When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
always returns a constant. It is not friendly to users if the address
cannot be used. Make it can be configured at Kconfig.
Signed-off-by: Jinyang He <[email protected]>
---
arch/mips/Kconfig | 5 +++++
arch/mips/kernel/relocate.c | 2 +-
2 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 1508829..1c95478 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2803,6 +2803,11 @@ config RELOCATION_TABLE_SIZE
If unsure, leave at the default value.
+config RELOCATE_DESTINATION
+ hex "Relocate address when RANDOMIZE_BASE is not set"
+ depends on RELOCATABLE && !RANDOMIZE_BASE
+ default "0xffffffff81000000"
+
config RANDOMIZE_BASE
bool "Randomize the address of the kernel image"
depends on RELOCATABLE
diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index 709cfa0..b7ea6ff 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -276,7 +276,7 @@ static inline void __init *determine_relocation_address(void)
* Choose a new address for the kernel
* For now we'll hard code the destination
*/
- return (void *)0xffffffff81000000;
+ return (void *)CONFIG_RELOCATE_DESTINATION;
}
#endif
--
2.1.0
Hello!
On 19.11.2020 5:29, Jinyang He wrote:
> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
> always returns a constant. It is not friendly to users if the address
> cannot be used. Make it can be configured at Kconfig.
Make it configurable?
> Signed-off-by: Jinyang He <[email protected]>
[...]
MBR, Sergei
Hi,
On 11/19/2020 04:06 PM, Sergei Shtylyov wrote:
> Hello!
>
> On 19.11.2020 5:29, Jinyang He wrote:
>
>> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
>> always returns a constant. It is not friendly to users if the address
>> cannot be used. Make it can be configured at Kconfig.
>
> Make it configurable?
Oh, yes. Sorry for the expression.
0xffffffff81000000 cannot be used on Loongson64 if CONFIG_RANDOMIZE_BASE
is disabled.
It's lower than address of _end. It makes relocation_addr_valid() return
0 always.
Thanks!
Jinyang
>> Signed-off-by: Jinyang He <[email protected]>
> [...]
>
> MBR, Sergei
On Thu, Nov 19, 2020 at 10:29:14AM +0800, Jinyang He wrote:
> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
> always returns a constant. It is not friendly to users if the address
> cannot be used. Make it can be configured at Kconfig.
and how do I get the information which address I need to enter ?
This looks more like platforms need to supply a working address and
not the user configuring the kernel...
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
Hi,
On 11/19/2020 08:45 PM, Thomas Bogendoerfer wrote:
> On Thu, Nov 19, 2020 at 10:29:14AM +0800, Jinyang He wrote:
>> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
>> always returns a constant. It is not friendly to users if the address
>> cannot be used. Make it can be configured at Kconfig.
> and how do I get the information which address I need to enter ?
> This looks more like platforms need to supply a working address and
> not the user configuring the kernel...
You are right.
We only have two address to enter if CONFIG_RANDOMIZE_BASE disabled. One
is 0xffffffff81000000 in the current if succeed, the other is the orignal
address if failed. From relocation_addr_valid() we see that the avaliable
address need to higher than &_end to avoid overlaps original kernel.
E.g. 0xffffffff83000000 and 0xffffffff84000000 both is avaliable on
Loongson64 platform when &_end == 0xffffffff82213f80. But
0xffffffff82000000 is not available in that case.
In reality test, I compiled kernel first and got &_end. And then modified
the relocate_address to avaliable and compiled kernel once more. It is
a bad idea.
Is it different from modifying CONFIG_PHYSICAL_START when just relocate
one address? Does it make sense if only one address to relocate?
Morever, RANDOMIZE_BASE is normally avaliable. Can we add a kernel
parameter like "relocation=0xffffffff81000000" to direct address?
At least, other architecture disabling RANDOMIZE_BASE looks like "nokaslr".
Thus, can we delete these code which RANDOMIZE_BASE disabled?
Thanks! :-)
Jinyang
> Thomas.
>