3:01 p.m.
This patch adds a --kaslr command line parameter for loading x86_64
crash dumps with kaslr enabled. This reuses the code from 32-bit
x86 relocations with some small changes. The ASLR offset is postive
instead of negative. Also had to move the code to traverse the
kernel section before the symbol storing code to figure out which
symbols were outside any sections and therefore were not relocated.
Also made a very small change in search_for_switch_to it was
searching through gdb command output which can be different under
different settings.
Tested: Tested by loading kdump files from kernels with aslr enabled
and not enabled. Ran bt, files, and struct file 0xXXXXXX.
Signed-off-by: Andy Honig <ahonig(a)google.com>
---
defs.h | 2 ++
main.c | 8 ++++++--
symbols.c | 66 +++++++++++++++++++++++++++++++++++++++++++++------------------
x86_64.c | 20 +++++++++++++------
4 files changed, 69 insertions(+), 27 deletions(-)
diff --git a/defs.h b/defs.h
index 83a4402..8de1fa4 100755
--- a/defs.h
+++ b/defs.h
@@ -2394,6 +2394,8 @@ struct symbol_table_data {
ulong __per_cpu_end;
off_t dwarf_debug_frame_file_offset;
ulong dwarf_debug_frame_size;
+ ulong first_section_start;
+ ulong last_section_end;
};
/* flags for st */
diff --git a/main.c b/main.c
index 3b469e3..5a41c1a 100755
--- a/main.c
+++ b/main.c
@@ -57,6 +57,7 @@ static struct option long_options[] = {
{"CRASHPAGER", 0, 0, 0},
{"no_scroll", 0, 0, 0},
{"reloc", required_argument, 0, 0},
+ {"kaslr", required_argument, 0, 0},
{"active", 0, 0, 0},
{"minimal", 0, 0, 0},
{"mod", required_argument, 0, 0},
@@ -216,12 +217,15 @@ main(int argc, char **argv)
else if (STREQ(long_options[option_index].name, "mod"))
kt->module_tree = optarg;
- else if (STREQ(long_options[option_index].name, "reloc")) {
+ else if (STREQ(long_options[option_index].name, "reloc") ||
+ STREQ(long_options[option_index].name, "kaslr")) {
if (!calculate(optarg, &kt->relocate, NULL, 0)) {
error(INFO, "invalid --reloc argument: %s\n",
optarg);
program_usage(SHORT_FORM);
- }
+ } else if (STREQ(long_options[option_index].name, "kaslr")) {
+ kt->relocate *= -1;
+ }
kt->flags |= RELOC_SET;
}
diff --git a/symbols.c b/symbols.c
index 93d9c8c..345c0de 100755
--- a/symbols.c
+++ b/symbols.c
@@ -192,22 +192,6 @@ symtab_init(void)
if (!check_gnu_debuglink(st->bfd))
no_debugging_data(FATAL);
}
-
- symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
-
- if (symcount <= 0)
- no_debugging_data(FATAL);
-
- sort_x = bfd_make_empty_symbol(st->bfd);
- sort_y = bfd_make_empty_symbol(st->bfd);
- if (sort_x == NULL || sort_y == NULL)
- error(FATAL, "bfd_make_empty_symbol() failed\n");
-
- gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
-
- store_symbols(st->bfd, FALSE, minisyms, symcount, size);
-
- free(minisyms);
/*
* Gather references to the kernel sections.
@@ -217,6 +201,7 @@ symtab_init(void)
error(FATAL, "symbol table section array malloc: %s\n",
strerror(errno));
BZERO(st->sections, st->bfd->section_count * sizeof(struct sec *));
+ st->first_section_start = st->last_section_end = 0;
bfd_map_over_sections(st->bfd, section_header_info, KERNEL_SECTIONS);
if ((st->flags & (NO_SEC_LOAD|NO_SEC_CONTENTS)) ==
@@ -227,6 +212,23 @@ symtab_init(void)
error(FATAL, DEBUGINFO_ERROR_MESSAGE2);
}
}
+
+ symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
+
+ if (symcount <= 0)
+ no_debugging_data(FATAL);
+
+ sort_x = bfd_make_empty_symbol(st->bfd);
+ sort_y = bfd_make_empty_symbol(st->bfd);
+ if (sort_x == NULL || sort_y == NULL)
+ error(FATAL, "bfd_make_empty_symbol() failed\n");
+
+ gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
+
+ store_symbols(st->bfd, FALSE, minisyms, symcount, size);
+
+ free(minisyms);
+
symname_hash_init();
symval_hash_init();
@@ -585,7 +587,7 @@ store_symbols(bfd *abfd, int dynamic, void *minisyms, long symcount,
st->symcnt = 0;
sp = st->symtable;
- if (machine_type("X86")) {
+ if (machine_type("X86") || machine_type("X86_64")) {
if (!(kt->flags & RELOC_SET))
kt->flags |= RELOC_FORCE;
} else
@@ -658,7 +660,7 @@ store_sysmap_symbols(void)
error(FATAL, "symbol table namespace malloc: %s\n",
strerror(errno));
- if (!machine_type("X86"))
+ if (!machine_type("X86") && !machine_type("X86_64"))
kt->flags &= ~RELOC_SET;
first = 0;
@@ -730,7 +732,17 @@ relocate(ulong symval, char *symname, int first_symbol)
break;
}
- return (symval - kt->relocate);
+ /*
+ * There are some symbols which are outside of any section
+ * either because they are offsets or because they are absolute
+ * addresses. These should not be relocated.
+ */
+ if (symval >= st->first_section_start &&
+ symval <= st->last_section_end) {
+ return (symval - kt->relocate);
+ } else {
+ return symval;
+ }
}
/*
@@ -9506,6 +9518,7 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
struct load_module *lm;
ulong request;
asection **sec;
+ ulong section_end_address;
request = ((ulong)reqptr);
@@ -9524,6 +9537,12 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
kt->etext_init = kt->stext_init +
(ulong)bfd_section_size(bfd, section);
}
+
+ if (STREQ(bfd_get_section_name(bfd, section), ".text")) {
+ st->first_section_start = (ulong)
+ bfd_get_section_vma(bfd, section);
+ }
+
if (STREQ(bfd_get_section_name(bfd, section), ".text") ||
STREQ(bfd_get_section_name(bfd, section), ".data")) {
if (!(bfd_get_section_flags(bfd, section) & SEC_LOAD))
@@ -9540,6 +9559,15 @@ section_header_info(bfd *bfd, asection *section, void *reqptr)
st->dwarf_debug_frame_file_offset = (off_t)section->filepos;
st->dwarf_debug_frame_size = (ulong)bfd_section_size(bfd, section);
}
+
+ if (st->first_section_start != 0) {
+ section_end_address =
+ (ulong) bfd_get_section_vma(bfd, section) +
+ (ulong) bfd_section_size(bfd, section);
+ if (section_end_address > st->last_section_end)
+ st->last_section_end = section_end_address;
+ }
+
break;
case (ulong)MODULE_SECTIONS:
diff --git a/x86_64.c b/x86_64.c
index 1d915b1..0c22ee1 100755
--- a/x86_64.c
+++ b/x86_64.c
@@ -5382,16 +5382,22 @@ search_for_switch_to(ulong start, ulong end)
{
ulong max_instructions, address;
char buf1[BUFSIZE];
- char buf2[BUFSIZE];
+ char search_string1[BUFSIZE];
+ char search_string2[BUFSIZE];
int found;
max_instructions = end - start;
found = FALSE;
sprintf(buf1, "x/%ldi 0x%lx", max_instructions, start);
- if (symbol_exists("__switch_to"))
- sprintf(buf2, "callq 0x%lx", symbol_value("__switch_to"));
- else
- buf2[0] = NULLCHAR;
+ if (symbol_exists("__switch_to")) {
+ sprintf(search_string1,
+ "call 0x%lx", symbol_value("__switch_to"));
+ sprintf(search_string2,
+ "callq 0x%lx", symbol_value("__switch_to"));
+ } else {
+ search_string1[0] = NULLCHAR;
+ search_string2[0] = NULLCHAR;
+ }
open_tmpfile();
@@ -5404,7 +5410,9 @@ search_for_switch_to(ulong start, ulong end)
break;
if (strstr(buf1, "<__switch_to>"))
found = TRUE;
- if (strlen(buf2) && strstr(buf1, buf2))
+ if (strlen(search_string1) && strstr(buf1, search_string1))
+ found = TRUE;
+ if (strlen(search_string2) && strstr(buf1, search_string2))
found = TRUE;
}
close_tmpfile();
--
1.8.4
3:21 p.m.
New subject: [PATCH v2] Add support for kASLR for offline vmcore files
Andy,
You must have missed my second question about the return value
of relocate() -- see below:
----- Original Message -----
This patch adds a --kaslr command line parameter for loading x86_64
crash dumps with kaslr enabled. This reuses the code from 32-bit
x86 relocations with some small changes. The ASLR offset is postive
instead of negative. Also had to move the code to traverse the
kernel section before the symbol storing code to figure out which
symbols were outside any sections and therefore were not relocated.
Also made a very small change in search_for_switch_to it was
searching through gdb command output which can be different under
different settings.
Tested: Tested by loading kdump files from kernels with aslr enabled
and not enabled. Ran bt, files, and struct file 0xXXXXXX.
Signed-off-by: Andy Honig <ahonig(a)google.com>
---
defs.h | 2 ++
main.c | 8 ++++++--
symbols.c | 66
+++++++++++++++++++++++++++++++++++++++++++++------------------
x86_64.c | 20 +++++++++++++------
4 files changed, 69 insertions(+), 27 deletions(-)
diff --git a/defs.h b/defs.h
index 83a4402..8de1fa4 100755
--- a/defs.h
+++ b/defs.h
@@ -2394,6 +2394,8 @@ struct symbol_table_data {
ulong __per_cpu_end;
off_t dwarf_debug_frame_file_offset;
ulong dwarf_debug_frame_size;
+ ulong first_section_start;
+ ulong last_section_end;
};
/* flags for st */
diff --git a/main.c b/main.c
index 3b469e3..5a41c1a 100755
--- a/main.c
+++ b/main.c
@@ -57,6 +57,7 @@ static struct option long_options[] = {
{"CRASHPAGER", 0, 0, 0},
{"no_scroll", 0, 0, 0},
{"reloc", required_argument, 0, 0},
+ {"kaslr", required_argument, 0, 0},
{"active", 0, 0, 0},
{"minimal", 0, 0, 0},
{"mod", required_argument, 0, 0},
@@ -216,12 +217,15 @@ main(int argc, char **argv)
else if (STREQ(long_options[option_index].name, "mod"))
kt->module_tree = optarg;
- else if (STREQ(long_options[option_index].name, "reloc")) {
+ else if (STREQ(long_options[option_index].name, "reloc") ||
+ STREQ(long_options[option_index].name, "kaslr")) {
if (!calculate(optarg, &kt->relocate, NULL, 0)) {
error(INFO, "invalid --reloc argument: %s\n",
optarg);
program_usage(SHORT_FORM);
- }
+ } else if (STREQ(long_options[option_index].name, "kaslr")) {
+ kt->relocate *= -1;
+ }
kt->flags |= RELOC_SET;
}
diff --git a/symbols.c b/symbols.c
index 93d9c8c..345c0de 100755
--- a/symbols.c
+++ b/symbols.c
@@ -192,22 +192,6 @@ symtab_init(void)
if (!check_gnu_debuglink(st->bfd))
no_debugging_data(FATAL);
}
-
- symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
-
- if (symcount <= 0)
- no_debugging_data(FATAL);
-
- sort_x = bfd_make_empty_symbol(st->bfd);
- sort_y = bfd_make_empty_symbol(st->bfd);
- if (sort_x == NULL || sort_y == NULL)
- error(FATAL, "bfd_make_empty_symbol() failed\n");
-
- gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
-
- store_symbols(st->bfd, FALSE, minisyms, symcount, size);
-
- free(minisyms);
/*
* Gather references to the kernel sections.
@@ -217,6 +201,7 @@ symtab_init(void)
error(FATAL, "symbol table section array malloc: %s\n",
strerror(errno));
BZERO(st->sections, st->bfd->section_count * sizeof(struct sec *));
+ st->first_section_start = st->last_section_end = 0;
bfd_map_over_sections(st->bfd, section_header_info, KERNEL_SECTIONS);
if ((st->flags & (NO_SEC_LOAD|NO_SEC_CONTENTS)) ==
@@ -227,6 +212,23 @@ symtab_init(void)
error(FATAL, DEBUGINFO_ERROR_MESSAGE2);
}
}
+
+ symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
+
+ if (symcount <= 0)
+ no_debugging_data(FATAL);
+
+ sort_x = bfd_make_empty_symbol(st->bfd);
+ sort_y = bfd_make_empty_symbol(st->bfd);
+ if (sort_x == NULL || sort_y == NULL)
+ error(FATAL, "bfd_make_empty_symbol() failed\n");
+
+ gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
+
+ store_symbols(st->bfd, FALSE, minisyms, symcount, size);
+
+ free(minisyms);
+
symname_hash_init();
symval_hash_init();
@@ -585,7 +587,7 @@ store_symbols(bfd *abfd, int dynamic, void *minisyms,
long symcount,
st->symcnt = 0;
sp = st->symtable;
- if (machine_type("X86")) {
+ if (machine_type("X86") || machine_type("X86_64")) {
if (!(kt->flags & RELOC_SET))
kt->flags |= RELOC_FORCE;
} else
@@ -658,7 +660,7 @@ store_sysmap_symbols(void)
error(FATAL, "symbol table namespace malloc: %s\n",
strerror(errno));
- if (!machine_type("X86"))
+ if (!machine_type("X86") && !machine_type("X86_64"))
kt->flags &= ~RELOC_SET;
first = 0;
@@ -730,7 +732,17 @@ relocate(ulong symval, char *symname, int first_symbol)
break;
}
- return (symval - kt->relocate);
+ /*
+ * There are some symbols which are outside of any section
+ * either because they are offsets or because they are absolute
+ * addresses. These should not be relocated.
+ */
+ if (symval >= st->first_section_start &&
+ symval <= st->last_section_end) {
+ return (symval - kt->relocate);
+ } else {
+ return symval;
+ }
}
The change above modifies the behavior for relocated 32-bit x86 relocated kernels
(i.e., not -kalsr x86 kernels).
I've never had any reports of problems with the old return value, so I'm a
little nervous about changing it for both arches. Should the change above
be restricted to --kalsr kernels?
Dave
3:39 p.m.
Yes, I did miss the second question, sorry about that.
Yes, I agree it's best not to disturb the 32-bit behavior that has
been working. I'd prefer not to restrict it to instances where
--kaslr was specified on the command line because I'd like to submit a
patch in the near future that auto-detects the aslr offset and makes
the argument unnecessary. How about a check for
MACHINE_TYPE("X86_64") for this behavior while MACHINE_TYPE("X86")
gets existing behavior?
On Wed, Oct 16, 2013 at 1:21 PM, Dave Anderson <anderson(a)redhat.com> wrote:
Andy,
You must have missed my second question about the return value
of relocate() -- see below:
----- Original Message -----
>
> This patch adds a --kaslr command line parameter for loading x86_64
> crash dumps with kaslr enabled. This reuses the code from 32-bit
> x86 relocations with some small changes. The ASLR offset is postive
> instead of negative. Also had to move the code to traverse the
> kernel section before the symbol storing code to figure out which
> symbols were outside any sections and therefore were not relocated.
>
> Also made a very small change in search_for_switch_to it was
> searching through gdb command output which can be different under
> different settings.
>
> Tested: Tested by loading kdump files from kernels with aslr enabled
> and not enabled. Ran bt, files, and struct file 0xXXXXXX.
>
> Signed-off-by: Andy Honig <ahonig(a)google.com>
> ---
> defs.h | 2 ++
> main.c | 8 ++++++--
> symbols.c | 66
> +++++++++++++++++++++++++++++++++++++++++++++------------------
> x86_64.c | 20 +++++++++++++------
> 4 files changed, 69 insertions(+), 27 deletions(-)
>
> diff --git a/defs.h b/defs.h
> index 83a4402..8de1fa4 100755
> --- a/defs.h
> +++ b/defs.h
> @@ -2394,6 +2394,8 @@ struct symbol_table_data {
> ulong __per_cpu_end;
> off_t dwarf_debug_frame_file_offset;
> ulong dwarf_debug_frame_size;
> + ulong first_section_start;
> + ulong last_section_end;
> };
>
> /* flags for st */
> diff --git a/main.c b/main.c
> index 3b469e3..5a41c1a 100755
> --- a/main.c
> +++ b/main.c
> @@ -57,6 +57,7 @@ static struct option long_options[] = {
> {"CRASHPAGER", 0, 0, 0},
> {"no_scroll", 0, 0, 0},
> {"reloc", required_argument, 0, 0},
> + {"kaslr", required_argument, 0, 0},
> {"active", 0, 0, 0},
> {"minimal", 0, 0, 0},
> {"mod", required_argument, 0, 0},
> @@ -216,12 +217,15 @@ main(int argc, char **argv)
> else if (STREQ(long_options[option_index].name,
"mod"))
> kt->module_tree = optarg;
>
> - else if (STREQ(long_options[option_index].name,
"reloc")) {
> + else if (STREQ(long_options[option_index].name,
"reloc") ||
> + STREQ(long_options[option_index].name,
"kaslr")) {
> if (!calculate(optarg, &kt->relocate, NULL, 0))
{
> error(INFO, "invalid --reloc argument:
%s\n",
> optarg);
> program_usage(SHORT_FORM);
> - }
> + } else if (STREQ(long_options[option_index].name,
"kaslr")) {
> + kt->relocate *= -1;
> + }
> kt->flags |= RELOC_SET;
> }
>
> diff --git a/symbols.c b/symbols.c
> index 93d9c8c..345c0de 100755
> --- a/symbols.c
> +++ b/symbols.c
> @@ -192,22 +192,6 @@ symtab_init(void)
> if (!check_gnu_debuglink(st->bfd))
> no_debugging_data(FATAL);
> }
> -
> - symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
> -
> - if (symcount <= 0)
> - no_debugging_data(FATAL);
> -
> - sort_x = bfd_make_empty_symbol(st->bfd);
> - sort_y = bfd_make_empty_symbol(st->bfd);
> - if (sort_x == NULL || sort_y == NULL)
> - error(FATAL, "bfd_make_empty_symbol() failed\n");
> -
> - gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
> -
> - store_symbols(st->bfd, FALSE, minisyms, symcount, size);
> -
> - free(minisyms);
>
> /*
> * Gather references to the kernel sections.
> @@ -217,6 +201,7 @@ symtab_init(void)
> error(FATAL, "symbol table section array malloc: %s\n",
> strerror(errno));
> BZERO(st->sections, st->bfd->section_count * sizeof(struct sec *));
> + st->first_section_start = st->last_section_end = 0;
>
> bfd_map_over_sections(st->bfd, section_header_info, KERNEL_SECTIONS);
> if ((st->flags & (NO_SEC_LOAD|NO_SEC_CONTENTS)) ==
> @@ -227,6 +212,23 @@ symtab_init(void)
> error(FATAL, DEBUGINFO_ERROR_MESSAGE2);
> }
> }
> +
> + symcount = bfd_read_minisymbols(st->bfd, FALSE, &minisyms, &size);
> +
> + if (symcount <= 0)
> + no_debugging_data(FATAL);
> +
> + sort_x = bfd_make_empty_symbol(st->bfd);
> + sort_y = bfd_make_empty_symbol(st->bfd);
> + if (sort_x == NULL || sort_y == NULL)
> + error(FATAL, "bfd_make_empty_symbol() failed\n");
> +
> + gnu_qsort(st->bfd, minisyms, symcount, size, sort_x, sort_y);
> +
> + store_symbols(st->bfd, FALSE, minisyms, symcount, size);
> +
> + free(minisyms);
> +
>
> symname_hash_init();
> symval_hash_init();
> @@ -585,7 +587,7 @@ store_symbols(bfd *abfd, int dynamic, void *minisyms,
> long symcount,
> st->symcnt = 0;
> sp = st->symtable;
>
> - if (machine_type("X86")) {
> + if (machine_type("X86") || machine_type("X86_64")) {
> if (!(kt->flags & RELOC_SET))
> kt->flags |= RELOC_FORCE;
> } else
> @@ -658,7 +660,7 @@ store_sysmap_symbols(void)
> error(FATAL, "symbol table namespace malloc: %s\n",
> strerror(errno));
>
> - if (!machine_type("X86"))
> + if (!machine_type("X86") &&
!machine_type("X86_64"))
> kt->flags &= ~RELOC_SET;
>
> first = 0;
> @@ -730,7 +732,17 @@ relocate(ulong symval, char *symname, int first_symbol)
> break;
> }
>
> - return (symval - kt->relocate);
> + /*
> + * There are some symbols which are outside of any section
> + * either because they are offsets or because they are absolute
> + * addresses. These should not be relocated.
> + */
> + if (symval >= st->first_section_start &&
> + symval <= st->last_section_end) {
> + return (symval - kt->relocate);
> + } else {
> + return symval;
> + }
> }
The change above modifies the behavior for relocated 32-bit x86 relocated kernels
(i.e., not -kalsr x86 kernels).
I've never had any reports of problems with the old return value, so I'm a
little nervous about changing it for both arches. Should the change above
be restricted to --kalsr kernels?
Dave
--
Crash-utility mailing list
Crash-utility(a)redhat.com
https://www.redhat.com/mailman/listinfo/crash-utility
3:47 p.m.
----- Original Message -----
Yes, I did miss the second question, sorry about that.
Yes, I agree it's best not to disturb the 32-bit behavior that has
been working. I'd prefer not to restrict it to instances where
--kaslr was specified on the command line because I'd like to submit a
patch in the near future that auto-detects the aslr offset and makes
the argument unnecessary. How about a check for
MACHINE_TYPE("X86_64") for this behavior while MACHINE_TYPE("X86")
gets existing behavior?
Works for me...
Thanks,
Dave
4059
days inactive
4059
days old
devel@lists.crash-utility.osci.io
3 comments
3 participants
participants (3)
-
Andrew Honig -
Andy Honig
-
Dave Anderson