MIPS: Avoid FP ELF checks when CONFIG_MIPS_FP_SUPPORT=n

When CONFIG_MIPS_FP_SUPPORT=n we don't support floating point, so we can
avoid needless checks of ELF headers specifying the FP ABI or NaN
encoding to use. Deselect CONFIG_ARCH_BINFMT_ELF_STATE in this case to
avoid the need for our arch_elf_pt_proc() & arch_check_elf() functions,
and stub out the mips_set_personality_nan() & mips_set_personality_fp()
functions such that SET_PERSONALITY() doesn't need to worry about any of
this.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/21011/
Cc: linux-mips@linux-mips.org

arch/mips/Kconfig

@@ -2,7 +2,7 @@
 config MIPS
 	bool
 	default y
-	select ARCH_BINFMT_ELF_STATE
+	select ARCH_BINFMT_ELF_STATE if MIPS_FP_SUPPORT
 	select ARCH_CLOCKSOURCE_DATA
 	select ARCH_DISCARD_MEMBLOCK
 	select ARCH_HAS_ELF_RANDOMIZE

arch/mips/include/asm/elf.h

@@ -481,6 +481,8 @@ struct linux_binprm;
 extern int arch_setup_additional_pages(struct linux_binprm *bprm,
 				       int uses_interp);
 
+#ifdef CONFIG_MIPS_FP_SUPPORT
+
 struct arch_elf_state {
 	int nan_2008;
 	int fp_abi;
@@ -497,19 +499,35 @@ struct arch_elf_state {
 	.overall_fp_mode = -1,			\
 }
 
-/* Whether to accept legacy-NaN and 2008-NaN user binaries.  */
-extern bool mips_use_nan_legacy;
-extern bool mips_use_nan_2008;
-
 extern int arch_elf_pt_proc(void *ehdr, void *phdr, struct file *elf,
 			    bool is_interp, struct arch_elf_state *state);
 
 extern int arch_check_elf(void *ehdr, bool has_interpreter, void *interp_ehdr,
 			  struct arch_elf_state *state);
 
+/* Whether to accept legacy-NaN and 2008-NaN user binaries.  */
+extern bool mips_use_nan_legacy;
+extern bool mips_use_nan_2008;
+
 extern void mips_set_personality_nan(struct arch_elf_state *state);
 extern void mips_set_personality_fp(struct arch_elf_state *state);
 
+#else /* !CONFIG_MIPS_FP_SUPPORT */
+
+struct arch_elf_state;
+
+static inline void mips_set_personality_nan(struct arch_elf_state *state)
+{
+	/* no-op */
+}
+
+static inline void mips_set_personality_fp(struct arch_elf_state *state)
+{
+	/* no-op */
+}
+
+#endif /* !CONFIG_MIPS_FP_SUPPORT */
+
 #define elf_read_implies_exec(ex, stk) mips_elf_read_implies_exec(&(ex), stk)
 extern int mips_elf_read_implies_exec(void *elf_ex, int exstack);
 

arch/mips/kernel/elf.c

@@ -16,6 +16,8 @@
 #include <asm/cpu-features.h>
 #include <asm/cpu-info.h>
 
+#ifdef CONFIG_MIPS_FP_SUPPORT
+
 /* Whether to accept legacy-NaN and 2008-NaN user binaries.  */
 bool mips_use_nan_legacy;
 bool mips_use_nan_2008;
@@ -326,6 +328,8 @@ void mips_set_personality_nan(struct arch_elf_state *state)
 	}
 }
 
+#endif /* CONFIG_MIPS_FP_SUPPORT */
+
 int mips_elf_read_implies_exec(void *elf_ex, int exstack)
 {
 	if (exstack != EXSTACK_DISABLE_X) {