From 597ce1723e0fa0bdbe2ae4c94f18da6e29b92635 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Fri, 22 Nov 2013 13:12:07 +0000 Subject: MIPS: Support for 64-bit FP with O32 binaries CPUs implementing MIPS32 R2 may include a 64-bit FPU, just as MIPS64 CPUs do. In order to preserve backwards compatibility a 64-bit FPU will act like a 32-bit FPU (by accessing doubles from the least significant 32 bits of an even-odd pair of FP registers) when the Status.FR bit is zero, again just like a mips64 CPU. The standard O32 ABI is defined expecting a 32-bit FPU, however recent toolchains support use of a 64-bit FPU from an O32 MIPS32 executable. When an ELF executable is built to use a 64-bit FPU a new flag (EF_MIPS_FP64) is set in the ELF header. With this patch the kernel will check the EF_MIPS_FP64 flag when executing an O32 binary, and set Status.FR accordingly. The addition of O32 64-bit FP support lessens the opportunity for optimisation in the FPU emulator, so a CONFIG_MIPS_O32_FP64_SUPPORT Kconfig option is introduced to allow this support to be disabled for those that don't require it. Inspired by an earlier patch by Leonid Yegoshin, but implemented more cleanly & correctly. Signed-off-by: Paul Burton Cc: linux-mips@linux-mips.org Cc: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/6154/ Signed-off-by: Ralf Baechle --- arch/mips/include/asm/elf.h | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) (limited to 'arch/mips/include/asm/elf.h') diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h index a66359ef4ece..d4144056e928 100644 --- a/arch/mips/include/asm/elf.h +++ b/arch/mips/include/asm/elf.h @@ -36,6 +36,7 @@ #define EF_MIPS_ABI2 0x00000020 #define EF_MIPS_OPTIONS_FIRST 0x00000080 #define EF_MIPS_32BITMODE 0x00000100 +#define EF_MIPS_FP64 0x00000200 #define EF_MIPS_ABI 0x0000f000 #define EF_MIPS_ARCH 0xf0000000 @@ -175,6 +176,18 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG]; #ifdef CONFIG_32BIT +/* + * In order to be sure that we don't attempt to execute an O32 binary which + * requires 64 bit FP (FR=1) on a system which does not support it we refuse + * to execute any binary which has bits specified by the following macro set + * in its ELF header flags. + */ +#ifdef CONFIG_MIPS_O32_FP64_SUPPORT +# define __MIPS_O32_FP64_MUST_BE_ZERO 0 +#else +# define __MIPS_O32_FP64_MUST_BE_ZERO EF_MIPS_FP64 +#endif + /* * This is used to ensure we don't load something for the wrong architecture. */ @@ -191,6 +204,8 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG]; __res = 0; \ if (((__h->e_flags & EF_MIPS_ABI) != 0) && \ ((__h->e_flags & EF_MIPS_ABI) != EF_MIPS_ABI_O32)) \ + __res = 0; \ + if (__h->e_flags & __MIPS_O32_FP64_MUST_BE_ZERO) \ __res = 0; \ \ __res; \ @@ -249,6 +264,11 @@ extern struct mips_abi mips_abi_n32; #define SET_PERSONALITY(ex) \ do { \ + if ((ex).e_flags & EF_MIPS_FP64) \ + clear_thread_flag(TIF_32BIT_FPREGS); \ + else \ + set_thread_flag(TIF_32BIT_FPREGS); \ + \ if (personality(current->personality) != PER_LINUX) \ set_personality(PER_LINUX); \ \ @@ -271,14 +291,18 @@ do { \ #endif #ifdef CONFIG_MIPS32_O32 -#define __SET_PERSONALITY32_O32() \ +#define __SET_PERSONALITY32_O32(ex) \ do { \ set_thread_flag(TIF_32BIT_REGS); \ set_thread_flag(TIF_32BIT_ADDR); \ + \ + if (!((ex).e_flags & EF_MIPS_FP64)) \ + set_thread_flag(TIF_32BIT_FPREGS); \ + \ current->thread.abi = &mips_abi_32; \ } while (0) #else -#define __SET_PERSONALITY32_O32() \ +#define __SET_PERSONALITY32_O32(ex) \ do { } while (0) #endif @@ -289,7 +313,7 @@ do { \ ((ex).e_flags & EF_MIPS_ABI) == 0) \ __SET_PERSONALITY32_N32(); \ else \ - __SET_PERSONALITY32_O32(); \ + __SET_PERSONALITY32_O32(ex); \ } while (0) #else #define __SET_PERSONALITY32(ex) do { } while (0) @@ -300,6 +324,7 @@ do { \ unsigned int p; \ \ clear_thread_flag(TIF_32BIT_REGS); \ + clear_thread_flag(TIF_32BIT_FPREGS); \ clear_thread_flag(TIF_32BIT_ADDR); \ \ if ((ex).e_ident[EI_CLASS] == ELFCLASS32) \ -- cgit v1.2.3