Re: [PATCH bpf-next] riscv, bpf: fix some compiler error
From: tongtiangen
Date: Tue Nov 02 2021 - 23:06:55 EST
On 2021/11/2 23:45, Björn Töpel wrote:
On Tue, 2 Nov 2021 at 15:40, Tong Tiangen <tongtiangen@xxxxxxxxxx> 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@xxxxxxxxxx>
---
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@xxxxxxx/
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
.