2 files changed, 31 insertions, 0 deletions

diff --git a/arch/mips/Kconfig.debug b/arch/mips/Kconfig.debug
index 3a2b775e8458..88a9f433f6fc 100644
--- a/arch/mips/Kconfig.debug
+++ b/arch/mips/Kconfig.debug
@@ -122,4 +122,17 @@ config SPINLOCK_TEST
         help
           Add several files to the debugfs to test spinlock speed.
 
+config FP32XX_HYBRID_FPRS
+        bool "Run FP32 & FPXX code with hybrid FPRs"
+        depends on MIPS_O32_FP64_SUPPORT
+        help
+          The hybrid FPR scheme is normally used only when a program needs to
+          execute a mix of FP32 & FP64A code, since the trapping & emulation
+          that it entails is expensive. When enabled, this option will lead
+          to the kernel running programs which use the FP32 & FPXX FP ABIs
+          using the hybrid FPR scheme, which can be useful for debugging
+          purposes.
+
+          If unsure, say N.
+
 endmenu
diff --git a/arch/mips/kernel/elf.c b/arch/mips/kernel/elf.c
index 0933e0726f64..c92b15df6893 100644
--- a/arch/mips/kernel/elf.c
+++ b/arch/mips/kernel/elf.c
@@ -134,6 +134,24 @@ int arch_check_elf(void *_ehdr, bool has_interpreter,
 
 void mips_set_personality_fp(struct arch_elf_state *state)
 {
+        if (config_enabled(CONFIG_FP32XX_HYBRID_FPRS)) {
+                /*
+                 * Use hybrid FPRs for all code which can correctly execute
+                 * with that mode.
+                 */
+                switch (state->overall_abi) {
+                case MIPS_ABI_FP_DOUBLE:
+                case MIPS_ABI_FP_SINGLE:
+                case MIPS_ABI_FP_SOFT:
+                case MIPS_ABI_FP_XX:
+                case MIPS_ABI_FP_ANY:
+                        /* FR=1, FRE=1 */
+                        clear_thread_flag(TIF_32BIT_FPREGS);
+                        set_thread_flag(TIF_HYBRID_FPREGS);
+                        return;
+                }
+        }
+
         switch (state->overall_abi) {
         case MIPS_ABI_FP_DOUBLE:
         case MIPS_ABI_FP_SINGLE: