Re: [PATCH] kvm-userspace: x86: Support for breakpoints in ROM code

[Jan Kiszka <jan.kiszka@siemens.com>]

Jan Kiszka wrote:
> Align qemu-kvm-x86 with upstream kvm support /wrt software breakpoint
> support in ROM code.

Hmm, this might not be needed as kvm-userspace is not protecting its
ROM. That's why I didn't pushed this so far. However, aligning isn't
bad. But dropping this duplication would be better...

Jan

> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
> 
>  qemu/qemu-kvm-x86.c |   29 ++++++++++++++++++++++++-----
>  1 files changed, 24 insertions(+), 5 deletions(-)
> 
> diff --git a/qemu/qemu-kvm-x86.c b/qemu/qemu-kvm-x86.c
> index 06ef775..05a9c4c 100644
> --- a/qemu/qemu-kvm-x86.c
> +++ b/qemu/qemu-kvm-x86.c
> @@ -680,12 +680,32 @@ void kvm_arch_cpu_reset(CPUState *env)
>      }
>  }
>  
> -int kvm_arch_insert_sw_breakpoint(CPUState *env, struct kvm_sw_breakpoint *bp)
> +#ifdef KVM_CAP_SET_GUEST_DEBUG
> +static int kvm_patch_opcode_byte(CPUState *env, target_ulong addr, uint8_t val)
>  {
> -    uint8_t int3 = 0xcc;
> +    target_phys_addr_t phys_page_addr;
> +    unsigned long pd;
> +    uint8_t *ptr;
> +
> +    phys_page_addr = cpu_get_phys_page_debug(env, addr & TARGET_PAGE_MASK);
> +    if (phys_page_addr == -1)
> +        return -EINVAL;
> +
> +    pd = cpu_get_physical_page_desc(phys_page_addr);
> +    if ((pd & ~TARGET_PAGE_MASK) != IO_MEM_RAM &&
> +        (pd & ~TARGET_PAGE_MASK) != IO_MEM_ROM && !(pd & IO_MEM_ROMD))
> +        return -EINVAL;
>  
> +    ptr = phys_ram_base + (pd & TARGET_PAGE_MASK)
> +                        + (addr & ~TARGET_PAGE_MASK);
> +    *ptr = val;
> +    return 0;
> +}
> +
> +int kvm_arch_insert_sw_breakpoint(CPUState *env, struct kvm_sw_breakpoint *bp)
> +{
>      if (cpu_memory_rw_debug(env, bp->pc, (uint8_t *)&bp->saved_insn, 1, 0) ||
> -        cpu_memory_rw_debug(env, bp->pc, &int3, 1, 1))
> +        kvm_patch_opcode_byte(env, bp->pc, 0xcc))
>          return -EINVAL;
>      return 0;
>  }
> @@ -695,12 +715,11 @@ int kvm_arch_remove_sw_breakpoint(CPUState *env, struct kvm_sw_breakpoint *bp)
>      uint8_t int3;
>  
>      if (cpu_memory_rw_debug(env, bp->pc, &int3, 1, 0) || int3 != 0xcc ||
> -        cpu_memory_rw_debug(env, bp->pc, (uint8_t *)&bp->saved_insn, 1, 1))
> +        kvm_patch_opcode_byte(env, bp->pc, bp->saved_insn))
>          return -EINVAL;
>      return 0;
>  }
>  
> -#ifdef KVM_CAP_SET_GUEST_DEBUG
>  static struct {
>      target_ulong addr;
>      int len;
> --
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