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Date: Wed, 3 Nov 2021 11:06:31 +0800
From: tongtiangen <tongtiangen@...wei.com>
To: Björn Töpel <bjorn.topel@...il.com>
CC: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Palmer Dabbelt <palmerdabbelt@...gle.com>,
Albert Ou <aou@...s.berkeley.edu>,
Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
linux-riscv <linux-riscv@...ts.infradead.org>,
LKML <linux-kernel@...r.kernel.org>,
Netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf-next] riscv, bpf: fix some compiler error
On 2021/11/2 23:45, Björn Töpel wrote:
> On Tue, 2 Nov 2021 at 15:40, Tong Tiangen <tongtiangen@...wei.com> wrote:
>>
>> This patch fix two compile errors:
>> 1. when CONFIG_BPF_JIT and CONFIG_ARCH_32I is open, There is the following
>> compiler error:
>> error: undefined symbol: rv_bpf_fixup_exception
>>
>
> Good catch for the RV32!
>
>> 2. when CONFIG_BPF_JIT and CONFIG_ARCH_64I is open, There is the following
>> compiler error (W=1):
>> error: no previous prototype for 'rv_bpf_fixup_exception'
>>
>> In this patch, asm/extable.h is introduced, the rv_bpf_fixup_exception
>> function declaration is added to this file. in addition, the definition of
>> exception_table_entry is moved from asm-generic/extable.h to this file.
>>
>
> This is way too complicated. More below.
>
>> Fixes: 252c765bd764 ("riscv, bpf: Add BPF exception tables")
>> Signed-off-by: Tong Tiangen <tongtiangen@...wei.com>
>> ---
>> arch/riscv/include/asm/Kbuild | 1 -
>> arch/riscv/include/asm/extable.h | 49 ++++++++++++++++++++++++++++++++
>> arch/riscv/include/asm/uaccess.h | 13 ---------
>> arch/riscv/mm/extable.c | 8 +-----
>> 4 files changed, 50 insertions(+), 21 deletions(-)
>> create mode 100644 arch/riscv/include/asm/extable.h
>>
>> diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
>> index 445ccc97305a..57b86fd9916c 100644
>> --- a/arch/riscv/include/asm/Kbuild
>> +++ b/arch/riscv/include/asm/Kbuild
>> @@ -1,6 +1,5 @@
>> # SPDX-License-Identifier: GPL-2.0
>> generic-y += early_ioremap.h
>> -generic-y += extable.h
>> generic-y += flat.h
>> generic-y += kvm_para.h
>> generic-y += user.h
>> diff --git a/arch/riscv/include/asm/extable.h b/arch/riscv/include/asm/extable.h
>> new file mode 100644
>> index 000000000000..aa0332b053fb
>> --- /dev/null
>> +++ b/arch/riscv/include/asm/extable.h
>> @@ -0,0 +1,49 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +#ifndef __ASM_EXTABLE_H
>> +#define __ASM_EXTABLE_H
>> +
>> +/*
>> + * The exception table consists of pairs of addresses: the first is the
>> + * address of an instruction that is allowed to fault, and the second is
>> + * the address at which the program should continue. No registers are
>> + * modified, so it is entirely up to the continuation code to figure out
>> + * what to do.
>> + *
>> + * All the routines below use bits of fixup code that are out of line
>> + * with the main instruction path. This means when everything is well,
>> + * we don't even have to jump over them. Further, they do not intrude
>> + * on our cache or tlb entries.
>> + */
>> +struct exception_table_entry {
>> + unsigned long insn, fixup;
>> +};
>> +
>> +struct pt_regs;
>> +int fixup_exception(struct pt_regs *regs);
>> +
>> +#if defined(CONFIG_MMU)
>> +static inline bool rv_in_bpf_jit(struct pt_regs *regs)
>> +{
>> + if (!IS_ENABLED(CONFIG_BPF_JIT) || !IS_ENABLED(CONFIG_64BIT))
>> + return false;
>> +
>> + return regs->epc >= BPF_JIT_REGION_START && regs->epc < BPF_JIT_REGION_END;
>> +}
>> +#else
>> +static inline bool rv_in_bpf_jit(struct pt_regs *regs)
>> +{
>> + return false;
>> +}
>> +#endif
>> +
>> +#if defined(CONFIG_BPF_JIT) && defined(CONFIG_64BIT)
>> +int rv_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs);
>> +#else
>> +static inline int rv_bpf_fixup_exception(const struct exception_table_entry *ex,
>> + struct pt_regs *regs)
>> +{
>> + return 0;
>> +}
>> +#endif
>> +
>> +#endif
>> diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
>> index f314ff44c48d..96ea91dc0e9c 100644
>> --- a/arch/riscv/include/asm/uaccess.h
>> +++ b/arch/riscv/include/asm/uaccess.h
>> @@ -56,19 +56,6 @@ static inline int __access_ok(unsigned long addr, unsigned long size)
>> return size <= TASK_SIZE && addr <= TASK_SIZE - size;
>> }
>>
>> -/*
>> - * The exception table consists of pairs of addresses: the first is the
>> - * address of an instruction that is allowed to fault, and the second is
>> - * the address at which the program should continue. No registers are
>> - * modified, so it is entirely up to the continuation code to figure out
>> - * what to do.
>> - *
>> - * All the routines below use bits of fixup code that are out of line
>> - * with the main instruction path. This means when everything is well,
>> - * we don't even have to jump over them. Further, they do not intrude
>> - * on our cache or tlb entries.
>> - */
>> -
>> #define __LSW 0
>> #define __MSW 1
>>
>> diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
>> index 18bf338303b6..264f465db5bb 100644
>> --- a/arch/riscv/mm/extable.c
>> +++ b/arch/riscv/mm/extable.c
>> @@ -11,10 +11,6 @@
>> #include <linux/module.h>
>> #include <linux/uaccess.h>
>>
>> -#ifdef CONFIG_BPF_JIT
>> -int rv_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs);
>> -#endif
>> -
>> int fixup_exception(struct pt_regs *regs)
>> {
>> const struct exception_table_entry *fixup;
>> @@ -23,10 +19,8 @@ int fixup_exception(struct pt_regs *regs)
>> if (!fixup)
>> return 0;
>>
>> -#ifdef CONFIG_BPF_JIT
>> - if (regs->epc >= BPF_JIT_REGION_START && regs->epc < BPF_JIT_REGION_END)
>> + if (rv_in_bpf_jit(regs))
>> return rv_bpf_fixup_exception(fixup, regs);
>> -#endif
>>
>
> The only changes that are needed are:
> 1. Simply gate with CONFIG_BPF_JIT && CONFIG_ARCH_RV64I, instead of of
> CONFIG_BPF_JIT
>
> 2. Forward declaration of the rv_bpf_fixup_exception() in bpf_jit_comp64.c.
>
Hi Björn:
From the perspective of development, introduce asm/extable.h is also prepare for the
subsequent modification of exception_table_entry, such as:
1. https://lkml.org/lkml/2021/10/20/591
2. https://lore.kernel.org/linux-arm-kernel/20211019160219.5202-11-mark.rutland@arm.com/
Therefore, the prototype declarations and definitions related to kernel config are placed in head file,
which can avoid compiler error and simplify the rendering of functions.
Thanks.
Tong.
>
> Björn
> .
>
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