int kexec_load_purgatory(struct kimage *image, unsigned long min,
         if (ret)
                 goto out;
 
-        *load_addr = pi->purgatory_load_addr;
         return 0;
 out:
         vfree(pi->sechdrs);