MIPS: ELF: fix loading o32 binaries on 64-bit kernels

Commit 90cee759 ("MIPS: ELF: Set FP mode according to .MIPS.abiflags")
introduced checking of the .MIPS.abiflags ELF section but did so through
the native sized "elfhdr" and "elf_phdr" structures regardless whether the
ELF was actually 32-bit or 64-bit. This produces wrong results when trying
to use a 64-bit kernel to load o32 ELF files.

Change the uses of the generic elf structures to their 32-bit versions.
Since the code bails out on any 64-bit cases, this is OK until they are
implemented.

Fixes: 90cee759 ("MIPS: ELF: Set FP mode according to .MIPS.abiflags")
Signed-off-by: James Cowgill <James.Cowgill@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Reviewed-by: Maciej W. Rozycki <macro@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/8932/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/elf.c

@@ -19,8 +19,8 @@ enum {
 int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf,
 		     bool is_interp, struct arch_elf_state *state)
 {
-	struct elfhdr *ehdr = _ehdr;
-	struct elf_phdr *phdr = _phdr;
+	struct elf32_hdr *ehdr = _ehdr;
+	struct elf32_phdr *phdr = _phdr;
 	struct mips_elf_abiflags_v0 abiflags;
 	int ret;
 
@@ -48,7 +48,7 @@ int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf,
 	return 0;
 }
 
-static inline unsigned get_fp_abi(struct elfhdr *ehdr, int in_abi)
+static inline unsigned get_fp_abi(struct elf32_hdr *ehdr, int in_abi)
 {
 	/* If the ABI requirement is provided, simply return that */
 	if (in_abi != -1)
@@ -65,7 +65,7 @@ static inline unsigned get_fp_abi(struct elfhdr *ehdr, int in_abi)
 int arch_check_elf(void *_ehdr, bool has_interpreter,
 		   struct arch_elf_state *state)
 {
-	struct elfhdr *ehdr = _ehdr;
+	struct elf32_hdr *ehdr = _ehdr;
 	unsigned fp_abi, interp_fp_abi, abi0, abi1;
 
 	/* Ignore non-O32 binaries */