riscv: Add the support for c.ebreak check in is_valid_bugaddr()

The macro __BUG_INSN currently is defined as the "ebreak" opcode.
The is_valid_bugaddr() function compares the instruction pointed to by
$sepc with macro __BUG_INSN to check whether the current trap exception
is caused by an "ebreak" instruction. However, this check flow is possibly
erroneous because if C extension is supported, the expected trap
instruction "ebreak" is possibly translated to "c.ebreak" by the assembler.
Therefore, it requires a mechanism to distinguish the length of the
instruction in $spec and compare it to the correct trap instruction.

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

diff --git a/arch/riscv/include/asm/bug.h b/arch/riscv/include/asm/bug.h
index 4d906d8..52a1fbd 100644 (file)
--- a/arch/riscv/include/asm/bug.h
+++ b/arch/riscv/include/asm/bug.h
@@ -21,7 +21,12 @@
 #include <asm/asm.h>
 
 #ifdef CONFIG_GENERIC_BUG
-#define __BUG_INSN     _AC(0x00100073, UL) /* ebreak */
+#define __INSN_LENGTH_MASK  _UL(0x3)
+#define __INSN_LENGTH_32    _UL(0x3)
+#define __COMPRESSED_INSN_MASK _UL(0xffff)
+
+#define __BUG_INSN_32  _UL(0x00100073) /* ebreak */
+#define __BUG_INSN_16  _UL(0x9002) /* c.ebreak */
 
 #ifndef __ASSEMBLY__
 typedef u32 bug_insn_t;

diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index cc94054..c34cc54 100644 (file)
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -118,6 +118,17 @@ DO_ERROR_INFO(do_trap_ecall_s,
 DO_ERROR_INFO(do_trap_ecall_m,
        SIGILL, ILL_ILLTRP, "environment call from M-mode");
 
+#ifdef CONFIG_GENERIC_BUG
+static inline unsigned long get_break_insn_length(unsigned long pc)
+{
+       bug_insn_t insn;
+
+       if (probe_kernel_address((bug_insn_t *)pc, insn))
+               return 0;
+       return (((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32) ? 4UL : 2UL);
+}
+#endif /* CONFIG_GENERIC_BUG */
+
 asmlinkage void do_trap_break(struct pt_regs *regs)
 {
 #ifdef CONFIG_GENERIC_BUG
@@ -129,8 +140,8 @@ asmlinkage void do_trap_break(struct pt_regs *regs)
                case BUG_TRAP_TYPE_NONE:
                        break;
                case BUG_TRAP_TYPE_WARN:
-                       regs->sepc += sizeof(bug_insn_t);
-                       return;
+                       regs->sepc += get_break_insn_length(regs->sepc);
+                       break;
                case BUG_TRAP_TYPE_BUG:
                        die(regs, "Kernel BUG");
                }
@@ -149,7 +160,10 @@ int is_valid_bugaddr(unsigned long pc)
                return 0;
        if (probe_kernel_address((bug_insn_t *)pc, insn))
                return 0;
-       return (insn == __BUG_INSN);
+       if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
+               return (insn == __BUG_INSN_32);
+       else
+               return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
 }
 #endif /* CONFIG_GENERIC_BUG */