From 283237a04fd332bddc2ac298e6ad7d23a1fc4b99 Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Tue, 28 May 2013 09:34:45 +0530 Subject: ARC: pt_regs update #1: Align pt_regs end with end of kernel stack page Historically, pt_regs would end at offset of 1 word from end of stack page. ----------------- -> START of page (task->stack) | | | thread_info | ----------------- | | ^ ~ ~ | ~ ~ | | | | | | <---- pt_regs used to END here ----------------- | 1 word GUTTER | ----------------- -> End of page (START of kernel stack) This required special "one-off" considerations in low level code. The root cause is very likely assumption of "empty" SP by the original ARC kernel hackers, despite ARC700 always been "full" SP. So finally RIP one word gutter ! Signed-off-by: Vineet Gupta --- arch/arc/include/asm/processor.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'arch/arc/include/asm/processor.h') diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h index 5f26b2c1cba0..81efbcae3839 100644 --- a/arch/arc/include/asm/processor.h +++ b/arch/arc/include/asm/processor.h @@ -50,7 +50,7 @@ struct task_struct; unsigned long thread_saved_pc(struct task_struct *t); #define task_pt_regs(p) \ - ((struct pt_regs *)(THREAD_SIZE - 4 + (void *)task_stack_page(p)) - 1) + ((struct pt_regs *)(THREAD_SIZE + (void *)task_stack_page(p)) - 1) /* Free all resources held by a thread. */ #define release_thread(thread) do { } while (0) -- cgit v1.2.3 From 16f9afe651e8197fb7ce6df0990d8e2ad779e1af Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Mon, 27 May 2013 21:43:41 +0530 Subject: ARC: pt_regs update #3: Remove unused gutter at start of callee_regs This is trickier than prev two: * context switching code saves kernel mode callee regs in the format of struct callee_regs thus needs adjustment. This also reduces the height of topmost kernel stack frame by 1 word. * Since kernel stack unwinder is sensitive to height of topmost kernel stack frame, that needs a word of adjustment too. ptrace needs a bit of updating since pt_regs now diverges from user_regs_struct. Signed-off-by: Vineet Gupta --- arch/arc/include/asm/processor.h | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'arch/arc/include/asm/processor.h') diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h index 81efbcae3839..8c77e623c4e5 100644 --- a/arch/arc/include/asm/processor.h +++ b/arch/arc/include/asm/processor.h @@ -19,6 +19,7 @@ #ifndef __ASSEMBLY__ #include /* for STATUS_E1_MASK et all */ +#include /* Arch specific stuff which needs to be saved per task. * However these items are not so important so as to earn a place in @@ -75,11 +76,15 @@ unsigned long thread_saved_pc(struct task_struct *t); /* * Where abouts of Task's sp, fp, blink when it was last seen in kernel mode. - * These can't be derived from pt_regs as that would give correp user-mode val + * Look in process.c for details of kernel stack layout */ #define KSTK_ESP(tsk) (tsk->thread.ksp) -#define KSTK_BLINK(tsk) (*((unsigned int *)((KSTK_ESP(tsk)) + (13+1+1)*4))) -#define KSTK_FP(tsk) (*((unsigned int *)((KSTK_ESP(tsk)) + (13+1)*4))) + +#define KSTK_REG(tsk, off) (*((unsigned int *)(KSTK_ESP(tsk) + \ + sizeof(struct callee_regs) + off))) + +#define KSTK_BLINK(tsk) KSTK_REG(tsk, 4) +#define KSTK_FP(tsk) KSTK_REG(tsk, 0) /* * Do necessary setup to start up a newly executed thread. -- cgit v1.2.3 From 359105bdb06f8421fd8e69ae47fd052e398b6778 Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Tue, 28 May 2013 13:50:41 +0530 Subject: ARC: pt_regs update #4: r25 saved/restored unconditionally (This is a VERY IMP change for low level interrupt/exception handling) ----------------------------------------------------------------------- WHAT ----------------------------------------------------------------------- * User 25 now saved in pt_regs->user_r25 (vs. tsk->thread_info.user_r25) * This allows Low level interrupt code to unconditionally save r25 (vs. the prev version which would only do it for U->K transition). Ofcourse for nested interrupts, only the pt_regs->user_r25 of bottom-most frame is useful. * simplifies the interrupt prologue/epilogue * Needed for ARCv2 ISA code and done here to keep design similar with ARCompact event handling ----------------------------------------------------------------------- WHY ------------------------------------------------------------------------- With CONFIG_ARC_CURR_IN_REG, r25 is used to cache "current" task pointer in kernel mode. So when entering kernel mode from User Mode - user r25 is specially safe-kept (it being a callee reg is NOT part of pt_regs which are saved by default on each interrupt/trap/exception) - r25 loaded with current task pointer. Further, if interrupt was taken in kernel mode, this is skipped since we know that r25 already has valid "current" pointer. With 2 level of interrupts in ARCompact ISA, detecting this is difficult but still possible, since we could be in kernel mode but r25 not already saved (in fact the stack itself might not have been switched). A. User mode B. L1 IRQ taken C. L2 IRQ taken (while on 1st line of L1 ISR) So in #C, although in kernel mode, r25 not saved (infact SP not switched at all) Given that ARcompact has manual stack switching, we could use a bit of trickey - The low level code would make sure that SP is only set to kernel mode value at the very end (after saving r25). So a non kernel mode SP, even if in kernel mode, meant r25 was NOT saved. The same paradigm won't work in ARCv2 ISA since SP is auto-switched so it's setting can't be delayed/constrained. Signed-off-by: Vineet Gupta --- arch/arc/include/asm/processor.h | 3 --- 1 file changed, 3 deletions(-) (limited to 'arch/arc/include/asm/processor.h') diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h index 8c77e623c4e5..b0b5d2d9b3d3 100644 --- a/arch/arc/include/asm/processor.h +++ b/arch/arc/include/asm/processor.h @@ -30,9 +30,6 @@ struct thread_struct { unsigned long callee_reg; /* pointer to callee regs */ unsigned long fault_address; /* dbls as brkpt holder as well */ unsigned long cause_code; /* Exception Cause Code (ECR) */ -#ifdef CONFIG_ARC_CURR_IN_REG - unsigned long user_r25; -#endif #ifdef CONFIG_ARC_FPU_SAVE_RESTORE struct arc_fpu fpu; #endif -- cgit v1.2.3 From 38a9ff6d247cf9afcbe55ea245b650b8955029fd Mon Sep 17 00:00:00 2001 From: Vineet Gupta Date: Wed, 12 Jun 2013 15:13:40 +0530 Subject: ARC: Remove explicit passing around of ECR With ECR now part of pt_regs * No need to propagate from lowest asm handlers as arg * No need to save it in tsk->thread.cause_code * Avoid bit chopping to access the bit-fields More code consolidation, cleanup Signed-off-by: Vineet Gupta --- arch/arc/include/asm/processor.h | 1 - 1 file changed, 1 deletion(-) (limited to 'arch/arc/include/asm/processor.h') diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h index b0b5d2d9b3d3..15334ab66b56 100644 --- a/arch/arc/include/asm/processor.h +++ b/arch/arc/include/asm/processor.h @@ -29,7 +29,6 @@ struct thread_struct { unsigned long ksp; /* kernel mode stack pointer */ unsigned long callee_reg; /* pointer to callee regs */ unsigned long fault_address; /* dbls as brkpt holder as well */ - unsigned long cause_code; /* Exception Cause Code (ECR) */ #ifdef CONFIG_ARC_FPU_SAVE_RESTORE struct arc_fpu fpu; #endif -- cgit v1.2.3