MIPS: Add IEEE Std 754 conformance mode selection
Add an `ieee754=' kernel parameter to control IEEE Std 754 conformance
mode.
Use separate flags copied from the respective CPU feature flags, and
adjusted according to the conformance mode selected, to make binaries
requesting individual NaN encoding modes accepted or rejected as needed.
Update the initial setting for FCSR and, in the full FPU emulation mode,
its read-only mask accordingly. Accept the mode selection requested for
legacy processors as well.
As with the EF_MIPS_NAN2008 ELF file header flag adjust both ABS2008 and
NAN2008 bits at the same time, to match the choice made for hardware
currently implemented.
Signed-off-by: Maciej W. Rozycki <macro@imgtec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Fortune <Matthew.Fortune@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/11481/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/kernel/elf.c b/arch/mips/kernel/elf.c
index f36a261..c3c234d 100644
--- a/arch/mips/kernel/elf.c
+++ b/arch/mips/kernel/elf.c
@@ -13,6 +13,10 @@
#include <asm/cpu-info.h>
+/* Whether to accept legacy-NaN and 2008-NaN user binaries. */
+bool mips_use_nan_legacy;
+bool mips_use_nan_2008;
+
/* FPU modes */
enum {
FP_FRE,
@@ -150,16 +154,16 @@
flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags;
/*
- * Determine the NaN personality, reject the binary if no hardware
- * support. Also ensure that any interpreter matches the executable.
+ * Determine the NaN personality, reject the binary if not allowed.
+ * Also ensure that any interpreter matches the executable.
*/
if (flags & EF_MIPS_NAN2008) {
- if (cpu_has_nan_2008)
+ if (mips_use_nan_2008)
state->nan_2008 = 1;
else
return -ENOEXEC;
} else {
- if (cpu_has_nan_legacy)
+ if (mips_use_nan_legacy)
state->nan_2008 = 0;
else
return -ENOEXEC;