| Message ID | 20170814125411.22604-21-ard.biesheuvel@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 14 Aug 2017, Ard Biesheuvel wrote: > Replace some unnecessary absolute references with relative ones. Also, > to prepare for runtime relocation, which occurs with the caches on, > defer taking the absolute address of cpu_resume_after_mmu() until after > the MMU is enabled. > > Cc: Russell King <linux@armlinux.org.uk> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > --- > arch/arm/kernel/sleep.S | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S > index 3026b119d3ff..9efd1c7d3552 100644 > --- a/arch/arm/kernel/sleep.S > +++ b/arch/arm/kernel/sleep.S > @@ -60,18 +60,17 @@ > ENTRY(__cpu_suspend) > stmfd sp!, {r4 - r11, lr} > #ifdef MULTI_CPU > - ldr r10, =processor > - ldr r4, [r10, #CPU_SLEEP_SIZE] @ size of CPU sleep state > + ldr_l r4, processor + CPU_SLEEP_SIZE @ size of CPU sleep state > #else > - ldr r4, =cpu_suspend_size > + adr_l r4, cpu_suspend_size > #endif > mov r5, sp @ current virtual SP > add r4, r4, #12 @ Space for pgd, virt sp, phys resume fn > sub sp, sp, r4 @ allocate CPU state on stack > - ldr r3, =sleep_save_sp > + adr_l r3, sleep_save_sp > stmfd sp!, {r0, r1} @ save suspend func arg and pointer > ldr r3, [r3, #SLEEP_SAVE_SP_VIRT] > - ALT_SMP(ldr r0, =mpidr_hash) > + ALT_SMP(adr_l r0, mpidr_hash) > ALT_UP_B(1f) The above is dangerous. adr_l expands to more than one instruction which is not what ALT_SMP() was designed for. Here it might happen to work anyway because it is combined with ALT_UP_B() but with ALT_UP() it wouldn't. This is a mistake waiting to happen. > /* This ldmia relies on the memory layout of the mpidr_hash struct */ > ldmia r0, {r1, r6-r8} @ r1 = mpidr mask (r6,r7,r8) = l[0,1,2] shifts > @@ -100,13 +99,13 @@ ENDPROC(cpu_suspend_abort) > .align 5 > .pushsection .idmap.text,"ax" > ENTRY(cpu_resume_mmu) > - ldr r3, =cpu_resume_after_mmu > instr_sync > mcr p15, 0, r0, c1, c0, 0 @ turn on MMU, I-cache, etc > mrc p15, 0, r0, c0, c0, 0 @ read id reg > instr_sync > mov r0, r0 > mov r0, r0 > + ldr r3, =cpu_resume_after_mmu > ret r3 @ jump to virtual address > ENDPROC(cpu_resume_mmu) > .popsection > -- > 2.11.0 > >
On 14 August 2017 at 17:02, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > On Mon, 14 Aug 2017, Ard Biesheuvel wrote: > >> Replace some unnecessary absolute references with relative ones. Also, >> to prepare for runtime relocation, which occurs with the caches on, >> defer taking the absolute address of cpu_resume_after_mmu() until after >> the MMU is enabled. >> >> Cc: Russell King <linux@armlinux.org.uk> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> >> --- >> arch/arm/kernel/sleep.S | 11 +++++------ >> 1 file changed, 5 insertions(+), 6 deletions(-) >> >> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S >> index 3026b119d3ff..9efd1c7d3552 100644 >> --- a/arch/arm/kernel/sleep.S >> +++ b/arch/arm/kernel/sleep.S >> @@ -60,18 +60,17 @@ >> ENTRY(__cpu_suspend) >> stmfd sp!, {r4 - r11, lr} >> #ifdef MULTI_CPU >> - ldr r10, =processor >> - ldr r4, [r10, #CPU_SLEEP_SIZE] @ size of CPU sleep state >> + ldr_l r4, processor + CPU_SLEEP_SIZE @ size of CPU sleep state >> #else >> - ldr r4, =cpu_suspend_size >> + adr_l r4, cpu_suspend_size >> #endif >> mov r5, sp @ current virtual SP >> add r4, r4, #12 @ Space for pgd, virt sp, phys resume fn >> sub sp, sp, r4 @ allocate CPU state on stack >> - ldr r3, =sleep_save_sp >> + adr_l r3, sleep_save_sp >> stmfd sp!, {r0, r1} @ save suspend func arg and pointer >> ldr r3, [r3, #SLEEP_SAVE_SP_VIRT] >> - ALT_SMP(ldr r0, =mpidr_hash) >> + ALT_SMP(adr_l r0, mpidr_hash) >> ALT_UP_B(1f) > > The above is dangerous. adr_l expands to more than one instruction which > is not what ALT_SMP() was designed for. Here it might happen to work > anyway because it is combined with ALT_UP_B() but with ALT_UP() it > wouldn't. This is a mistake waiting to happen. > OK. I will use the opencoded sequence instead in this case. I.e., - ALT_SMP(ldr r0, =mpidr_hash) +0: ALT_SMP(adr r0, 2f) ALT_UP_B(1f) + ldr r1, [r0] + add r0, r0, r1 and ENDPROC(__cpu_suspend) + .align 2 +2: .long mpidr_hash - . .ltorg
On Mon, 14 Aug 2017, Ard Biesheuvel wrote: > On 14 August 2017 at 17:02, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > > On Mon, 14 Aug 2017, Ard Biesheuvel wrote: > > > >> Replace some unnecessary absolute references with relative ones. Also, > >> to prepare for runtime relocation, which occurs with the caches on, > >> defer taking the absolute address of cpu_resume_after_mmu() until after > >> the MMU is enabled. > >> > >> Cc: Russell King <linux@armlinux.org.uk> > >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> > >> --- > >> arch/arm/kernel/sleep.S | 11 +++++------ > >> 1 file changed, 5 insertions(+), 6 deletions(-) > >> > >> diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S > >> index 3026b119d3ff..9efd1c7d3552 100644 > >> --- a/arch/arm/kernel/sleep.S > >> +++ b/arch/arm/kernel/sleep.S > >> @@ -60,18 +60,17 @@ > >> ENTRY(__cpu_suspend) > >> stmfd sp!, {r4 - r11, lr} > >> #ifdef MULTI_CPU > >> - ldr r10, =processor > >> - ldr r4, [r10, #CPU_SLEEP_SIZE] @ size of CPU sleep state > >> + ldr_l r4, processor + CPU_SLEEP_SIZE @ size of CPU sleep state > >> #else > >> - ldr r4, =cpu_suspend_size > >> + adr_l r4, cpu_suspend_size > >> #endif > >> mov r5, sp @ current virtual SP > >> add r4, r4, #12 @ Space for pgd, virt sp, phys resume fn > >> sub sp, sp, r4 @ allocate CPU state on stack > >> - ldr r3, =sleep_save_sp > >> + adr_l r3, sleep_save_sp > >> stmfd sp!, {r0, r1} @ save suspend func arg and pointer > >> ldr r3, [r3, #SLEEP_SAVE_SP_VIRT] > >> - ALT_SMP(ldr r0, =mpidr_hash) > >> + ALT_SMP(adr_l r0, mpidr_hash) > >> ALT_UP_B(1f) > > > > The above is dangerous. adr_l expands to more than one instruction which > > is not what ALT_SMP() was designed for. Here it might happen to work > > anyway because it is combined with ALT_UP_B() but with ALT_UP() it > > wouldn't. This is a mistake waiting to happen. > > > > OK. I will use the opencoded sequence instead in this case. I.e., > > - ALT_SMP(ldr r0, =mpidr_hash) > +0: ALT_SMP(adr r0, 2f) > ALT_UP_B(1f) > + ldr r1, [r0] > + add r0, r0, r1 > > and > > ENDPROC(__cpu_suspend) > + .align 2 > +2: .long mpidr_hash - . > .ltorg > Yeah... I see no way around it. And if you make this particular case into a commit of its own, then the commit log may carry the above reasoning. Nicolas
diff --git a/arch/arm/kernel/sleep.S b/arch/arm/kernel/sleep.S index 3026b119d3ff..9efd1c7d3552 100644 --- a/arch/arm/kernel/sleep.S +++ b/arch/arm/kernel/sleep.S @@ -60,18 +60,17 @@ ENTRY(__cpu_suspend) stmfd sp!, {r4 - r11, lr} #ifdef MULTI_CPU - ldr r10, =processor - ldr r4, [r10, #CPU_SLEEP_SIZE] @ size of CPU sleep state + ldr_l r4, processor + CPU_SLEEP_SIZE @ size of CPU sleep state #else - ldr r4, =cpu_suspend_size + adr_l r4, cpu_suspend_size #endif mov r5, sp @ current virtual SP add r4, r4, #12 @ Space for pgd, virt sp, phys resume fn sub sp, sp, r4 @ allocate CPU state on stack - ldr r3, =sleep_save_sp + adr_l r3, sleep_save_sp stmfd sp!, {r0, r1} @ save suspend func arg and pointer ldr r3, [r3, #SLEEP_SAVE_SP_VIRT] - ALT_SMP(ldr r0, =mpidr_hash) + ALT_SMP(adr_l r0, mpidr_hash) ALT_UP_B(1f) /* This ldmia relies on the memory layout of the mpidr_hash struct */ ldmia r0, {r1, r6-r8} @ r1 = mpidr mask (r6,r7,r8) = l[0,1,2] shifts @@ -100,13 +99,13 @@ ENDPROC(cpu_suspend_abort) .align 5 .pushsection .idmap.text,"ax" ENTRY(cpu_resume_mmu) - ldr r3, =cpu_resume_after_mmu instr_sync mcr p15, 0, r0, c1, c0, 0 @ turn on MMU, I-cache, etc mrc p15, 0, r0, c0, c0, 0 @ read id reg instr_sync mov r0, r0 mov r0, r0 + ldr r3, =cpu_resume_after_mmu ret r3 @ jump to virtual address ENDPROC(cpu_resume_mmu) .popsection
Replace some unnecessary absolute references with relative ones. Also, to prepare for runtime relocation, which occurs with the caches on, defer taking the absolute address of cpu_resume_after_mmu() until after the MMU is enabled. Cc: Russell King <linux@armlinux.org.uk> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm/kernel/sleep.S | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)