RISC-V Fixes for 6.2-rc7

* A build fix to avoid static branches in cpu_relax(), which greatly
   inflates the jump tables and breaks at least
   CONFIG_CC_OPTIMIZE_FOR_SIZE=y.
 * A fix for a kernel panic when probing impossible instruction
   positions.
 * A fix to disable unwind tables, which are enabled by default for
   GCC-13 and result in unhandled relocations in modules.
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Merge tag 'riscv-for-linus-6.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:

 - A build fix to avoid static branches in cpu_relax(), which greatly
   inflates the jump tables and breaks at least
   CONFIG_CC_OPTIMIZE_FOR_SIZE=y.

 - A fix for a kernel panic when probing impossible instruction
   positions.

 - A fix to disable unwind tables, which are enabled by default for
   GCC-13 and result in unhandled relocations in modules.

* tag 'riscv-for-linus-6.2-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: disable generation of unwind tables
  riscv: kprobe: Fixup kernel panic when probing an illegal position
  riscv: Fix build with CONFIG_CC_OPTIMIZE_FOR_SIZE=y

arch/riscv/Makefile

@@ -80,6 +80,9 @@ ifeq ($(CONFIG_PERF_EVENTS),y)
         KBUILD_CFLAGS += -fno-omit-frame-pointer
 endif
 
+# Avoid generating .eh_frame sections.
+KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables
+
 KBUILD_CFLAGS_MODULE += $(call cc-option,-mno-relax)
 KBUILD_AFLAGS_MODULE += $(call as-option,-Wa$(comma)-mno-relax)
 

arch/riscv/include/asm/hwcap.h

@@ -70,7 +70,6 @@ static_assert(RISCV_ISA_EXT_ID_MAX <= RISCV_ISA_EXT_MAX);
  */
 enum riscv_isa_ext_key {
 	RISCV_ISA_EXT_KEY_FPU,		/* For 'F' and 'D' */
-	RISCV_ISA_EXT_KEY_ZIHINTPAUSE,
 	RISCV_ISA_EXT_KEY_SVINVAL,
 	RISCV_ISA_EXT_KEY_MAX,
 };
@@ -91,8 +90,6 @@ static __always_inline int riscv_isa_ext2key(int num)
 		return RISCV_ISA_EXT_KEY_FPU;
 	case RISCV_ISA_EXT_d:
 		return RISCV_ISA_EXT_KEY_FPU;
-	case RISCV_ISA_EXT_ZIHINTPAUSE:
-		return RISCV_ISA_EXT_KEY_ZIHINTPAUSE;
 	case RISCV_ISA_EXT_SVINVAL:
 		return RISCV_ISA_EXT_KEY_SVINVAL;
 	default:

arch/riscv/include/asm/vdso/processor.h

@@ -4,30 +4,26 @@
 
 #ifndef __ASSEMBLY__
 
-#include <linux/jump_label.h>
 #include <asm/barrier.h>
-#include <asm/hwcap.h>
 
 static inline void cpu_relax(void)
 {
-	if (!static_branch_likely(&riscv_isa_ext_keys[RISCV_ISA_EXT_KEY_ZIHINTPAUSE])) {
 #ifdef __riscv_muldiv
-		int dummy;
-		/* In lieu of a halt instruction, induce a long-latency stall. */
-		__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
+	int dummy;
+	/* In lieu of a halt instruction, induce a long-latency stall. */
+	__asm__ __volatile__ ("div %0, %0, zero" : "=r" (dummy));
 #endif
-	} else {
-		/*
-		 * Reduce instruction retirement.
-		 * This assumes the PC changes.
-		 */
-#ifdef CONFIG_TOOLCHAIN_HAS_ZIHINTPAUSE
-		__asm__ __volatile__ ("pause");
+
+#ifdef __riscv_zihintpause
+	/*
+	 * Reduce instruction retirement.
+	 * This assumes the PC changes.
+	 */
+	__asm__ __volatile__ ("pause");
 #else
-		/* Encoding of the pause instruction */
-		__asm__ __volatile__ (".4byte 0x100000F");
+	/* Encoding of the pause instruction */
+	__asm__ __volatile__ (".4byte 0x100000F");
 #endif
-	}
 	barrier();
 }
 

arch/riscv/kernel/probes/kprobes.c

@@ -48,6 +48,21 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
 	post_kprobe_handler(p, kcb, regs);
 }
 
+static bool __kprobes arch_check_kprobe(struct kprobe *p)
+{
+	unsigned long tmp  = (unsigned long)p->addr - p->offset;
+	unsigned long addr = (unsigned long)p->addr;
+
+	while (tmp <= addr) {
+		if (tmp == addr)
+			return true;
+
+		tmp += GET_INSN_LENGTH(*(u16 *)tmp);
+	}
+
+	return false;
+}
+
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	unsigned long probe_addr = (unsigned long)p->addr;
@@ -55,6 +70,9 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
 	if (probe_addr & 0x1)
 		return -EILSEQ;
 
+	if (!arch_check_kprobe(p))
+		return -EILSEQ;
+
 	/* copy instruction */
 	p->opcode = *p->addr;