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.

Signed-off-by: Philipp Rudo <pr...@linux.vnet.ibm.com>
Reviewed-by: Martin Schwidefsky <schwidef...@de.ibm.com>
---
 arch/powerpc/kernel/kexec_elf_64.c |  9 +++++----
 arch/x86/kernel/kexec-bzimage64.c  |  8 ++++----
 include/linux/kexec.h              |  7 +------
 kernel/kexec_file.c                | 29 ++++++++++++++++-------------
 4 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/kernel/kexec_elf_64.c 
b/arch/powerpc/kernel/kexec_elf_64.c
index 9a42309b091a..82448c03502d 100644
--- a/arch/powerpc/kernel/kexec_elf_64.c
+++ b/arch/powerpc/kernel/kexec_elf_64.c
@@ -572,7 +572,7 @@ static void *elf64_load(struct kimage *image, char 
*kernel_buf,
 {
        int ret;
        unsigned int fdt_size;
-       unsigned long kernel_load_addr, purgatory_load_addr;
+       unsigned long kernel_load_addr;
        unsigned long initrd_load_addr = 0, fdt_load_addr;
        void *fdt;
        const void *slave_code;
@@ -580,6 +580,8 @@ static void *elf64_load(struct kimage *image, char 
*kernel_buf,
        struct elf_info elf_info;
        struct kexec_buf kbuf = { .image = image, .buf_min = 0,
                                  .buf_max = ppc64_rma_size };
+       struct kexec_buf pbuf = { .image = image, .buf_min = 0,
+                                 .buf_max = ppc64_rma_size, .top_down = true };
 
        ret = build_elf_exec_info(kernel_buf, kernel_len, &ehdr, &elf_info);
        if (ret)
@@ -591,14 +593,13 @@ static void *elf64_load(struct kimage *image, char 
*kernel_buf,
 
        pr_debug("Loaded the kernel at 0x%lx\n", kernel_load_addr);
 
-       ret = kexec_load_purgatory(image, 0, ppc64_rma_size, true,
-                                  &purgatory_load_addr);
+       ret = kexec_load_purgatory(image, &pbuf);
        if (ret) {
                pr_err("Loading purgatory failed.\n");
                goto out;
        }
 
-       pr_debug("Loaded purgatory at 0x%lx\n", purgatory_load_addr);
+       pr_debug("Loaded purgatory at 0x%lx\n", pbuf.mem);
 
        if (initrd != NULL) {
                kbuf.buffer = initrd;
diff --git a/arch/x86/kernel/kexec-bzimage64.c 
b/arch/x86/kernel/kexec-bzimage64.c
index fb095ba0c02f..df183585928f 100644
--- a/arch/x86/kernel/kexec-bzimage64.c
+++ b/arch/x86/kernel/kexec-bzimage64.c
@@ -334,7 +334,6 @@ static void *bzImage64_load(struct kimage *image, char 
*kernel,
        unsigned long setup_header_size, params_cmdline_sz;
        struct boot_params *params;
        unsigned long bootparam_load_addr, kernel_load_addr, initrd_load_addr;
-       unsigned long purgatory_load_addr;
        struct bzimage64_data *ldata;
        struct kexec_entry64_regs regs64;
        void *stack;
@@ -342,6 +341,8 @@ static void *bzImage64_load(struct kimage *image, char 
*kernel,
        unsigned int efi_map_offset, efi_map_sz, efi_setup_data_offset;
        struct kexec_buf kbuf = { .image = image, .buf_max = ULONG_MAX,
                                  .top_down = true };
+       struct kexec_buf pbuf = { .image = image, .buf_min = MIN_PURGATORY_ADDR,
+                                 .buf_max = ULONG_MAX, .top_down = true };
 
        header = (struct setup_header *)(kernel + setup_hdr_offset);
        setup_sects = header->setup_sects;
@@ -379,14 +380,13 @@ static void *bzImage64_load(struct kimage *image, char 
*kernel,
         * Load purgatory. For 64bit entry point, purgatory  code can be
         * anywhere.
         */
-       ret = kexec_load_purgatory(image, MIN_PURGATORY_ADDR, ULONG_MAX, 1,
-                                  &purgatory_load_addr);
+       ret = kexec_load_purgatory(image, &pbuf);
        if (ret) {
                pr_err("Loading purgatory failed\n");
                return ERR_PTR(ret);
        }
 
-       pr_debug("Loaded purgatory at 0x%lx\n", purgatory_load_addr);
+       pr_debug("Loaded purgatory at 0x%lx\n", pbuf.mem);
 
 
        /*
diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index f15446be0e25..1cd9c5f49859 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -114,9 +114,6 @@ struct purgatory_info {
         * relocation. This memory can be freed post image load.
         */
        void *purgatory_buf;
-
-       /* Address where purgatory is finally loaded and is executed from */
-       unsigned long purgatory_load_addr;
 };
 
 struct kimage;
@@ -237,9 +234,7 @@ extern asmlinkage long sys_kexec_load(unsigned long entry,
 extern int kernel_kexec(void);
 extern struct page *kimage_alloc_control_pages(struct kimage *image,
                                                unsigned int order);
-extern int kexec_load_purgatory(struct kimage *image, unsigned long min,
-                               unsigned long max, int top_down,
-                               unsigned long *load_addr);
+extern int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf);
 extern int kexec_purgatory_get_set_symbol(struct kimage *image,
                                          const char *name, void *buf,
                                          unsigned int size, bool get_value);
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 25b44d1a664a..d69d1bf9e7a2 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -669,8 +669,8 @@ 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))
@@ -702,7 +702,6 @@ 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:
@@ -836,27 +835,32 @@ 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;
 
@@ -864,7 +868,6 @@ 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);
-- 
2.13.5

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