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| author |   Paul Burton <paul.burton@imgtec.com> | 2013-11-22 13:12:07 +0000 |
|---|---|---|
| committer |   Ralf Baechle <ralf@linux-mips.org> | 2014-01-13 23:40:56 +0100 |
| commit | 597ce1723e0fa0bdbe2ae4c94f18da6e29b92635 (patch) | |
| tree | 21f67268915b8457dd305c6bcf7ac905772fd0ee /arch/mips/kernel/binfmt_elfo32.c | |
| parent | MIPS: Remove unused {en,dis}able_fpu macros (diff) | |
| download | linux-dev-597ce1723e0fa0bdbe2ae4c94f18da6e29b92635.tar.xz linux-dev-597ce1723e0fa0bdbe2ae4c94f18da6e29b92635.zip | |
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 <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>
Diffstat (limited to 'arch/mips/kernel/binfmt_elfo32.c')
| -rw-r--r-- | arch/mips/kernel/binfmt_elfo32.c | 14 |
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/mips/kernel/binfmt_elfo32.c b/arch/mips/kernel/binfmt_elfo32.c index 202e581e6096..7faf5f2bee25 100644 --- a/arch/mips/kernel/binfmt_elfo32.c +++ b/arch/mips/kernel/binfmt_elfo32.c @@ -28,6 +28,18 @@ typedef double elf_fpreg_t; typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG]; /* + * 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. */ #define elf_check_arch(hdr) \ @@ -44,6 +56,8 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG]; 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; \ }) |