| Message ID | 1349256170-4367-1-git-send-email-dave.martin@linaro.org |
|---|---|
| State | Accepted |
| Headers | show |
On Wed, Oct 03, 2012 at 10:22:50AM +0100, Dave Martin wrote: > Because mov pc,<Rn> never switches instruction set when executed in > Thumb code, Thumb-2 kernels will silently execute the target code > after cpu_reset as Thumb code, even if the passed code pointer > denotes ARM (bit 0 clear). > > This patch uses bx instead, ensuring the correct instruction set > for the target code. > > Thumb code in the kernel is not supported prior to ARMv7, so other > CPUs are not affected. > > Signed-off-by: Dave Martin <dave.martin@linaro.org> > --- > arch/arm/mm/proc-v7.S | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) I pondered why kexec was working, but we have the following in the purgatory code: /* Jump to relocated kernel */ mov lr,r1 mov r0,#0 ldr r1,kexec_mach_type ldr r2,kexec_boot_atags ARM( mov pc, lr ) THUMB( bx lr ) > diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S > index c2e2b66..ca5b575 100644 > --- a/arch/arm/mm/proc-v7.S > +++ b/arch/arm/mm/proc-v7.S > @@ -57,7 +57,7 @@ ENTRY(cpu_v7_reset) > THUMB( bic r1, r1, #1 << 30 ) @ SCTLR.TE (Thumb exceptions) > mcr p15, 0, r1, c1, c0, 0 @ disable MMU > isb > - mov pc, r0 > + bx r0 > ENDPROC(cpu_v7_reset) > .popsection So this looks fine to me: Acked-by: Will Deacon <will.deacon@arm.com> Cheers, Will
On Wed, 3 Oct 2012, Dave Martin wrote: > Because mov pc,<Rn> never switches instruction set when executed in > Thumb code, Thumb-2 kernels will silently execute the target code > after cpu_reset as Thumb code, even if the passed code pointer > denotes ARM (bit 0 clear). > > This patch uses bx instead, ensuring the correct instruction set > for the target code. > > Thumb code in the kernel is not supported prior to ARMv7, so other > CPUs are not affected. > > Signed-off-by: Dave Martin <dave.martin@linaro.org> Acked-by: Nicolas Pitre <nico@linaro.org> > --- > arch/arm/mm/proc-v7.S | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S > index c2e2b66..ca5b575 100644 > --- a/arch/arm/mm/proc-v7.S > +++ b/arch/arm/mm/proc-v7.S > @@ -57,7 +57,7 @@ ENTRY(cpu_v7_reset) > THUMB( bic r1, r1, #1 << 30 ) @ SCTLR.TE (Thumb exceptions) > mcr p15, 0, r1, c1, c0, 0 @ disable MMU > isb > - mov pc, r0 > + bx r0 > ENDPROC(cpu_v7_reset) > .popsection > > -- > 1.7.4.1 >
diff --git a/arch/arm/mm/proc-v7.S b/arch/arm/mm/proc-v7.S index c2e2b66..ca5b575 100644 --- a/arch/arm/mm/proc-v7.S +++ b/arch/arm/mm/proc-v7.S @@ -57,7 +57,7 @@ ENTRY(cpu_v7_reset) THUMB( bic r1, r1, #1 << 30 ) @ SCTLR.TE (Thumb exceptions) mcr p15, 0, r1, c1, c0, 0 @ disable MMU isb - mov pc, r0 + bx r0 ENDPROC(cpu_v7_reset) .popsection
Because mov pc,<Rn> never switches instruction set when executed in Thumb code, Thumb-2 kernels will silently execute the target code after cpu_reset as Thumb code, even if the passed code pointer denotes ARM (bit 0 clear). This patch uses bx instead, ensuring the correct instruction set for the target code. Thumb code in the kernel is not supported prior to ARMv7, so other CPUs are not affected. Signed-off-by: Dave Martin <dave.martin@linaro.org> --- arch/arm/mm/proc-v7.S | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)