[v3][PATCH 0/6] powerpc/book3e: make kgdb to work well

[v3][PATCH 0/6] powerpc/book3e: make kgdb to work well

[Tiejun Chen]

This patchset is used to support kgdb/gdb on book3e.

Validated on p4080ds and p5040ds with test single step and breakpoint

v3:

* make work when enable CONFIG_RELOCATABLE
* fix one typo in patch,
  "powerpc/book3e: store critical/machine/debug exception thread info": 
	ld	r1,PACAKSAVE(r13);
    ->  ld	r14,PACAKSAVE(r13);
* remove copying the thread_info since booke and book3e always copy
  the thead_info now when we enter the debug exception, and so drop
  the v2 patch, "book3e/kgdb: Fix a single stgep case of lazy IRQ"

v2:

* Make sure we cover CONFIG_PPC_BOOK3E_64 safely
* Use LOAD_REG_IMMEDIATE() to load properly
	the value of the constant expression in load debug exception stack 
* Copy thread infor form the kernel stack coming from usr
* Rebase latest powerpc git tree

v1:
* Copy thread info only when we are from !user mode since we'll get kernel stack
  coming from usr directly.
* remove save/restore EX_R14/EX_R15 since DBG_EXCEPTION_PROLOG already covered
  this.
* use CURRENT_THREAD_INFO() conveniently to get thread.
* fix some typos
* add a patch to make sure gdb can generate a single step properly to invoke a
  kgdb state.
* add a patch to if we need to replay an interrupt, we shouldn't restore that
  previous backup thread info to make sure we can replay an interrupt lately
  with a proper thread info.
* rebase latest powerpc git tree

v0:
This patchset is used to support kgdb for book3e.

------
Tiejun Chen (6):
      powerpc/book3e: load critical/machine/debug exception stack
      powerpc/book3e: store critical/machine/debug exception thread info
      book3e/kgdb: update thread's dbcr0
      powerpc/book3e: support kgdb for kernel space
      kgdb/kgdbts: support ppc64
      powerpc/kgdb: remove copying the thread_info

 arch/powerpc/kernel/exceptions-64e.S |   69 ++++++++++++++++++++++++++++++++--
 arch/powerpc/kernel/kgdb.c           |   41 +++++---------------
 drivers/misc/kgdbts.c                |    2 +
 3 files changed, 77 insertions(+), 35 deletions(-)

Tiejun

[v3][PATCH 1/6] powerpc/book3e: load critical/machine/debug exception stack

[Tiejun Chen]

We always alloc critical/machine/debug check exceptions. This is
different from the normal exception. So we should load these exception
stack properly like we did for booke.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/exceptions-64e.S |   49 +++++++++++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 1e7782b..7fd6af0 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -36,6 +36,37 @@
  */
 #define	SPECIAL_EXC_FRAME_SIZE	INT_FRAME_SIZE
 
+/* only on book3e */
+#define DBG_STACK_BASE		dbgirq_ctx
+#define MC_STACK_BASE		mcheckirq_ctx
+#define CRIT_STACK_BASE		critirq_ctx
+
+#ifdef CONFIG_RELOCATABLE
+#define LOAD_STACK_BASE(reg, level)			\
+	tovirt(r2,r2);					\
+	LOAD_REG_ADDR(reg, level##_STACK_BASE);
+#else
+#define LOAD_STACK_BASE(reg, level)			\
+	LOAD_REG_IMMEDIATE(reg, level##_STACK_BASE);
+#endif
+
+#ifdef CONFIG_SMP
+#define BOOK3E_LOAD_EXC_LEVEL_STACK(level)		\
+	mfspr	r14,SPRN_PIR;				\
+	slwi	r14,r14,3;				\
+	LOAD_STACK_BASE(r10, level);			\
+	add	r10,r10,r14;				\
+	ld	r10,0(r10);				\
+	addi	r10,r10,THREAD_SIZE;			\
+	std	r10,PACA_##level##_STACK(r13);
+#else
+#define BOOK3E_LOAD_EXC_LEVEL_STACK(level)		\
+	LOAD_STACK_BASE(r10, level);			\
+	ld	r10,0(r10);				\
+	addi	r10,r10,THREAD_SIZE;			\
+	std	r10,PACA_##level##_STACK(r13);
+#endif
+
 /* Exception prolog code for all exceptions */
 #define EXCEPTION_PROLOG(n, intnum, type, addition)	    		    \
 	mtspr	SPRN_SPRG_##type##_SCRATCH,r13;	/* get spare registers */   \
@@ -68,20 +99,32 @@
 #define SPRN_GDBELL_SRR1	SPRN_GSRR1
 
 #define CRIT_SET_KSTACK						            \
+	andi.	r10,r11,MSR_PR;							\
+	bne	1f;								\
+	BOOK3E_LOAD_EXC_LEVEL_STACK(CRIT);					\
 	ld	r1,PACA_CRIT_STACK(r13);				    \
-	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;
+	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;					\
+1:
 #define SPRN_CRIT_SRR0	SPRN_CSRR0
 #define SPRN_CRIT_SRR1	SPRN_CSRR1
 
 #define DBG_SET_KSTACK						            \
+	andi.	r10,r11,MSR_PR;							\
+	bne	1f;								\
+	BOOK3E_LOAD_EXC_LEVEL_STACK(DBG);					\
 	ld	r1,PACA_DBG_STACK(r13);					    \
-	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;
+	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;					\
+1:
 #define SPRN_DBG_SRR0	SPRN_DSRR0
 #define SPRN_DBG_SRR1	SPRN_DSRR1
 
 #define MC_SET_KSTACK						            \
+	andi.	r10,r11,MSR_PR;							\
+	bne	1f;								\
+	BOOK3E_LOAD_EXC_LEVEL_STACK(MC);					\
 	ld	r1,PACA_MC_STACK(r13);					    \
-	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;
+	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;					\
+1:
 #define SPRN_MC_SRR0	SPRN_MCSRR0
 #define SPRN_MC_SRR1	SPRN_MCSRR1
 
-- 
1.7.9.5

[v3][PATCH 2/6] powerpc/book3e: store critical/machine/debug exception thread info

[Tiejun Chen]

We need to store thread info to these exception thread info like something
we already did for PPC32.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/exceptions-64e.S |   15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 7fd6af0..7df9a1f 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -67,6 +67,18 @@
 	std	r10,PACA_##level##_STACK(r13);
 #endif
 
+/* Store something to exception thread info */
+#define	BOOK3E_STORE_EXC_LEVEL_THEAD_INFO(type)					\
+	ld	r14,PACAKSAVE(r13);						\
+	CURRENT_THREAD_INFO(r14, r14);						\
+	CURRENT_THREAD_INFO(r15, r1);						\
+	ld	r10,TI_FLAGS(r14);		     				\
+	std	r10,TI_FLAGS(r15);			     			\
+	ld	r10,TI_PREEMPT(r14);		     				\
+	std	r10,TI_PREEMPT(r15);		     				\
+	ld	r10,TI_TASK(r14);			     			\
+	std	r10,TI_TASK(r15);
+
 /* Exception prolog code for all exceptions */
 #define EXCEPTION_PROLOG(n, intnum, type, addition)	    		    \
 	mtspr	SPRN_SPRG_##type##_SCRATCH,r13;	/* get spare registers */   \
@@ -104,6 +116,7 @@
 	BOOK3E_LOAD_EXC_LEVEL_STACK(CRIT);					\
 	ld	r1,PACA_CRIT_STACK(r13);				    \
 	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;					\
+	BOOK3E_STORE_EXC_LEVEL_THEAD_INFO(CRIT);				\
 1:
 #define SPRN_CRIT_SRR0	SPRN_CSRR0
 #define SPRN_CRIT_SRR1	SPRN_CSRR1
@@ -114,6 +127,7 @@
 	BOOK3E_LOAD_EXC_LEVEL_STACK(DBG);					\
 	ld	r1,PACA_DBG_STACK(r13);					    \
 	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;					\
+	BOOK3E_STORE_EXC_LEVEL_THEAD_INFO(DBG);					\
 1:
 #define SPRN_DBG_SRR0	SPRN_DSRR0
 #define SPRN_DBG_SRR1	SPRN_DSRR1
@@ -124,6 +138,7 @@
 	BOOK3E_LOAD_EXC_LEVEL_STACK(MC);					\
 	ld	r1,PACA_MC_STACK(r13);					    \
 	subi	r1,r1,SPECIAL_EXC_FRAME_SIZE;					\
+	BOOK3E_STORE_EXC_LEVEL_THEAD_INFO(MC);					\
 1:
 #define SPRN_MC_SRR0	SPRN_MCSRR0
 #define SPRN_MC_SRR1	SPRN_MCSRR1
-- 
1.7.9.5

[v3][PATCH 3/6] book3e/kgdb: update thread's dbcr0

[Tiejun Chen]

gdb always need to generate a single step properly to invoke
a kgdb state. But with lazy interrupt, book3e can't always
trigger a debug exception with a single step since the current
is blocked for handling those pending exception, then we miss
that expected dbcr configuration at last to generate a debug
exception.

So here we also update thread's dbcr0 to make sure the current
can go back with that missed dbcr0 configuration.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/kgdb.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 5ca82cd..1a57307 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -410,7 +410,7 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 			       struct pt_regs *linux_regs)
 {
 	char *ptr = &remcom_in_buffer[1];
-	unsigned long addr;
+	unsigned long addr, dbcr0;
 
 	switch (remcom_in_buffer[0]) {
 		/*
@@ -427,8 +427,15 @@ int kgdb_arch_handle_exception(int vector, int signo, int err_code,
 		/* set the trace bit if we're stepping */
 		if (remcom_in_buffer[0] == 's') {
 #ifdef CONFIG_PPC_ADV_DEBUG_REGS
-			mtspr(SPRN_DBCR0,
-			      mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM);
+			dbcr0 = mfspr(SPRN_DBCR0) | DBCR0_IC | DBCR0_IDM;
+			mtspr(SPRN_DBCR0, dbcr0);
+#ifdef CONFIG_PPC_BOOK3E_64
+			/* With lazy interrut we have to update thread dbcr0 here
+			 * to make sure we can set debug properly at last to invoke
+			 * kgdb again to work well.
+			 */
+			current->thread.dbcr0 = dbcr0;
+#endif
 			linux_regs->msr |= MSR_DE;
 #else
 			linux_regs->msr |= MSR_SE;
-- 
1.7.9.5

[v3][PATCH 4/6] powerpc/book3e: support kgdb for kernel space

[Tiejun Chen]

Currently we need to skip this for supporting KGDB.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/exceptions-64e.S |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 7df9a1f..800e2a3 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -598,11 +598,14 @@ kernel_dbg_exc:
 	rfdi
 
 	/* Normal debug exception */
+1:
+#ifndef CONFIG_KGDB
 	/* XXX We only handle coming from userspace for now since we can't
 	 *     quite save properly an interrupted kernel state yet
 	 */
-1:	andi.	r14,r11,MSR_PR;		/* check for userspace again */
+	andi.	r14,r11,MSR_PR;		/* check for userspace again */
 	beq	kernel_dbg_exc;		/* if from kernel mode */
+#endif
 
 	/* Now we mash up things to make it look like we are coming on a
 	 * normal exception
-- 
1.7.9.5

[v3][PATCH 5/6] kgdb/kgdbts: support ppc64

[Tiejun Chen]

We can't look up the address of the entry point of the function simply
via that function symbol for all architectures.

For PPC64 ABI, actually there is a function descriptors structure.

A function descriptor is a three doubleword data structure that contains
the following values:
	* The first doubleword contains the address of the entry point of
		the function.
	* The second doubleword contains the TOC base address for
		the function.
	* The third doubleword contains the environment pointer for
		languages such as Pascal and PL/1.

So we should call a wapperred dereference_function_descriptor() to get
the address of the entry point of the function.

Note this is also safe for other architecture after refer to
"include/asm-generic/sections.h" since:

dereference_function_descriptor(p) always is (p) if without arched definition.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 drivers/misc/kgdbts.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/misc/kgdbts.c b/drivers/misc/kgdbts.c
index 3aa9a96..4799e1f 100644
--- a/drivers/misc/kgdbts.c
+++ b/drivers/misc/kgdbts.c
@@ -103,6 +103,7 @@
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/module.h>
+#include <asm/sections.h>
 
 #define v1printk(a...) do { \
 	if (verbose) \
@@ -222,6 +223,7 @@ static unsigned long lookup_addr(char *arg)
 		addr = (unsigned long)do_fork;
 	else if (!strcmp(arg, "hw_break_val"))
 		addr = (unsigned long)&hw_break_val;
+	addr = (unsigned long )dereference_function_descriptor((void *)addr);
 	return addr;
 }
 
-- 
1.7.9.5

[v3][PATCH 6/6] powerpc/kgdb: remove copying the thread_info

[Tiejun Chen]

Currently BookE and Book3E always copy the thread_info from
the kernel stack when we enter the debug exception, so we can
remove these action here to avoid copying again.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/kgdb.c |   28 ----------------------------
 1 file changed, 28 deletions(-)

diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c
index 1a57307..e954888 100644
--- a/arch/powerpc/kernel/kgdb.c
+++ b/arch/powerpc/kernel/kgdb.c
@@ -153,39 +153,11 @@ static int kgdb_handle_breakpoint(struct pt_regs *regs)
 
 static int kgdb_singlestep(struct pt_regs *regs)
 {
-	struct thread_info *thread_info, *exception_thread_info;
-	struct thread_info *backup_current_thread_info;
-
 	if (user_mode(regs))
 		return 0;
 
-	backup_current_thread_info = (struct thread_info *)kmalloc(sizeof(struct thread_info), GFP_KERNEL);
-	/*
-	 * On Book E and perhaps other processors, singlestep is handled on
-	 * the critical exception stack.  This causes current_thread_info()
-	 * to fail, since it it locates the thread_info by masking off
-	 * the low bits of the current stack pointer.  We work around
-	 * this issue by copying the thread_info from the kernel stack
-	 * before calling kgdb_handle_exception, and copying it back
-	 * afterwards.  On most processors the copy is avoided since
-	 * exception_thread_info == thread_info.
-	 */
-	thread_info = (struct thread_info *)(regs->gpr[1] & ~(THREAD_SIZE-1));
-	exception_thread_info = current_thread_info();
-
-	if (thread_info != exception_thread_info) {
-		/* Save the original current_thread_info. */
-		memcpy(backup_current_thread_info, exception_thread_info, sizeof *thread_info);
-		memcpy(exception_thread_info, thread_info, sizeof *thread_info);
-	}
-
 	kgdb_handle_exception(0, SIGTRAP, 0, regs);
 
-	if (thread_info != exception_thread_info)
-		/* Restore current_thread_info lastly. */
-		memcpy(exception_thread_info, backup_current_thread_info, sizeof *thread_info);
-
-	kfree(backup_current_thread_info);
 	return 1;
 }
 
-- 
1.7.9.5

Re: [v3][PATCH 0/6] powerpc/book3e: make kgdb to work well

[tiejun.chen]

On 02/27/2013 11:04 AM, Tiejun Chen wrote:
> This patchset is used to support kgdb/gdb on book3e.
>
> Validated on p4080ds and p5040ds with test single step and breakpoint

Please ignore this thread since looks I'm missing to CC Jason :(

Tiejun

>
> v3:
>
> * make work when enable CONFIG_RELOCATABLE
> * fix one typo in patch,
>    "powerpc/book3e: store critical/machine/debug exception thread info":
> 	ld	r1,PACAKSAVE(r13);
>      ->  ld	r14,PACAKSAVE(r13);
> * remove copying the thread_info since booke and book3e always copy
>    the thead_info now when we enter the debug exception, and so drop
>    the v2 patch, "book3e/kgdb: Fix a single stgep case of lazy IRQ"
>
> v2:
>
> * Make sure we cover CONFIG_PPC_BOOK3E_64 safely
> * Use LOAD_REG_IMMEDIATE() to load properly
> 	the value of the constant expression in load debug exception stack
> * Copy thread infor form the kernel stack coming from usr
> * Rebase latest powerpc git tree
>
> v1:
> * Copy thread info only when we are from !user mode since we'll get kernel stack
>    coming from usr directly.
> * remove save/restore EX_R14/EX_R15 since DBG_EXCEPTION_PROLOG already covered
>    this.
> * use CURRENT_THREAD_INFO() conveniently to get thread.
> * fix some typos
> * add a patch to make sure gdb can generate a single step properly to invoke a
>    kgdb state.
> * add a patch to if we need to replay an interrupt, we shouldn't restore that
>    previous backup thread info to make sure we can replay an interrupt lately
>    with a proper thread info.
> * rebase latest powerpc git tree
>
> v0:
> This patchset is used to support kgdb for book3e.
>
> ------
> Tiejun Chen (6):
>        powerpc/book3e: load critical/machine/debug exception stack
>        powerpc/book3e: store critical/machine/debug exception thread info
>        book3e/kgdb: update thread's dbcr0
>        powerpc/book3e: support kgdb for kernel space
>        kgdb/kgdbts: support ppc64
>        powerpc/kgdb: remove copying the thread_info
>
>   arch/powerpc/kernel/exceptions-64e.S |   69 ++++++++++++++++++++++++++++++++--
>   arch/powerpc/kernel/kgdb.c           |   41 +++++---------------
>   drivers/misc/kgdbts.c                |    2 +
>   3 files changed, 77 insertions(+), 35 deletions(-)
>
> Tiejun
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/linuxppc-dev
>
>

[v3][PATCH 4/6] powerpc/book3e: support kgdb for kernel space

[Tiejun Chen]

Currently we need to skip this for supporting KGDB.

Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
 arch/powerpc/kernel/exceptions-64e.S |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 7df9a1f..800e2a3 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -598,11 +598,14 @@ kernel_dbg_exc:
 	rfdi
 
 	/* Normal debug exception */
+1:
+#ifndef CONFIG_KGDB
 	/* XXX We only handle coming from userspace for now since we can't
 	 *     quite save properly an interrupted kernel state yet
 	 */
-1:	andi.	r14,r11,MSR_PR;		/* check for userspace again */
+	andi.	r14,r11,MSR_PR;		/* check for userspace again */
 	beq	kernel_dbg_exc;		/* if from kernel mode */
+#endif
 
 	/* Now we mash up things to make it look like we are coming on a
 	 * normal exception
-- 
1.7.9.5