[PATCH] Only search page_offset_base when KASLR mm code is compiled in

[Baoquan He]

Otherwise it will print false positve message as below. So add
a check when do the search.

"Cannot get kernel page_offset_base symbol address"

Signed-off-by: Baoquan He <***@redhat.com>
---
kexec/arch/i386/crashdump-x86.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
index 88aeee3..b2c1be5 100644
--- a/kexec/arch/i386/crashdump-x86.c
+++ b/kexec/arch/i386/crashdump-x86.c
@@ -150,8 +150,6 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
off_t size;
uint32_t elf_flags = 0;
uint64_t stext_sym;
- const unsigned long long pud_mask = ~((1 << 30) - 1);
- unsigned long long vaddr, lowest_vaddr = 0;

if (elf_info->machine != EM_X86_64)
return 0;
@@ -181,8 +179,11 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),

end_phdr = &ehdr.e_phdr[ehdr.e_phnum];

+#ifdef CONFIG_RANDOMIZE_MEMORY
/* Search for the real PAGE_OFFSET when KASLR memory randomization
* is enabled */
+ const unsigned long long pud_mask = ~((1 << 30) - 1);
+ unsigned long long vaddr, lowest_vaddr = 0;
if (get_kernel_sym("page_offset_base") != 0) {
for(phdr = ehdr.e_phdr; phdr != end_phdr; phdr++) {
if (phdr->p_type == PT_LOAD) {
@@ -194,6 +195,7 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
if (lowest_vaddr != 0)
elf_info->page_offset = lowest_vaddr;
}
+#endif

/* Traverse through the Elf headers and find the region where
* _stext symbol is located in. That's where kernel is mapped */

[Dave Young]

Post by Baoquan He
Otherwise it will print false positve message as below. So add
a check when do the search.
"Cannot get kernel page_offset_base symbol address"
---
kexec/arch/i386/crashdump-x86.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
index 88aeee3..b2c1be5 100644
--- a/kexec/arch/i386/crashdump-x86.c
+++ b/kexec/arch/i386/crashdump-x86.c
@@ -150,8 +150,6 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
off_t size;
uint32_t elf_flags = 0;
uint64_t stext_sym;
- const unsigned long long pud_mask = ~((1 << 30) - 1);
- unsigned long long vaddr, lowest_vaddr = 0;
if (elf_info->machine != EM_X86_64)
return 0;
@@ -181,8 +179,11 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
end_phdr = &ehdr.e_phdr[ehdr.e_phnum];
+#ifdef CONFIG_RANDOMIZE_MEMORY

It does not work in userspace code.

Maybe mute the error message or move it to kexec --debug is more
reasonable..

Post by Baoquan He
/* Search for the real PAGE_OFFSET when KASLR memory randomization
* is enabled */
+ const unsigned long long pud_mask = ~((1 << 30) - 1);
+ unsigned long long vaddr, lowest_vaddr = 0;
if (get_kernel_sym("page_offset_base") != 0) {
for(phdr = ehdr.e_phdr; phdr != end_phdr; phdr++) {
if (phdr->p_type == PT_LOAD) {
@@ -194,6 +195,7 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
if (lowest_vaddr != 0)
elf_info->page_offset = lowest_vaddr;
}
+#endif
/* Traverse through the Elf headers and find the region where
* _stext symbol is located in. That's where kernel is mapped */
--
2.5.5
_______________________________________________
kexec mailing list
http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave

[Baoquan He]

Post by Dave Young

Post by Baoquan He
Otherwise it will print false positve message as below. So add
a check when do the search.
"Cannot get kernel page_offset_base symbol address"
---
kexec/arch/i386/crashdump-x86.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c
index 88aeee3..b2c1be5 100644
--- a/kexec/arch/i386/crashdump-x86.c
+++ b/kexec/arch/i386/crashdump-x86.c
@@ -150,8 +150,6 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
off_t size;
uint32_t elf_flags = 0;
uint64_t stext_sym;
- const unsigned long long pud_mask = ~((1 << 30) - 1);
- unsigned long long vaddr, lowest_vaddr = 0;
if (elf_info->machine != EM_X86_64)
return 0;
@@ -181,8 +179,11 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
end_phdr = &ehdr.e_phdr[ehdr.e_phnum];
+#ifdef CONFIG_RANDOMIZE_MEMORY

It does not work in userspace code.

Could be it only works when make header and install. Otherwise it can't
be seen by user space. I built a rhel kernel package and test passed.

Anyway, since it doesn't work in all cases, I have made another way to
fix it, just take out the error message and put it where get_kernel_sym
is called.

Post by Dave Young
Maybe mute the error message or move it to kexec --debug is more
reasonable..

Post by Baoquan He
/* Search for the real PAGE_OFFSET when KASLR memory randomization
* is enabled */
+ const unsigned long long pud_mask = ~((1 << 30) - 1);
+ unsigned long long vaddr, lowest_vaddr = 0;
if (get_kernel_sym("page_offset_base") != 0) {
for(phdr = ehdr.e_phdr; phdr != end_phdr; phdr++) {
if (phdr->p_type == PT_LOAD) {
@@ -194,6 +195,7 @@ static int get_kernel_vaddr_and_size(struct kexec_info *UNUSED(info),
if (lowest_vaddr != 0)
elf_info->page_offset = lowest_vaddr;
}
+#endif
/* Traverse through the Elf headers and find the region where
* _stext symbol is located in. That's where kernel is mapped */
--
2.5.5
_______________________________________________
kexec mailing list
http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave
_______________________________________________
kexec mailing list
http://lists.infradead.org/mailman/listinfo/kexec