Unverified Commit ee72e0e7 authored by Vincent Chen's avatar Vincent Chen Committed by Palmer Dabbelt
Browse files

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: default avatarVincent Chen <vincentc@andestech.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarPalmer Dabbelt <palmer@sifive.com>
parent d18ebc27

arch/riscv/include/asm/bug.h

+6 −1
Original line number Diff line number Diff line
@@ -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;

arch/riscv/kernel/traps.c

+17 −3
Original line number Diff line number Diff line
@@ -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 */