[PATCH] kexec/ppc: Fix kernel program entry point while changing the load addr

[PATCH] kexec/ppc: Fix kernel program entry point while changing the load addr

[Suzuki K. Poulose]

From: Suzuki K. Poulose <suzuki@in.ibm.com>

uImage probe fills the entry point (ep) based on the load_addr
from the uImage headers. If we change the load_addr, we should
accordingly update the entry point.

For ELF, calculate the offset of e_entry from the virtual start
address and add it to the physical start address to find the
physical address of kernel entry.

i.e,
  pa (e_entry) = pa(phdr[0].p_vaddr) + (e_entry - phdr[0].p_vaddr)
               = kernel_addr + (e_entry - phdr[0].p_vaddr)

Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Matthew McClintock <msm@freescale.com>
---
 kexec/arch/ppc/kexec-elf-ppc.c    |   12 ++++++++----
 kexec/arch/ppc/kexec-uImage-ppc.c |    6 +++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/kexec/arch/ppc/kexec-elf-ppc.c b/kexec/arch/ppc/kexec-elf-ppc.c
index 8e408cc..5f63a64 100644
--- a/kexec/arch/ppc/kexec-elf-ppc.c
+++ b/kexec/arch/ppc/kexec-elf-ppc.c
@@ -397,10 +397,14 @@ int elf_ppc_load(int argc, char **argv,	const char *buf, off_t len,
 		die("Error device tree not loadded to address it was expecting to be loaded too!\n");
 	}
 
-	/* set various variables for the purgatory  ehdr.e_entry is a
-	 * virtual address, we can use kernel_addr which
-	 * should be the physical start address of the kernel */
-	addr = kernel_addr;
+	/* 
+	 * set various variables for the purgatory.
+	 * ehdr.e_entry is a virtual address. we know physical start
+	 * address of the kernel (kernel_addr). Find the offset of
+	 * e_entry from the virtual start address(e_phdr[0].p_vaddr)
+	 * and calculate the actual physical address of the 'kernel entry'.
+	 */
+	addr = kernel_addr + (ehdr.e_entry - ehdr.e_phdr[0].p_vaddr);
 	elf_rel_set_symbol(&info->rhdr, "kernel", &addr, sizeof(addr));
 
 	addr = dtb_addr;
diff --git a/kexec/arch/ppc/kexec-uImage-ppc.c b/kexec/arch/ppc/kexec-uImage-ppc.c
index e0bc7bb..900cd16 100644
--- a/kexec/arch/ppc/kexec-uImage-ppc.c
+++ b/kexec/arch/ppc/kexec-uImage-ppc.c
@@ -159,15 +159,19 @@ static int ppc_load_bare_bits(int argc, char **argv, const char *buf,
 
 	/*
 	 * If the provided load_addr cannot be allocated, find a new
-	 * area.
+	 * area. Rebase the entry point based on the new load_addr.
 	 */
 	if (!valid_memory_range(info, load_addr, load_addr + (len + _1MiB))) {
+		int ep_offset = ep - load_addr;
+
 		load_addr = locate_hole(info, len + _1MiB, 0, 0, max_addr, 1);
 		if (load_addr == ULONG_MAX) {
 			printf("Can't allocate memory for kernel of len %ld\n",
 					len + _1MiB);
 			return -1;
 		}
+
+		ep = load_addr + ep_offset;
 	}
 
 	add_segment(info, buf, len, load_addr, len + _1MiB);


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

Re: [PATCH] kexec/ppc: Fix kernel program entry point while changing the load addr

[Simon Horman]

[ Cc: linuxppc-dev@lists.ozlabs.org ]

On Sun, Mar 03, 2013 at 01:06:00PM +0530, Suzuki K. Poulose wrote:
> From: Suzuki K. Poulose <suzuki@in.ibm.com>
> 
> uImage probe fills the entry point (ep) based on the load_addr
> from the uImage headers. If we change the load_addr, we should
> accordingly update the entry point.
> 
> For ELF, calculate the offset of e_entry from the virtual start
> address and add it to the physical start address to find the
> physical address of kernel entry.
> 
> i.e,
>   pa (e_entry) = pa(phdr[0].p_vaddr) + (e_entry - phdr[0].p_vaddr)
>                = kernel_addr + (e_entry - phdr[0].p_vaddr)

Would it be possible for someone to provide a review of this change?

> 
> Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Cc: Matthew McClintock <msm@freescale.com>
> ---
>  kexec/arch/ppc/kexec-elf-ppc.c    |   12 ++++++++----
>  kexec/arch/ppc/kexec-uImage-ppc.c |    6 +++++-
>  2 files changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/kexec/arch/ppc/kexec-elf-ppc.c b/kexec/arch/ppc/kexec-elf-ppc.c
> index 8e408cc..5f63a64 100644
> --- a/kexec/arch/ppc/kexec-elf-ppc.c
> +++ b/kexec/arch/ppc/kexec-elf-ppc.c
> @@ -397,10 +397,14 @@ int elf_ppc_load(int argc, char **argv,	const char *buf, off_t len,
>  		die("Error device tree not loadded to address it was expecting to be loaded too!\n");
>  	}
>  
> -	/* set various variables for the purgatory  ehdr.e_entry is a
> -	 * virtual address, we can use kernel_addr which
> -	 * should be the physical start address of the kernel */
> -	addr = kernel_addr;
> +	/* 
> +	 * set various variables for the purgatory.
> +	 * ehdr.e_entry is a virtual address. we know physical start
> +	 * address of the kernel (kernel_addr). Find the offset of
> +	 * e_entry from the virtual start address(e_phdr[0].p_vaddr)
> +	 * and calculate the actual physical address of the 'kernel entry'.
> +	 */
> +	addr = kernel_addr + (ehdr.e_entry - ehdr.e_phdr[0].p_vaddr);
>  	elf_rel_set_symbol(&info->rhdr, "kernel", &addr, sizeof(addr));
>  
>  	addr = dtb_addr;
> diff --git a/kexec/arch/ppc/kexec-uImage-ppc.c b/kexec/arch/ppc/kexec-uImage-ppc.c
> index e0bc7bb..900cd16 100644
> --- a/kexec/arch/ppc/kexec-uImage-ppc.c
> +++ b/kexec/arch/ppc/kexec-uImage-ppc.c
> @@ -159,15 +159,19 @@ static int ppc_load_bare_bits(int argc, char **argv, const char *buf,
>  
>  	/*
>  	 * If the provided load_addr cannot be allocated, find a new
> -	 * area.
> +	 * area. Rebase the entry point based on the new load_addr.
>  	 */
>  	if (!valid_memory_range(info, load_addr, load_addr + (len + _1MiB))) {
> +		int ep_offset = ep - load_addr;
> +
>  		load_addr = locate_hole(info, len + _1MiB, 0, 0, max_addr, 1);
>  		if (load_addr == ULONG_MAX) {
>  			printf("Can't allocate memory for kernel of len %ld\n",
>  					len + _1MiB);
>  			return -1;
>  		}
> +
> +		ep = load_addr + ep_offset;
>  	}
>  
>  	add_segment(info, buf, len, load_addr, len + _1MiB);
> 
> 
> _______________________________________________
> 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

Re: [PATCH] kexec/ppc: Fix kernel program entry point while changing the load addr

[Suzuki K. Poulose]

On 03/04/2013 07:11 AM, Simon Horman wrote:
> [ Cc: linuxppc-dev@lists.ozlabs.org ]
>
> On Sun, Mar 03, 2013 at 01:06:00PM +0530, Suzuki K. Poulose wrote:
>> From: Suzuki K. Poulose <suzuki@in.ibm.com>
>>
>> uImage probe fills the entry point (ep) based on the load_addr
>> from the uImage headers. If we change the load_addr, we should
>> accordingly update the entry point.
>>
>> For ELF, calculate the offset of e_entry from the virtual start
>> address and add it to the physical start address to find the
>> physical address of kernel entry.
>>
>> i.e,
>>    pa (e_entry) = pa(phdr[0].p_vaddr) + (e_entry - phdr[0].p_vaddr)
>>                 = kernel_addr + (e_entry - phdr[0].p_vaddr)
>
> Would it be possible for someone to provide a review of this change?
To make it bit more clear :

The entry point of the kernel is usually at 0 offset from the first
PT_LOAD section. The current code makes this assumption and uses the 
pa(phdr[0].p_vaddr) as the kernel entry.

But this *may* not be true always, in such a case the kexec would fail.
While I fixed the uImage case, I thought it would be better to handle 
the same case in ELF.

Btw, this calculation is not specific to ppc32.

Thanks
Suzuki

>
>>
>> Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com>
>> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>> Cc: Matthew McClintock <msm@freescale.com>
>> ---
>>   kexec/arch/ppc/kexec-elf-ppc.c    |   12 ++++++++----
>>   kexec/arch/ppc/kexec-uImage-ppc.c |    6 +++++-
>>   2 files changed, 13 insertions(+), 5 deletions(-)
>>
>> diff --git a/kexec/arch/ppc/kexec-elf-ppc.c b/kexec/arch/ppc/kexec-elf-ppc.c
>> index 8e408cc..5f63a64 100644
>> --- a/kexec/arch/ppc/kexec-elf-ppc.c
>> +++ b/kexec/arch/ppc/kexec-elf-ppc.c
>> @@ -397,10 +397,14 @@ int elf_ppc_load(int argc, char **argv,	const char *buf, off_t len,
>>   		die("Error device tree not loadded to address it was expecting to be loaded too!\n");
>>   	}
>>
>> -	/* set various variables for the purgatory  ehdr.e_entry is a
>> -	 * virtual address, we can use kernel_addr which
>> -	 * should be the physical start address of the kernel */
>> -	addr = kernel_addr;
>> +	/*
>> +	 * set various variables for the purgatory.
>> +	 * ehdr.e_entry is a virtual address. we know physical start
>> +	 * address of the kernel (kernel_addr). Find the offset of
>> +	 * e_entry from the virtual start address(e_phdr[0].p_vaddr)
>> +	 * and calculate the actual physical address of the 'kernel entry'.
>> +	 */
>> +	addr = kernel_addr + (ehdr.e_entry - ehdr.e_phdr[0].p_vaddr);
>>   	elf_rel_set_symbol(&info->rhdr, "kernel", &addr, sizeof(addr));
>>
>>   	addr = dtb_addr;
>> diff --git a/kexec/arch/ppc/kexec-uImage-ppc.c b/kexec/arch/ppc/kexec-uImage-ppc.c
>> index e0bc7bb..900cd16 100644
>> --- a/kexec/arch/ppc/kexec-uImage-ppc.c
>> +++ b/kexec/arch/ppc/kexec-uImage-ppc.c
>> @@ -159,15 +159,19 @@ static int ppc_load_bare_bits(int argc, char **argv, const char *buf,
>>
>>   	/*
>>   	 * If the provided load_addr cannot be allocated, find a new
>> -	 * area.
>> +	 * area. Rebase the entry point based on the new load_addr.
>>   	 */
>>   	if (!valid_memory_range(info, load_addr, load_addr + (len + _1MiB))) {
>> +		int ep_offset = ep - load_addr;
>> +
>>   		load_addr = locate_hole(info, len + _1MiB, 0, 0, max_addr, 1);
>>   		if (load_addr == ULONG_MAX) {
>>   			printf("Can't allocate memory for kernel of len %ld\n",
>>   					len + _1MiB);
>>   			return -1;
>>   		}
>> +
>> +		ep = load_addr + ep_offset;
>>   	}
>>
>>   	add_segment(info, buf, len, load_addr, len + _1MiB);
>>
>>
>> _______________________________________________
>> kexec mailing list
>> kexec@lists.infradead.org
>> http://lists.infradead.org/mailman/listinfo/kexec
>>
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>


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

Re: [PATCH] kexec/ppc: Fix kernel program entry point while changing the load addr

[Simon Horman]

On Mon, Mar 04, 2013 at 11:26:24AM +0530, Suzuki K. Poulose wrote:
> On 03/04/2013 07:11 AM, Simon Horman wrote:
> >[ Cc: linuxppc-dev@lists.ozlabs.org ]
> >
> >On Sun, Mar 03, 2013 at 01:06:00PM +0530, Suzuki K. Poulose wrote:
> >>From: Suzuki K. Poulose <suzuki@in.ibm.com>
> >>
> >>uImage probe fills the entry point (ep) based on the load_addr
> >>from the uImage headers. If we change the load_addr, we should
> >>accordingly update the entry point.
> >>
> >>For ELF, calculate the offset of e_entry from the virtual start
> >>address and add it to the physical start address to find the
> >>physical address of kernel entry.
> >>
> >>i.e,
> >>   pa (e_entry) = pa(phdr[0].p_vaddr) + (e_entry - phdr[0].p_vaddr)
> >>                = kernel_addr + (e_entry - phdr[0].p_vaddr)
> >
> >Would it be possible for someone to provide a review of this change?
> To make it bit more clear :
> 
> The entry point of the kernel is usually at 0 offset from the first
> PT_LOAD section. The current code makes this assumption and uses the
> pa(phdr[0].p_vaddr) as the kernel entry.
> 
> But this *may* not be true always, in such a case the kexec would fail.
> While I fixed the uImage case, I thought it would be better to
> handle the same case in ELF.
> 
> Btw, this calculation is not specific to ppc32.

Thanks, I have applied the patch.

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