Nasm isn't willing to emit near jump

[Techel]

Consider following code:

Code: Select all

org 0x12345
bits 32
lolo:
hlt
jmp near lolo

Then the code is compiled with nasm, the output is:

Code: Select all

F4 E9 [b]FA FF FF FF [/b]

As you can see, this isn't a near jump but a short one. How can I bring nasm to emit a near jump?

[Octocontrabass]

That is a near jump. What you want is a short jump.

[Techel]

Ah, I thought near means intrasegment absolute and short means relative, but near jumps can also be relative
There isn't a jump instruction with a absolute immediate destination, except far jump? No there is none, I know

[Brendan]

Hi,

Ah, I thought near means intrasegment absolute and short means relative, but near jumps can also be relative

"Short" is 1-byte (signed) displacement, "near" is 2-byte or 4-byte (signed) displacement.

There isn't a jump instruction with a absolute immediate destination, except far jump? No there is none, I know

You can jump to an absolute target in a register (e.g. "jmp eax") and you can use indirect jumps (e.g. "jmp [pointer]"); but there's no jumping to an absolute immediate.

Note that there's very few cases where "jump to absolute immediate" makes sense but can't be converted into a near jump. The only case I can think of is jumping from position independent code to code at a fixed/known address.


Cheers,

Brendan