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* [PATCH] Only search page_offset_base when KASLR mm code is compiled in
@ 2017-02-24 10:38 Baoquan He
  2017-02-28  6:06 ` Dave Young
  0 siblings, 1 reply; 3+ messages in thread
From: Baoquan He @ 2017-02-24 10:38 UTC (permalink / raw)
  To: horms; +Cc: kexec, Baoquan He, piliu

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 <bhe@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 */
-- 
2.5.5


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http://lists.infradead.org/mailman/listinfo/kexec

^ permalink raw reply related	[flat|nested] 3+ messages in thread
* Re: [PATCH] Only search page_offset_base when KASLR mm code is compiled in
  2017-02-24 10:38 [PATCH] Only search page_offset_base when KASLR mm code is compiled in Baoquan He
@ 2017-02-28  6:06 ` Dave Young
  2017-03-02  9:36   ` Baoquan He
  0 siblings, 1 reply; 3+ messages in thread
From: Dave Young @ 2017-02-28  6:06 UTC (permalink / raw)
  To: Baoquan He; +Cc: horms, kexec, piliu

On 02/24/17 at 06:38pm, Baoquan He wrote:
> 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 <bhe@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

It does not work in userspace code.

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

>  	/* 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
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave

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

^ permalink raw reply	[flat|nested] 3+ messages in thread
* Re: [PATCH] Only search page_offset_base when KASLR mm code is compiled in
  2017-02-28  6:06 ` Dave Young
@ 2017-03-02  9:36   ` Baoquan He
  0 siblings, 0 replies; 3+ messages in thread
From: Baoquan He @ 2017-03-02  9:36 UTC (permalink / raw)
  To: Dave Young; +Cc: horms, kexec, piliu

On 02/28/17 at 02:06pm, Dave Young wrote:
> On 02/24/17 at 06:38pm, Baoquan He wrote:
> > 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 <bhe@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
> 
> 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.

> 
> Maybe mute the error message or move it to kexec --debug is more
> reasonable..
> 
> >  	/* 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
> > kexec@lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kexec
> 
> Thanks
> Dave
> 
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

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

^ permalink raw reply	[flat|nested] 3+ messages in thread
end of thread, other threads:[~2017-03-02  9:37 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2017-02-24 10:38 [PATCH] Only search page_offset_base when KASLR mm code is compiled in Baoquan He
2017-02-28  6:06 ` Dave Young
2017-03-02  9:36   ` Baoquan He

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