[RFC PATCH 0/4] makedumpfile/arm64: support flipped VA and 52-bit kernel VA

[RFC PATCH 0/4] makedumpfile/arm64: support flipped VA and 52-bit kernel VA

[kazuhito.hagio]

Hi Bhupesh, Alexander, Pingfan and arm64 guys,

I've rewritten Bhupesh's v5 patch [1] in order to avoid some limitations and
now this patchset
- can be built on some old arm64 environments hopefully,
- can be built on x86_64 machines with TARGET=aarch64,
- can process vmcores on different version of kernel from captured version.

Could you test this?  The patchset is also on GitHub [2] and the commit
messages are to be written later.

However the following conditions are probably not supported:
- 5.11-rc is not taken into account
- 5.4 <= kernels <= 5.8 (*1)
  * if PA_BITS=52 && VA_BITS!=52
  * with -x option if vabits_actual=52
- kernels < 5.4 with CONFIG_ARM64_USER_VA_BITS_52=y (e.g. RHEL8 kernels)

(*1) supported with kernel commit bbdbc11804ff and 1d50e5d0c5052.

I think especially MAX_PHYSMEM_BITS cannot be guessed correctly only with
the entries in vmcoreinfo (even with Bhupesh's original patch), so basically
I would like distributions that uses 5.4 to 5.8 to backport Bhupesh's kernel
patches above if the patchset does not work well.

[1] http://lists.infradead.org/pipermail/kexec/2020-September/021336.html
[2] https://github.com/k-hagio/makedumpfile/commits/arm64.kh.test2

Kazuhito Hagio (4):
  Use ELF vmcoreinfo note for --mem-usage option
  arm64: use NUMBER(VA_BITS) in vmcoreinfo
  Get kernel version from OSRELEASE in vmcoreinfo
  arm64: support flipped VA and 52-bit kernel VA

 arch/arm64.c   | 155 ++++++++++++++++++++++++++++++++++++++++++++-------------
 makedumpfile.c |  32 ++++++++++--
 makedumpfile.h |   1 +
 3 files changed, 149 insertions(+), 39 deletions(-)

-- 
2.9.3


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[RFC PATCH 1/4] Use ELF vmcoreinfo note for --mem-usage option

[kazuhito.hagio]

From: Kazuhito Hagio <k-hagio-ab@nec.com>

Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
---
 makedumpfile.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/makedumpfile.c b/makedumpfile.c
index ecd63fa..199748b 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -11426,6 +11426,7 @@ int show_mem_usage(void)
 {
 	uint64_t vmcoreinfo_addr, vmcoreinfo_len;
 	struct cycle cycle = {0};
+	int vmcoreinfo = FALSE;
 
 	if (!is_crashkernel_mem_reserved()) {
 		ERRMSG("No memory is reserved for crashkernel!\n");
@@ -11437,9 +11438,22 @@ int show_mem_usage(void)
 	if (!open_files_for_creating_dumpfile())
 		return FALSE;
 
-	if (!get_elf_loads(info->fd_memory, info->name_memory))
+	if (!get_elf_info(info->fd_memory, info->name_memory))
 		return FALSE;
 
+	/*
+	 * /proc/kcore on Linux 4.19 and later kernels have vmcoreinfo note in
+	 * NOTE segment.  See commit 23c85094fe18.
+	 */
+	if (has_vmcoreinfo()) {
+		off_t offset;
+		unsigned long size;
+
+		get_vmcoreinfo(&offset, &size);
+		vmcoreinfo = read_vmcoreinfo_from_vmcore(offset, size, FALSE);
+		DEBUG_MSG("Read vmcoreinfo from NOTE segment: %d\n", vmcoreinfo);
+	}
+
 	if (!get_page_offset())
 		return FALSE;
 
@@ -11447,11 +11461,13 @@ int show_mem_usage(void)
 	if (!get_phys_base())
 		return FALSE;
 
-	if (!get_sys_kernel_vmcoreinfo(&vmcoreinfo_addr, &vmcoreinfo_len))
-		return FALSE;
+	if (!vmcoreinfo) {
+		if (!get_sys_kernel_vmcoreinfo(&vmcoreinfo_addr, &vmcoreinfo_len))
+			return FALSE;
 
-	if (!set_kcore_vmcoreinfo(vmcoreinfo_addr, vmcoreinfo_len))
-		return FALSE;
+		if (!set_kcore_vmcoreinfo(vmcoreinfo_addr, vmcoreinfo_len))
+			return FALSE;
+	}
 
 	if (!initial())
 		return FALSE;
-- 
2.9.3


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[RFC PATCH 2/4] arm64: use NUMBER(VA_BITS) in vmcoreinfo

[kazuhito.hagio]

From: Kazuhito Hagio <k-hagio-ab@nec.com>

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
---
 arch/arm64.c | 64 ++++++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 43 insertions(+), 21 deletions(-)

diff --git a/arch/arm64.c b/arch/arm64.c
index 3d7b416..61ec89a 100644
--- a/arch/arm64.c
+++ b/arch/arm64.c
@@ -345,6 +345,44 @@ get_stext_symbol(void)
 	return(found ? kallsym : FALSE);
 }
 
+static int
+get_va_bits_from_stext_arm64(void)
+{
+	ulong _stext;
+
+	_stext = get_stext_symbol();
+	if (!_stext) {
+		ERRMSG("Can't get the symbol of _stext.\n");
+		return FALSE;
+	}
+
+	/*
+	 * Derive va_bits as per arch/arm64/Kconfig. Note that this is a
+	 * best case approximation at the moment, as there can be
+	 * inconsistencies in this calculation (for e.g., for
+	 * 52-bit kernel VA case, the 48th bit is set in
+	 * the _stext symbol).
+	 */
+	if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
+		va_bits = 48;
+	} else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
+		va_bits = 47;
+	} else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
+		va_bits = 42;
+	} else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
+		va_bits = 39;
+	} else if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
+		va_bits = 36;
+	} else {
+		ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n");
+		return FALSE;
+	}
+
+	DEBUG_MSG("va_bits       : %d (approximation via _stext)\n", va_bits);
+
+	return TRUE;
+}
+
 int
 get_machdep_info_arm64(void)
 {
@@ -398,27 +436,11 @@ get_xen_info_arm64(void)
 int
 get_versiondep_info_arm64(void)
 {
-	ulong _stext;
-
-	_stext = get_stext_symbol();
-	if (!_stext) {
-		ERRMSG("Can't get the symbol of _stext.\n");
-		return FALSE;
-	}
-
-	/* Derive va_bits as per arch/arm64/Kconfig */
-	if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
-		va_bits = 36;
-	} else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
-		va_bits = 39;
-	} else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
-		va_bits = 42;
-	} else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
-		va_bits = 47;
-	} else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
-		va_bits = 48;
-	} else {
-		ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n");
+	if (NUMBER(VA_BITS) != NOT_FOUND_NUMBER) {
+		va_bits = NUMBER(VA_BITS);
+		DEBUG_MSG("va_bits      : %d (vmcoreinfo)\n", va_bits);
+	} else if (get_va_bits_from_stext_arm64() == FALSE) {
+		ERRMSG("Can't determine va_bits.\n");
 		return FALSE;
 	}
 
-- 
2.9.3


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[RFC PATCH 3/4] Get kernel version from OSRELEASE in vmcoreinfo

[kazuhito.hagio]

From: Kazuhito Hagio <k-hagio-ab@nec.com>

Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
---
 makedumpfile.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/makedumpfile.c b/makedumpfile.c
index 199748b..fdfe437 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -1182,6 +1182,7 @@ check_release(void)
 		}
 	}
 
+	info->kernel_version = FALSE;
 	info->kernel_version = get_kernel_version(info->system_utsname.release);
 	if (info->kernel_version == FALSE) {
 		ERRMSG("Can't get the kernel version.\n");
@@ -2480,6 +2481,9 @@ read_vmcoreinfo_basic_info(void)
 			if (strlen(info->release))
 				continue;
 			strcpy(info->release, buf + strlen(STR_OSRELEASE));
+
+			if (!info->kernel_version)
+				info->kernel_version = get_kernel_version(info->release);
 		}
 		if (strncmp(buf, STR_PAGESIZE, strlen(STR_PAGESIZE)) == 0) {
 			page_size = strtol(buf+strlen(STR_PAGESIZE),&endp,10);
-- 
2.9.3


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[RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA

[kazuhito.hagio]

From: Kazuhito Hagio <k-hagio-ab@nec.com>

Based on Bhupesh's patch and contains Pingfan's idea.

Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
---
 arch/arm64.c   | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 makedumpfile.c |  2 ++
 makedumpfile.h |  1 +
 3 files changed, 83 insertions(+), 15 deletions(-)

diff --git a/arch/arm64.c b/arch/arm64.c
index 61ec89a..4ece19d 100644
--- a/arch/arm64.c
+++ b/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;
 }
@@ -383,22 +394,54 @@ 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");
@@ -409,7 +452,6 @@ 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;
@@ -444,10 +486,33 @@ 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
+		 *  58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
+		 */
+		if (SYMBOL(mem_section) & (1UL << (52 - 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 fdfe437..37788ff 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -2396,6 +2396,7 @@ 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
@@ -2838,6 +2839,7 @@ 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 5f50080..a151da2 100644
--- a/makedumpfile.h
+++ b/makedumpfile.h
@@ -1999,6 +1999,7 @@ 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
-- 
2.9.3


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Re: [RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA

[piliu]

On 1/14/21 4:25 PM, kazuhito.hagio@gmail.com wrote:
> From: Kazuhito Hagio <k-hagio-ab@nec.com>
> 
> Based on Bhupesh's patch and contains Pingfan's idea.
> 
> Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
> Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> ---
>   arch/arm64.c   | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
>   makedumpfile.c |  2 ++
>   makedumpfile.h |  1 +
>   3 files changed, 83 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64.c b/arch/arm64.c
> index 61ec89a..4ece19d 100644
> --- a/arch/arm64.c
> +++ b/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;
>   }
> @@ -383,22 +394,54 @@ 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");
> @@ -409,7 +452,6 @@ 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;
> @@ -444,10 +486,33 @@ 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
> +		 *  58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
> +		 */
> +		if (SYMBOL(mem_section) & (1UL << (52 - 1)))

Sorry but I do not think any SYMBOL(x) is inside the range of linear 
mapping address. All of them should be beyond kimage_vaddr.

Having vabits_actual is introduced and precise to resolve 
is_lm_address(), but if it is not available, could we survive?

_PAGE_OFFSET(52) < _PAGE_END(52) < _PAGE_OFFSET(48) < _PAGE_END(48)
Translating into numbers:
0xfff0000000000000 < 0xfff8000000000000 < 0xffff000000000000 < 
0xffff800000000000

Refer to linux/Documentation/arm64/memory.rst, the line
     ffffa00010000000      fffff81ffffeffff         ~88TB          vmalloc

It comes to the conclusion that any symbol > SYMBOL(_text) > _PAGE_END(48).

So is_lm_address() can looks like
if (addr > _PAGE_END(48)), it is kimage
else, it is linear mapping

So even more aggressive, we can exclude the need of vabits_actual 
totally in this patch.

Thanks,
	Pingfan


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Re: [RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA

[Bhupesh SHARMA]

Hi Kazu,

On Thu, Jan 14, 2021 at 3:33 PM piliu <piliu@redhat.com> wrote:
>
>
>
> On 1/14/21 4:25 PM, kazuhito.hagio@gmail.com wrote:
> > From: Kazuhito Hagio <k-hagio-ab@nec.com>
> >
> > Based on Bhupesh's patch and contains Pingfan's idea.
> >
> > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
> > Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> > ---
> >   arch/arm64.c   | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
> >   makedumpfile.c |  2 ++
> >   makedumpfile.h |  1 +
> >   3 files changed, 83 insertions(+), 15 deletions(-)
> >
> > diff --git a/arch/arm64.c b/arch/arm64.c
> > index 61ec89a..4ece19d 100644
> > --- a/arch/arm64.c
> > +++ b/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;
> >   }
> > @@ -383,22 +394,54 @@ 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");
> > @@ -409,7 +452,6 @@ 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;
> > @@ -444,10 +486,33 @@ 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
> > +              *  58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
> > +              */
> > +             if (SYMBOL(mem_section) & (1UL << (52 - 1)))
>
> Sorry but I do not think any SYMBOL(x) is inside the range of linear
> mapping address. All of them should be beyond kimage_vaddr.
>
> Having vabits_actual is introduced and precise to resolve
> is_lm_address(), but if it is not available, could we survive?
>
> _PAGE_OFFSET(52) < _PAGE_END(52) < _PAGE_OFFSET(48) < _PAGE_END(48)
> Translating into numbers:
> 0xfff0000000000000 < 0xfff8000000000000 < 0xffff000000000000 <
> 0xffff800000000000
>
> Refer to linux/Documentation/arm64/memory.rst, the line
>      ffffa00010000000      fffff81ffffeffff         ~88TB          vmalloc
>
> It comes to the conclusion that any symbol > SYMBOL(_text) > _PAGE_END(48).
>
> So is_lm_address() can looks like
> if (addr > _PAGE_END(48)), it is kimage
> else, it is linear mapping
>
> So even more aggressive, we can exclude the need of vabits_actual
> totally in this patch.

As Pingfan noted, this approach still has issues and it failed on my
arm64 board in the limited testing I did today.

I will do some more testing tomorrow and come back with an approach
which addresses the same and also takes into account Pingfan's
concerns.

Thanks,
Bhupesh

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RE: [RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA

[HAGIO KAZUHITO(萩尾 一仁)]

Hi Pingfan, Bhupesh,

Thank you for your comments!

-----Original Message-----
> Hi Kazu,
> 
> On Thu, Jan 14, 2021 at 3:33 PM piliu <piliu@redhat.com> wrote:
> >
> >
> >
> > On 1/14/21 4:25 PM, kazuhito.hagio@gmail.com wrote:
> > > From: Kazuhito Hagio <k-hagio-ab@nec.com>
> > >
> > > Based on Bhupesh's patch and contains Pingfan's idea.
> > >
> > > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
> > > Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> > > ---
> > >   arch/arm64.c   | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
> > >   makedumpfile.c |  2 ++
> > >   makedumpfile.h |  1 +
> > >   3 files changed, 83 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/arch/arm64.c b/arch/arm64.c
> > > index 61ec89a..4ece19d 100644
> > > --- a/arch/arm64.c
> > > +++ b/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;
> > >   }
> > > @@ -383,22 +394,54 @@ 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");
> > > @@ -409,7 +452,6 @@ 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;
> > > @@ -444,10 +486,33 @@ 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
> > > +              *  58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
> > > +              */
> > > +             if (SYMBOL(mem_section) & (1UL << (52 - 1)))
> >
> > Sorry but I do not think any SYMBOL(x) is inside the range of linear
> > mapping address. All of them should be beyond kimage_vaddr.

As for this, SYMBOL(mem_section) is a bit special and shows the value in the
mem_section variable, not the address of it, by kernel commit a0b1280368d1.

Actually on my tiny arm64 board..

# strings /proc/kcore | less
...
OSRELEASE=5.4.0-1025-raspi
PAGESIZE=4096
SYMBOL(init_uts_ns)=ffffd6db0fa10568
SYMBOL(node_online_map)=ffffd6db0fa0a808
SYMBOL(swapper_pg_dir)=ffffd6db0f42b000
SYMBOL(_stext)=ffffd6db0e481000
SYMBOL(vmap_area_list)=ffffd6db0fa51680
SYMBOL(mem_map)=ffffd6db0fbc0240
SYMBOL(contig_page_data)=ffffd6db0faed6c0
SYMBOL(mem_section)=ffff0000eb809300   <<--
LENGTH(mem_section)=1024
SIZE(mem_section)=16
OFFSET(mem_section.section_mem_map)=0
...
NUMBER(VA_BITS)=48

So at least if the kernel is configured with CONFIG_SPARSEMEM_EXTREME,
I thought this would work.  This is just a user tool effort to broaden
supported kernels, instead of necessary information from the kernel,
no need to support all kernels.

And the current makedumpfile's implementation, SYMBOL(mem_section) is set
to the address of the mem_section variable with -x option, so I wrote on
the cover letter that this patchset doesn't support "with -x option if
vabits_actual=52" case yet.

> >
> > Having vabits_actual is introduced and precise to resolve
> > is_lm_address(), but if it is not available, could we survive?
> >
> > _PAGE_OFFSET(52) < _PAGE_END(52) < _PAGE_OFFSET(48) < _PAGE_END(48)
> > Translating into numbers:
> > 0xfff0000000000000 < 0xfff8000000000000 < 0xffff000000000000 <
> > 0xffff800000000000
> >
> > Refer to linux/Documentation/arm64/memory.rst, the line
> >      ffffa00010000000      fffff81ffffeffff         ~88TB          vmalloc
> >
> > It comes to the conclusion that any symbol > SYMBOL(_text) > _PAGE_END(48).
> >
> > So is_lm_address() can looks like
> > if (addr > _PAGE_END(48)), it is kimage
> > else, it is linear mapping

This sounds good and will work.

> >
> > So even more aggressive, we can exclude the need of vabits_actual
> > totally in this patch.

Interesting, but if vabits_actual is not available, I wonder how we can
get info->page_offset.  Seems it's used mainly for p2v conversion and
is_kvaddr(), which still has a problem though.

> 
> As Pingfan noted, this approach still has issues and it failed on my
> arm64 board in the limited testing I did today.

Can I have what configuration, error and debug messages you see,
for reference?

> I will do some more testing tomorrow and come back with an approach
> which addresses the same and also takes into account Pingfan's
> concerns.

ok, thanks!

Kazu


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Re: [RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA

[piliu]

On 1/15/21 8:40 AM, HAGIO KAZUHITO(萩尾 一仁) wrote:
> Hi Pingfan, Bhupesh,
> 
> Thank you for your comments!
> 
> -----Original Message-----
>> Hi Kazu,
>>
>> On Thu, Jan 14, 2021 at 3:33 PM piliu <piliu@redhat.com> wrote:
>>>
>>>
>>>
>>> On 1/14/21 4:25 PM, kazuhito.hagio@gmail.com wrote:
>>>> From: Kazuhito Hagio <k-hagio-ab@nec.com>
>>>>
>>>> Based on Bhupesh's patch and contains Pingfan's idea.
>>>>
>>>> Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
>>>> Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
>>>> ---
>>>>    arch/arm64.c   | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
>>>>    makedumpfile.c |  2 ++
>>>>    makedumpfile.h |  1 +
>>>>    3 files changed, 83 insertions(+), 15 deletions(-)
>>>>
>>>> diff --git a/arch/arm64.c b/arch/arm64.c
>>>> index 61ec89a..4ece19d 100644
>>>> --- a/arch/arm64.c
>>>> +++ b/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;
>>>>    }
>>>> @@ -383,22 +394,54 @@ 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");
>>>> @@ -409,7 +452,6 @@ 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;
>>>> @@ -444,10 +486,33 @@ 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
>>>> +              *  58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
>>>> +              */
>>>> +             if (SYMBOL(mem_section) & (1UL << (52 - 1)))
>>>
>>> Sorry but I do not think any SYMBOL(x) is inside the range of linear
>>> mapping address. All of them should be beyond kimage_vaddr.
> 
> As for this, SYMBOL(mem_section) is a bit special and shows the value in the
> mem_section variable, not the address of it, by kernel commit a0b1280368d1.
> 
> Actually on my tiny arm64 board..
> 
> # strings /proc/kcore | less
> ...
> OSRELEASE=5.4.0-1025-raspi
> PAGESIZE=4096
> SYMBOL(init_uts_ns)=ffffd6db0fa10568
> SYMBOL(node_online_map)=ffffd6db0fa0a808
> SYMBOL(swapper_pg_dir)=ffffd6db0f42b000
> SYMBOL(_stext)=ffffd6db0e481000
> SYMBOL(vmap_area_list)=ffffd6db0fa51680
> SYMBOL(mem_map)=ffffd6db0fbc0240
> SYMBOL(contig_page_data)=ffffd6db0faed6c0
> SYMBOL(mem_section)=ffff0000eb809300   <<--
> LENGTH(mem_section)=1024
> SIZE(mem_section)=16
> OFFSET(mem_section.section_mem_map)=0
> ...
> NUMBER(VA_BITS)=48
> 
> So at least if the kernel is configured with CONFIG_SPARSEMEM_EXTREME,
You are right. Exactly, your method works in this case.

> I thought this would work.  This is just a user tool effort to broaden
> supported kernels, instead of necessary information from the kernel,
> no need to support all kernels.

I hold a private opinion against the solution based on kernel version,  
since it raises extra effort to cope with different releases which back  
port some upstream patches without advancing kernel version.
> 
> And the current makedumpfile's implementation, SYMBOL(mem_section) is set
> to the address of the mem_section variable with -x option, so I wrote on
> the cover letter that this patchset doesn't support "with -x option if
> vabits_actual=52" case yet.
> 
>>>
>>> Having vabits_actual is introduced and precise to resolve
>>> is_lm_address(), but if it is not available, could we survive?
>>>
>>> _PAGE_OFFSET(52) < _PAGE_END(52) < _PAGE_OFFSET(48) < _PAGE_END(48)
>>> Translating into numbers:
>>> 0xfff0000000000000 < 0xfff8000000000000 < 0xffff000000000000 <
>>> 0xffff800000000000
>>>
>>> Refer to linux/Documentation/arm64/memory.rst, the line
>>>       ffffa00010000000      fffff81ffffeffff         ~88TB          vmalloc
>>>
>>> It comes to the conclusion that any symbol > SYMBOL(_text) > _PAGE_END(48).
>>>
>>> So is_lm_address() can looks like
>>> if (addr > _PAGE_END(48)), it is kimage
>>> else, it is linear mapping
> 
> This sounds good and will work.
> 
>>>
>>> So even more aggressive, we can exclude the need of vabits_actual
>>> totally in this patch.
> 
> Interesting, but if vabits_actual is not available, I wonder how we can
> get info->page_offset.  Seems it's used mainly for p2v conversion and

Ashamed. I will make the best of the fact that va_bits=52 kernel only  
has _PAGE_OFFSET(52). It looks not elegant, but should work.

Regards,
	Pingfan


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RE: [RFC PATCH 4/4] arm64: support flipped VA and 52-bit kernel VA

[HAGIO KAZUHITO(萩尾 一仁)]

Hi Pingfan,

-----Original Message-----
> >>> On 1/14/21 4:25 PM, kazuhito.hagio@gmail.com wrote:
> >>>> From: Kazuhito Hagio <k-hagio-ab@nec.com>
> >>>>
> >>>> Based on Bhupesh's patch and contains Pingfan's idea.
> >>>>
> >>>> Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com>
> >>>> Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>
> >>>> ---
> >>>>    arch/arm64.c   | 95 ++++++++++++++++++++++++++++++++++++++++++++++++----------
> >>>>    makedumpfile.c |  2 ++
> >>>>    makedumpfile.h |  1 +
> >>>>    3 files changed, 83 insertions(+), 15 deletions(-)
> >>>>
> >>>> diff --git a/arch/arm64.c b/arch/arm64.c
> >>>> index 61ec89a..4ece19d 100644
> >>>> --- a/arch/arm64.c
> >>>> +++ b/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;
> >>>>    }
> >>>> @@ -383,22 +394,54 @@ 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");
> >>>> @@ -409,7 +452,6 @@ 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;
> >>>> @@ -444,10 +486,33 @@ 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
> >>>> +              *  58-bit: 0xfff0000000000000 - 0xfff7ffffffffffff
> >>>> +              */
> >>>> +             if (SYMBOL(mem_section) & (1UL << (52 - 1)))
> >>>
> >>> Sorry but I do not think any SYMBOL(x) is inside the range of linear
> >>> mapping address. All of them should be beyond kimage_vaddr.
> >
> > As for this, SYMBOL(mem_section) is a bit special and shows the value in the
> > mem_section variable, not the address of it, by kernel commit a0b1280368d1.
> >
> > Actually on my tiny arm64 board..
> >
> > # strings /proc/kcore | less
> > ...
> > OSRELEASE=5.4.0-1025-raspi
> > PAGESIZE=4096
> > SYMBOL(init_uts_ns)=ffffd6db0fa10568
> > SYMBOL(node_online_map)=ffffd6db0fa0a808
> > SYMBOL(swapper_pg_dir)=ffffd6db0f42b000
> > SYMBOL(_stext)=ffffd6db0e481000
> > SYMBOL(vmap_area_list)=ffffd6db0fa51680
> > SYMBOL(mem_map)=ffffd6db0fbc0240
> > SYMBOL(contig_page_data)=ffffd6db0faed6c0
> > SYMBOL(mem_section)=ffff0000eb809300   <<--
> > LENGTH(mem_section)=1024
> > SIZE(mem_section)=16
> > OFFSET(mem_section.section_mem_map)=0
> > ...
> > NUMBER(VA_BITS)=48
> >
> > So at least if the kernel is configured with CONFIG_SPARSEMEM_EXTREME,
> You are right. Exactly, your method works in this case.
> 
> > I thought this would work.  This is just a user tool effort to broaden
> > supported kernels, instead of necessary information from the kernel,
> > no need to support all kernels.
> 
> I hold a private opinion against the solution based on kernel version,
> since it raises extra effort to cope with different releases which back
> port some upstream patches without advancing kernel version.

I agree with you, we should avoid depending on kernel version if we can.

I left the 3/4 patch intact for possible use of kernel version method,
but for now, the patchset doesn't use kernel version with your idea! :)

> >
> > And the current makedumpfile's implementation, SYMBOL(mem_section) is set
> > to the address of the mem_section variable with -x option, so I wrote on
> > the cover letter that this patchset doesn't support "with -x option if
> > vabits_actual=52" case yet.
> >
> >>>
> >>> Having vabits_actual is introduced and precise to resolve
> >>> is_lm_address(), but if it is not available, could we survive?
> >>>
> >>> _PAGE_OFFSET(52) < _PAGE_END(52) < _PAGE_OFFSET(48) < _PAGE_END(48)
> >>> Translating into numbers:
> >>> 0xfff0000000000000 < 0xfff8000000000000 < 0xffff000000000000 <
> >>> 0xffff800000000000
> >>>
> >>> Refer to linux/Documentation/arm64/memory.rst, the line
> >>>       ffffa00010000000      fffff81ffffeffff         ~88TB          vmalloc
> >>>
> >>> It comes to the conclusion that any symbol > SYMBOL(_text) > _PAGE_END(48).
> >>>
> >>> So is_lm_address() can looks like
> >>> if (addr > _PAGE_END(48)), it is kimage
> >>> else, it is linear mapping
> >
> > This sounds good and will work.
> >
> >>>
> >>> So even more aggressive, we can exclude the need of vabits_actual
> >>> totally in this patch.
> >
> > Interesting, but if vabits_actual is not available, I wonder how we can
> > get info->page_offset.  Seems it's used mainly for p2v conversion and
> 
> Ashamed. I will make the best of the fact that va_bits=52 kernel only
> has _PAGE_OFFSET(52). It looks not elegant, but should work.

ok, thanks for your help!

Kazu


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