kernel/kexec_file.c: split up __kexec_load_puragory

When inspecting __kexec_load_purgatory you find that it has two tasks

	1) setting up the kexec_buffer for the new kernel and,
	2) setting up pi->sechdrs for the final load address.

The two tasks are independent of each other.  To improve readability
split up __kexec_load_purgatory into two functions, one for each task,
and call them directly from kexec_load_purgatory.

Link: http://lkml.kernel.org/r/20180321112751.22196-7-prudo@linux.vnet.ibm.com
Signed-off-by: Philipp Rudo <prudo@linux.vnet.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: Martin Schwidefsky <schwidefsky@de.ibm.com>
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>

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 5c70f7f..878b97b 100644 (file)
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -710,39 +710,97 @@ out:
 }
 
 #ifdef CONFIG_ARCH_HAS_KEXEC_PURGATORY
-/* Actually load purgatory. Lot of code taken from kexec-tools */
-static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
-                                 unsigned long max, int top_down)
+/*
+ * kexec_purgatory_setup_kbuf - prepare buffer to load purgatory.
+ * @pi:                Purgatory to be loaded.
+ * @kbuf:      Buffer to setup.
+ *
+ * Allocates the memory needed for the buffer. Caller is responsible to free
+ * the memory after use.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+static int kexec_purgatory_setup_kbuf(struct purgatory_info *pi,
+                                     struct kexec_buf *kbuf)
 {
-       struct purgatory_info *pi = &image->purgatory_info;
-       unsigned long align, bss_align, bss_sz, bss_pad;
-       unsigned long entry, load_addr, curr_load_addr, bss_addr, offset;
-       unsigned char *buf_addr, *src;
-       int i, ret = 0, entry_sidx = -1;
-       const Elf_Shdr *sechdrs_c;
-       Elf_Shdr *sechdrs = NULL;
-       struct kexec_buf kbuf = { .image = image, .bufsz = 0, .buf_align = 1,
-                                 .buf_min = min, .buf_max = max,
-                                 .top_down = top_down };
+       const Elf_Shdr *sechdrs;
+       unsigned long bss_align;
+       unsigned long bss_sz;
+       unsigned long align;
+       int i, ret;
 
-       /*
-        * sechdrs_c points to section headers in purgatory and are read
-        * only. No modifications allowed.
-        */
-       sechdrs_c = (void *)pi->ehdr + pi->ehdr->e_shoff;
+       sechdrs = (void *)pi->ehdr + pi->ehdr->e_shoff;
+       bss_align = 1;
+       bss_sz = 0;
+
+       for (i = 0; i < pi->ehdr->e_shnum; i++) {
+               if (!(sechdrs[i].sh_flags & SHF_ALLOC))
+                       continue;
+
+               align = sechdrs[i].sh_addralign;
+               if (sechdrs[i].sh_type != SHT_NOBITS) {
+                       if (kbuf->buf_align < align)
+                               kbuf->buf_align = align;
+                       kbuf->bufsz = ALIGN(kbuf->bufsz, align);
+                       kbuf->bufsz += sechdrs[i].sh_size;
+               } else {
+                       if (bss_align < align)
+                               bss_align = align;
+                       bss_sz = ALIGN(bss_sz, align);
+                       bss_sz += sechdrs[i].sh_size;
+               }
+       }
+       kbuf->bufsz = ALIGN(kbuf->bufsz, bss_align);
+       kbuf->memsz = kbuf->bufsz + bss_sz;
+       if (kbuf->buf_align < bss_align)
+               kbuf->buf_align = bss_align;
+
+       kbuf->buffer = vzalloc(kbuf->bufsz);
+       if (!kbuf->buffer)
+               return -ENOMEM;
+       pi->purgatory_buf = kbuf->buffer;
+
+       ret = kexec_add_buffer(kbuf);
+       if (ret)
+               goto out;
+       pi->purgatory_load_addr = kbuf->mem;
+
+       return 0;
+out:
+       vfree(pi->purgatory_buf);
+       pi->purgatory_buf = NULL;
+       return ret;
+}
+
+/*
+ * kexec_purgatory_setup_sechdrs - prepares the pi->sechdrs buffer.
+ * @pi:                Purgatory to be loaded.
+ * @kbuf:      Buffer prepared to store purgatory.
+ *
+ * Allocates the memory needed for the buffer. Caller is responsible to free
+ * the memory after use.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+static int kexec_purgatory_setup_sechdrs(struct purgatory_info *pi,
+                                        struct kexec_buf *kbuf)
+{
+       unsigned long curr_load_addr;
+       unsigned long load_addr;
+       unsigned long bss_addr;
+       unsigned long offset;
+       unsigned char *buf_addr;
+       unsigned char *src;
+       Elf_Shdr *sechdrs;
+       int entry_sidx = -1;
+       int i;
 
-       /*
-        * We can not modify sechdrs_c[] and its fields. It is read only.
-        * Copy it over to a local copy where one can store some temporary
-        * data and free it at the end. We need to modify ->sh_addr and
-        * ->sh_offset fields to keep track of permanent and temporary
-        * locations of sections.
-        */
        sechdrs = vzalloc(pi->ehdr->e_shnum * sizeof(Elf_Shdr));
        if (!sechdrs)
                return -ENOMEM;
-
-       memcpy(sechdrs, sechdrs_c, pi->ehdr->e_shnum * sizeof(Elf_Shdr));
+       memcpy(sechdrs, (void *)pi->ehdr + pi->ehdr->e_shoff,
+              pi->ehdr->e_shnum * sizeof(Elf_Shdr));
+       pi->sechdrs = sechdrs;
 
        /*
         * We seem to have multiple copies of sections. First copy is which
@@ -770,7 +828,7 @@ static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
         * Identify entry point section and make entry relative to section
         * start.
         */
-       entry = pi->ehdr->e_entry;
+       kbuf->image->start = pi->ehdr->e_entry;
        for (i = 0; i < pi->ehdr->e_shnum; i++) {
                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;
@@ -783,63 +841,19 @@ static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
                    ((sechdrs[i].sh_addr + sechdrs[i].sh_size) >
                     pi->ehdr->e_entry)) {
                        entry_sidx = i;
-                       entry -= sechdrs[i].sh_addr;
+                       kbuf->image->start -= sechdrs[i].sh_addr;
                        break;
                }
        }
 
-       /* Determine how much memory is needed to load relocatable object. */
-       bss_align = 1;
-       bss_sz = 0;
-
-       for (i = 0; i < pi->ehdr->e_shnum; i++) {
-               if (!(sechdrs[i].sh_flags & SHF_ALLOC))
-                       continue;
-
-               align = sechdrs[i].sh_addralign;
-               if (sechdrs[i].sh_type != SHT_NOBITS) {
-                       if (kbuf.buf_align < align)
-                               kbuf.buf_align = align;
-                       kbuf.bufsz = ALIGN(kbuf.bufsz, align);
-                       kbuf.bufsz += sechdrs[i].sh_size;
-               } else {
-                       /* bss section */
-                       if (bss_align < align)
-                               bss_align = align;
-                       bss_sz = ALIGN(bss_sz, align);
-                       bss_sz += sechdrs[i].sh_size;
-               }
-       }
-
-       /* Determine the bss padding required to align bss properly */
-       bss_pad = 0;
-       if (kbuf.bufsz & (bss_align - 1))
-               bss_pad = bss_align - (kbuf.bufsz & (bss_align - 1));
-
-       kbuf.memsz = kbuf.bufsz + bss_pad + bss_sz;
-
-       /* Allocate buffer for purgatory */
-       kbuf.buffer = vzalloc(kbuf.bufsz);
-       if (!kbuf.buffer) {
-               ret = -ENOMEM;
-               goto out;
-       }
-
-       if (kbuf.buf_align < bss_align)
-               kbuf.buf_align = bss_align;
-
-       /* Add buffer to segment list */
-       ret = kexec_add_buffer(&kbuf);
-       if (ret)
-               goto out;
-       pi->purgatory_load_addr = kbuf.mem;
-
        /* Load SHF_ALLOC sections */
-       buf_addr = kbuf.buffer;
-       load_addr = curr_load_addr = pi->purgatory_load_addr;
-       bss_addr = load_addr + kbuf.bufsz + bss_pad;
+       buf_addr = kbuf->buffer;
+       load_addr = curr_load_addr = kbuf->mem;
+       bss_addr = load_addr + kbuf->bufsz;
 
        for (i = 0; i < pi->ehdr->e_shnum; i++) {
+               unsigned long align;
+
                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
                        continue;
 
@@ -871,24 +885,9 @@ static int __kexec_load_purgatory(struct kimage *image, unsigned long min,
 
        /* Update entry point based on load address of text section */
        if (entry_sidx >= 0)
-               entry += sechdrs[entry_sidx].sh_addr;
-
-       /* Make kernel jump to purgatory after shutdown */
-       image->start = entry;
-
-       /* Used later to get/set symbol values */
-       pi->sechdrs = sechdrs;
+               kbuf->image->start += sechdrs[entry_sidx].sh_addr;
 
-       /*
-        * Used later to identify which section is purgatory and skip it
-        * from checksumming.
-        */
-       pi->purgatory_buf = kbuf.buffer;
-       return ret;
-out:
-       vfree(sechdrs);
-       vfree(kbuf.buffer);
-       return ret;
+       return 0;
 }
 
 static int kexec_apply_relocations(struct kimage *image)
@@ -958,16 +957,23 @@ int kexec_load_purgatory(struct kimage *image, unsigned long min,
 {
        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_load_purgatory(image, min, max, top_down);
+       ret = kexec_purgatory_setup_kbuf(pi, &kbuf);
        if (ret)
                return ret;
 
+       ret = kexec_purgatory_setup_sechdrs(pi, &kbuf);
+       if (ret)
+               goto out_free_kbuf;
+
        ret = kexec_apply_relocations(image);
        if (ret)
                goto out;
@@ -977,7 +983,7 @@ int kexec_load_purgatory(struct kimage *image, unsigned long min,
 out:
        vfree(pi->sechdrs);
        pi->sechdrs = NULL;
-
+out_free_kbuf:
        vfree(pi->purgatory_buf);
        pi->purgatory_buf = NULL;
        return ret;