Merge branch 'master' of github.com:fxlin/p1-kernel

fxlin · Feb 29, 2024 · 29a4228 · 29a4228
2 parents 2a3e599 + 913b72f
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diff --git a/docs/exp6/rpi-os.md b/docs/exp6/rpi-os.md
@@ -76,8 +76,8 @@ Notable points:
 
 * MMU starts memory translation process by locating the base address of PGD. MMU locates the base address from the `TTBRx_EL1` register which should be set by the kernel. TTBR = translation table base register.
 
-  * bits [63-47] = 0xffff (all 1s). MMU uses `ttbr1_el1`. This is meant for the kernel space. 
-  * bits [63-47] = 0x0 (all 1s). MMU uses `ttbr0_el1`. This is meant for the user process. 
+  * bits [63-48] = 0xffff (all 1s). MMU uses `ttbr1_el1`. This is meant for the kernel space. 
+  * bits [63-48] = 0x0 (all 0s). MMU uses `ttbr0_el1`. This is meant for the user process. 
   * Each process has its own address space. Therefore, it has its own copy of page table tree, starting from PGD. Therefore, the kernel keeps a separate PGD base address for each process. That is, the kernel virtualizes PGD for processes. During a context switch, the kernel loads the PGD base of the next process to `ttbr0_el1`.
 
 * MMU walks the pgtable tree to look up the physical address. A virtual address uses only 48 out of 64 available bits.  When doing a translation, MMU splits an address into 4 parts:
@@ -823,7 +823,7 @@ All other details of the forking procedure work exactly in the same way, as they
 
 > Q: does our fork() implement COW? 
 
-<!--- ### Allocating new pages on demand --->
+<!--- ### Nope... it copies over all pages & contents. --->
 
 ## Demand paging
 

diff --git a/docs/gdb.md b/docs/gdb.md
@@ -124,7 +124,11 @@ print (short[10])*mem_map
 ```
 b *0xffff0000
 ```
+### Disassemble at given addr
 
+```
+disas 0xffff0000
+```
 ### Function/source lookup
 
 Look up type of a given symbol 
@@ -142,7 +146,11 @@ List source at a given addr
 list *0x10000000
 list *fn 
 ```
-
+### Watchpoint 
+Will break if the given memory addr is altered 
+```
+watch *0xffff0000
+```
 ## The GDB "dashboard" enhancement
 
 The basic GDB UI is too primitive to beginners. We provide you an enhancement called GDB-dashboard. The upstream source is [here](https://github.com/fxlin/gdb-dashboard-aarch64). I adapted it for aarch64. Screenshot: