[Qemu-devel] Monitoring write to memory

[Qemu-devel] Monitoring write to memory

[Jun Koi]

[-- Attachment #1: Type: text/plain, Size: 1025 bytes --]

Hello,

I am trying to monitor all the memory writing events inside Qemu by
instrumenting tcg_gen_qemu_st8, tcg_gen_qemu_st16, tcg_gen_qemu_st32,
tcg_gen_qemu_st64,
as followings:


// in tcg-op.h

void helper_checkmem(int64_t data, int64_t address);  // this is declared
elsewhere

static inline void tcg_gen_qemu_st8(struct uc_struct *uc, TCGv arg, TCGv
addr, int mem_index)
{
#if TARGET_LONG_BITS == 32
    TCGArg args[2] = { GET_TCGV_I32(arg), GET_TCGV_I32(addr) };
#else
    TCGArg args[2] = { GET_TCGV_I64(arg), GET_TCGV_I64(addr) };
#endif
    tcg_gen_callN(&tcg_ctx, helper_checkmem, dh_retvar_void, 2, args);
    tcg_gen_qemu_st_tl(uc, arg, addr, mem_index, MO_UB);
}


However, when I compile, helper_checkmem() is never called at runtime when
memory is accessed.
What is wrong with my code?


Another problem is that: how can I cast i32 to i64? I wanted to do:

    TCGArg args[2] = { GET_TCGV_I32(arg), GET_TCGV_I64(addr) };

but in 32bit mode, addr is TCGv, so GET_TCGV_I64(addr) gets error report.


Thank you.

[-- Attachment #2: Type: text/html, Size: 1390 bytes --]

Re: [Qemu-devel] Monitoring write to memory

[Christopher Covington]

On 07/01/2015 08:23 AM, Jun Koi wrote:
> Hello,
> 
> I am trying to monitor all the memory writing events inside Qemu by
> instrumenting tcg_gen_qemu_st8, tcg_gen_qemu_st16, tcg_gen_qemu_st32,
> tcg_gen_qemu_st64, as followings:
> 
> 
> // in tcg-op.h
> 
> void helper_checkmem(int64_t data, int64_t address);  // this is declared
> elsewhere
> 
> static inline void tcg_gen_qemu_st8(struct uc_struct *uc, TCGv arg, TCGv addr,
> int mem_index)
> {
> #if TARGET_LONG_BITS == 32
>     TCGArg args[2] = { GET_TCGV_I32(arg), GET_TCGV_I32(addr) };
> #else
>     TCGArg args[2] = { GET_TCGV_I64(arg), GET_TCGV_I64(addr) };
> #endif
>     tcg_gen_callN(&tcg_ctx, helper_checkmem, dh_retvar_void, 2, args);
>     tcg_gen_qemu_st_tl(uc, arg, addr, mem_index, MO_UB);
> }
> 
> 
> However, when I compile, helper_checkmem() is never called at runtime when
> memory is accessed.
> What is wrong with my code?

What guest code are you running? Does it have a strb instruction? If you're
able to code a simple bare metal test case you should be able to debug qemu
with gdb to see what code paths are taken and why the ones you anticipated aren't.

Chris

-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project