| Message ID | 20210322012859.17083-1-yunqiang.su@cipunited.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v8] MIPS: force use FR=0 for FPXX binaries | expand |
Sorry. This is a bad version. I will send v9 later. YunQiang Su <yunqiang.su@cipunited.com> 于2021年3月22日周一 上午9:31写道： > > The MIPS FPU may have 3 mode: > FR=0: MIPS I style, all of the FPR are single. > FR=1: all 32 FPR can be double. > FRE: redirecting the rw of odd-FPR to the upper 32bit of even-double FPR. > > The binary may have 3 mode: > FP32: can only work with FR=0 and FRE mode > FPXX: can work with all of FR=0/FR=1/FRE mode. > FP64: can only work with FR=1 mode > > Some binary, for example the output of golang, may be mark as FPXX, > while in fact they are FP32. It is caused by the bug of design and linker: > Object produced by pure Go has no FP annotation while in fact they are FP32; > if we link them with the C module which marked as FPXX, > the result will be marked as FPXX. If these fake-FPXX binaries is executed > in FR=1 mode, some problem will happen. > > In Golang, now we add the FP32 annotation, so the future golang programs > won't have this problem. While for the existing binaries, we need a > kernel workaround. > > Currently, FR=1 mode is used for all FPXX binary if O32_FP64 supported is enabled, > it makes some wrong behivour of the binaries. > Since FPXX binary can work with both FR=1 and FR=0, we force it to use FR=0. > > Reference: > > https://web.archive.org/web/20180828210612/https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking > > https://go-review.googlesource.com/c/go/+/239217 > https://go-review.googlesource.com/c/go/+/237058 > > Signed-off-by: YunQiang Su <yunqiang.su@cipunited.com> > Cc: stable@vger.kernel.org # 4.19+ > --- > arch/mips/kernel/elf.c | 20 +++++++++++++------- > 1 file changed, 13 insertions(+), 7 deletions(-) > > diff --git a/arch/mips/kernel/elf.c b/arch/mips/kernel/elf.c > index 7b045d2a0b51..311c4fde910d 100644 > --- a/arch/mips/kernel/elf.c > +++ b/arch/mips/kernel/elf.c > @@ -232,11 +232,16 @@ int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr, > * that inherently require the hybrid FP mode. > * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or > * fpxx case. This is because, in any-ABI (or no-ABI) we have no FPU > - * instructions so we don't care about the mode. We will simply use > - * the one preferred by the hardware. In fpxx case, that ABI can > - * handle both FR=1 and FR=0, so, again, we simply choose the one > - * preferred by the hardware. Next, if we only use single-precision > - * FPU instructions, and the default ABI FPU mode is not good > + * instructions so we don't care about the mode. > + * In fpxx case, that ABI can handle all of FR=1/FR=0/FRE mode. > + * Here, we need to use FR=0 mode instead of FR=1, because some binaries > + * may be mark as FPXX by mistake due to bugs of design and linker: > + * The object produced by pure Go has no FP annotation, > + * then is treated as any-ABI by linker, although in fact they are FP32; > + * if any-ABI object is linked with FPXX object, the result will be mark as FPXX. > + * Then the problem happens: run FP32 binaries in FR=1 mode. > + * - If we only use single-precision FPU instructions, > + * and the default ABI FPU mode is not good > * (ie single + any ABI combination), we set again the FPU mode to the > * one is preferred by the hardware. Next, if we know that the code > * will only use single-precision instructions, shown by single being > @@ -248,8 +253,9 @@ int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr, > */ > if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1) > state->overall_fp_mode = FP_FRE; > - else if ((prog_req.fr1 && prog_req.frdefault) || > - (prog_req.single && !prog_req.frdefault)) > + else if (prog_req.fr1 && prog_req.frdefault) > + state->overall_fp_mode = FP_FR0; > + else if (prog_req.single && !prog_req.frdefault) > /* Make sure 64-bit MIPS III/IV/64R1 will not pick FR1 */ > state->overall_fp_mode = ((raw_current_cpu_data.fpu_id & MIPS_FPIR_F64) && > cpu_has_mips_r2_r6) ? > -- > 2.20.1 >
diff --git a/arch/mips/kernel/elf.c b/arch/mips/kernel/elf.c index 7b045d2a0b51..311c4fde910d 100644 --- a/arch/mips/kernel/elf.c +++ b/arch/mips/kernel/elf.c @@ -232,11 +232,16 @@ int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr, * that inherently require the hybrid FP mode. * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or * fpxx case. This is because, in any-ABI (or no-ABI) we have no FPU - * instructions so we don't care about the mode. We will simply use - * the one preferred by the hardware. In fpxx case, that ABI can - * handle both FR=1 and FR=0, so, again, we simply choose the one - * preferred by the hardware. Next, if we only use single-precision - * FPU instructions, and the default ABI FPU mode is not good + * instructions so we don't care about the mode. + * In fpxx case, that ABI can handle all of FR=1/FR=0/FRE mode. + * Here, we need to use FR=0 mode instead of FR=1, because some binaries + * may be mark as FPXX by mistake due to bugs of design and linker: + * The object produced by pure Go has no FP annotation, + * then is treated as any-ABI by linker, although in fact they are FP32; + * if any-ABI object is linked with FPXX object, the result will be mark as FPXX. + * Then the problem happens: run FP32 binaries in FR=1 mode. + * - If we only use single-precision FPU instructions, + * and the default ABI FPU mode is not good * (ie single + any ABI combination), we set again the FPU mode to the * one is preferred by the hardware. Next, if we know that the code * will only use single-precision instructions, shown by single being @@ -248,8 +253,9 @@ int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr, */ if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1) state->overall_fp_mode = FP_FRE; - else if ((prog_req.fr1 && prog_req.frdefault) || - (prog_req.single && !prog_req.frdefault)) + else if (prog_req.fr1 && prog_req.frdefault) + state->overall_fp_mode = FP_FR0; + else if (prog_req.single && !prog_req.frdefault) /* Make sure 64-bit MIPS III/IV/64R1 will not pick FR1 */ state->overall_fp_mode = ((raw_current_cpu_data.fpu_id & MIPS_FPIR_F64) && cpu_has_mips_r2_r6) ?
The MIPS FPU may have 3 mode: FR=0: MIPS I style, all of the FPR are single. FR=1: all 32 FPR can be double. FRE: redirecting the rw of odd-FPR to the upper 32bit of even-double FPR. The binary may have 3 mode: FP32: can only work with FR=0 and FRE mode FPXX: can work with all of FR=0/FR=1/FRE mode. FP64: can only work with FR=1 mode Some binary, for example the output of golang, may be mark as FPXX, while in fact they are FP32. It is caused by the bug of design and linker: Object produced by pure Go has no FP annotation while in fact they are FP32; if we link them with the C module which marked as FPXX, the result will be marked as FPXX. If these fake-FPXX binaries is executed in FR=1 mode, some problem will happen. In Golang, now we add the FP32 annotation, so the future golang programs won't have this problem. While for the existing binaries, we need a kernel workaround. Currently, FR=1 mode is used for all FPXX binary if O32_FP64 supported is enabled, it makes some wrong behivour of the binaries. Since FPXX binary can work with both FR=1 and FR=0, we force it to use FR=0. Reference: https://web.archive.org/web/20180828210612/https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking https://go-review.googlesource.com/c/go/+/239217 https://go-review.googlesource.com/c/go/+/237058 Signed-off-by: YunQiang Su <yunqiang.su@cipunited.com> Cc: stable@vger.kernel.org # 4.19+ --- arch/mips/kernel/elf.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)