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MIPS: Support for 64-bit FP with O32 binaries

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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 <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/6154/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton
2013-11-22 13:12:07 +00:00
committed by Ralf Baechle
parent 56a22d21bf
commit 597ce1723e
19 changed files with 449 additions and 236 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
arch/mips/include/asm/elf.h
View File

@@ -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) \