RISCV: Clean up the common architectural code

This version of coreboot successfully starts a Harvey (Plan 9) kernel as a payload,
entering main() with no supporting assembly code for startup. The Harvey port
is not complete so it just panics but ... it gets started.

We provide a standard payload function that takes a pointer argument
and makes the jump from machine to supervisor mode;
the days of kernels running in machine mode are over.

We do some small tweaks to the virtual memory code. We temporarily
disable two functions that won't work on some targets as register
numbers changed between 1.7 and 1.9. Once lowrisc catches up
we'll reenable them.

We add the PAGETABLES to the memlayout.ld and use _pagetables in the virtual
memory setup code.

We now use the _stack and _estack from memlayout so we know where things are.
As time goes on maybe we can kill all the magic numbers.

Change-Id: I6caadfa9627fa35e31580492be01d4af908d31d9
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: https://review.coreboot.org/17058
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>

1 files changed, 32 insertions, 14 deletions

diff --git a/src/arch/riscv/virtual_memory.c b/src/arch/riscv/virtual_memory.c
index be8b4884d454..999d73cec8a2 100644
--- a/src/arch/riscv/virtual_memory.c
+++ b/src/arch/riscv/virtual_memory.c
@@ -21,6 +21,7 @@
 #include <console/console.h>
 #include <stdint.h>
 #include <vm.h>
+#include <symbols.h>
 
 pte_t* root_page_table;
 
@@ -94,7 +95,7 @@ static void print_page_table_at(pte_t *pt, intptr_t virt_addr, int level)
 
 /* Print the page table structures to the console */
 void print_page_table(void) {
-	print_page_table_at(root_page_table, 0, 0);
+	print_page_table_at((void *)(read_csr(sptbr) << RISCV_PGSHIFT), 0, 0);
 }
 
 void flush_tlb(void)
@@ -115,17 +116,17 @@ pte_t ptd_create(uintptr_t ppn)
 pte_t pte_create(uintptr_t ppn, int prot, int user)
 {
 	pte_t pte = (ppn << PTE_PPN_SHIFT) | PTE_R | PTE_V;
-	if (prot & PROT_WRITE)
+	if (prot & PTE_W)
 		pte |= PTE_W;
-	if (prot & PROT_EXEC)
+	if (prot & PTE_X)
 		pte |= PTE_X;
 	if (user)
 		pte |= PTE_U;
 	return pte;
 }
 
-void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, uintptr_t pageTableStart) {
-	pte_t* sbi_pt = (pte_t*) pageTableStart;
+void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, pte_t *sbi_pt)
+{
 	memset(sbi_pt, 0, RISCV_PGSIZE);
 	// need to leave room for sbi page
 	uintptr_t memorySize = 0x7F000000; // 0xFFF... - 0xFFFFFFFF81000000 - RISCV_PGSIZE
@@ -147,21 +148,32 @@ void init_vm(uintptr_t virtMemStart, uintptr_t physMemStart, uintptr_t pageTable
 		int l2_shift = RISCV_PGLEVEL_BITS + RISCV_PGSHIFT;
 		size_t l2_idx = (virtMemStart >> l2_shift) & ((1 << RISCV_PGLEVEL_BITS)-1);
 		l2_idx += ((vaddr - virtMemStart) >> l2_shift);
-		middle_pt[l2_idx] = pte_create(paddr >> RISCV_PGSHIFT, PROT_READ|PROT_WRITE|PROT_EXEC, 0);
+		middle_pt[l2_idx] = pte_create(paddr >> RISCV_PGSHIFT,
+					       PTE_U|PTE_R|PTE_W|PTE_X, 0);
 	}
 
 	// map SBI at top of vaddr space
-	uintptr_t num_sbi_pages = 1; // only need to map a single page for sbi interface
+	// only need to map a single page for sbi interface
+	uintptr_t num_sbi_pages = 1;
 	uintptr_t sbiStartAddress = (uintptr_t) &sbi_page;
 	uintptr_t sbiAddr = sbiStartAddress;
 	for (uintptr_t i = 0; i < num_sbi_pages; i++) {
 		uintptr_t idx = (1 << RISCV_PGLEVEL_BITS) - num_sbi_pages + i;
-		sbi_pt[idx] = pte_create(sbiAddr >> RISCV_PGSHIFT, PROT_READ|PROT_EXEC, 0);
+		sbi_pt[idx] = pte_create(sbiAddr >> RISCV_PGSHIFT,
+					 PTE_R|PTE_X, 0);
 		sbiAddr += RISCV_PGSIZE;
 	}
 	pte_t* sbi_pte = middle_pt + ((num_middle_pts << RISCV_PGLEVEL_BITS)-1);
 	*sbi_pte = ptd_create((uintptr_t)sbi_pt >> RISCV_PGSHIFT);
 
+	// IO space.
+	root_pt[0] = pte_create(0, PTE_W|PTE_R, 0);
+	root_pt[1] = pte_create(0x40000000>>RISCV_PGSHIFT,
+				PTE_W|PTE_R, 0);
+
+	// Start of RAM
+	root_pt[2] = pte_create(0x80000000>>RISCV_PGSHIFT,
+				PTE_W|PTE_R, 0);
 	mb();
 	root_page_table = root_pt;
 	uintptr_t ptbr = ((uintptr_t) root_pt) >> RISCV_PGSHIFT;
@@ -185,12 +197,13 @@ void initVirtualMemory(void) {
 		printk(BIOS_DEBUG, "-----------------------------\n");
 	}
 
+	// TODO: Figure out how to grab this from cbfs
 	printk(BIOS_DEBUG, "Initializing virtual memory...\n");
-	uintptr_t physicalStart = 0x90000000; // TODO: Figure out how to grab this from cbfs
-	uintptr_t virtualStart = 0xffffffff80000000;
-	uintptr_t pageTableStart = 0x91400000;
-	init_vm(virtualStart, physicalStart, pageTableStart);
+	uintptr_t physicalStart = 0x81000000;
+	uintptr_t virtualStart = 0xffffffff81000000;
+	init_vm(virtualStart, physicalStart, (pte_t *)_pagetables);
 	mb();
+	flush_tlb();
 
 #if IS_ENABLED(CONFIG_DEBUG_PRINT_PAGE_TABLES)
 	printk(BIOS_DEBUG, "Finished initializing virtual memory, starting walk...\n");
@@ -220,7 +233,12 @@ void mstatus_init(void)
 			| (1 << CAUSE_USER_ECALL)
 	);
 
+
 	/* Enable all user/supervisor-mode counters */
-	write_csr(mscounteren, 0b111);
-	write_csr(mucounteren, 0b111);
+	/* We'll turn these on once lowrisc gets their bitstream up to
+	 * 1.9. Right now there's no agreement on the values for these
+	 * architectural registers.
+	 */
+	//write_csr(mscounteren, 0b111);
+	//write_csr(mucounteren, 0b111);
 }