Embedded and Real-Time Operating Systems by K. C. Wang

Author:K. C. Wang
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

1.create a child process ready to run in Kmode, return −1 if fails;

2.copy a section of parent’s ustack from parent.usp all the way back to where it called

pid = vfork(), e.g. the bottom 1024 entries; set child usp = parent usp - 1204;

3.let child pgdir = parent pgdir, so that they share the same page table;

4.mark child as vforked; return child pid;

For simplicity, in the vfork algorithm we do not mark the shared page table entries READ-ONLY. Corresponding to vfork, the exec function must be modified to account for possible shared images. The following shows the modified exec algorithm

/******************** Modified exec algorithm *********************/

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