From a0216b678a95f099a16172cc4a67ad5aa6a89583 Mon Sep 17 00:00:00 2001
From: Kazuhito Hagio <k-hagio-ab@nec.com>
Date: Fri, 29 Jan 2021 11:40:25 +0900
Subject: [PATCH] [PATCH 3/3] arm64: support flipped VA and 52-bit kernel VA

Linux 5.4 and later kernels for arm64 changed the kernel VA space
arrangement and introduced 52-bit kernel VAs by merging branch
commit b333b0ba2346.  Support 5.9+ kernels with vmcoreinfo entries
and 5.4+ kernels with best guessing.

However, the following conditions are not supported for now due to
no necessary information provided from kernel:
(1) 5.4 <= kernels <= 5.8 and
    - if PA_BITS=52 && VA_BITS!=52
    - with -x option if vabits_actual=52
(2) kernels < 5.4 with CONFIG_ARM64_USER_VA_BITS_52=y

(1) should be supported with kernel commit bbdbc11804ff and
1d50e5d0c5052 adding necessary information to vmcoreinfo.

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
Reviewed-by: Pingfan Liu <piliu@redhat.com>
---
 arch/arm64.c   | 100 +++++++++++++++++++++++++++++++++++++++++--------
 makedumpfile.c |   2 +
 makedumpfile.h |   1 +
 3 files changed, 88 insertions(+), 15 deletions(-)

diff --git a/arch/arm64.c b/arch/arm64.c
index 2916b4f..1072178 100644
--- a/makedumpfile-1.6.7/arch/arm64.c
+++ b/makedumpfile-1.6.7/arch/arm64.c
@@ -47,6 +47,8 @@ typedef struct {
 static int lpa_52_bit_support_available;
 static int pgtable_level;
 static int va_bits;
+static int vabits_actual;
+static int flipped_va;
 static unsigned long kimage_voffset;
 
 #define SZ_4K			4096
@@ -58,7 +60,6 @@ static unsigned long kimage_voffset;
 #define PAGE_OFFSET_42		((0xffffffffffffffffUL) << 42)
 #define PAGE_OFFSET_47		((0xffffffffffffffffUL) << 47)
 #define PAGE_OFFSET_48		((0xffffffffffffffffUL) << 48)
-#define PAGE_OFFSET_52		((0xffffffffffffffffUL) << 52)
 
 #define pgd_val(x)		((x).pgd)
 #define pud_val(x)		(pgd_val((x).pgd))
@@ -218,12 +219,20 @@ pmd_page_paddr(pmd_t pmd)
 #define pte_index(vaddr)		(((vaddr) >> PAGESHIFT()) & (PTRS_PER_PTE - 1))
 #define pte_offset(dir, vaddr)		(pmd_page_paddr((*dir)) + pte_index(vaddr) * sizeof(pte_t))
 
+/*
+ * The linear kernel range starts at the bottom of the virtual address
+ * space. Testing the top bit for the start of the region is a
+ * sufficient check and avoids having to worry about the tag.
+ */
+#define is_linear_addr(addr)	(flipped_va ?	\
+	(!((unsigned long)(addr) & (1UL << (vabits_actual - 1)))) : \
+	(!!((unsigned long)(addr) & (1UL << (vabits_actual - 1)))))
+
 static unsigned long long
 __pa(unsigned long vaddr)
 {
-	if (kimage_voffset == NOT_FOUND_NUMBER ||
-			(vaddr >= PAGE_OFFSET))
-		return (vaddr - PAGE_OFFSET + info->phys_base);
+	if (kimage_voffset == NOT_FOUND_NUMBER || is_linear_addr(vaddr))
+		return ((vaddr & ~PAGE_OFFSET) + info->phys_base);
 	else
 		return (vaddr - kimage_voffset);
 }
@@ -253,6 +262,7 @@ static int calculate_plat_config(void)
 			(PAGESIZE() == SZ_64K && va_bits == 42)) {
 		pgtable_level = 2;
 	} else if ((PAGESIZE() == SZ_64K && va_bits == 48) ||
+			(PAGESIZE() == SZ_64K && va_bits == 52) ||
 			(PAGESIZE() == SZ_4K && va_bits == 39) ||
 			(PAGESIZE() == SZ_16K && va_bits == 47)) {
 		pgtable_level = 3;
@@ -263,6 +273,7 @@ static int calculate_plat_config(void)
 				PAGESIZE(), va_bits);
 		return FALSE;
 	}
+	DEBUG_MSG("pgtable_level: %d\n", pgtable_level);
 
 	return TRUE;
 }
@@ -270,6 +281,9 @@ static int calculate_plat_config(void)
 unsigned long
 get_kvbase_arm64(void)
 {
+	if (flipped_va)
+		return PAGE_OFFSET;
+
 	return (0xffffffffffffffffUL << va_bits);
 }
 
@@ -382,22 +396,54 @@ get_va_bits_from_stext_arm64(void)
 	return TRUE;
 }
 
+static void
+get_page_offset_arm64(void)
+{
+	ulong page_end;
+	int vabits_min;
+
+	/*
+	 * See arch/arm64/include/asm/memory.h for more details of
+	 * the PAGE_OFFSET calculation.
+	 */
+	vabits_min = (va_bits > 48) ? 48 : va_bits;
+	page_end = -(1UL << (vabits_min - 1));
+
+	if (SYMBOL(_stext) > page_end) {
+		flipped_va = TRUE;
+		info->page_offset = -(1UL << vabits_actual);
+	} else {
+		flipped_va = FALSE;
+		info->page_offset = -(1UL << (vabits_actual - 1));
+	}
+
+	DEBUG_MSG("page_offset   : %lx (from page_end check)\n",
+		info->page_offset);
+}
+
 int
 get_machdep_info_arm64(void)
 {
+	/* Check if va_bits is still not initialized. If still 0, call
+	 * get_versiondep_info() to initialize the same.
+	 */
+	if (!va_bits)
+		get_versiondep_info_arm64();
+
 	/* Determine if the PA address range is 52-bits: ARMv8.2-LPA */
 	if (NUMBER(MAX_PHYSMEM_BITS) != NOT_FOUND_NUMBER) {
 		info->max_physmem_bits = NUMBER(MAX_PHYSMEM_BITS);
+		DEBUG_MSG("max_physmem_bits : %ld (vmcoreinfo)\n", info->max_physmem_bits);
 		if (info->max_physmem_bits == 52)
 			lpa_52_bit_support_available = 1;
-	} else
-		info->max_physmem_bits = 48;
+	} else {
+		if (va_bits == 52)
+			info->max_physmem_bits = 52; /* just guess */
+		else
+			info->max_physmem_bits = 48;
 
-	/* Check if va_bits is still not initialized. If still 0, call
-	 * get_versiondep_info() to initialize the same.
-	 */
-	if (!va_bits)
-		get_versiondep_info_arm64();
+		DEBUG_MSG("max_physmem_bits : %ld (guess)\n", info->max_physmem_bits);
+	}
 
 	if (!calculate_plat_config()) {
 		ERRMSG("Can't determine platform config values\n");
@@ -408,7 +454,6 @@ get_machdep_info_arm64(void)
 	info->section_size_bits = SECTIONS_SIZE_BITS;
 
 	DEBUG_MSG("kimage_voffset   : %lx\n", kimage_voffset);
-	DEBUG_MSG("max_physmem_bits : %ld\n", info->max_physmem_bits);
 	DEBUG_MSG("section_size_bits: %ld\n", info->section_size_bits);
 
 	return TRUE;
@@ -443,10 +488,35 @@ get_versiondep_info_arm64(void)
 		return FALSE;
 	}
 
-	info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
+	/*
+	 * See TCR_EL1, Translation Control Register (EL1) register
+	 * description in the ARMv8 Architecture Reference Manual.
+	 * Basically, we can use the TCR_EL1.T1SZ value to determine
+	 * the virtual addressing range supported in the kernel-space
+	 * (i.e. vabits_actual) since Linux 5.9.
+	 */
+	if (NUMBER(TCR_EL1_T1SZ) != NOT_FOUND_NUMBER) {
+		vabits_actual = 64 - NUMBER(TCR_EL1_T1SZ);
+		DEBUG_MSG("vabits_actual : %d (vmcoreinfo)\n", vabits_actual);
+	} else if ((va_bits == 52) && (SYMBOL(mem_section) != NOT_FOUND_SYMBOL)) {
+		/*
+		 * Linux 5.4 through 5.10 have the following linear space:
+		 *   48-bit: 0xffff000000000000 - 0xffff7fffffffffff
+		 *   52-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
+		 * and SYMBOL(mem_section) should be in linear space if
+		 * the kernel is configured with COMFIG_SPARSEMEM_EXTREME=y.
+		 */
+		if (SYMBOL(mem_section) & (1UL << (va_bits - 1)))
+			vabits_actual = 48;
+		else
+			vabits_actual = 52;
+		DEBUG_MSG("vabits_actual : %d (guess from mem_section)\n", vabits_actual);
+	} else {
+		vabits_actual = va_bits;
+		DEBUG_MSG("vabits_actual : %d (same as va_bits)\n", vabits_actual);
+	}
 
-	DEBUG_MSG("va_bits      : %d\n", va_bits);
-	DEBUG_MSG("page_offset  : %lx\n", info->page_offset);
+	get_page_offset_arm64();
 
 	return TRUE;
 }
diff --git a/makedumpfile.c b/makedumpfile.c
index 768eda4..fcd766b 100644
--- a/makedumpfile-1.6.7/makedumpfile.c
+++ b/makedumpfile-1.6.7/makedumpfile.c
@@ -2397,6 +2397,7 @@ write_vmcoreinfo_data(void)
 	WRITE_NUMBER("HUGETLB_PAGE_DTOR", HUGETLB_PAGE_DTOR);
 #ifdef __aarch64__
 	WRITE_NUMBER("VA_BITS", VA_BITS);
+	/* WRITE_NUMBER("TCR_EL1_T1SZ", TCR_EL1_T1SZ); should not exists */
 	WRITE_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
 	WRITE_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
 #endif
@@ -2836,6 +2837,7 @@ read_vmcoreinfo(void)
 	READ_NUMBER("KERNEL_IMAGE_SIZE", KERNEL_IMAGE_SIZE);
 #ifdef __aarch64__
 	READ_NUMBER("VA_BITS", VA_BITS);
+	READ_NUMBER("TCR_EL1_T1SZ", TCR_EL1_T1SZ);
 	READ_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
 	READ_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
 #endif
diff --git a/makedumpfile.h b/makedumpfile.h
index 0ed6417..97a5554 100644
--- a/makedumpfile-1.6.7/makedumpfile.h
+++ b/makedumpfile-1.6.7makedumpfile.h
@@ -2049,6 +2049,7 @@ struct number_table {
 	long	KERNEL_IMAGE_SIZE;
 #ifdef __aarch64__
 	long 	VA_BITS;
+	long	TCR_EL1_T1SZ;
 	unsigned long	PHYS_OFFSET;
 	unsigned long	kimage_voffset;
 #endif