[PATCH 0/2] Limit the size of vmcore-dmesg.txt to 2G

[PATCH 0/2] Limit the size of vmcore-dmesg.txt to 2G

[Lianbo Jiang]

[PATCH 1/2] cleanup: move it back from util_lib/elf_info.c
Some code related to vmcore-dmesg.c is put into the util_lib, which
is not very reasonable, so lets move it back and tidy up those code.
    
In addition, that will also help to limit the size of vmcore-dmesg.txt.

[PATCH 2/2] Limit the size of vmcore-dmesg.txt to 2G
With some corrupted vmcore files, the vmcore-dmesg.txt file may
grow forever till the kdump disk becomes full. Lets limit the
size of vmcore-dmesg.txt to avoid such problems.

BTW: I tested this patch on x86 64 and arm64, it also worked well.

Lianbo Jiang (2):
  cleanup: move it back from util_lib/elf_info.c
  Limit the size of vmcore-dmesg.txt to 2G

 kexec/arch/arm64/kexec-arm64.c |  2 +-
 util_lib/elf_info.c            | 73 ++++++++--------------------------
 util_lib/include/elf_info.h    |  8 +++-
 vmcore-dmesg/vmcore-dmesg.c    | 54 ++++++++++++++++++++++---
 4 files changed, 71 insertions(+), 66 deletions(-)

-- 
2.17.1


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[PATCH 1/2] cleanup: move it back from util_lib/elf_info.c

[Lianbo Jiang]

Some code related to vmcore-dmesg.c is put into the util_lib, which
is not very reasonable, so lets move it back and tidy up those code.

In addition, that will also help to limit the size of vmcore-dmesg.txt.

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
 kexec/arch/arm64/kexec-arm64.c |  2 +-
 util_lib/elf_info.c            | 73 ++++++++--------------------------
 util_lib/include/elf_info.h    |  8 +++-
 vmcore-dmesg/vmcore-dmesg.c    | 44 +++++++++++++++++---
 4 files changed, 61 insertions(+), 66 deletions(-)

diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
index eb3a3a37307c..6ad3b0a134b3 100644
--- a/kexec/arch/arm64/kexec-arm64.c
+++ b/kexec/arch/arm64/kexec-arm64.c
@@ -889,7 +889,7 @@ int get_phys_base_from_pt_load(unsigned long *phys_offset)
 		return EFAILED;
 	}
 
-	read_elf_kcore(fd);
+	read_elf(fd);
 
 	for (i = 0; get_pt_load(i,
 		    &phys_start, NULL, &virt_start, NULL);
diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
index 90a3b21662e7..2f254e972721 100644
--- a/util_lib/elf_info.c
+++ b/util_lib/elf_info.c
@@ -20,7 +20,6 @@
 /* The 32bit and 64bit note headers make it clear we don't care */
 typedef Elf32_Nhdr Elf_Nhdr;
 
-static const char *fname;
 static Elf64_Ehdr ehdr;
 static Elf64_Phdr *phdr;
 static int num_pt_loads;
@@ -120,8 +119,8 @@ void read_elf32(int fd)
 
 	ret = pread(fd, &ehdr32, sizeof(ehdr32), 0);
 	if (ret != sizeof(ehdr32)) {
-		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
-			fname, strerror(errno));
+		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
+				__func__, strerror(errno));
 		exit(10);
 	}
 
@@ -193,8 +192,8 @@ void read_elf64(int fd)
 
 	ret = pread(fd, &ehdr64, sizeof(ehdr64), 0);
 	if (ret < 0 || (size_t)ret != sizeof(ehdr)) {
-		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
-			fname, strerror(errno));
+		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
+				__func__, strerror(errno));
 		exit(10);
 	}
 
@@ -531,19 +530,7 @@ static int32_t read_file_s32(int fd, uint64_t addr)
 	return read_file_u32(fd, addr);
 }
 
-static void write_to_stdout(char *buf, unsigned int nr)
-{
-	ssize_t ret;
-
-	ret = write(STDOUT_FILENO, buf, nr);
-	if (ret != nr) {
-		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
-			" %s\n", strerror(errno));
-		exit(54);
-	}
-}
-
-static void dump_dmesg_legacy(int fd)
+void dump_dmesg_legacy(int fd, handler_t handler)
 {
 	uint64_t log_buf, log_buf_offset;
 	unsigned log_end, logged_chars, log_end_wrapped;
@@ -604,7 +591,7 @@ static void dump_dmesg_legacy(int fd)
 	 */
 	logged_chars = log_end < log_buf_len ? log_end : log_buf_len;
 
-	write_to_stdout(buf + (log_buf_len - logged_chars), logged_chars);
+	handler(buf + (log_buf_len - logged_chars), logged_chars);
 }
 
 static inline uint16_t struct_val_u16(char *ptr, unsigned int offset)
@@ -623,7 +610,7 @@ static inline uint64_t struct_val_u64(char *ptr, unsigned int offset)
 }
 
 /* Read headers of log records and dump accordingly */
-static void dump_dmesg_structured(int fd)
+void dump_dmesg_structured(int fd, handler_t handler)
 {
 #define OUT_BUF_SIZE	4096
 	uint64_t log_buf, log_buf_offset, ts_nsec;
@@ -733,7 +720,7 @@ static void dump_dmesg_structured(int fd)
 				out_buf[len++] = c;
 
 			if (len >= OUT_BUF_SIZE - 64) {
-				write_to_stdout(out_buf, len);
+				handler(out_buf, len);
 				len = 0;
 			}
 		}
@@ -753,25 +740,24 @@ static void dump_dmesg_structured(int fd)
 	}
 	free(buf);
 	if (len)
-		write_to_stdout(out_buf, len);
+		handler(out_buf, len);
 }
 
-static void dump_dmesg(int fd)
+int check_log_first_idx_vaddr(void)
 {
 	if (log_first_idx_vaddr)
-		dump_dmesg_structured(fd);
-	else
-		dump_dmesg_legacy(fd);
+		return 1;
+
+	return 0;
 }
 
-static int read_elf(int fd)
+int read_elf(int fd)
 {
 	int ret;
 
 	ret = pread(fd, ehdr.e_ident, EI_NIDENT, 0);
 	if (ret != EI_NIDENT) {
-		fprintf(stderr, "Read of e_ident from %s failed: %s\n",
-			fname, strerror(errno));
+		fprintf(stderr, "Read of e_ident failed: %s\n", strerror(errno));
 		return 3;
 	}
 	if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0) {
@@ -808,40 +794,13 @@ static int read_elf(int fd)
 	return 0;
 }
 
-int read_elf_vmcore(int fd)
-{
-	int ret;
-
-	ret = read_elf(fd);
-	if (ret > 0) {
-		fprintf(stderr, "Unable to read ELF information"
-			" from vmcore\n");
-		return ret;
-	}
-
-	dump_dmesg(fd);
-
-	return 0;
-}
-
-int read_elf_kcore(int fd)
-{
-	int ret;
-
-	ret = read_elf(fd);
-	if (ret != 0)
-		return ret;
-
-	return 0;
-}
-
 int read_phys_offset_elf_kcore(int fd, unsigned long *phys_off)
 {
 	int ret;
 
 	*phys_off = UINT64_MAX;
 
-	ret = read_elf_kcore(fd);
+	ret = read_elf(fd);
 	if (!ret) {
 		/* If we have a valid 'PHYS_OFFSET' by now,
 		 * return it to the caller now.
diff --git a/util_lib/include/elf_info.h b/util_lib/include/elf_info.h
index 1a4debd2d4ba..8ee7d3e2763f 100644
--- a/util_lib/include/elf_info.h
+++ b/util_lib/include/elf_info.h
@@ -23,13 +23,17 @@
 #include <inttypes.h>
 #include <ctype.h>
 
+typedef void (*handler_t)(char *msg, unsigned int bytes);
+
 int get_pt_load(int idx,
 	unsigned long long *phys_start,
 	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_elf_kcore(int fd);
-int read_elf_vmcore(int fd);
+int check_log_first_idx_vaddr(void);
+void dump_dmesg_structured(int fd, handler_t handler);
+void dump_dmesg_legacy(int fd, handler_t handler);
+int read_elf(int fd);
 
 #endif /* ELF_INFO_H */
diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
index 7a386b380291..ff0d540c9130 100644
--- a/vmcore-dmesg/vmcore-dmesg.c
+++ b/vmcore-dmesg/vmcore-dmesg.c
@@ -1,21 +1,53 @@
 #include <elf_info.h>
 
-/* The 32bit and 64bit note headers make it clear we don't care */
-typedef Elf32_Nhdr Elf_Nhdr;
+static void write_to_stdout(char *buf, unsigned int nr)
+{
+	ssize_t ret;
+
+	ret = write(STDOUT_FILENO, buf, nr);
+	if (ret != nr) {
+		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
+				" %s\n", strerror(errno));
+		exit(54);
+	}
+}
+
+static void dump_dmesg(int fd, handler_t handler)
+{
+	if (check_log_first_idx_vaddr())
+		dump_dmesg_structured(fd, handler);
+	else
+		dump_dmesg_legacy(fd, handler);
+}
 
-static const char *fname;
+static int read_vmcore_dmesg(int fd)
+{
+        int ret;
+
+        ret = read_elf(fd);
+        if (ret > 0) {
+                fprintf(stderr, "Unable to read ELF information"
+                        " from vmcore\n");
+                return ret;
+        }
+
+        dump_dmesg(fd, write_to_stdout);
+
+        return 0;
+}
 
 int main(int argc, char **argv)
 {
 	ssize_t ret;
 	int fd;
+	const char *fname;
 
 	if (argc != 2) {
 		fprintf(stderr, "usage: %s <kernel core file>\n", argv[0]);
 		return 1;
 	}
-	fname = argv[1];
 
+	fname = argv[1];
 	fd = open(fname, O_RDONLY);
 	if (fd < 0) {
 		fprintf(stderr, "Cannot open %s: %s\n",
@@ -23,8 +55,8 @@ int main(int argc, char **argv)
 		return 2;
 	}
 
-	ret = read_elf_vmcore(fd);
-	
+	ret = read_vmcore_dmesg(fd);
+
 	close(fd);
 
 	return ret;
-- 
2.17.1


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Re: [PATCH 1/2] cleanup: move it back from util_lib/elf_info.c

[Simon Horman]

Hi Lianbo,

I like where this patch is going but I would like to request a few changes.
Please see comments inline.

On Thu, Aug 15, 2019 at 11:37:55AM +0800, Lianbo Jiang wrote:
> Some code related to vmcore-dmesg.c is put into the util_lib, which
> is not very reasonable, so lets move it back and tidy up those code.
> 
> In addition, that will also help to limit the size of vmcore-dmesg.txt.
> 
> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> ---
>  kexec/arch/arm64/kexec-arm64.c |  2 +-
>  util_lib/elf_info.c            | 73 ++++++++--------------------------
>  util_lib/include/elf_info.h    |  8 +++-
>  vmcore-dmesg/vmcore-dmesg.c    | 44 +++++++++++++++++---
>  4 files changed, 61 insertions(+), 66 deletions(-)
> 
> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
> index eb3a3a37307c..6ad3b0a134b3 100644
> --- a/kexec/arch/arm64/kexec-arm64.c
> +++ b/kexec/arch/arm64/kexec-arm64.c
> @@ -889,7 +889,7 @@ int get_phys_base_from_pt_load(unsigned long *phys_offset)
>  		return EFAILED;
>  	}
>  
> -	read_elf_kcore(fd);
> +	read_elf(fd);
>  
>  	for (i = 0; get_pt_load(i,
>  		    &phys_start, NULL, &virt_start, NULL);
> diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
> index 90a3b21662e7..2f254e972721 100644
> --- a/util_lib/elf_info.c
> +++ b/util_lib/elf_info.c
> @@ -20,7 +20,6 @@
>  /* The 32bit and 64bit note headers make it clear we don't care */
>  typedef Elf32_Nhdr Elf_Nhdr;
>  
> -static const char *fname;
>  static Elf64_Ehdr ehdr;
>  static Elf64_Phdr *phdr;
>  static int num_pt_loads;
> @@ -120,8 +119,8 @@ void read_elf32(int fd)
>  
>  	ret = pread(fd, &ehdr32, sizeof(ehdr32), 0);
>  	if (ret != sizeof(ehdr32)) {
> -		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
> -			fname, strerror(errno));
> +		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
> +				__func__, strerror(errno));

I'm not sure of the merit of changing the loging output.
And moreover I don't think it belongs in this patch
as it doesn't seem related to the other changes.

>  		exit(10);
>  	}
>  
> @@ -193,8 +192,8 @@ void read_elf64(int fd)
>  
>  	ret = pread(fd, &ehdr64, sizeof(ehdr64), 0);
>  	if (ret < 0 || (size_t)ret != sizeof(ehdr)) {
> -		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
> -			fname, strerror(errno));
> +		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
> +				__func__, strerror(errno));
>  		exit(10);
>  	}
>  
> @@ -531,19 +530,7 @@ static int32_t read_file_s32(int fd, uint64_t addr)
>  	return read_file_u32(fd, addr);
>  }
>  
> -static void write_to_stdout(char *buf, unsigned int nr)
> -{
> -	ssize_t ret;
> -
> -	ret = write(STDOUT_FILENO, buf, nr);
> -	if (ret != nr) {
> -		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
> -			" %s\n", strerror(errno));
> -		exit(54);
> -	}
> -}
> -
> -static void dump_dmesg_legacy(int fd)
> +void dump_dmesg_legacy(int fd, handler_t handler)
>  {
>  	uint64_t log_buf, log_buf_offset;
>  	unsigned log_end, logged_chars, log_end_wrapped;
> @@ -604,7 +591,7 @@ static void dump_dmesg_legacy(int fd)
>  	 */
>  	logged_chars = log_end < log_buf_len ? log_end : log_buf_len;
>  
> -	write_to_stdout(buf + (log_buf_len - logged_chars), logged_chars);
> +	handler(buf + (log_buf_len - logged_chars), logged_chars);
>  }
>  
>  static inline uint16_t struct_val_u16(char *ptr, unsigned int offset)
> @@ -623,7 +610,7 @@ static inline uint64_t struct_val_u64(char *ptr, unsigned int offset)
>  }
>  
>  /* Read headers of log records and dump accordingly */
> -static void dump_dmesg_structured(int fd)
> +void dump_dmesg_structured(int fd, handler_t handler)
>  {
>  #define OUT_BUF_SIZE	4096
>  	uint64_t log_buf, log_buf_offset, ts_nsec;
> @@ -733,7 +720,7 @@ static void dump_dmesg_structured(int fd)
>  				out_buf[len++] = c;
>  
>  			if (len >= OUT_BUF_SIZE - 64) {
> -				write_to_stdout(out_buf, len);
> +				handler(out_buf, len);
>  				len = 0;
>  			}
>  		}
> @@ -753,25 +740,24 @@ static void dump_dmesg_structured(int fd)
>  	}
>  	free(buf);
>  	if (len)
> -		write_to_stdout(out_buf, len);
> +		handler(out_buf, len);
>  }
>  
> -static void dump_dmesg(int fd)
> +int check_log_first_idx_vaddr(void)
>  {
>  	if (log_first_idx_vaddr)
> -		dump_dmesg_structured(fd);
> -	else
> -		dump_dmesg_legacy(fd);
> +		return 1;
> +
> +	return 0;
>  }
>  
> -static int read_elf(int fd)
> +int read_elf(int fd)
>  {
>  	int ret;
>  
>  	ret = pread(fd, ehdr.e_ident, EI_NIDENT, 0);
>  	if (ret != EI_NIDENT) {
> -		fprintf(stderr, "Read of e_ident from %s failed: %s\n",
> -			fname, strerror(errno));
> +		fprintf(stderr, "Read of e_ident failed: %s\n", strerror(errno));
>  		return 3;
>  	}
>  	if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0) {
> @@ -808,40 +794,13 @@ static int read_elf(int fd)
>  	return 0;
>  }
>  
> -int read_elf_vmcore(int fd)
> -{
> -	int ret;
> -
> -	ret = read_elf(fd);
> -	if (ret > 0) {
> -		fprintf(stderr, "Unable to read ELF information"
> -			" from vmcore\n");
> -		return ret;
> -	}
> -
> -	dump_dmesg(fd);
> -
> -	return 0;
> -}
> -
> -int read_elf_kcore(int fd)
> -{
> -	int ret;
> -
> -	ret = read_elf(fd);
> -	if (ret != 0)
> -		return ret;
> -
> -	return 0;
> -}

I think that removing read_elf_kcore is not related to the rest of this
patch and should be in a separate patch - it is a nice cleanup.

> -
>  int read_phys_offset_elf_kcore(int fd, unsigned long *phys_off)
>  {
>  	int ret;
>  
>  	*phys_off = UINT64_MAX;
>  
> -	ret = read_elf_kcore(fd);
> +	ret = read_elf(fd);
>  	if (!ret) {
>  		/* If we have a valid 'PHYS_OFFSET' by now,
>  		 * return it to the caller now.
> diff --git a/util_lib/include/elf_info.h b/util_lib/include/elf_info.h
> index 1a4debd2d4ba..8ee7d3e2763f 100644
> --- a/util_lib/include/elf_info.h
> +++ b/util_lib/include/elf_info.h
> @@ -23,13 +23,17 @@
>  #include <inttypes.h>
>  #include <ctype.h>
>  
> +typedef void (*handler_t)(char *msg, unsigned int bytes);

I would prefer it if we did not add new typedefs.

> +
>  int get_pt_load(int idx,
>  	unsigned long long *phys_start,
>  	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_elf_kcore(int fd);
> -int read_elf_vmcore(int fd);
> +int check_log_first_idx_vaddr(void);
> +void dump_dmesg_structured(int fd, handler_t handler);
> +void dump_dmesg_legacy(int fd, handler_t handler);
> +int read_elf(int fd);
>  
>  #endif /* ELF_INFO_H */
> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
> index 7a386b380291..ff0d540c9130 100644
> --- a/vmcore-dmesg/vmcore-dmesg.c
> +++ b/vmcore-dmesg/vmcore-dmesg.c
> @@ -1,21 +1,53 @@
>  #include <elf_info.h>
>  
> -/* The 32bit and 64bit note headers make it clear we don't care */
> -typedef Elf32_Nhdr Elf_Nhdr;
> +static void write_to_stdout(char *buf, unsigned int nr)
> +{
> +	ssize_t ret;
> +
> +	ret = write(STDOUT_FILENO, buf, nr);
> +	if (ret != nr) {
> +		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
> +				" %s\n", strerror(errno));
> +		exit(54);
> +	}
> +}
> +
> +static void dump_dmesg(int fd, handler_t handler)
> +{
> +	if (check_log_first_idx_vaddr())
> +		dump_dmesg_structured(fd, handler);
> +	else
> +		dump_dmesg_legacy(fd, handler);
> +}

I think that dump_dmesg() could stay in kexec-arm64.c,
it does not seem specific to vmcore handling.

> -static const char *fname;
> +static int read_vmcore_dmesg(int fd)
> +{
> +        int ret;
> +
> +        ret = read_elf(fd);
> +        if (ret > 0) {
> +                fprintf(stderr, "Unable to read ELF information"
> +                        " from vmcore\n");
> +                return ret;
> +        }
> +
> +        dump_dmesg(fd, write_to_stdout);
> +
> +        return 0;
> +}
>  
>  int main(int argc, char **argv)
>  {
>  	ssize_t ret;
>  	int fd;
> +	const char *fname;
>  
>  	if (argc != 2) {
>  		fprintf(stderr, "usage: %s <kernel core file>\n", argv[0]);
>  		return 1;
>  	}
> -	fname = argv[1];
>  
> +	fname = argv[1];
>  	fd = open(fname, O_RDONLY);
>  	if (fd < 0) {
>  		fprintf(stderr, "Cannot open %s: %s\n",
> @@ -23,8 +55,8 @@ int main(int argc, char **argv)
>  		return 2;
>  	}
>  
> -	ret = read_elf_vmcore(fd);
> -	
> +	ret = read_vmcore_dmesg(fd);
> +
>  	close(fd);
>  
>  	return ret;
> -- 
> 2.17.1
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 

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Re: [PATCH 1/2] cleanup: move it back from util_lib/elf_info.c

[lijiang]

在 2019年08月22日 16:51, Simon Horman 写道:
> Hi Lianbo,
> 
> I like where this patch is going but I would like to request a few changes.
> Please see comments inline.
> 

Thanks for your comment, Simon.

> On Thu, Aug 15, 2019 at 11:37:55AM +0800, Lianbo Jiang wrote:
>> Some code related to vmcore-dmesg.c is put into the util_lib, which
>> is not very reasonable, so lets move it back and tidy up those code.
>>
>> In addition, that will also help to limit the size of vmcore-dmesg.txt.
>>
>> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
>> ---
>>  kexec/arch/arm64/kexec-arm64.c |  2 +-
>>  util_lib/elf_info.c            | 73 ++++++++--------------------------
>>  util_lib/include/elf_info.h    |  8 +++-
>>  vmcore-dmesg/vmcore-dmesg.c    | 44 +++++++++++++++++---
>>  4 files changed, 61 insertions(+), 66 deletions(-)
>>
>> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
>> index eb3a3a37307c..6ad3b0a134b3 100644
>> --- a/kexec/arch/arm64/kexec-arm64.c
>> +++ b/kexec/arch/arm64/kexec-arm64.c
>> @@ -889,7 +889,7 @@ int get_phys_base_from_pt_load(unsigned long *phys_offset)
>>  		return EFAILED;
>>  	}
>>  
>> -	read_elf_kcore(fd);
>> +	read_elf(fd);
>>  
>>  	for (i = 0; get_pt_load(i,
>>  		    &phys_start, NULL, &virt_start, NULL);
>> diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
>> index 90a3b21662e7..2f254e972721 100644
>> --- a/util_lib/elf_info.c
>> +++ b/util_lib/elf_info.c
>> @@ -20,7 +20,6 @@
>>  /* The 32bit and 64bit note headers make it clear we don't care */
>>  typedef Elf32_Nhdr Elf_Nhdr;
>>  
>> -static const char *fname;
>>  static Elf64_Ehdr ehdr;
>>  static Elf64_Phdr *phdr;
>>  static int num_pt_loads;
>> @@ -120,8 +119,8 @@ void read_elf32(int fd)
>>  
>>  	ret = pread(fd, &ehdr32, sizeof(ehdr32), 0);
>>  	if (ret != sizeof(ehdr32)) {
>> -		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
>> -			fname, strerror(errno));
>> +		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
>> +				__func__, strerror(errno));
> 
> I'm not sure of the merit of changing the loging output.

The variable 'fname' is defined two twice, the first definition is in the vmcore-dmesg.c, and the
second definition is in the elf_info.c. That is confused although it's a static type, because i do
not see the place where the value of variable 'fname' is set in elf_info.c. So i guess that it should
be a same variable within the vmcore-dmesg.c and also need to clean up.

> And moreover I don't think it belongs in this patch
> as it doesn't seem related to the other changes.
> 

Good question. I will consider how to clean up. Probably, it should be a separate patch.

>>  		exit(10);
>>  	}
>>  
>> @@ -193,8 +192,8 @@ void read_elf64(int fd)
>>  
>>  	ret = pread(fd, &ehdr64, sizeof(ehdr64), 0);
>>  	if (ret < 0 || (size_t)ret != sizeof(ehdr)) {
>> -		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
>> -			fname, strerror(errno));
>> +		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
>> +				__func__, strerror(errno));
>>  		exit(10);
>>  	}
>>  
>> @@ -531,19 +530,7 @@ static int32_t read_file_s32(int fd, uint64_t addr)
>>  	return read_file_u32(fd, addr);
>>  }
>>  
>> -static void write_to_stdout(char *buf, unsigned int nr)
>> -{
>> -	ssize_t ret;
>> -
>> -	ret = write(STDOUT_FILENO, buf, nr);
>> -	if (ret != nr) {
>> -		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
>> -			" %s\n", strerror(errno));
>> -		exit(54);
>> -	}
>> -}
>> -
>> -static void dump_dmesg_legacy(int fd)
>> +void dump_dmesg_legacy(int fd, handler_t handler)
>>  {
>>  	uint64_t log_buf, log_buf_offset;
>>  	unsigned log_end, logged_chars, log_end_wrapped;
>> @@ -604,7 +591,7 @@ static void dump_dmesg_legacy(int fd)
>>  	 */
>>  	logged_chars = log_end < log_buf_len ? log_end : log_buf_len;
>>  
>> -	write_to_stdout(buf + (log_buf_len - logged_chars), logged_chars);
>> +	handler(buf + (log_buf_len - logged_chars), logged_chars);
>>  }
>>  
>>  static inline uint16_t struct_val_u16(char *ptr, unsigned int offset)
>> @@ -623,7 +610,7 @@ static inline uint64_t struct_val_u64(char *ptr, unsigned int offset)
>>  }
>>  
>>  /* Read headers of log records and dump accordingly */
>> -static void dump_dmesg_structured(int fd)
>> +void dump_dmesg_structured(int fd, handler_t handler)
>>  {
>>  #define OUT_BUF_SIZE	4096
>>  	uint64_t log_buf, log_buf_offset, ts_nsec;
>> @@ -733,7 +720,7 @@ static void dump_dmesg_structured(int fd)
>>  				out_buf[len++] = c;
>>  
>>  			if (len >= OUT_BUF_SIZE - 64) {
>> -				write_to_stdout(out_buf, len);
>> +				handler(out_buf, len);
>>  				len = 0;
>>  			}
>>  		}
>> @@ -753,25 +740,24 @@ static void dump_dmesg_structured(int fd)
>>  	}
>>  	free(buf);
>>  	if (len)
>> -		write_to_stdout(out_buf, len);
>> +		handler(out_buf, len);
>>  }
>>  
>> -static void dump_dmesg(int fd)
>> +int check_log_first_idx_vaddr(void)
>>  {
>>  	if (log_first_idx_vaddr)
>> -		dump_dmesg_structured(fd);
>> -	else
>> -		dump_dmesg_legacy(fd);
>> +		return 1;
>> +
>> +	return 0;
>>  }
>>  
>> -static int read_elf(int fd)
>> +int read_elf(int fd)
>>  {
>>  	int ret;
>>  
>>  	ret = pread(fd, ehdr.e_ident, EI_NIDENT, 0);
>>  	if (ret != EI_NIDENT) {
>> -		fprintf(stderr, "Read of e_ident from %s failed: %s\n",
>> -			fname, strerror(errno));
>> +		fprintf(stderr, "Read of e_ident failed: %s\n", strerror(errno));
>>  		return 3;
>>  	}
>>  	if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0) {
>> @@ -808,40 +794,13 @@ static int read_elf(int fd)
>>  	return 0;
>>  }
>>  
>> -int read_elf_vmcore(int fd)
>> -{
>> -	int ret;
>> -
>> -	ret = read_elf(fd);
>> -	if (ret > 0) {
>> -		fprintf(stderr, "Unable to read ELF information"
>> -			" from vmcore\n");
>> -		return ret;
>> -	}
>> -
>> -	dump_dmesg(fd);
>> -
>> -	return 0;
>> -}
>> -
>> -int read_elf_kcore(int fd)
>> -{
>> -	int ret;
>> -
>> -	ret = read_elf(fd);
>> -	if (ret != 0)
>> -		return ret;
>> -
>> -	return 0;
>> -}
> 
> I think that removing read_elf_kcore is not related to the rest of this
> patch and should be in a separate patch - it is a nice cleanup.
> 
Good idea, i will split them into a separate patch.

>> -
>>  int read_phys_offset_elf_kcore(int fd, unsigned long *phys_off)
>>  {
>>  	int ret;
>>  
>>  	*phys_off = UINT64_MAX;
>>  
>> -	ret = read_elf_kcore(fd);
>> +	ret = read_elf(fd);
>>  	if (!ret) {
>>  		/* If we have a valid 'PHYS_OFFSET' by now,
>>  		 * return it to the caller now.
>> diff --git a/util_lib/include/elf_info.h b/util_lib/include/elf_info.h
>> index 1a4debd2d4ba..8ee7d3e2763f 100644
>> --- a/util_lib/include/elf_info.h
>> +++ b/util_lib/include/elf_info.h
>> @@ -23,13 +23,17 @@
>>  #include <inttypes.h>
>>  #include <ctype.h>
>>  
>> +typedef void (*handler_t)(char *msg, unsigned int bytes);
> 
> I would prefer it if we did not add new typedefs.
> 

OK. I'm considering how to handle it. Any suggestions?

>> +
>>  int get_pt_load(int idx,
>>  	unsigned long long *phys_start,
>>  	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_elf_kcore(int fd);
>> -int read_elf_vmcore(int fd);
>> +int check_log_first_idx_vaddr(void);
>> +void dump_dmesg_structured(int fd, handler_t handler);
>> +void dump_dmesg_legacy(int fd, handler_t handler);
>> +int read_elf(int fd);
>>  
>>  #endif /* ELF_INFO_H */
>> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
>> index 7a386b380291..ff0d540c9130 100644
>> --- a/vmcore-dmesg/vmcore-dmesg.c
>> +++ b/vmcore-dmesg/vmcore-dmesg.c
>> @@ -1,21 +1,53 @@
>>  #include <elf_info.h>
>>  
>> -/* The 32bit and 64bit note headers make it clear we don't care */
>> -typedef Elf32_Nhdr Elf_Nhdr;
>> +static void write_to_stdout(char *buf, unsigned int nr)
>> +{
>> +	ssize_t ret;
>> +
>> +	ret = write(STDOUT_FILENO, buf, nr);
>> +	if (ret != nr) {
>> +		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
>> +				" %s\n", strerror(errno));
>> +		exit(54);
>> +	}
>> +}
>> +
>> +static void dump_dmesg(int fd, handler_t handler)
>> +{
>> +	if (check_log_first_idx_vaddr())
>> +		dump_dmesg_structured(fd, handler);
>> +	else
>> +		dump_dmesg_legacy(fd, handler);
>> +}
> 
> I think that dump_dmesg() could stay in kexec-arm64.c,
> it does not seem specific to vmcore handling.
> 

The dump_dmesg() should be a common function, not only arm64 will use it, but
x86 64 will also call it. It would be good to put the dump_dmesg() to a common
place.

>> -static const char *fname;
>> +static int read_vmcore_dmesg(int fd)
>> +{
>> +        int ret;
>> +
>> +        ret = read_elf(fd);
>> +        if (ret > 0) {
>> +                fprintf(stderr, "Unable to read ELF information"
>> +                        " from vmcore\n");
>> +                return ret;
>> +        }
>> +
>> +        dump_dmesg(fd, write_to_stdout);
>> +
>> +        return 0;
>> +}
>>  
>>  int main(int argc, char **argv)
>>  {
>>  	ssize_t ret;
>>  	int fd;
>> +	const char *fname;
>>  
>>  	if (argc != 2) {
>>  		fprintf(stderr, "usage: %s <kernel core file>\n", argv[0]);
>>  		return 1;
>>  	}
>> -	fname = argv[1];
>>  
>> +	fname = argv[1];
>>  	fd = open(fname, O_RDONLY);
>>  	if (fd < 0) {
>>  		fprintf(stderr, "Cannot open %s: %s\n",
>> @@ -23,8 +55,8 @@ int main(int argc, char **argv)
>>  		return 2;
>>  	}
>>  
>> -	ret = read_elf_vmcore(fd);
>> -	
>> +	ret = read_vmcore_dmesg(fd);
>> +
>>  	close(fd);
>>  
>>  	return ret;
>> -- 
>> 2.17.1
>>
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec
>>

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Re: [PATCH 1/2] cleanup: move it back from util_lib/elf_info.c

[lijiang]

在 2019年08月23日 13:24, lijiang 写道:
> 在 2019年08月22日 16:51, Simon Horman 写道:
>> Hi Lianbo,
>>
>> I like where this patch is going but I would like to request a few changes.
>> Please see comments inline.
>>
> 
> Thanks for your comment, Simon.
> 
>> On Thu, Aug 15, 2019 at 11:37:55AM +0800, Lianbo Jiang wrote:
>>> Some code related to vmcore-dmesg.c is put into the util_lib, which
>>> is not very reasonable, so lets move it back and tidy up those code.
>>>
>>> In addition, that will also help to limit the size of vmcore-dmesg.txt.
>>>
>>> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
>>> ---
>>>  kexec/arch/arm64/kexec-arm64.c |  2 +-
>>>  util_lib/elf_info.c            | 73 ++++++++--------------------------
>>>  util_lib/include/elf_info.h    |  8 +++-
>>>  vmcore-dmesg/vmcore-dmesg.c    | 44 +++++++++++++++++---
>>>  4 files changed, 61 insertions(+), 66 deletions(-)
>>>
>>> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
>>> index eb3a3a37307c..6ad3b0a134b3 100644
>>> --- a/kexec/arch/arm64/kexec-arm64.c
>>> +++ b/kexec/arch/arm64/kexec-arm64.c
>>> @@ -889,7 +889,7 @@ int get_phys_base_from_pt_load(unsigned long *phys_offset)
>>>  		return EFAILED;
>>>  	}
>>>  
>>> -	read_elf_kcore(fd);
>>> +	read_elf(fd);
>>>  
>>>  	for (i = 0; get_pt_load(i,
>>>  		    &phys_start, NULL, &virt_start, NULL);
>>> diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
>>> index 90a3b21662e7..2f254e972721 100644
>>> --- a/util_lib/elf_info.c
>>> +++ b/util_lib/elf_info.c
>>> @@ -20,7 +20,6 @@
>>>  /* The 32bit and 64bit note headers make it clear we don't care */
>>>  typedef Elf32_Nhdr Elf_Nhdr;
>>>  
>>> -static const char *fname;
>>>  static Elf64_Ehdr ehdr;
>>>  static Elf64_Phdr *phdr;
>>>  static int num_pt_loads;
>>> @@ -120,8 +119,8 @@ void read_elf32(int fd)
>>>  
>>>  	ret = pread(fd, &ehdr32, sizeof(ehdr32), 0);
>>>  	if (ret != sizeof(ehdr32)) {
>>> -		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
>>> -			fname, strerror(errno));
>>> +		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
>>> +				__func__, strerror(errno));
>>
>> I'm not sure of the merit of changing the loging output.
> 
> The variable 'fname' is defined two twice, the first definition is in the vmcore-dmesg.c, and the
> second definition is in the elf_info.c. That is confused although it's a static type, because i do
> not see the place where the value of variable 'fname' is set in elf_info.c. So i guess that it should
> be a same variable within the vmcore-dmesg.c and also need to clean up.
> 
BTW: i guess the original definition of 'fname' should look like this:

diff --git a/util_lib/elf_info.c b/util_lib/elf_info.c
index d9397ecd8626..5d0efaafab53 100644
--- a/util_lib/elf_info.c
+++ b/util_lib/elf_info.c
@@ -20,7 +20,7 @@
 /* The 32bit and 64bit note headers make it clear we don't care */
 typedef Elf32_Nhdr Elf_Nhdr;
 
-static const char *fname;
+const char *fname;
 static Elf64_Ehdr ehdr;
 static Elf64_Phdr *phdr;
 static int num_pt_loads;
diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
index 7a386b380291..bebc348a657e 100644
--- a/vmcore-dmesg/vmcore-dmesg.c
+++ b/vmcore-dmesg/vmcore-dmesg.c
@@ -3,7 +3,7 @@
 /* The 32bit and 64bit note headers make it clear we don't care */
 typedef Elf32_Nhdr Elf_Nhdr;
 
-static const char *fname;
+extern const char *fname;
 
 int main(int argc, char **argv)
 {

>> And moreover I don't think it belongs in this patch
>> as it doesn't seem related to the other changes.
>>
> 
> Good question. I will consider how to clean up. Probably, it should be a separate patch.
> 
>>>  		exit(10);
>>>  	}
>>>  
>>> @@ -193,8 +192,8 @@ void read_elf64(int fd)
>>>  
>>>  	ret = pread(fd, &ehdr64, sizeof(ehdr64), 0);
>>>  	if (ret < 0 || (size_t)ret != sizeof(ehdr)) {
>>> -		fprintf(stderr, "Read of Elf header from %s failed: %s\n",
>>> -			fname, strerror(errno));
>>> +		fprintf(stderr, "Read of Elf header failed in %s: %s\n",
>>> +				__func__, strerror(errno));
>>>  		exit(10);
>>>  	}
>>>  
>>> @@ -531,19 +530,7 @@ static int32_t read_file_s32(int fd, uint64_t addr)
>>>  	return read_file_u32(fd, addr);
>>>  }
>>>  
>>> -static void write_to_stdout(char *buf, unsigned int nr)
>>> -{
>>> -	ssize_t ret;
>>> -
>>> -	ret = write(STDOUT_FILENO, buf, nr);
>>> -	if (ret != nr) {
>>> -		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
>>> -			" %s\n", strerror(errno));
>>> -		exit(54);
>>> -	}
>>> -}
>>> -
>>> -static void dump_dmesg_legacy(int fd)
>>> +void dump_dmesg_legacy(int fd, handler_t handler)
>>>  {
>>>  	uint64_t log_buf, log_buf_offset;
>>>  	unsigned log_end, logged_chars, log_end_wrapped;
>>> @@ -604,7 +591,7 @@ static void dump_dmesg_legacy(int fd)
>>>  	 */
>>>  	logged_chars = log_end < log_buf_len ? log_end : log_buf_len;
>>>  
>>> -	write_to_stdout(buf + (log_buf_len - logged_chars), logged_chars);
>>> +	handler(buf + (log_buf_len - logged_chars), logged_chars);
>>>  }
>>>  
>>>  static inline uint16_t struct_val_u16(char *ptr, unsigned int offset)
>>> @@ -623,7 +610,7 @@ static inline uint64_t struct_val_u64(char *ptr, unsigned int offset)
>>>  }
>>>  
>>>  /* Read headers of log records and dump accordingly */
>>> -static void dump_dmesg_structured(int fd)
>>> +void dump_dmesg_structured(int fd, handler_t handler)
>>>  {
>>>  #define OUT_BUF_SIZE	4096
>>>  	uint64_t log_buf, log_buf_offset, ts_nsec;
>>> @@ -733,7 +720,7 @@ static void dump_dmesg_structured(int fd)
>>>  				out_buf[len++] = c;
>>>  
>>>  			if (len >= OUT_BUF_SIZE - 64) {
>>> -				write_to_stdout(out_buf, len);
>>> +				handler(out_buf, len);
>>>  				len = 0;
>>>  			}
>>>  		}
>>> @@ -753,25 +740,24 @@ static void dump_dmesg_structured(int fd)
>>>  	}
>>>  	free(buf);
>>>  	if (len)
>>> -		write_to_stdout(out_buf, len);
>>> +		handler(out_buf, len);
>>>  }
>>>  
>>> -static void dump_dmesg(int fd)
>>> +int check_log_first_idx_vaddr(void)
>>>  {
>>>  	if (log_first_idx_vaddr)
>>> -		dump_dmesg_structured(fd);
>>> -	else
>>> -		dump_dmesg_legacy(fd);
>>> +		return 1;
>>> +
>>> +	return 0;
>>>  }
>>>  
>>> -static int read_elf(int fd)
>>> +int read_elf(int fd)
>>>  {
>>>  	int ret;
>>>  
>>>  	ret = pread(fd, ehdr.e_ident, EI_NIDENT, 0);
>>>  	if (ret != EI_NIDENT) {
>>> -		fprintf(stderr, "Read of e_ident from %s failed: %s\n",
>>> -			fname, strerror(errno));
>>> +		fprintf(stderr, "Read of e_ident failed: %s\n", strerror(errno));
>>>  		return 3;
>>>  	}
>>>  	if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) != 0) {
>>> @@ -808,40 +794,13 @@ static int read_elf(int fd)
>>>  	return 0;
>>>  }
>>>  
>>> -int read_elf_vmcore(int fd)
>>> -{
>>> -	int ret;
>>> -
>>> -	ret = read_elf(fd);
>>> -	if (ret > 0) {
>>> -		fprintf(stderr, "Unable to read ELF information"
>>> -			" from vmcore\n");
>>> -		return ret;
>>> -	}
>>> -
>>> -	dump_dmesg(fd);
>>> -
>>> -	return 0;
>>> -}
>>> -
>>> -int read_elf_kcore(int fd)
>>> -{
>>> -	int ret;
>>> -
>>> -	ret = read_elf(fd);
>>> -	if (ret != 0)
>>> -		return ret;
>>> -
>>> -	return 0;
>>> -}
>>
>> I think that removing read_elf_kcore is not related to the rest of this
>> patch and should be in a separate patch - it is a nice cleanup.
>>
> Good idea, i will split them into a separate patch.
> 
>>> -
>>>  int read_phys_offset_elf_kcore(int fd, unsigned long *phys_off)
>>>  {
>>>  	int ret;
>>>  
>>>  	*phys_off = UINT64_MAX;
>>>  
>>> -	ret = read_elf_kcore(fd);
>>> +	ret = read_elf(fd);
>>>  	if (!ret) {
>>>  		/* If we have a valid 'PHYS_OFFSET' by now,
>>>  		 * return it to the caller now.
>>> diff --git a/util_lib/include/elf_info.h b/util_lib/include/elf_info.h
>>> index 1a4debd2d4ba..8ee7d3e2763f 100644
>>> --- a/util_lib/include/elf_info.h
>>> +++ b/util_lib/include/elf_info.h
>>> @@ -23,13 +23,17 @@
>>>  #include <inttypes.h>
>>>  #include <ctype.h>
>>>  
>>> +typedef void (*handler_t)(char *msg, unsigned int bytes);
>>
>> I would prefer it if we did not add new typedefs.
>>
> 
> OK. I'm considering how to handle it. Any suggestions?
> 
>>> +
>>>  int get_pt_load(int idx,
>>>  	unsigned long long *phys_start,
>>>  	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_elf_kcore(int fd);
>>> -int read_elf_vmcore(int fd);
>>> +int check_log_first_idx_vaddr(void);
>>> +void dump_dmesg_structured(int fd, handler_t handler);
>>> +void dump_dmesg_legacy(int fd, handler_t handler);
>>> +int read_elf(int fd);
>>>  
>>>  #endif /* ELF_INFO_H */
>>> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
>>> index 7a386b380291..ff0d540c9130 100644
>>> --- a/vmcore-dmesg/vmcore-dmesg.c
>>> +++ b/vmcore-dmesg/vmcore-dmesg.c
>>> @@ -1,21 +1,53 @@
>>>  #include <elf_info.h>
>>>  
>>> -/* The 32bit and 64bit note headers make it clear we don't care */
>>> -typedef Elf32_Nhdr Elf_Nhdr;
>>> +static void write_to_stdout(char *buf, unsigned int nr)
>>> +{
>>> +	ssize_t ret;
>>> +
>>> +	ret = write(STDOUT_FILENO, buf, nr);
>>> +	if (ret != nr) {
>>> +		fprintf(stderr, "Failed to write out the dmesg log buffer!:"
>>> +				" %s\n", strerror(errno));
>>> +		exit(54);
>>> +	}
>>> +}
>>> +
>>> +static void dump_dmesg(int fd, handler_t handler)
>>> +{
>>> +	if (check_log_first_idx_vaddr())
>>> +		dump_dmesg_structured(fd, handler);
>>> +	else
>>> +		dump_dmesg_legacy(fd, handler);
>>> +}
>>
>> I think that dump_dmesg() could stay in kexec-arm64.c,
>> it does not seem specific to vmcore handling.
>>
> 
> The dump_dmesg() should be a common function, not only arm64 will use it, but
> x86 64 will also call it. It would be good to put the dump_dmesg() to a common
> place.
> 
>>> -static const char *fname;
>>> +static int read_vmcore_dmesg(int fd)
>>> +{
>>> +        int ret;
>>> +
>>> +        ret = read_elf(fd);
>>> +        if (ret > 0) {
>>> +                fprintf(stderr, "Unable to read ELF information"
>>> +                        " from vmcore\n");
>>> +                return ret;
>>> +        }
>>> +
>>> +        dump_dmesg(fd, write_to_stdout);
>>> +
>>> +        return 0;
>>> +}
>>>  
>>>  int main(int argc, char **argv)
>>>  {
>>>  	ssize_t ret;
>>>  	int fd;
>>> +	const char *fname;
>>>  
>>>  	if (argc != 2) {
>>>  		fprintf(stderr, "usage: %s <kernel core file>\n", argv[0]);
>>>  		return 1;
>>>  	}
>>> -	fname = argv[1];
>>>  
>>> +	fname = argv[1];
>>>  	fd = open(fname, O_RDONLY);
>>>  	if (fd < 0) {
>>>  		fprintf(stderr, "Cannot open %s: %s\n",
>>> @@ -23,8 +55,8 @@ int main(int argc, char **argv)
>>>  		return 2;
>>>  	}
>>>  
>>> -	ret = read_elf_vmcore(fd);
>>> -	
>>> +	ret = read_vmcore_dmesg(fd);
>>> +
>>>  	close(fd);
>>>  
>>>  	return ret;
>>> -- 
>>> 2.17.1
>>>
>>>
>>> _______________________________________________
>>> kexec mailing list
>>> kexec@lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/kexec
>>>

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[PATCH 2/2] Limit the size of vmcore-dmesg.txt to 2G

[Lianbo Jiang]

With some corrupted vmcore files, the vmcore-dmesg.txt file may grow
forever till the kdump disk becomes full, and also probably causes
the disk error messages as follow:
...
sd 0:0:0:0: [sda] tag#6 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
sd 0:0:0:0: [sda] tag#6 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
blk_update_request: I/O error, dev sda, sector 134630552
sd 0:0:0:0: [sda] tag#7 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
sd 0:0:0:0: [sda] tag#7 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
blk_update_request: I/O error, dev sda, sector 134630552
...

If vmcore-dmesg.txt occupies the whole disk, the vmcore can not be
saved, this is also a problem.

Lets limit the size of vmcore-dmesg.txt to avoid such problems.

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
 vmcore-dmesg/vmcore-dmesg.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
index ff0d540c9130..5ada3566972b 100644
--- a/vmcore-dmesg/vmcore-dmesg.c
+++ b/vmcore-dmesg/vmcore-dmesg.c
@@ -1,8 +1,18 @@
 #include <elf_info.h>
 
+/* stole this macro from kernel printk.c */
+#define LOG_BUF_LEN_MAX (uint32_t)(1 << 31)
+
 static void write_to_stdout(char *buf, unsigned int nr)
 {
 	ssize_t ret;
+	static uint32_t n_bytes = 0;
+
+	n_bytes += nr;
+	if (n_bytes > LOG_BUF_LEN_MAX) {
+		fprintf(stderr, "The vmcore-dmesg.txt over 2G in size is not supported.\n");
+		exit(55);
+	}
 
 	ret = write(STDOUT_FILENO, buf, nr);
 	if (ret != nr) {
-- 
2.17.1


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Re: [PATCH 2/2] Limit the size of vmcore-dmesg.txt to 2G

[Simon Horman]

On Thu, Aug 15, 2019 at 11:37:56AM +0800, Lianbo Jiang wrote:
> With some corrupted vmcore files, the vmcore-dmesg.txt file may grow
> forever till the kdump disk becomes full, and also probably causes
> the disk error messages as follow:
> ...
> sd 0:0:0:0: [sda] tag#6 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
> sd 0:0:0:0: [sda] tag#6 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
> blk_update_request: I/O error, dev sda, sector 134630552
> sd 0:0:0:0: [sda] tag#7 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
> sd 0:0:0:0: [sda] tag#7 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
> blk_update_request: I/O error, dev sda, sector 134630552
> ...
> 
> If vmcore-dmesg.txt occupies the whole disk, the vmcore can not be
> saved, this is also a problem.
> 
> Lets limit the size of vmcore-dmesg.txt to avoid such problems.
> 
> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>

Thanks, this looks good to me.

Please repost this patch with an updated version of Patch 1/2.

> ---
>  vmcore-dmesg/vmcore-dmesg.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
> index ff0d540c9130..5ada3566972b 100644
> --- a/vmcore-dmesg/vmcore-dmesg.c
> +++ b/vmcore-dmesg/vmcore-dmesg.c
> @@ -1,8 +1,18 @@
>  #include <elf_info.h>
>  
> +/* stole this macro from kernel printk.c */
> +#define LOG_BUF_LEN_MAX (uint32_t)(1 << 31)
> +
>  static void write_to_stdout(char *buf, unsigned int nr)
>  {
>  	ssize_t ret;
> +	static uint32_t n_bytes = 0;
> +
> +	n_bytes += nr;
> +	if (n_bytes > LOG_BUF_LEN_MAX) {
> +		fprintf(stderr, "The vmcore-dmesg.txt over 2G in size is not supported.\n");
> +		exit(55);
> +	}
>  
>  	ret = write(STDOUT_FILENO, buf, nr);
>  	if (ret != nr) {
> -- 
> 2.17.1
> 
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
> 

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Re: [PATCH 2/2] Limit the size of vmcore-dmesg.txt to 2G

[lijiang]

在 2019年08月22日 16:52, Simon Horman 写道:
> On Thu, Aug 15, 2019 at 11:37:56AM +0800, Lianbo Jiang wrote:
>> With some corrupted vmcore files, the vmcore-dmesg.txt file may grow
>> forever till the kdump disk becomes full, and also probably causes
>> the disk error messages as follow:
>> ...
>> sd 0:0:0:0: [sda] tag#6 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
>> sd 0:0:0:0: [sda] tag#6 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
>> blk_update_request: I/O error, dev sda, sector 134630552
>> sd 0:0:0:0: [sda] tag#7 FAILED Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK
>> sd 0:0:0:0: [sda] tag#7 CDB: Read(10) 28 00 08 06 4c 98 00 00 08 00
>> blk_update_request: I/O error, dev sda, sector 134630552
>> ...
>>
>> If vmcore-dmesg.txt occupies the whole disk, the vmcore can not be
>> saved, this is also a problem.
>>
>> Lets limit the size of vmcore-dmesg.txt to avoid such problems.
>>
>> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> 
> Thanks, this looks good to me.
> 
> Please repost this patch with an updated version of Patch 1/2.
> 

OK, thank you, Simon. I will improve them and post again.

>> ---
>>  vmcore-dmesg/vmcore-dmesg.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c
>> index ff0d540c9130..5ada3566972b 100644
>> --- a/vmcore-dmesg/vmcore-dmesg.c
>> +++ b/vmcore-dmesg/vmcore-dmesg.c
>> @@ -1,8 +1,18 @@
>>  #include <elf_info.h>
>>  
>> +/* stole this macro from kernel printk.c */
>> +#define LOG_BUF_LEN_MAX (uint32_t)(1 << 31)
>> +
>>  static void write_to_stdout(char *buf, unsigned int nr)
>>  {
>>  	ssize_t ret;
>> +	static uint32_t n_bytes = 0;
>> +
>> +	n_bytes += nr;
>> +	if (n_bytes > LOG_BUF_LEN_MAX) {
>> +		fprintf(stderr, "The vmcore-dmesg.txt over 2G in size is not supported.\n");
>> +		exit(55);
>> +	}
>>  
>>  	ret = write(STDOUT_FILENO, buf, nr);
>>  	if (ret != nr) {
>> -- 
>> 2.17.1
>>
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec
>>

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