| Message ID | 1496657199-29589-1-git-send-email-hoeun.ryu@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/06/17 11:06, Hoeun Ryu wrote: > Clearing TTBCR.T1SZ explicitly when kernel runs on a configuration of > PHYS_OFFSET > PAGE_OFFSET. > Reading TTBCR in early boot stage might returns the value of the > previous kernel's configuration, especially in case of kexec. For > example, if normal kernel (first kernel) had run on a configuration > of PHYS_OFFSET <= PAGE_OFFSET and crash kernel (second kernel) is > running on a configuration PHYS_OFFSET > PAGE_OFFSET, which can happen > because it depends on the reserved area for crash kernel, reading > TTBCR and using the value without clearing TTBCR.T1SZ might risky > because the value doesn't have a reset value for TTBCR.T1SZ. Hmm, but isn't that also strictly true of all the other fields we're ORing TTB_FLAGS_* into? Given that this is initial setup, I wonder whether we need to care about the previous TTBCR value at all - is there any reason for not simply building up the value we want from scratch? Robin. > Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com> > --- > arch/arm/mm/proc-v7-3level.S | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S > index 5e5720e..81404b8 100644 > --- a/arch/arm/mm/proc-v7-3level.S > +++ b/arch/arm/mm/proc-v7-3level.S > @@ -140,6 +140,7 @@ ENDPROC(cpu_v7_set_pte_ext) > * otherwise booting secondary CPUs would end up using TTBR1 for the > * identity mapping set up in TTBR0. > */ > + bichi \tmp, \tmp, #(7 << 16) @ clear TTBCR.T1SZ > orrls \tmp, \tmp, #TTBR1_SIZE @ TTBCR.T1SZ > mcr p15, 0, \tmp, c2, c0, 2 @ TTBCR > mov \tmp, \ttbr1, lsr #20 >
>> On Jun 5, 2017, at 7:30 PM, Robin Murphy <robin.murphy@arm.com> wrote: >> >> On 05/06/17 11:06, Hoeun Ryu wrote: >> Clearing TTBCR.T1SZ explicitly when kernel runs on a configuration of >> PHYS_OFFSET > PAGE_OFFSET. >> Reading TTBCR in early boot stage might returns the value of the >> previous kernel's configuration, especially in case of kexec. For >> example, if normal kernel (first kernel) had run on a configuration >> of PHYS_OFFSET <= PAGE_OFFSET and crash kernel (second kernel) is >> running on a configuration PHYS_OFFSET > PAGE_OFFSET, which can happen >> because it depends on the reserved area for crash kernel, reading >> TTBCR and using the value without clearing TTBCR.T1SZ might risky >> because the value doesn't have a reset value for TTBCR.T1SZ. > > Hmm, but isn't that also strictly true of all the other fields we're > ORing TTB_FLAGS_* into? Given that this is initial setup, I wonder > whether we need to care about the previous TTBCR value at all - is there > any reason for not simply building up the value we want from scratch? Your idea seems better. I'll send a new patch to build TTBCR from scratch without reading it for the initial value. Russell, do you have any opinion ? Thank toy for the review. > > Robin. > >> Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com> >> --- >> arch/arm/mm/proc-v7-3level.S | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S >> index 5e5720e..81404b8 100644 >> --- a/arch/arm/mm/proc-v7-3level.S >> +++ b/arch/arm/mm/proc-v7-3level.S >> @@ -140,6 +140,7 @@ ENDPROC(cpu_v7_set_pte_ext) >> * otherwise booting secondary CPUs would end up using TTBR1 for the >> * identity mapping set up in TTBR0. >> */ >> + bichi \tmp, \tmp, #(7 << 16) @ clear TTBCR.T1SZ >> orrls \tmp, \tmp, #TTBR1_SIZE @ TTBCR.T1SZ >> mcr p15, 0, \tmp, c2, c0, 2 @ TTBCR >> mov \tmp, \ttbr1, lsr #20 >
diff --git a/arch/arm/mm/proc-v7-3level.S b/arch/arm/mm/proc-v7-3level.S index 5e5720e..81404b8 100644 --- a/arch/arm/mm/proc-v7-3level.S +++ b/arch/arm/mm/proc-v7-3level.S @@ -140,6 +140,7 @@ ENDPROC(cpu_v7_set_pte_ext) * otherwise booting secondary CPUs would end up using TTBR1 for the * identity mapping set up in TTBR0. */ + bichi \tmp, \tmp, #(7 << 16) @ clear TTBCR.T1SZ orrls \tmp, \tmp, #TTBR1_SIZE @ TTBCR.T1SZ mcr p15, 0, \tmp, c2, c0, 2 @ TTBCR mov \tmp, \ttbr1, lsr #20
Clearing TTBCR.T1SZ explicitly when kernel runs on a configuration of PHYS_OFFSET > PAGE_OFFSET. Reading TTBCR in early boot stage might returns the value of the previous kernel's configuration, especially in case of kexec. For example, if normal kernel (first kernel) had run on a configuration of PHYS_OFFSET <= PAGE_OFFSET and crash kernel (second kernel) is running on a configuration PHYS_OFFSET > PAGE_OFFSET, which can happen because it depends on the reserved area for crash kernel, reading TTBCR and using the value without clearing TTBCR.T1SZ might risky because the value doesn't have a reset value for TTBCR.T1SZ. Signed-off-by: Hoeun Ryu <hoeun.ryu@gmail.com> --- arch/arm/mm/proc-v7-3level.S | 1 + 1 file changed, 1 insertion(+)