Implement and enable context tracking for arm64 (which is a prerequisite for FULL_NOHZ support). This patchset builds upon earlier work by Kevin Hilman and is based on 3.15-rc2.
Kevin Hilman (1): arm64: add support for context tracking
Larry Bassel (2): arm64: adjust el0_sync so that a function can be called arm64: enable context tracking
arch/arm64/Kconfig | 1 + arch/arm64/include/asm/thread_info.h | 1 + arch/arm64/kernel/entry.S | 33 ++++++++++++++++++++++++++++----- 3 files changed, 30 insertions(+), 5 deletions(-)
To implement the context tracker properly on arm64, a function call needs to be made after debugging and interrupts are turned on, but before the lr is changed to point to ret_from_exception(). If the function call is made after the lr is changed the function will not return to the correct place. For similar reasons, defer the setting of x0 so that it doesn't need to be saved around the function call.
Signed-off-by: Larry Bassel larry.bassel@linaro.org Reviewed-by: Kevin Hilman khilman@linaro.org --- arch/arm64/kernel/entry.S | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 39ac630..eda7755 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -349,11 +349,11 @@ el0_sync: lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class cmp x24, #ESR_EL1_EC_SVC64 // SVC in 64-bit state b.eq el0_svc - adr lr, ret_from_exception cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0 b.eq el0_da cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0 b.eq el0_ia + adr lr, ret_from_exception cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access b.eq el0_fpsimd_acc cmp x24, #ESR_EL1_EC_FP_EXC64 // FP/ASIMD exception @@ -378,11 +378,11 @@ el0_sync_compat: lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class cmp x24, #ESR_EL1_EC_SVC32 // SVC in 32-bit state b.eq el0_svc_compat - adr lr, ret_from_exception cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0 b.eq el0_da cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0 b.eq el0_ia + adr lr, ret_from_exception cmp x24, #ESR_EL1_EC_FP_ASIMD // FP/ASIMD access b.eq el0_fpsimd_acc cmp x24, #ESR_EL1_EC_FP_EXC32 // FP/ASIMD exception @@ -421,28 +421,30 @@ el0_da: /* * Data abort handling */ - mrs x0, far_el1 - bic x0, x0, #(0xff << 56) disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq + mrs x0, far_el1 + bic x0, x0, #(0xff << 56) mov x1, x25 mov x2, sp + adr lr, ret_from_exception b do_mem_abort el0_ia: /* * Instruction abort handling */ - mrs x0, far_el1 disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq + mrs x0, far_el1 orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts mov x2, sp + adr lr, ret_from_exception b do_mem_abort el0_fpsimd_acc: /*
On Sun, Apr 27, 2014 at 08:44:12PM +0100, Larry Bassel wrote:
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 39ac630..eda7755 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S
[...]
@@ -421,28 +421,30 @@ el0_da: /* * Data abort handling */
- mrs x0, far_el1
- bic x0, x0, #(0xff << 56) disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq
- mrs x0, far_el1
- bic x0, x0, #(0xff << 56) mov x1, x25 mov x2, sp
- adr lr, ret_from_exception b do_mem_abort
Reading the far_el1 after enable_dbg and enable_irq is racy, we can no longer guarantee its value in the original data abort context.
el0_ia: /* * Instruction abort handling */
- mrs x0, far_el1 disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq
- mrs x0, far_el1 orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts mov x2, sp
- adr lr, ret_from_exception b do_mem_abort
el0_fpsimd_acc:
Same here.
[+ Mark R. since we looked at this together a little at ELC]
Catalin Marinas catalin.marinas@arm.com writes:
On Sun, Apr 27, 2014 at 08:44:12PM +0100, Larry Bassel wrote:
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 39ac630..eda7755 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S
[...]
@@ -421,28 +421,30 @@ el0_da: /* * Data abort handling */
- mrs x0, far_el1
- bic x0, x0, #(0xff << 56) disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq
- mrs x0, far_el1
- bic x0, x0, #(0xff << 56) mov x1, x25 mov x2, sp
b do_mem_abort
Reading the far_el1 after enable_dbg and enable_irq is racy, we can no longer guarantee its value in the original data abort context.
Catalin, can you confirm x26 would be a safe place to stash far_el1 and then restore it after ct_user_exit. Something like this (which seems to work for me):
el0_da: /* * Data abort handling */ mrs x26, far_el1 disable_step x1 isb enable_dbg // enable interrupts before calling the main handler enable_irq ct_user_exit mov x0, x26 bic x0, x0, #(0xff << 56) mov x1, x25 mov x2, sp adr lr, ret_from_exception b do_mem_abort
Kevin
From: Kevin Hilman khilman@linaro.org
Add the macros and defines needed to implement context tracking on arm64.
Signed-off-by: Kevin Hilman khilman@linaro.org Signed-off-by: Larry Bassel larry.bassel@linaro.org --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/thread_info.h | 1 + arch/arm64/kernel/entry.S | 16 ++++++++++++++++ 3 files changed, 18 insertions(+)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index e6e4d37..152d92b 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -55,6 +55,7 @@ config ARM64 select RTC_LIB select SPARSE_IRQ select SYSCTL_EXCEPTION_TRACE + select HAVE_CONTEXT_TRACKING help ARM 64-bit (AArch64) Linux support.
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 720e70b..301ea6a 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -108,6 +108,7 @@ static inline struct thread_info *current_thread_info(void) #define TIF_SINGLESTEP 21 #define TIF_32BIT 22 /* 32bit process */ #define TIF_SWITCH_MM 23 /* deferred switch_mm */ +#define TIF_NOHZ 24
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index eda7755..76b09d8 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -30,6 +30,22 @@ #include <asm/unistd32.h>
/* + * Context tracking subsystem. Used to instrument transitions + * between user and kernel mode. + */ + .macro ct_user_exit +#ifdef CONFIG_CONTEXT_TRACKING + bl context_tracking_user_exit +#endif + .endm + + .macro ct_user_enter +#ifdef CONFIG_CONTEXT_TRACKING + bl context_tracking_user_enter +#endif + .endm + +/* * Bad Abort numbers *----------------- */
Make calls to ct_user_enter when the kernel is exited and ct_user_exit when the kernel is entered (in el0_da, el0_ia, el0_svc, el0_irq).
These macros expand to function calls which will only work properly if el0_sync and related code has been rearranged (in a previous patch of this series).
The calls to ct_user_exit are made after hw debugging has been enabled (enable_dbg).
The call to ct_user_enter is made at the end of the kernel_exit macro.
Signed-off-by: Kevin Hilman khilman@linaro.org Signed-off-by: Larry Bassel larry.bassel@linaro.org --- arch/arm64/kernel/entry.S | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 76b09d8..e949435 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -104,6 +104,7 @@ .macro kernel_exit, el, ret = 0 ldp x21, x22, [sp, #S_PC] // load ELR, SPSR .if \el == 0 + ct_user_enter ldr x23, [sp, #S_SP] // load return stack pointer .endif .if \ret @@ -442,6 +443,7 @@ el0_da: enable_dbg // enable interrupts before calling the main handler enable_irq + ct_user_exit mrs x0, far_el1 bic x0, x0, #(0xff << 56) mov x1, x25 @@ -457,6 +459,7 @@ el0_ia: enable_dbg // enable interrupts before calling the main handler enable_irq + ct_user_exit mrs x0, far_el1 orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts mov x2, sp @@ -525,6 +528,7 @@ el0_irq_naked: bl trace_hardirqs_off #endif
+ ct_user_exit irq_handler get_thread_info tsk
@@ -647,6 +651,7 @@ el0_svc_naked: // compat entry point isb enable_dbg enable_irq + ct_user_exit
get_thread_info tsk ldr x16, [tsk, #TI_FLAGS] // check for syscall tracing
On Sun, Apr 27, 2014 at 08:44:14PM +0100, Larry Bassel wrote:
Make calls to ct_user_enter when the kernel is exited and ct_user_exit when the kernel is entered (in el0_da, el0_ia, el0_svc, el0_irq).
These macros expand to function calls which will only work properly if el0_sync and related code has been rearranged (in a previous patch of this series).
The calls to ct_user_exit are made after hw debugging has been enabled (enable_dbg).
The call to ct_user_enter is made at the end of the kernel_exit macro.
Signed-off-by: Kevin Hilman khilman@linaro.org Signed-off-by: Larry Bassel larry.bassel@linaro.org
You could actually merge this patch with 2/3.
linaro-kernel@lists.linaro.org
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Catalin Marinas -
Kevin Hilman -
Larry Bassel