Re: Point where target instructions are read

[Richard Henderson <richard.henderson@linaro.org>]

On 4/1/24 09:50, Gautam Bhat wrote:
> Hi,
> 
> Some background: I am trying to write a CPU emulator for MSP430 with
> Qemu. I am loading the MSP430 program as follows using the generic
> device loader:
> 
> /qemu-system-msp430 -machine msp430-launchpad -device
> loader,file=simple_test -d in_asm,out_asm
> 
> I have implemented somewhat the TranslatorOps callbacks and my sample
> output with some prints is as follows:
> 
> ===msp430_tr_disas_log:204===
> 
> OUT: [size=51]
>   -- guest addr 0x00000000000007fa + tb prologue
> 0x7fff6403fe00:  8b 5d f0                 movl     -0x10(%rbp), %ebx
> 0x7fff6403fe03:  85 db                    testl    %ebx, %ebx
> 0x7fff6403fe05:  0f 8c 1c 00 00 00        jl       0x7fff6403fe27
> 0x7fff6403fe0b:  c6 45 f4 01              movb     $1, -0xc(%rbp)
> 0x7fff6403fe0f:  e9 00 00 00 00           jmp      0x7fff6403fe14
> 0x7fff6403fe14:  c7 45 00 fc 07 00 00     movl     $0x7fc, (%rbp)
> 0x7fff6403fe1b:  48 8d 05 1e ff ff ff     leaq     -0xe2(%rip), %rax
> 0x7fff6403fe22:  e9 f1 01 fc ff           jmp      0x7fff64000018
> 0x7fff6403fe27:  48 8d 05 15 ff ff ff     leaq     -0xeb(%rip), %rax
> 0x7fff6403fe2e:  e9 e5 01 fc ff           jmp      0x7fff64000018
> 
> ===gen_intermediate_code:251===
> ===msp430_tr_init_disas_context:84===
> ===msp430_tr_tb_start:99===
> ===msp430_tr_insn_start:107===
> ===msp430_tr_translate_insn:122===
> CTX Dump State
> ==============
> pc_first 2044
> pc_next 2044
> is_jmp 0
> max_insns 1
> num_insns 1
> TB flags: 1
> TB cflags: 4278190081
> TB CS base: 0
> TB PC: 2044
> ==============
> Opcode: 0
> is_jmp: 1
> DISAS_TOO_MANY ===msp430_tr_tb_stop:170===
> 
> I was trying to find out where exactly in the Qemu code does it read
> the target instructions from the file loaded (I could trace it to
> load_elf(...) loading the FW file)

Yes, the contents of the file are loaded within load_elf().


> and call my TranslatorOps
> callbacks.  I get the above output continuously in a loop. Also when
> the device generic loader is used, should I set the program counter to
> a specific value?

The boot process must cooperate somehow.

When using loader, you must link the image such that it loads at the pc reset address 
defined by the architecture manual.


r~