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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 <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-05-27 21:43:41 +05:30
parent 2fa919045b
commit 16f9afe651
9 changed files with 24 additions and 31 deletions
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14
arch/arc/include/asm/entry.h
View File

@ -124,8 +124,6 @@
st.a r25, [sp, -4]
#endif
/* move up by 1 word to "create" callee_regs->"stack_place_holder" */
sub sp, sp, 4
.endm
/*--------------------------------------------------------------
@ -148,10 +146,9 @@
st.a r23, [sp, -4]
st.a r24, [sp, -4]
#ifdef CONFIG_ARC_CURR_IN_REG
sub sp, sp, 8
sub sp, sp, 4
#else
st.a r25, [sp, -4]
sub sp, sp, 4
#endif
.endm
@ -168,14 +165,11 @@
*-------------------------------------------------------------*/
.macro RESTORE_CALLEE_SAVED_KERNEL
#ifdef CONFIG_ARC_CURR_IN_REG
add sp, sp, 8 /* skip callee_reg gutter and user r25 placeholder */
add sp, sp, 4 /* skip usual r25 placeholder */
#else
add sp, sp, 4 /* skip "callee_regs->stack_place_holder" */
ld.ab r25, [sp, 4]
#endif
ld.ab r24, [sp, 4]
ld.ab r23, [sp, 4]
ld.ab r22, [sp, 4]
@ -203,8 +197,6 @@
*-------------------------------------------------------------*/
.macro RESTORE_CALLEE_SAVED_USER
add sp, sp, 4 /* skip "callee_regs->stack_place_holder" */
#ifdef CONFIG_ARC_CURR_IN_REG
ld.ab r12, [sp, 4]
st r12, [r25, TASK_THREAD + THREAD_USER_R25]
@ -230,7 +222,7 @@
* Super FAST Restore callee saved regs by simply re-adjusting SP
*-------------------------------------------------------------*/
.macro DISCARD_CALLEE_SAVED_USER
add sp, sp, 14 * 4
add sp, sp, SZ_CALLEE_REGS
.endm
/*--------------------------------------------------------------

11
arch/arc/include/asm/processor.h
View File

@ -19,6 +19,7 @@
#ifndef __ASSEMBLY__
#include <asm/arcregs.h> /* for STATUS_E1_MASK et all */
#include <asm/ptrace.h>
/* 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.

1
arch/arc/include/asm/ptrace.h
View File

@ -59,7 +59,6 @@ struct pt_regs {
/* Callee saved registers - need to be saved only when you are scheduled out */
struct callee_regs {
long res; /* Again this is not needed */
long r25;
long r24;
long r23;

2
arch/arc/include/uapi/asm/ptrace.h
View File

@ -38,8 +38,8 @@ struct user_regs_struct {
long r12, r11, r10, r9, r8, r7, r6, r5, r4, r3, r2, r1, r0;
long sp;
} scratch;
long pad2;
struct {
long pad;
long r25, r24, r23, r22, r21, r20;
long r19, r18, r17, r16, r15, r14, r13;
} callee;

1
arch/arc/kernel/asm-offsets.c
View File

@ -60,5 +60,6 @@ int main(void)
DEFINE(PT_r6, offsetof(struct pt_regs, r6));
DEFINE(PT_r7, offsetof(struct pt_regs, r7));
DEFINE(SZ_CALLEE_REGS, sizeof(struct callee_regs));
return 0;
}

14
arch/arc/kernel/ctx_sw.c
View File

@ -23,10 +23,6 @@ __switch_to(struct task_struct *prev_task, struct task_struct *next_task)
unsigned int tmp;
unsigned int prev = (unsigned int)prev_task;
unsigned int next = (unsigned int)next_task;
int num_words_to_skip = 1;
#ifdef CONFIG_ARC_CURR_IN_REG
num_words_to_skip++;
#endif
__asm__ __volatile__(
/* FP/BLINK save generated by gcc (standard function prologue */
@ -44,8 +40,9 @@ __switch_to(struct task_struct *prev_task, struct task_struct *next_task)
"st.a r24, [sp, -4] \n\t"
#ifndef CONFIG_ARC_CURR_IN_REG
"st.a r25, [sp, -4] \n\t"
#else
"sub sp, sp, 4 \n\t" /* usual r25 placeholder */
#endif
"sub sp, sp, %4 \n\t" /* create gutter at top */
/* set ksp of outgoing task in tsk->thread.ksp */
"st.as sp, [%3, %1] \n\t"
@ -76,10 +73,10 @@ __switch_to(struct task_struct *prev_task, struct task_struct *next_task)
/* start loading it's CALLEE reg file */
"add sp, sp, %4 \n\t" /* skip gutter at top */
#ifndef CONFIG_ARC_CURR_IN_REG
"ld.ab r25, [sp, 4] \n\t"
#else
"add sp, sp, 4 \n\t"
#endif
"ld.ab r24, [sp, 4] \n\t"
"ld.ab r23, [sp, 4] \n\t"
@ -100,8 +97,7 @@ __switch_to(struct task_struct *prev_task, struct task_struct *next_task)
/* FP/BLINK restore generated by gcc (standard func epilogue */
: "=r"(tmp)
: "n"((TASK_THREAD + THREAD_KSP) / 4), "r"(next), "r"(prev),
"n"(num_words_to_skip * 4)
: "n"((TASK_THREAD + THREAD_KSP) / 4), "r"(next), "r"(prev)
: "blink"
);

4
arch/arc/kernel/process.c
View File

@ -55,10 +55,8 @@ asmlinkage void ret_from_fork(void);
* | ... |
* | unused |
* | |
* ------------------ <==== top of Stack (thread.ksp)
* | UNUSED 1 word|
* ------------------
* | r25 |
* | r25 | <==== top of Stack (thread.ksp)
* ~ ~
* | --to-- | (CALLEE Regs of user mode)
* | r13 |

6
arch/arc/kernel/ptrace.c
View File

@ -48,6 +48,7 @@ static int genregs_get(struct task_struct *target,
REG_O_ZERO(pad);
REG_O_CHUNK(scratch, callee, ptregs);
REG_O_ZERO(pad2);
REG_O_CHUNK(callee, efa, cregs);
REG_O_CHUNK(efa, stop_pc, &target->thread.fault_address);
@ -96,8 +97,9 @@ static int genregs_set(struct task_struct *target,
offsetof(struct user_regs_struct, LOC) + 4);
REG_IGNORE_ONE(pad);
/* TBD: disallow updates to STATUS32, orig_r8 etc*/
REG_IN_CHUNK(scratch, callee, ptregs); /* pt_regs[bta..orig_r8] */
/* TBD: disallow updates to STATUS32 etc*/
REG_IN_CHUNK(scratch, pad2, ptregs); /* pt_regs[bta..sp] */
REG_IGNORE_ONE(pad2);
REG_IN_CHUNK(callee, efa, cregs); /* callee_regs[r25..r13] */
REG_IGNORE_ONE(efa); /* efa update invalid */
REG_IN_ONE(stop_pc, &ptregs->ret); /* stop_pc: PC update */

2
arch/arc/kernel/stacktrace.c
View File

@ -79,7 +79,7 @@ static void seed_unwind_frame_info(struct task_struct *tsk,
* assembly code
*/
frame_info->regs.r27 = 0;
frame_info->regs.r28 += 64;
frame_info->regs.r28 += 60;
frame_info->call_frame = 0;
} else {