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

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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>
This commit is contained in:
Vincent Chen 2019-03-05 11:23:34 +08:00 committed by Palmer Dabbelt
parent d18ebc274c
commit ee72e0e70c
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GPG Key ID: EF4CA1502CCBAB41
2 changed files with 23 additions and 4 deletions
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7
arch/riscv/include/asm/bug.h
View File

@ -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;

20
arch/riscv/kernel/traps.c
View File

@ -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 */