[Crash-utility] [PATCH] Improve error handling when architecture doesn't match
Currently, crash prints always
crash: vmcore: not a supported file format
if you try to open a dump file which is not supported. However, it can be
misleading if you have a valid ELF core dump, but just use crash for the wrong
architecture. In the case I observed the user had a ELF64 x86 dump file and
assumed it's x86-64. However, it just was a i386 core dump which was ELF64
because kexec was called with --elf64-core-headers which makes sense
if the i386 machine has PAE and possibly more than 4 GiB of physical RAM.
After that patch is applied, an example output is
Looks like a valid ELF dump, but host architecture (X86_64) \
doesn't match dump architecture (IA64).
or if I try to open a PPC64 dump on x86-64:
Looks like a valid ELF dump, but host endianess (LE) \
doesn't match target endianess (BE)
Please review and consider applying.
Signed-off-by: Bernhard Walle <bwalle(a)suse.de>
---
defs.h | 3 ++-
netdump.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
tools.c | 9 ++++++++-
3 files changed, 53 insertions(+), 7 deletions(-)
--- a/defs.h
+++ b/defs.h
@@ -3198,7 +3198,8 @@ void stall(ulong);
char *pages_to_size(ulong, char *);
int clean_arg(void);
int empty_list(ulong);
-int machine_type(char *);
+int machine_type(const char *);
+int is_big_endian(void);
void command_not_supported(void);
void option_not_supported(int);
void please_wait(char *);
--- a/netdump.c
+++ b/netdump.c
@@ -36,6 +36,32 @@ static void check_dumpfile_size(char *);
#define ELFREAD 0
#define MIN_PAGE_SIZE (4096)
+
+
+/*
+ * Checks if the machine type of the host matches required_type.
+ * If not, it prints a short error message for the user.
+ */
+static int machine_type_error(const char *required_type)
+{
+ if (machine_type(required_type))
+ return 1;
+ else {
+ fprintf(stderr, "Looks like a valid ELF dump, but host "
+ "architecture (%s) doesn't match dump "
+ "architecture (%s).\n",
+ MACHINE_TYPE, required_type);
+ return 0;
+ }
+}
+
+/*
+ * Returns endianess in a string
+ */
+static const char *endianess_to_string(int big_endian)
+{
+ return big_endian ? "BE" : "LE";
+}
/*
* Determine whether a file is a netdump/diskdump/kdump creation,
@@ -98,6 +124,18 @@ is_netdump(char *file, ulong source_quer
* If either kdump difference is seen, presume kdump -- this
* is obviously subject to change.
*/
+
+ /* check endianess */
+ if ((STRNEQ(elf32->e_ident, ELFMAG) || STRNEQ(elf64->e_ident, ELFMAG)) &&
+ (elf32->e_type == ET_CORE || elf64->e_type == ET_CORE) &&
+ (elf32->e_ident[EI_DATA] == ELFDATA2LSB && is_big_endian()) ||
+ (elf32->e_ident[EI_DATA] == ELFDATA2MSB && !is_big_endian()))
+ fprintf(stderr, "Looks like a valid ELF dump, but host "
+ "endianess (%s) doesn't match target "
+ "endianess (%s)\n",
+ endianess_to_string(is_big_endian()),
+ endianess_to_string(elf32->e_ident[EI_DATA] == ELFDATA2MSB));
+
if (STRNEQ(elf32->e_ident, ELFMAG) &&
(elf32->e_ident[EI_CLASS] == ELFCLASS32) &&
(elf32->e_ident[EI_DATA] == ELFDATA2LSB) &&
@@ -108,7 +146,7 @@ is_netdump(char *file, ulong source_quer
switch (elf32->e_machine)
{
case EM_386:
- if (machine_type("X86"))
+ if (machine_type_error("X86"))
break;
default:
goto bailout;
@@ -133,28 +171,28 @@ is_netdump(char *file, ulong source_quer
{
case EM_IA_64:
if ((elf64->e_ident[EI_DATA] == ELFDATA2LSB) &&
- machine_type("IA64"))
+ machine_type_error("IA64"))
break;
else
goto bailout;
case EM_PPC64:
if ((elf64->e_ident[EI_DATA] == ELFDATA2MSB) &&
- machine_type("PPC64"))
+ machine_type_error("PPC64"))
break;
else
goto bailout;
case EM_X86_64:
if ((elf64->e_ident[EI_DATA] == ELFDATA2LSB) &&
- machine_type("X86_64"))
+ machine_type_error("X86_64"))
break;
else
goto bailout;
case EM_386:
if ((elf64->e_ident[EI_DATA] == ELFDATA2LSB) &&
- machine_type("X86"))
+ machine_type_error("X86"))
break;
else
goto bailout;
--- a/tools.c
+++ b/tools.c
@@ -4518,11 +4518,18 @@ empty_list(ulong list_head_addr)
}
int
-machine_type(char *type)
+machine_type(const char *type)
{
return STREQ(MACHINE_TYPE, type);
}
+int
+is_big_endian(void)
+{
+ unsigned short value = 0xff;
+ return *((unsigned char *)&value) != 0xff;
+}
+
void
command_not_supported()
{