| Message ID | 1605752954-10368-3-git-send-email-hejinyang@loongson.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel | expand |
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 <hejinyang@loongson.cn> [...] 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 <hejinyang@loongson.cn> > [...] > > 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.
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. >
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
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 <hejinyang@loongson.cn> --- arch/mips/Kconfig | 5 +++++ arch/mips/kernel/relocate.c | 2 +- 2 files changed, 6 insertions(+), 1 deletion(-)