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authorPaul Burton <paul.burton@imgtec.com>2013-11-22 13:12:07 +0000
committerRalf Baechle <ralf@linux-mips.org>2014-01-13 23:40:56 +0100
commit597ce1723e0fa0bdbe2ae4c94f18da6e29b92635 (patch)
tree21f67268915b8457dd305c6bcf7ac905772fd0ee /arch/mips/kernel/binfmt_elfo32.c
parent56a22d21bf9744315f56b2bbd6416170f27b7765 (diff)
downloadop-kernel-dev-597ce1723e0fa0bdbe2ae4c94f18da6e29b92635.zip
op-kernel-dev-597ce1723e0fa0bdbe2ae4c94f18da6e29b92635.tar.gz
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.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/arch/mips/kernel/binfmt_elfo32.c b/arch/mips/kernel/binfmt_elfo32.c
index 202e581..7faf5f2 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; \
})
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