[PATCH 0/3] arm64: make phys_to_virt() correct

[PATCH 0/3] arm64: make phys_to_virt() correct

[Pingfan Liu]

Currently phys_to_virt() does not work well on 52-bits VA arm64 kernel.
One issue is contributed by phys_offset not signed.
The other is contributed by wrong page_offset.

This series fixes them so vmcore-dmesg can work on 52-bits VA kernel

Pingfan Liu (3):
  arm64: make phys_offset signed
  arm64/crashdump: unify routine to get page_offset
  arm64: read VA_BITS from kcore for 52-bits VA kernel

 kexec/arch/arm64/crashdump-arm64.c | 23 +---------------
 kexec/arch/arm64/kexec-arm64.c     | 43 +++++++++++++++++++++++-------
 kexec/arch/arm64/kexec-arm64.h     |  4 ++-
 util_lib/elf_info.c                |  7 ++++-
 util_lib/include/elf_info.h        |  2 +-
 5 files changed, 44 insertions(+), 35 deletions(-)

-- 
2.31.1


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[PATCH 1/3] arm64: make phys_offset signed

[Pingfan Liu]

After kernel commit 7bc1a0f9e176 ("arm64: mm: use single quantity to
represent the PA to VA translation"), phys_offset can be negative if
running 52-bits kernel on 48-bits hardware.

So changing phys_offset from unsigned to signed.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
---
 kexec/arch/arm64/kexec-arm64.c | 8 ++++----
 kexec/arch/arm64/kexec-arm64.h | 2 +-
 util_lib/elf_info.c            | 2 +-
 util_lib/include/elf_info.h    | 2 +-
 4 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
index 6f572ed..7373fa3 100644
--- a/kexec/arch/arm64/kexec-arm64.c
+++ b/kexec/arch/arm64/kexec-arm64.c
@@ -859,7 +859,7 @@ void add_segment(struct kexec_info *info, const void *buf, size_t bufsz,
 	add_segment_phys_virt(info, buf, bufsz, base, memsz, 1);
 }
 
-static inline void set_phys_offset(uint64_t v, char *set_method)
+static inline void set_phys_offset(long v, char *set_method)
 {
 	if (arm64_mem.phys_offset == arm64_mem_ngv
 		|| v < arm64_mem.phys_offset) {
@@ -928,7 +928,7 @@ static int get_page_offset(void)
  * from VMCOREINFO note inside 'kcore'.
  */
 
-static int get_phys_offset_from_vmcoreinfo_pt_note(unsigned long *phys_offset)
+static int get_phys_offset_from_vmcoreinfo_pt_note(long *phys_offset)
 {
 	int fd, ret = 0;
 
@@ -948,7 +948,7 @@ static int get_phys_offset_from_vmcoreinfo_pt_note(unsigned long *phys_offset)
  * from PT_LOADs inside 'kcore'.
  */
 
-int get_phys_base_from_pt_load(unsigned long *phys_offset)
+int get_phys_base_from_pt_load(long *phys_offset)
 {
 	int i, fd, ret;
 	unsigned long long phys_start;
@@ -997,7 +997,7 @@ static bool to_be_excluded(char *str)
 int get_memory_ranges(struct memory_range **range, int *ranges,
 	unsigned long kexec_flags)
 {
-	unsigned long phys_offset = UINT64_MAX;
+	long phys_offset = (long)UINT64_MAX;
 	FILE *fp;
 	const char *iomem = proc_iomem();
 	char line[MAX_LINE], *str;
diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
index ed447ac..1844b67 100644
--- a/kexec/arch/arm64/kexec-arm64.h
+++ b/kexec/arch/arm64/kexec-arm64.h
@@ -58,7 +58,7 @@ extern off_t initrd_size;
  */
 
 struct arm64_mem {
-	uint64_t phys_offset;
+	long phys_offset;
 	uint64_t text_offset;
 	uint64_t image_size;
 	uint64_t vp_offset;
diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
index 51d8b92..5574c7f 100644
--- a/util_lib/elf_info.c
+++ b/util_lib/elf_info.c
@@ -1236,7 +1236,7 @@ int read_elf(int fd)
 	return 0;
 }
 
-int read_phys_offset_elf_kcore(int fd, unsigned long *phys_off)
+int read_phys_offset_elf_kcore(int fd, long *phys_off)
 {
 	int ret;
 
diff --git a/util_lib/include/elf_info.h b/util_lib/include/elf_info.h
index 4bc9279..f550d86 100644
--- a/util_lib/include/elf_info.h
+++ b/util_lib/include/elf_info.h
@@ -28,7 +28,7 @@ int get_pt_load(int idx,
 	unsigned long long *phys_end,
 	unsigned long long *virt_start,
 	unsigned long long *virt_end);
-int read_phys_offset_elf_kcore(int fd, unsigned long *phys_off);
+int read_phys_offset_elf_kcore(int fd, long *phys_off);
 int read_elf(int fd);
 void dump_dmesg(int fd, void (*handler)(char*, unsigned int));
 
-- 
2.31.1


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[PATCH 2/3] arm64/crashdump: unify routine to get page_offset

[Pingfan Liu]

There are two funcs to get page_offset:
  get_kernel_page_offset()
  get_page_offset()

Since get_kernel_page_offset() does not observe the kernel formula, and
remove it. Unify them in order to introduce 52-bits VA kernel more
easily in the coming patch.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
---
 kexec/arch/arm64/crashdump-arm64.c | 23 +----------------------
 kexec/arch/arm64/kexec-arm64.c     |  4 ++--
 kexec/arch/arm64/kexec-arm64.h     |  1 +
 3 files changed, 4 insertions(+), 24 deletions(-)

diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c
index a02019a..0a8d44c 100644
--- a/kexec/arch/arm64/crashdump-arm64.c
+++ b/kexec/arch/arm64/crashdump-arm64.c
@@ -46,27 +46,6 @@ static struct crash_elf_info elf_info = {
 	.machine	= EM_AARCH64,
 };
 
-/*
- * Note: The returned value is correct only if !CONFIG_RANDOMIZE_BASE.
- */
-static uint64_t get_kernel_page_offset(void)
-{
-	int i;
-
-	if (elf_info.kern_vaddr_start == UINT64_MAX)
-		return UINT64_MAX;
-
-	/* Current max virtual memory range is 48-bits. */
-	for (i = 48; i > 0; i--)
-		if (!(elf_info.kern_vaddr_start & (1UL << i)))
-			break;
-
-	if (i <= 0)
-		return UINT64_MAX;
-	else
-		return UINT64_MAX << i;
-}
-
 /*
  * iomem_range_callback() - callback called for each iomem region
  * @data: not used
@@ -198,7 +177,7 @@ int load_crashdump_segments(struct kexec_info *info)
 	if (err)
 		return EFAILED;
 
-	elf_info.page_offset = get_kernel_page_offset();
+	get_page_offset(&elf_info.page_offset);
 	dbgprintf("%s: page_offset:   %016llx\n", __func__,
 			elf_info.page_offset);
 
diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
index 7373fa3..bd650e6 100644
--- a/kexec/arch/arm64/kexec-arm64.c
+++ b/kexec/arch/arm64/kexec-arm64.c
@@ -909,7 +909,7 @@ static int get_va_bits(void)
  * get_page_offset - Helper for getting PAGE_OFFSET
  */
 
-static int get_page_offset(void)
+int get_page_offset(unsigned long *page_offset)
 {
 	int ret;
 
@@ -954,7 +954,7 @@ int get_phys_base_from_pt_load(long *phys_offset)
 	unsigned long long phys_start;
 	unsigned long long virt_start;
 
-	ret = get_page_offset();
+	ret = get_page_offset(&page_offset);
 	if (ret < 0)
 		return ret;
 
diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
index 1844b67..ed99d9d 100644
--- a/kexec/arch/arm64/kexec-arm64.h
+++ b/kexec/arch/arm64/kexec-arm64.h
@@ -69,6 +69,7 @@ extern struct arm64_mem arm64_mem;
 
 uint64_t get_phys_offset(void);
 uint64_t get_vp_offset(void);
+int get_page_offset(unsigned long *offset);
 
 static inline void reset_vp_offset(void)
 {
-- 
2.31.1


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[PATCH 3/3] arm64: read VA_BITS from kcore for 52-bits VA kernel

[Pingfan Liu]

phys_to_virt() calculates virtual address. As a important factor,
page_offset is excepted to be accurate.

Since arm64 kernel exposes va_bits through vmcore, using it.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
---
 kexec/arch/arm64/kexec-arm64.c | 31 +++++++++++++++++++++++++++----
 kexec/arch/arm64/kexec-arm64.h |  1 +
 util_lib/elf_info.c            |  5 +++++
 3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
index bd650e6..ccc92db 100644
--- a/kexec/arch/arm64/kexec-arm64.c
+++ b/kexec/arch/arm64/kexec-arm64.c
@@ -54,7 +54,7 @@
 static bool try_read_phys_offset_from_kcore = false;
 
 /* Machine specific details. */
-static int va_bits;
+static int va_bits = -1;
 static unsigned long page_offset;
 
 /* Global varables the core kexec routines expect. */
@@ -876,7 +876,15 @@ static inline void set_phys_offset(long v, char *set_method)
 
 static int get_va_bits(void)
 {
-	unsigned long long stext_sym_addr = get_kernel_sym("_stext");
+	unsigned long long stext_sym_addr;
+
+	/*
+	 * if already got from kcore
+	 */
+	if (va_bits != -1)
+		goto out;
+
+	stext_sym_addr = get_kernel_sym("_stext");
 
 	if (stext_sym_addr == 0) {
 		fprintf(stderr, "Can't get the symbol of _stext.\n");
@@ -900,6 +908,7 @@ static int get_va_bits(void)
 		return -1;
 	}
 
+out:
 	dbgprintf("va_bits : %d\n", va_bits);
 
 	return 0;
@@ -917,14 +926,27 @@ int get_page_offset(unsigned long *page_offset)
 	if (ret < 0)
 		return ret;
 
-	page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
+	if (va_bits < 52)
+		*page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
+	else
+		*page_offset = (0xffffffffffffffffUL) << va_bits;
+
 	dbgprintf("page_offset : %lx\n", page_offset);
 
 	return 0;
 }
 
+static void arm64_scan_vmcoreinfo(char *pos)
+{
+	const char *str;
+
+	str = "NUMBER(VA_BITS)=";
+	if (memcmp(str, pos, strlen(str)) == 0)
+		va_bits = strtoul(pos + strlen(str), NULL, 10);
+}
+
 /**
- * get_phys_offset_from_vmcoreinfo_pt_note - Helper for getting PHYS_OFFSET
+ * get_phys_offset_from_vmcoreinfo_pt_note - Helper for getting PHYS_OFFSET (and va_bits)
  * from VMCOREINFO note inside 'kcore'.
  */
 
@@ -937,6 +959,7 @@ static int get_phys_offset_from_vmcoreinfo_pt_note(long *phys_offset)
 		return EFAILED;
 	}
 
+	arch_scan_vmcoreinfo = arm64_scan_vmcoreinfo;
 	ret = read_phys_offset_elf_kcore(fd, phys_offset);
 
 	close(fd);
diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
index ed99d9d..d291705 100644
--- a/kexec/arch/arm64/kexec-arm64.h
+++ b/kexec/arch/arm64/kexec-arm64.h
@@ -66,6 +66,7 @@ struct arm64_mem {
 
 #define arm64_mem_ngv UINT64_MAX
 extern struct arm64_mem arm64_mem;
+extern void (*arch_scan_vmcoreinfo)(char *pos);
 
 uint64_t get_phys_offset(void);
 uint64_t get_vp_offset(void);
diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
index 5574c7f..d252eff 100644
--- a/util_lib/elf_info.c
+++ b/util_lib/elf_info.c
@@ -310,6 +310,8 @@ int get_pt_load(int idx,
 
 #define NOT_FOUND_LONG_VALUE		(-1)
 
+void (*arch_scan_vmcoreinfo)(char *pos);
+
 void scan_vmcoreinfo(char *start, size_t size)
 {
 	char *last = start + size - 1;
@@ -551,6 +553,9 @@ void scan_vmcoreinfo(char *start, size_t size)
 			}
 		}
 
+		if (arch_scan_vmcoreinfo != NULL)
+			(*arch_scan_vmcoreinfo)(pos);
+
 		if (last_line)
 			break;
 	}
-- 
2.31.1


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Re: [PATCH 0/3] arm64: make phys_to_virt() correct

[Pingfan Liu]

+ AKASHI Takahiro
+ Simon Horman

Thank you guys for any suggestions.
And vmcore-dmesg just can not work for 52-bits VA arm64 now.

Thanks,
Pingfan

On Fri, Dec 10, 2021 at 11:07 AM Pingfan Liu <piliu@redhat.com> wrote:
>
> Currently phys_to_virt() does not work well on 52-bits VA arm64 kernel.
> One issue is contributed by phys_offset not signed.
> The other is contributed by wrong page_offset.
>
> This series fixes them so vmcore-dmesg can work on 52-bits VA kernel
>
> Pingfan Liu (3):
>   arm64: make phys_offset signed
>   arm64/crashdump: unify routine to get page_offset
>   arm64: read VA_BITS from kcore for 52-bits VA kernel
>
>  kexec/arch/arm64/crashdump-arm64.c | 23 +---------------
>  kexec/arch/arm64/kexec-arm64.c     | 43 +++++++++++++++++++++++-------
>  kexec/arch/arm64/kexec-arm64.h     |  4 ++-
>  util_lib/elf_info.c                |  7 ++++-
>  util_lib/include/elf_info.h        |  2 +-
>  5 files changed, 44 insertions(+), 35 deletions(-)
>
> --
> 2.31.1
>


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Re: [PATCH 3/3] arm64: read VA_BITS from kcore for 52-bits VA kernel

[Philipp Rudo]

Hi Pingfang,

On Fri, 10 Dec 2021 11:07:35 +0800
Pingfan Liu <piliu@redhat.com> wrote:

> phys_to_virt() calculates virtual address. As a important factor,
> page_offset is excepted to be accurate.
> 
> Since arm64 kernel exposes va_bits through vmcore, using it.
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> ---
>  kexec/arch/arm64/kexec-arm64.c | 31 +++++++++++++++++++++++++++----
>  kexec/arch/arm64/kexec-arm64.h |  1 +
>  util_lib/elf_info.c            |  5 +++++
>  3 files changed, 33 insertions(+), 4 deletions(-)
> 
> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> index bd650e6..ccc92db 100644
> --- a/kexec/arch/arm64/kexec-arm64.c
> +++ b/kexec/arch/arm64/kexec-arm64.c
> @@ -54,7 +54,7 @@
>  static bool try_read_phys_offset_from_kcore = false;
>  
>  /* Machine specific details. */
> -static int va_bits;
> +static int va_bits = -1;
>  static unsigned long page_offset;
>  
>  /* Global varables the core kexec routines expect. */
> @@ -876,7 +876,15 @@ static inline void set_phys_offset(long v, char *set_method)
>  
>  static int get_va_bits(void)
>  {
> -	unsigned long long stext_sym_addr = get_kernel_sym("_stext");
> +	unsigned long long stext_sym_addr;
> +
> +	/*
> +	 * if already got from kcore
> +	 */
> +	if (va_bits != -1)
> +		goto out;
> +
> +	stext_sym_addr = get_kernel_sym("_stext");
>  
>  	if (stext_sym_addr == 0) {
>  		fprintf(stderr, "Can't get the symbol of _stext.\n");
> @@ -900,6 +908,7 @@ static int get_va_bits(void)
>  		return -1;
>  	}
>  
> +out:
>  	dbgprintf("va_bits : %d\n", va_bits);
>  
>  	return 0;
> @@ -917,14 +926,27 @@ int get_page_offset(unsigned long *page_offset)
>  	if (ret < 0)
>  		return ret;
>  
> -	page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> +	if (va_bits < 52)
> +		*page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> +	else
> +		*page_offset = (0xffffffffffffffffUL) << va_bits;

wouldn't it make sense to use ULONG_MAX here? At least for me it would
be much better readable.

>  	dbgprintf("page_offset : %lx\n", page_offset);
>  
>  	return 0;
>  }
>  
> +static void arm64_scan_vmcoreinfo(char *pos)
> +{
> +	const char *str;
> +
> +	str = "NUMBER(VA_BITS)=";
> +	if (memcmp(str, pos, strlen(str)) == 0)
> +		va_bits = strtoul(pos + strlen(str), NULL, 10);
> +}
> +
>  /**
> - * get_phys_offset_from_vmcoreinfo_pt_note - Helper for getting PHYS_OFFSET
> + * get_phys_offset_from_vmcoreinfo_pt_note - Helper for getting PHYS_OFFSET (and va_bits)
>   * from VMCOREINFO note inside 'kcore'.
>   */
>  
> @@ -937,6 +959,7 @@ static int get_phys_offset_from_vmcoreinfo_pt_note(long *phys_offset)
>  		return EFAILED;
>  	}
>  
> +	arch_scan_vmcoreinfo = arm64_scan_vmcoreinfo;
>  	ret = read_phys_offset_elf_kcore(fd, phys_offset);
>  
>  	close(fd);
> diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
> index ed99d9d..d291705 100644
> --- a/kexec/arch/arm64/kexec-arm64.h
> +++ b/kexec/arch/arm64/kexec-arm64.h
> @@ -66,6 +66,7 @@ struct arm64_mem {
>  
>  #define arm64_mem_ngv UINT64_MAX
>  extern struct arm64_mem arm64_mem;
> +extern void (*arch_scan_vmcoreinfo)(char *pos);

This definition isn't arm64 specific. I think this should go to
util_lib/include/elf_info.h.

Thanks
Philipp

>  
>  uint64_t get_phys_offset(void);
>  uint64_t get_vp_offset(void);
> diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
> index 5574c7f..d252eff 100644
> --- a/util_lib/elf_info.c
> +++ b/util_lib/elf_info.c
> @@ -310,6 +310,8 @@ int get_pt_load(int idx,
>  
>  #define NOT_FOUND_LONG_VALUE		(-1)
>  
> +void (*arch_scan_vmcoreinfo)(char *pos);
> +
>  void scan_vmcoreinfo(char *start, size_t size)
>  {
>  	char *last = start + size - 1;
> @@ -551,6 +553,9 @@ void scan_vmcoreinfo(char *start, size_t size)
>  			}
>  		}
>  
> +		if (arch_scan_vmcoreinfo != NULL)
> +			(*arch_scan_vmcoreinfo)(pos);
> +
>  		if (last_line)
>  			break;
>  	}


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Re: [PATCH 2/3] arm64/crashdump: unify routine to get page_offset

[Philipp Rudo]

Hi Pinfang,

On Fri, 10 Dec 2021 11:07:34 +0800
Pingfan Liu <piliu@redhat.com> wrote:

> There are two funcs to get page_offset:
>   get_kernel_page_offset()
>   get_page_offset()
> 
> Since get_kernel_page_offset() does not observe the kernel formula, and
> remove it. Unify them in order to introduce 52-bits VA kernel more
> easily in the coming patch.
> 
> Signed-off-by: Pingfan Liu <piliu@redhat.com>
> ---
>  kexec/arch/arm64/crashdump-arm64.c | 23 +----------------------
>  kexec/arch/arm64/kexec-arm64.c     |  4 ++--
>  kexec/arch/arm64/kexec-arm64.h     |  1 +
>  3 files changed, 4 insertions(+), 24 deletions(-)
> 
> diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c
> index a02019a..0a8d44c 100644
> --- a/kexec/arch/arm64/crashdump-arm64.c
> +++ b/kexec/arch/arm64/crashdump-arm64.c

[...]

> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> index 7373fa3..bd650e6 100644
> --- a/kexec/arch/arm64/kexec-arm64.c
> +++ b/kexec/arch/arm64/kexec-arm64.c
> @@ -909,7 +909,7 @@ static int get_va_bits(void)
>   * get_page_offset - Helper for getting PAGE_OFFSET
>   */
>  
> -static int get_page_offset(void)
> +int get_page_offset(unsigned long *page_offset)
>  {
>  	int ret;
>  

The new page_offset is never used in this patch. There's still the line
left with the global page_offset but that will cause a type miss-match
(unsigend long vs unsigned log *). In the next patch you do the update
(page_offset -> *page_offset) but in the meantime the code is broken.

Thanks
Philipp

> @@ -954,7 +954,7 @@ int get_phys_base_from_pt_load(long *phys_offset)
>  	unsigned long long phys_start;
>  	unsigned long long virt_start;
>  
> -	ret = get_page_offset();
> +	ret = get_page_offset(&page_offset);
>  	if (ret < 0)
>  		return ret;
>  
> diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
> index 1844b67..ed99d9d 100644
> --- a/kexec/arch/arm64/kexec-arm64.h
> +++ b/kexec/arch/arm64/kexec-arm64.h
> @@ -69,6 +69,7 @@ extern struct arm64_mem arm64_mem;
>  
>  uint64_t get_phys_offset(void);
>  uint64_t get_vp_offset(void);
> +int get_page_offset(unsigned long *offset);
>  
>  static inline void reset_vp_offset(void)
>  {


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Re: [PATCH 3/3] arm64: read VA_BITS from kcore for 52-bits VA kernel

[Pingfan Liu]

On Wed, Dec 15, 2021 at 9:06 PM Signed-off-by@vergenet.net:Simon
Horman <horms@verge.net.au> wrote:
>
> On Fri, Dec 10, 2021 at 11:07:35AM +0800, Pingfan Liu wrote:
> > phys_to_virt() calculates virtual address. As a important factor,
> > page_offset is excepted to be accurate.
> >
> > Since arm64 kernel exposes va_bits through vmcore, using it.
> >
> > Signed-off-by: Pingfan Liu <piliu@redhat.com>
> > ---
> >  kexec/arch/arm64/kexec-arm64.c | 31 +++++++++++++++++++++++++++----
> >  kexec/arch/arm64/kexec-arm64.h |  1 +
> >  util_lib/elf_info.c            |  5 +++++
> >  3 files changed, 33 insertions(+), 4 deletions(-)
> >
> > diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> > index bd650e6..ccc92db 100644
> > --- a/kexec/arch/arm64/kexec-arm64.c
> > +++ b/kexec/arch/arm64/kexec-arm64.c
> > @@ -54,7 +54,7 @@
> >  static bool try_read_phys_offset_from_kcore = false;
> >
> >  /* Machine specific details. */
> > -static int va_bits;
> > +static int va_bits = -1;
> >  static unsigned long page_offset;
> >
> >  /* Global varables the core kexec routines expect. */
> > @@ -876,7 +876,15 @@ static inline void set_phys_offset(long v, char *set_method)
> >
> >  static int get_va_bits(void)
> >  {
> > -     unsigned long long stext_sym_addr = get_kernel_sym("_stext");
> > +     unsigned long long stext_sym_addr;
> > +
> > +     /*
> > +      * if already got from kcore
> > +      */
> > +     if (va_bits != -1)
> > +             goto out;
>
> If va_bits is exposed by the kernel then it will be used.
> Else we continue here. Are there actually cases (old kernels) where
> we expect to continue. Or could we get rid of the fallback code here?
>

va_bits is exposed by kernel commit 84c57dbd3c48 ("arm64: kernel:
arch_crash_save_vmcoreinfo() should depend on CONFIG_CRASH_CORE")
And the first kernel which contains VA_BITS is v4.19.
I have no idea about the need for old kernels. Maybe just keep the
compatible code and throw a warning to remind users?

> > +
> > +     stext_sym_addr = get_kernel_sym("_stext");
> >
> >       if (stext_sym_addr == 0) {
> >               fprintf(stderr, "Can't get the symbol of _stext.\n");
> > @@ -900,6 +908,7 @@ static int get_va_bits(void)
> >               return -1;
> >       }
> >
> > +out:
> >       dbgprintf("va_bits : %d\n", va_bits);
> >
> >       return 0;
> > @@ -917,14 +926,27 @@ int get_page_offset(unsigned long *page_offset)
> >       if (ret < 0)
> >               return ret;
> >
>
> I'm confused about why there is both a (va_bits - 1)
> and va_bits case here.
>

It originates from the changes of memory layout on arm64.
And mostly it is contributed by kernel commit 14c127c957c1 ("arm64:
mm: Flip kernel VA space"),
where sees the changes:
-#define PAGE_OFFSET            (UL(0xffffffffffffffff) - \
        (UL(1) << (VA_BITS - 1)) + 1)
+#define PAGE_OFFSET            (UL(0xffffffffffffffff) - \
+       (UL(1) << VA_BITS) + 1)


Thanks,

Pingfan


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Re: [PATCH 3/3] arm64: read VA_BITS from kcore for 52-bits VA kernel

[Pingfan Liu]

On Wed, Dec 15, 2021 at 9:35 PM Philipp Rudo <prudo@redhat.com> wrote:
>
> Hi Pingfang,
>
> On Fri, 10 Dec 2021 11:07:35 +0800
> Pingfan Liu <piliu@redhat.com> wrote:
>
> > phys_to_virt() calculates virtual address. As a important factor,
> > page_offset is excepted to be accurate.
> >
> > Since arm64 kernel exposes va_bits through vmcore, using it.
> >
> > Signed-off-by: Pingfan Liu <piliu@redhat.com>
> > ---
> >  kexec/arch/arm64/kexec-arm64.c | 31 +++++++++++++++++++++++++++----
> >  kexec/arch/arm64/kexec-arm64.h |  1 +
> >  util_lib/elf_info.c            |  5 +++++
> >  3 files changed, 33 insertions(+), 4 deletions(-)
> >
> > diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> > index bd650e6..ccc92db 100644
> > --- a/kexec/arch/arm64/kexec-arm64.c
> > +++ b/kexec/arch/arm64/kexec-arm64.c
> > @@ -54,7 +54,7 @@
> >  static bool try_read_phys_offset_from_kcore = false;
> >
> >  /* Machine specific details. */
> > -static int va_bits;
> > +static int va_bits = -1;
> >  static unsigned long page_offset;
> >
> >  /* Global varables the core kexec routines expect. */
> > @@ -876,7 +876,15 @@ static inline void set_phys_offset(long v, char *set_method)
> >
> >  static int get_va_bits(void)
> >  {
> > -     unsigned long long stext_sym_addr = get_kernel_sym("_stext");
> > +     unsigned long long stext_sym_addr;
> > +
> > +     /*
> > +      * if already got from kcore
> > +      */
> > +     if (va_bits != -1)
> > +             goto out;
> > +
> > +     stext_sym_addr = get_kernel_sym("_stext");
> >
> >       if (stext_sym_addr == 0) {
> >               fprintf(stderr, "Can't get the symbol of _stext.\n");
> > @@ -900,6 +908,7 @@ static int get_va_bits(void)
> >               return -1;
> >       }
> >
> > +out:
> >       dbgprintf("va_bits : %d\n", va_bits);
> >
> >       return 0;
> > @@ -917,14 +926,27 @@ int get_page_offset(unsigned long *page_offset)
> >       if (ret < 0)
> >               return ret;
> >
> > -     page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> > +     if (va_bits < 52)
> > +             *page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> > +     else
> > +             *page_offset = (0xffffffffffffffffUL) << va_bits;
>
> wouldn't it make sense to use ULONG_MAX here? At least for me it would
> be much better readable.
>

Yes, I tend to agree and will update it in V2 (if there is no need to
compile it on 32-bits machine, which I consider as a rare case
nowadays.)


> >       dbgprintf("page_offset : %lx\n", page_offset);
> >
> >       return 0;
> >  }
> >
> > +static void arm64_scan_vmcoreinfo(char *pos)
> > +{
> > +     const char *str;
> > +
> > +     str = "NUMBER(VA_BITS)=";
> > +     if (memcmp(str, pos, strlen(str)) == 0)
> > +             va_bits = strtoul(pos + strlen(str), NULL, 10);
> > +}
> > +
> >  /**
> > - * get_phys_offset_from_vmcoreinfo_pt_note - Helper for getting PHYS_OFFSET
> > + * get_phys_offset_from_vmcoreinfo_pt_note - Helper for getting PHYS_OFFSET (and va_bits)
> >   * from VMCOREINFO note inside 'kcore'.
> >   */
> >
> > @@ -937,6 +959,7 @@ static int get_phys_offset_from_vmcoreinfo_pt_note(long *phys_offset)
> >               return EFAILED;
> >       }
> >
> > +     arch_scan_vmcoreinfo = arm64_scan_vmcoreinfo;
> >       ret = read_phys_offset_elf_kcore(fd, phys_offset);
> >
> >       close(fd);
> > diff --git a/kexec/arch/arm64/kexec-arm64.h b/kexec/arch/arm64/kexec-arm64.h
> > index ed99d9d..d291705 100644
> > --- a/kexec/arch/arm64/kexec-arm64.h
> > +++ b/kexec/arch/arm64/kexec-arm64.h
> > @@ -66,6 +66,7 @@ struct arm64_mem {
> >
> >  #define arm64_mem_ngv UINT64_MAX
> >  extern struct arm64_mem arm64_mem;
> > +extern void (*arch_scan_vmcoreinfo)(char *pos);
>
> This definition isn't arm64 specific. I think this should go to
> util_lib/include/elf_info.h.
>
Good suggestion and update it in V2.


Thanks,

Pingfan


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Re: [PATCH 2/3] arm64/crashdump: unify routine to get page_offset

[Pingfan Liu]

On Wed, Dec 15, 2021 at 9:35 PM Philipp Rudo <prudo@redhat.com> wrote:
>
> Hi Pinfang,
>
> On Fri, 10 Dec 2021 11:07:34 +0800
> Pingfan Liu <piliu@redhat.com> wrote:
>
> > There are two funcs to get page_offset:
> >   get_kernel_page_offset()
> >   get_page_offset()
> >
> > Since get_kernel_page_offset() does not observe the kernel formula, and
> > remove it. Unify them in order to introduce 52-bits VA kernel more
> > easily in the coming patch.
> >
> > Signed-off-by: Pingfan Liu <piliu@redhat.com>
> > ---
> >  kexec/arch/arm64/crashdump-arm64.c | 23 +----------------------
> >  kexec/arch/arm64/kexec-arm64.c     |  4 ++--
> >  kexec/arch/arm64/kexec-arm64.h     |  1 +
> >  3 files changed, 4 insertions(+), 24 deletions(-)
> >
> > diff --git a/kexec/arch/arm64/crashdump-arm64.c b/kexec/arch/arm64/crashdump-arm64.c
> > index a02019a..0a8d44c 100644
> > --- a/kexec/arch/arm64/crashdump-arm64.c
> > +++ b/kexec/arch/arm64/crashdump-arm64.c
>
> [...]
>
> > diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> > index 7373fa3..bd650e6 100644
> > --- a/kexec/arch/arm64/kexec-arm64.c
> > +++ b/kexec/arch/arm64/kexec-arm64.c
> > @@ -909,7 +909,7 @@ static int get_va_bits(void)
> >   * get_page_offset - Helper for getting PAGE_OFFSET
> >   */
> >
> > -static int get_page_offset(void)
> > +int get_page_offset(unsigned long *page_offset)
> >  {
> >       int ret;
> >
>
> The new page_offset is never used in this patch. There's still the line
> left with the global page_offset but that will cause a type miss-match
> (unsigend long vs unsigned log *). In the next patch you do the update
> (page_offset -> *page_offset) but in the meantime the code is broken.
>
I will fix it in V2.

Thanks,

Pingfan


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Re: [PATCH 3/3] arm64: read VA_BITS from kcore for 52-bits VA kernel

[Pingfan Liu]

On Thu, Dec 16, 2021 at 10:46 AM Pingfan Liu <piliu@redhat.com> wrote:
>
> On Wed, Dec 15, 2021 at 9:35 PM Philipp Rudo <prudo@redhat.com> wrote:
> >
> > Hi Pingfang,
> >
> > On Fri, 10 Dec 2021 11:07:35 +0800
> > Pingfan Liu <piliu@redhat.com> wrote:
> >
> > > phys_to_virt() calculates virtual address. As a important factor,
> > > page_offset is excepted to be accurate.
> > >
> > > Since arm64 kernel exposes va_bits through vmcore, using it.
> > >
> > > Signed-off-by: Pingfan Liu <piliu@redhat.com>
> > > ---
> > >  kexec/arch/arm64/kexec-arm64.c | 31 +++++++++++++++++++++++++++----
> > >  kexec/arch/arm64/kexec-arm64.h |  1 +
> > >  util_lib/elf_info.c            |  5 +++++
> > >  3 files changed, 33 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> > > index bd650e6..ccc92db 100644
> > > --- a/kexec/arch/arm64/kexec-arm64.c
> > > +++ b/kexec/arch/arm64/kexec-arm64.c
> > > @@ -54,7 +54,7 @@
> > >  static bool try_read_phys_offset_from_kcore = false;
> > >
> > >  /* Machine specific details. */
> > > -static int va_bits;
> > > +static int va_bits = -1;
> > >  static unsigned long page_offset;
> > >
> > >  /* Global varables the core kexec routines expect. */
> > > @@ -876,7 +876,15 @@ static inline void set_phys_offset(long v, char *set_method)
> > >
> > >  static int get_va_bits(void)
> > >  {
> > > -     unsigned long long stext_sym_addr = get_kernel_sym("_stext");
> > > +     unsigned long long stext_sym_addr;
> > > +
> > > +     /*
> > > +      * if already got from kcore
> > > +      */
> > > +     if (va_bits != -1)
> > > +             goto out;
> > > +
> > > +     stext_sym_addr = get_kernel_sym("_stext");
> > >
> > >       if (stext_sym_addr == 0) {
> > >               fprintf(stderr, "Can't get the symbol of _stext.\n");
> > > @@ -900,6 +908,7 @@ static int get_va_bits(void)
> > >               return -1;
> > >       }
> > >
> > > +out:
> > >       dbgprintf("va_bits : %d\n", va_bits);
> > >
> > >       return 0;
> > > @@ -917,14 +926,27 @@ int get_page_offset(unsigned long *page_offset)
> > >       if (ret < 0)
> > >               return ret;
> > >
> > > -     page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> > > +     if (va_bits < 52)
> > > +             *page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> > > +     else
> > > +             *page_offset = (0xffffffffffffffffUL) << va_bits;
> >
> > wouldn't it make sense to use ULONG_MAX here? At least for me it would
> > be much better readable.
> >
>
> Yes, I tend to agree and will update it in V2 (if there is no need to
> compile it on 32-bits machine, which I consider as a rare case
> nowadays.)
>

I think UINT64_MAX can free of this issue


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Re: [PATCH 3/3] arm64: read VA_BITS from kcore for 52-bits VA kernel

[Simon Horman]

On Thu, Dec 16, 2021 at 09:59:42AM +0800, Pingfan Liu wrote:
> On Wed, Dec 15, 2021 at 9:06 PM Signed-off-by@vergenet.net:Simon
> Horman <horms@verge.net.au> wrote:
> >
> > On Fri, Dec 10, 2021 at 11:07:35AM +0800, Pingfan Liu wrote:
> > > phys_to_virt() calculates virtual address. As a important factor,
> > > page_offset is excepted to be accurate.
> > >
> > > Since arm64 kernel exposes va_bits through vmcore, using it.
> > >
> > > Signed-off-by: Pingfan Liu <piliu@redhat.com>
> > > ---
> > >  kexec/arch/arm64/kexec-arm64.c | 31 +++++++++++++++++++++++++++----
> > >  kexec/arch/arm64/kexec-arm64.h |  1 +
> > >  util_lib/elf_info.c            |  5 +++++
> > >  3 files changed, 33 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> > > index bd650e6..ccc92db 100644
> > > --- a/kexec/arch/arm64/kexec-arm64.c
> > > +++ b/kexec/arch/arm64/kexec-arm64.c
> > > @@ -54,7 +54,7 @@
> > >  static bool try_read_phys_offset_from_kcore = false;
> > >
> > >  /* Machine specific details. */
> > > -static int va_bits;
> > > +static int va_bits = -1;
> > >  static unsigned long page_offset;
> > >
> > >  /* Global varables the core kexec routines expect. */
> > > @@ -876,7 +876,15 @@ static inline void set_phys_offset(long v, char *set_method)
> > >
> > >  static int get_va_bits(void)
> > >  {
> > > -     unsigned long long stext_sym_addr = get_kernel_sym("_stext");
> > > +     unsigned long long stext_sym_addr;
> > > +
> > > +     /*
> > > +      * if already got from kcore
> > > +      */
> > > +     if (va_bits != -1)
> > > +             goto out;
> >
> > If va_bits is exposed by the kernel then it will be used.
> > Else we continue here. Are there actually cases (old kernels) where
> > we expect to continue. Or could we get rid of the fallback code here?
> >
> 
> va_bits is exposed by kernel commit 84c57dbd3c48 ("arm64: kernel:
> arch_crash_save_vmcoreinfo() should depend on CONFIG_CRASH_CORE")
> And the first kernel which contains VA_BITS is v4.19.
> I have no idea about the need for old kernels. Maybe just keep the
> compatible code and throw a warning to remind users?

I suspect that kexec for ARM64 was present in v4.19, so we
should leave this part as-is.

> > > +
> > > +     stext_sym_addr = get_kernel_sym("_stext");
> > >
> > >       if (stext_sym_addr == 0) {
> > >               fprintf(stderr, "Can't get the symbol of _stext.\n");
> > > @@ -900,6 +908,7 @@ static int get_va_bits(void)
> > >               return -1;
> > >       }
> > >
> > > +out:
> > >       dbgprintf("va_bits : %d\n", va_bits);
> > >
> > >       return 0;
> > > @@ -917,14 +926,27 @@ int get_page_offset(unsigned long *page_offset)
> > >       if (ret < 0)
> > >               return ret;
> > >
> >
> > I'm confused about why there is both a (va_bits - 1)
> > and va_bits case here.
> >
> 
> It originates from the changes of memory layout on arm64.
> And mostly it is contributed by kernel commit 14c127c957c1 ("arm64:
> mm: Flip kernel VA space"),
> where sees the changes:
> -#define PAGE_OFFSET            (UL(0xffffffffffffffff) - \
>         (UL(1) << (VA_BITS - 1)) + 1)
> +#define PAGE_OFFSET            (UL(0xffffffffffffffff) - \
> +       (UL(1) << VA_BITS) + 1)
> 
> 
> Thanks,
> 
> Pingfan
> 

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