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samuri25404
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Joined: 04 May 2007
Posts: 955
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 Posted: Mon Oct 29, 2007 2:44 pm Post subject: assemblerunit.pas |
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I was looking through the assemblerunit.pas file in the source (I'm writing a program, and I'm curious on how to get the opcodes), and I found the following:
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//opcode part (bytes)
type Textraopcode=(eo_none,
eo_reg0,eo_reg1,eo_reg2,eo_reg3,eo_reg4,eo_reg5,eo_reg6,eo_reg7, // /digit
eo_reg, // /r
eo_cb,eo_cw,eo_cd,eo_cp,
eo_ib,eo_iw,eo_id,
eo_prb,eo_prw,eo_prd,
eo_pi
);
//parameter part
type tparam=(par_noparam,
//constant
par_1,
par_3,
par_al,
par_ax,
par_eax,
par_cl,
par_dx,
par_cs,
par_ds,
par_es,
par_ss,
par_fs,
par_gs,
//regs
par_r8,
par_r16,
par_r32,
par_mm,
par_xmm,
par_st,
par_st0,
par_sreg,
par_cr,
par_dr,
//memorylocs
par_m8,
par_m16,
par_m32,
par_m64,
par_m80,
par_m128,
par_moffs8,
par_moffs16,
par_moffs32,
//regs+memorylocs
par_rm8,
par_rm16,
par_rm32,
par_r32_m16,
par_mm_m32,
par_mm_m64,
par_xmm_m32,
par_xmm_m64,
par_xmm_m128,
//values
par_imm8,
par_imm16,
par_imm32,
//relatives
par_rel8,
par_rel16,
par_rel32);
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I know Pascal well enough (Computer Science I) to understand the type definitions, but I'm not exactly sure what they're all supposed to mean, why they're there, etc
I saw the gigantic opcode list, and I saw the parameters and extraopcodes being used, but I'm really not sure what they all mean; I understand the simple things like
| Code: |
par_ax,
par_eax,
par_al
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etc, but I'm not far enough into Assembly to really understand the mm/xmm (for example).
I don't understand any of the "extraopcode" thing.
Would someone please clarify this?
~~~
On a side note, it took me long enough, but I realized how good at Delphi/Assembly DB really is. Don't ridicule me on my late discovery...
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Dark Byte
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Joined: 09 May 2003
Posts: 25788
Location: The netherlands
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| Posted: Mon Oct 29, 2007 3:49 pm Post subject: |
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get the intel instruction set reference book i'll help with the meaning of the instructions (e.g eo_reg1 etc...)
Anyhow, the extraopcode part is used for assembler instructions that extend the instruction into the modmr byte (e.g ADD and AND, they both have a situtation where the byte starts with 80 and then followed by a modrm where the R field constains a 0 (add) or a 4 (and) , so thats why add is defined as eo_reg0, and and as eo_reg4)
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samuri25404
Grandmaster Cheater
Reputation: 7
Joined: 04 May 2007
Posts: 955
Location: Why do you care?
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| Posted: Mon Oct 29, 2007 4:42 pm Post subject: |
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That would make a lot of sense if I knew what modrm meant (Google provided nothing usefull).
I understand that the last byte of the opcode is based on parameters alone (I've tested many times), and I understand that the first couple of bytes are related to the opcode--however there are some opcodes with the same names but different parameters, and I'm guessing that the extraopcode is used to help find the correct opcode.
Edit:
Ok, I've found a PDF file of the book you're talking about, and it explains everything--which I thank you quite heavily for.
Anyways, I'm going on a school trip today (out of state), so I can read up on it during then.
Muchos gracias, senor!
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