powerpc/8xx: Map 32Mb of RAM at init.

At the time being, initial MMU setup allows 24 Mbytes
of DATA and 8 Mbytes of code.

Some debug setup like CONFIG_KASAN generate huge
kernels with text size over the 8M limit and data over the
24 Mbytes limit.

Here is an 8xx kernel compiled with CONFIG_KASAN_INLINE for
one of my boards:

[root@po16846vm linux-powerpc]# size -x vmlinux
   text	   data	    bss	    dec	    hex	filename
0x111019c	0x41b0d4	0x490de0	26984528	19bc050	vmlinux

This patch maps up to 32 Mbytes code based on _einittext symbol
and allows 32 Mbytes of memory instead of 24.
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/head_8xx.S

@@ -337,8 +337,8 @@ InstructionTLBMiss:
 	rlwinm	r10, r10, 16, 0xfff8
 	cmpli	cr0, r10, PAGE_OFFSET@h
 #ifndef CONFIG_PIN_TLB_TEXT
-	/* It is assumed that kernel code fits into the first 8M page */
-0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x0800000)@h
+	/* It is assumed that kernel code fits into the first 32M */
+0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x2000000)@h
 	patch_site	0b, patch__itlbmiss_linmem_top
 #endif
 #endif
@@ -434,7 +434,7 @@ DataStoreTLBMiss:
 #ifndef CONFIG_PIN_TLB_IMMR
 	cmpli	cr6, r10, VIRT_IMMR_BASE@h
 #endif
-0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x1800000)@h
+0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x2000000)@h
 	patch_site	0b, patch__dtlbmiss_linmem_top
 
 	mfspr	r10, SPRN_M_TWB	/* Get level 1 table */
@@ -886,28 +886,11 @@ initial_mmu:
 	mtspr	SPRN_MD_CTR, r10	/* remove PINNED DTLB entries */
 
 	tlbia			/* Invalidate all TLB entries */
-#ifdef CONFIG_PIN_TLB_TEXT
-	lis	r8, MI_RSV4I@h
-	ori	r8, r8, 0x1c00
-
-	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
-#endif
-
 #ifdef CONFIG_PIN_TLB_DATA
 	oris	r10, r10, MD_RSV4I@h
 	mtspr	SPRN_MD_CTR, r10	/* Set data TLB control */
 #endif
 
-	/* Now map the lower 8 Meg into the ITLB. */
-	lis	r8, KERNELBASE@h	/* Create vaddr for TLB */
-	ori	r8, r8, MI_EVALID	/* Mark it valid */
-	mtspr	SPRN_MI_EPN, r8
-	li	r8, MI_PS8MEG /* Set 8M byte page */
-	ori	r8, r8, MI_SVALID	/* Make it valid */
-	mtspr	SPRN_MI_TWC, r8
-	li	r8, MI_BOOTINIT		/* Create RPN for address 0 */
-	mtspr	SPRN_MI_RPN, r8		/* Store TLB entry */
-
 	lis	r8, MI_APG_INIT@h	/* Set protection modes */
 	ori	r8, r8, MI_APG_INIT@l
 	mtspr	SPRN_MI_AP, r8
@@ -937,6 +920,34 @@ initial_mmu:
 	mtspr	SPRN_MD_RPN, r8
 #endif
 
+	/* Now map the lower RAM (up to 32 Mbytes) into the ITLB. */
+#ifdef CONFIG_PIN_TLB_TEXT
+	lis	r8, MI_RSV4I@h
+	ori	r8, r8, 0x1c00
+#endif
+	li	r9, 4				/* up to 4 pages of 8M */
+	mtctr	r9
+	lis	r9, KERNELBASE@h		/* Create vaddr for TLB */
+	li	r10, MI_PS8MEG | MI_SVALID	/* Set 8M byte page */
+	li	r11, MI_BOOTINIT		/* Create RPN for address 0 */
+	lis	r12, _einittext@h
+	ori	r12, r12, _einittext@l
+1:
+#ifdef CONFIG_PIN_TLB_TEXT
+	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
+	addi	r8, r8, 0x100
+#endif
+
+	ori	r0, r9, MI_EVALID		/* Mark it valid */
+	mtspr	SPRN_MI_EPN, r0
+	mtspr	SPRN_MI_TWC, r10
+	mtspr	SPRN_MI_RPN, r11		/* Store TLB entry */
+	addis	r9, r9, 0x80
+	addis	r11, r11, 0x80
+
+	cmpl	cr0, r9, r12
+	bdnzf	gt, 1b
+
 	/* Since the cache is enabled according to the information we
 	 * just loaded into the TLB, invalidate and enable the caches here.
 	 * We should probably check/set other modes....later.

arch/powerpc/mm/8xx_mmu.c

@@ -112,6 +112,9 @@ unsigned long __init mmu_mapin_ram(unsigned long top)
 			mmu_patch_cmp_limit(&patch__itlbmiss_linmem_top, 0);
 	} else {
 		mapped = top & ~(LARGE_PAGE_SIZE_8M - 1);
+		if (!IS_ENABLED(CONFIG_PIN_TLB_TEXT))
+			mmu_patch_cmp_limit(&patch__itlbmiss_linmem_top,
+					    _ALIGN(__pa(_einittext), 8 << 20));
 	}
 
 	mmu_patch_cmp_limit(&patch__dtlbmiss_linmem_top, mapped);
@@ -140,8 +143,8 @@ void __init setup_initial_memory_limit(phys_addr_t first_memblock_base,
 	 */
 	BUG_ON(first_memblock_base != 0);
 
-	/* 8xx can only access 24MB at the moment */
-	memblock_set_current_limit(min_t(u64, first_memblock_size, 0x01800000));
+	/* 8xx can only access 32MB at the moment */
+	memblock_set_current_limit(min_t(u64, first_memblock_size, 0x02000000));
 }
 
 /*