shim: New handover mechanism from Shim (a.k.a. Entry.S + Start.c) to …

…kernel. WIP.

See the 'Bootstrapping' section from README.md.

Signed-off-by: TunaCici <[email protected]>

Kernel/Arch/ARM64/Entry.S

@@ -1,6 +1,6 @@
 /*
- * Entry point for the WesterOS kernel for ARMv8
- * Initialize the Stack pointer, clear the BSS and jump to Start.c
+ * Entry point for the WesterOS kernel for ARM64
+ * Initializes stack pointer, clears the BSS and jump to Start.c
  *
  * Originally from: sudharson14/xv6-OS-for-arm-v8
  * Modified by: Tuna CICI	
@@ -16,13 +16,13 @@ _start:
 	msr     spsel, x0
 	isb
 
-	/* Init stack (`init_stktop` bytes) */
-	adrp    x0, init_stktop
+	/* Init stack (`_shim_stack_top` bytes) */
+	adrp    x0, _shim_stack_top
 	mov     sp, x0
 
-	/* Clear the entry bss section, the svc stack, and kernel page table */
-	ldr     x1, =edata_entry
-	ldr     x2, =end_entry
+	/* Clear the shim bss section & the svc stack */
+	ldr     x1, =_shim_bss_start
+	ldr     x2, =_shim_end
 	mov     x3, #0x00
 
 	/* Enable access to FPU & Advanced SIMD (NEON) */

Kernel/Start.c → Kernel/Arch/ARM64/Start.c

@@ -1,31 +1,36 @@
 /*
- * Early boot stage. Sanity checks for hardware devices & "calls" kmain(...)
+ * Entry point for the WesterOS kernel for ARM64 cntd.
+ * Initialize CPU cores, setup the iniital page tables & enable MMU
+ * Finally, pass information & control to the kernel
  *
  * Author: Tuna CICI
  */
 
 #include <stdint.h>
-#include <stdarg.h>
 
 #include "ARM64/Machine.h"
 #include "ARM64/RegisterSet.h"
 #include "ARM64/Memory.h"
 
+#include "Boot.h"
 #include "MemoryLayout.h"
 
 /* in Main.c */
-extern void kmain(uint64_t l0_pgtbl[], uint64_t l1_pgtbl[], uint64_t vector_tbl,
-                  void* dtb, uint32_t dtb_size);
+extern void kmain(boot_sysinfo, uint64_t);
 
 /* in Kernel/kernel.ld */
-extern uint64_t kstart;
-extern uint64_t kend;
-extern uint64_t kvma_base;
-uint64_t kernel_start = (uint64_t) (&kstart);
+extern uint64_t _k_phy_base;
+extern uint64_t _k_vir_base;
+extern uint64_t _k_size;
+extern uint64_t _k_stack_top;
+uint64_t k_phy_base = (uint64_t) (&_k_phy_base);
+uint64_t k_vir_base = (uint64_t) (&_k_vir_base);
+uint64_t k_size = (uint64_t) (&_k_size);
+uint64_t k_stack_top = (uint64_t) (&_k_stack_top);
 
 /* in Kernel/Arch/ARM64/Vector.S */
-extern uint64_t vector_table; 
-uint64_t vector_tbl = (uint64_t) (&vector_table);
+extern uint64_t _vector_table; 
+uint64_t vector_table = (uint64_t) (&_vector_table);
 
 /* Higher half - TTBR1_EL1 */
 uint64_t k_l0_pgtbl[ENTRY_SIZE] __attribute__((aligned(GRANULE_SIZE)));
@@ -103,7 +108,7 @@ void _init_kernel_pgtbl(void)
                 blk = BLK_SET_AF(blk, 1);
                 blk = BLK_SET_NG(blk, 0);
 
-                blk = BLK_SET_L1_OA(blk, kernel_start);
+                blk = BLK_SET_L1_OA(blk, k_phy_base);
 
                 blk = BLK_SET_HINT(blk, 0);
                 blk = BLK_SET_PXN(blk, 0);
@@ -174,7 +179,7 @@ void _init_user_pgtbl(void)
                 blk = BLK_SET_AIDX(blk, DEVICE_nGnRE_IDX);
                 blk = BLK_SET_NS(blk, 0);
                 blk = BLK_SET_AP(blk, AP_PRIV_RW);
-                blk = BLK_SET_SH(blk, SH_OUTER);
+                blk = BLK_SET_SH(blk, SH_NON);
                 blk = BLK_SET_AF(blk, 1);
                 blk = BLK_SET_NG(blk, 0);
 
@@ -280,11 +285,13 @@ void _init_sctlr(void)
 
 void start(void)
 {
-        volatile uint32_t arch = 0;
-        volatile uint32_t val32 = 0;
-        volatile uint64_t val64 = 0;
+        uint32_t arch = 0;
+        uint32_t val32 = 0;
+        uint64_t val64 = 0;
         char buff[64] = {0};
 
+        boot_sysinfo boot_params = {0};
+
         /* Hard-coded device/board info */
         /* TODO: Replace this with a DTB parser */
         const char      *_cpuModel  = "Cortex A-72";
@@ -351,6 +358,16 @@ void start(void)
                 break;
         }
 
+        /* Populate boot_sysinfo - will be passed to the kernel */
+        boot_params.k_phy_base = k_phy_base;
+        boot_params.k_vir_base = k_vir_base;
+        boot_params.k_size = k_size;
+
+        boot_params.vector_base = vector_table;
+
+        boot_params.dtb_base = DTB_START;
+        boot_params.dtb_size = DTB_SIZE;
+
         /* Disable interrupts */
         debug_disable();
         irq_enable();
@@ -391,7 +408,7 @@ void start(void)
                 _puts("Unmasked\n");
         }
 
-        MSR("VBAR_EL1", vector_tbl);
+        MSR("VBAR_EL1", vector_table);
         isb();
 
         _puts("Initializing Translation Control Register (TCR)\n");
@@ -423,5 +440,8 @@ void start(void)
         _puts("| Everything is OK. Calling the kernel now...        |\n");
         _puts("+----------------------------------------------------+\n");
 
-        kmain(0 , 0, 0, 0, 0);
+        /* Jump the stack pointer the stack pointer */
+        asm volatile ("mov sp, %0" :: "r" (k_stack_top));
+
+        kmain(boot_params, 0);
 }

Kernel/Arch/ARM64/Vector.S

@@ -6,7 +6,7 @@
 
 .text
 .balign 2048
-.global vector_table
+.global _vector_table
 
 .macro store_regs
         stp     x0,  x1,  [sp, #16 * 0]
@@ -63,7 +63,7 @@
         ldp     x0,  x1,  [sp, #16 * 0]
 .endm
 
-vector_table:
+_vector_table:
 
 /*
  * 1. Current EL where SP -> SP_EL0 - TODO

Kernel/Main.c

@@ -7,7 +7,8 @@
 #include <stdint.h>
 
 #include "ARM64/Machine.h"
-#include "Memory/Virtual.h"
+
+#include "Boot.h"
 #include "MemoryLayout.h"
 
 #include "LibKern/String.h"
@@ -20,8 +21,6 @@
 #include "Memory/Physical.h"
 #include "Memory/Virtual.h"
 
-extern uint64_t kend; /* in Kernel/kernel.ld */
-
 /*
  * Kernel entry.
  *
@@ -32,12 +31,11 @@ extern uint64_t kend; /* in Kernel/kernel.ld */
  *      dtb: Device Tree Blob base address
  *      dtb_size: Device Tree Blob size in bytes
  */
-void kmain(uint64_t l0_pgtbl[], uint64_t l1_pgtbl[], uint64_t vector_tbl,
-           void* dtb, uint32_t dtb_size)
+void kmain(boot_sysinfo boot_params)
 {
-        const void *kernel_end = &kend;
-
+        volatile void *important_ahh = &boot_params;
         uint64_t mem_start = 0x0;
+        volatile void *important_ahh2 = &mem_start;
         uint64_t mem_end = 0x0;
 
         /* 0. Get HW Information */
@@ -62,8 +60,8 @@ void kmain(uint64_t l0_pgtbl[], uint64_t l1_pgtbl[], uint64_t vector_tbl,
         }
 
         /* X. Setup vector tables */
-        if (vector_tbl) {
-                MSR("VBAR_EL1", vector_tbl);
+        if (boot_params.vector_base) {
+                MSR("VBAR_EL1", boot_params.vector_base);
                 isb();
         } else {
                 klog("[kmain] NULL vector table is given!\n");
@@ -72,7 +70,7 @@ void kmain(uint64_t l0_pgtbl[], uint64_t l1_pgtbl[], uint64_t vector_tbl,
         /* 1. Init BootMem */
         klog("[kmain] Initializing early memory manager...\n");
 
-        uint64_t pageCount = bootmem_init(kernel_end);
+        uint64_t pageCount = bootmem_init((const void*) (boot_params.k_phy_base + boot_params.k_size));
 
         klog("[kmain] Pages available: %lu (%lu KiB) in bootmem\n",
                 pageCount, (pageCount * PAGE_SIZE) / 1024
@@ -82,7 +80,7 @@ void kmain(uint64_t l0_pgtbl[], uint64_t l1_pgtbl[], uint64_t vector_tbl,
         klog("[kmain] Initializing physical memory manager...\n");
 
         uint64_t blockCount = init_allocator(
-                (const void *) kernel_end + pageCount * PAGE_SIZE,
+                (const void *) boot_params.k_phy_base + boot_params.k_size + pageCount * PAGE_SIZE,
                 (const void *) mem_end
         );
 

Makefile

@@ -66,14 +66,14 @@ GTEST_CXXFLAGS = ${INCLUDES} -g -Wall -Wextra -std=c++20 \
 # Without it I'd get errors like: undefined symbol "_kernel_pgtbl".
 # The files like Kernel/Main.c uses symbols defined in Kernel/Kernel.ld
 # When compiling tests ALL objects are are given to the clang/ld.
-# Since Start.C and Main.c will [probably] never gonna get unit tested
+# Since Start.c and Main.c will [probably] never gonna get unit tested
 # We can just ignore "unreslved symbols" with -dead-strip.
 # > maybe in the future I can find a better way. who knows...
 
 # Project source files
 SRCS = \
+	Kernel/Arch/ARM64/Start.c \
 	Kernel/Arch/ARM64/Exception.c \
-	Kernel/Start.c \
 	Kernel/Main.c \
 	Kernel/Library/LibKern/DeviceTree.c \
 	Kernel/Library/LibKern/Console.c \