CODEWITHSUNDEEP
kernelmipscpu-architecturemips32
Henok Tesfaye
Henok Tesfaye

Reputation: 9570

How does the kernel stores the read string input from the user in MIPS?

The instructions to read and store string input from the keyboard is not clear in MIPS. How is the read string put into the label namespace?

.data
    namespace: .space 20
.txt
    li $v0,8
    la $a0,namespace
    li $a1,20
    syscall

Upvotes: 0

Views: 177

Answers (1)

Peter Cordes
Peter Cordes

Reputation: 364532

The kernel can use user-space memory mappings and addresses, and you passed it the address in $a0. You also passed the buffer length in $a1, so it knows how many bytes it's allowed to store.

So the kernel gets data from an I/O device and then uses sw or sb instructions to store it into the buffer you passed.

(Or if you're using MARS / SPIM, syscall traps to the interpreter / emulator / simulator code, and isn't running MIPS instructions at all. Unlike a real MIPS machine running Linux or whatever.)

Upvotes: 1

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