[PATCH v5 7/7] kexec_elf: support 32 bit ELF files

[Sven Schnelle]

The powerpc version only supported 64 bit. Add some
code to switch decoding of fields during runtime so
we can kexec a 32 bit kernel from a 64 bit kernel and
vice versa.

Signed-off-by: Sven Schnelle <sv...@stackframe.org>
Reviewed-by: Thiago Jung Bauermann <bauer...@linux.ibm.com>
---
 kernel/kexec_elf.c | 57 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 42 insertions(+), 15 deletions(-)

diff --git a/kernel/kexec_elf.c b/kernel/kexec_elf.c
index 85f2bd177d6e..d3689632e8b9 100644
--- a/kernel/kexec_elf.c
+++ b/kernel/kexec_elf.c
@@ -21,8 +21,6 @@
 #include <linux/slab.h>
 #include <linux/types.h>
 
-#define elf_addr_to_cpu        elf64_to_cpu
-
 static inline bool elf_is_elf_file(const struct elfhdr *ehdr)
 {
        return memcmp(ehdr->e_ident, ELFMAG, SELFMAG) == 0;
@@ -152,9 +150,6 @@ static int elf_read_ehdr(const char *buf, size_t len, 
struct elfhdr *ehdr)
        ehdr->e_type      = elf16_to_cpu(ehdr, buf_ehdr->e_type);
        ehdr->e_machine   = elf16_to_cpu(ehdr, buf_ehdr->e_machine);
        ehdr->e_version   = elf32_to_cpu(ehdr, buf_ehdr->e_version);
-       ehdr->e_entry     = elf_addr_to_cpu(ehdr, buf_ehdr->e_entry);
-       ehdr->e_phoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_phoff);
-       ehdr->e_shoff     = elf_addr_to_cpu(ehdr, buf_ehdr->e_shoff);
        ehdr->e_flags     = elf32_to_cpu(ehdr, buf_ehdr->e_flags);
        ehdr->e_phentsize = elf16_to_cpu(ehdr, buf_ehdr->e_phentsize);
        ehdr->e_phnum     = elf16_to_cpu(ehdr, buf_ehdr->e_phnum);
@@ -162,6 +157,24 @@ static int elf_read_ehdr(const char *buf, size_t len, 
struct elfhdr *ehdr)
        ehdr->e_shnum     = elf16_to_cpu(ehdr, buf_ehdr->e_shnum);
        ehdr->e_shstrndx  = elf16_to_cpu(ehdr, buf_ehdr->e_shstrndx);
 
+       switch (ehdr->e_ident[EI_CLASS]) {
+       case ELFCLASS64:
+               ehdr->e_entry = elf64_to_cpu(ehdr, buf_ehdr->e_entry);
+               ehdr->e_phoff = elf64_to_cpu(ehdr, buf_ehdr->e_phoff);
+               ehdr->e_shoff = elf64_to_cpu(ehdr, buf_ehdr->e_shoff);
+               break;
+
+       case ELFCLASS32:
+               ehdr->e_entry = elf32_to_cpu(ehdr, buf_ehdr->e_entry);
+               ehdr->e_phoff = elf32_to_cpu(ehdr, buf_ehdr->e_phoff);
+               ehdr->e_shoff = elf32_to_cpu(ehdr, buf_ehdr->e_shoff);
+               break;
+
+       default:
+               pr_debug("Unknown ELF class.\n");
+               return -EINVAL;
+       }
+
        return elf_is_ehdr_sane(ehdr, len) ? 0 : -ENOEXEC;
 }
 
@@ -192,6 +205,7 @@ static int elf_read_phdr(const char *buf, size_t len,
 {
        /* Override the const in proghdrs, we are the ones doing the loading. */
        struct elf_phdr *phdr = (struct elf_phdr *) &elf_info->proghdrs[idx];
+       const struct elfhdr *ehdr = elf_info->ehdr;
        const char *pbuf;
        struct elf_phdr *buf_phdr;
 
@@ -199,18 +213,31 @@ static int elf_read_phdr(const char *buf, size_t len,
        buf_phdr = (struct elf_phdr *) pbuf;
 
        phdr->p_type   = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_type);
-       phdr->p_offset = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_offset);
-       phdr->p_paddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_paddr);
-       phdr->p_vaddr  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_vaddr);
        phdr->p_flags  = elf32_to_cpu(elf_info->ehdr, buf_phdr->p_flags);
 
-       /*
-        * The following fields have a type equivalent to Elf_Addr
-        * both in 32 bit and 64 bit ELF.
-        */
-       phdr->p_filesz = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_filesz);
-       phdr->p_memsz  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_memsz);
-       phdr->p_align  = elf_addr_to_cpu(elf_info->ehdr, buf_phdr->p_align);
+       switch (ehdr->e_ident[EI_CLASS]) {
+       case ELFCLASS64:
+               phdr->p_offset = elf64_to_cpu(ehdr, buf_phdr->p_offset);
+               phdr->p_paddr  = elf64_to_cpu(ehdr, buf_phdr->p_paddr);
+               phdr->p_vaddr  = elf64_to_cpu(ehdr, buf_phdr->p_vaddr);
+               phdr->p_filesz = elf64_to_cpu(ehdr, buf_phdr->p_filesz);
+               phdr->p_memsz  = elf64_to_cpu(ehdr, buf_phdr->p_memsz);
+               phdr->p_align  = elf64_to_cpu(ehdr, buf_phdr->p_align);
+               break;
+
+       case ELFCLASS32:
+               phdr->p_offset = elf32_to_cpu(ehdr, buf_phdr->p_offset);
+               phdr->p_paddr  = elf32_to_cpu(ehdr, buf_phdr->p_paddr);
+               phdr->p_vaddr  = elf32_to_cpu(ehdr, buf_phdr->p_vaddr);
+               phdr->p_filesz = elf32_to_cpu(ehdr, buf_phdr->p_filesz);
+               phdr->p_memsz  = elf32_to_cpu(ehdr, buf_phdr->p_memsz);
+               phdr->p_align  = elf32_to_cpu(ehdr, buf_phdr->p_align);
+               break;
+
+       default:
+               pr_debug("Unknown ELF class.\n");
+               return -EINVAL;
+       }
 
        return elf_is_phdr_sane(phdr, len) ? 0 : -ENOEXEC;
 }
-- 
2.23.0.rc1