riscv: switch to relative extable and other improvements

Similar as other architectures such as arm64, x86 and so on, use
offsets relative to the exception table entry values rather than
absolute addresses for both the exception locationand the fixup.
And recently, arm64 and x86 remove anonymous out-of-line fixups, we
want to acchieve the same result.

1 files changed, 52 insertions, 14 deletions

diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
index ddb7d3b99e89..05978f78579f 100644
--- a/arch/riscv/mm/extable.c
+++ b/arch/riscv/mm/extable.c
@@ -7,27 +7,65 @@
  */
 
 
+#include <linux/bitfield.h>
 #include <linux/extable.h>
 #include <linux/module.h>
 #include <linux/uaccess.h>
+#include <asm/asm-extable.h>
+#include <asm/ptrace.h>
 
-#if defined(CONFIG_BPF_JIT) && defined(CONFIG_ARCH_RV64I)
-int rv_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs);
-#endif
+static inline unsigned long
+get_ex_fixup(const struct exception_table_entry *ex)
+{
+	return ((unsigned long)&ex->fixup + ex->fixup);
+}
+
+static bool ex_handler_fixup(const struct exception_table_entry *ex,
+			     struct pt_regs *regs)
+{
+	regs->epc = get_ex_fixup(ex);
+	return true;
+}
+
+static inline void regs_set_gpr(struct pt_regs *regs, unsigned int offset,
+				unsigned long val)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return;
+
+	if (!offset)
+		*(unsigned long *)((unsigned long)regs + offset) = val;
+}
+
+static bool ex_handler_uaccess_err_zero(const struct exception_table_entry *ex,
+					struct pt_regs *regs)
+{
+	int reg_err = FIELD_GET(EX_DATA_REG_ERR, ex->data);
+	int reg_zero = FIELD_GET(EX_DATA_REG_ZERO, ex->data);
+
+	regs_set_gpr(regs, reg_err, -EFAULT);
+	regs_set_gpr(regs, reg_zero, 0);
+
+	regs->epc = get_ex_fixup(ex);
+	return true;
+}
 
-int fixup_exception(struct pt_regs *regs)
+bool fixup_exception(struct pt_regs *regs)
 {
-	const struct exception_table_entry *fixup;
+	const struct exception_table_entry *ex;
 
-	fixup = search_exception_tables(regs->epc);
-	if (!fixup)
-		return 0;
+	ex = search_exception_tables(regs->epc);
+	if (!ex)
+		return false;
 
-#if defined(CONFIG_BPF_JIT) && defined(CONFIG_ARCH_RV64I)
-	if (regs->epc >= BPF_JIT_REGION_START && regs->epc < BPF_JIT_REGION_END)
-		return rv_bpf_fixup_exception(fixup, regs);
-#endif
+	switch (ex->type) {
+	case EX_TYPE_FIXUP:
+		return ex_handler_fixup(ex, regs);
+	case EX_TYPE_BPF:
+		return ex_handler_bpf(ex, regs);
+	case EX_TYPE_UACCESS_ERR_ZERO:
+		return ex_handler_uaccess_err_zero(ex, regs);
+	}
 
-	regs->epc = fixup->fixup;
-	return 1;
+	BUG();
 }