[PATCH 04/50] arm/asm: Add loglvl to c_backtrace()

[PATCH 04/50] arm/asm: Add loglvl to c_backtrace()

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Add log level argument to c_backtrace() as a preparation for introducing
show_stack_loglvl().

Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: clang-built-linux@googlegroups.com
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm/include/asm/bug.h     |  3 ++-
 arch/arm/include/asm/traps.h   |  3 ++-
 arch/arm/kernel/traps.c        |  9 +++++----
 arch/arm/kernel/unwind.c       |  2 +-
 arch/arm/lib/backtrace-clang.S |  9 +++++++--
 arch/arm/lib/backtrace.S       | 14 ++++++++++----
 6 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
index deef4d0cb3b5..673c7dd75ab9 100644
--- a/arch/arm/include/asm/bug.h
+++ b/arch/arm/include/asm/bug.h
@@ -82,7 +82,8 @@ void hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int,
 				       struct pt_regs *),
 		     int sig, int code, const char *name);
 
-extern asmlinkage void c_backtrace(unsigned long fp, int pmode);
+extern asmlinkage void c_backtrace(unsigned long fp, int pmode,
+				   const char *loglvl);
 
 struct mm_struct;
 void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr);
diff --git a/arch/arm/include/asm/traps.h b/arch/arm/include/asm/traps.h
index 172b08ff3760..987fefb0a4db 100644
--- a/arch/arm/include/asm/traps.h
+++ b/arch/arm/include/asm/traps.h
@@ -29,7 +29,8 @@ static inline int __in_irqentry_text(unsigned long ptr)
 }
 
 extern void __init early_trap_init(void *);
-extern void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long frame);
+extern void dump_backtrace_entry(unsigned long where, unsigned long from,
+				 unsigned long frame, const char *loglvl);
 extern void ptrace_break(struct pt_regs *regs);
 
 extern void *vectors_page;
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index c053abd1fb53..7c3f32b26585 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -62,7 +62,8 @@ __setup("user_debug=", user_debug_setup);
 
 static void dump_mem(const char *, const char *, unsigned long, unsigned long);
 
-void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long frame)
+void dump_backtrace_entry(unsigned long where, unsigned long from,
+			  unsigned long frame, const char *loglvl)
 {
 #ifdef CONFIG_KALLSYMS
 	printk("[<%08lx>] (%ps) from [<%08lx>] (%pS)\n", where, (void *)where, from, (void *)from);
@@ -74,7 +75,7 @@ void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long
 		dump_mem("", "Exception stack", frame + 4, frame + 4 + sizeof(struct pt_regs));
 }
 
-void dump_backtrace_stm(u32 *stack, u32 instruction)
+void dump_backtrace_stm(u32 *stack, u32 instruction, const char *loglvl)
 {
 	char str[80], *p;
 	unsigned int x;
@@ -236,7 +237,7 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	pr_cont("\n");
 
 	if (ok)
-		c_backtrace(fp, mode);
+		c_backtrace(fp, mode, NULL);
 }
 #endif
 
@@ -662,7 +663,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
 		dump_instr("", regs);
 		if (user_mode(regs)) {
 			__show_regs(regs);
-			c_backtrace(frame_pointer(regs), processor_mode(regs));
+			c_backtrace(frame_pointer(regs), processor_mode(regs), NULL);
 		}
 	}
 #endif
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 4574e6aea0a5..0a65005e10f0 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -493,7 +493,7 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 		urc = unwind_frame(&frame);
 		if (urc < 0)
 			break;
-		dump_backtrace_entry(where, frame.pc, frame.sp - 4);
+		dump_backtrace_entry(where, frame.pc, frame.sp - 4, NULL);
 	}
 }
 
diff --git a/arch/arm/lib/backtrace-clang.S b/arch/arm/lib/backtrace-clang.S
index 2ff375144b55..6174c45f53a5 100644
--- a/arch/arm/lib/backtrace-clang.S
+++ b/arch/arm/lib/backtrace-clang.S
@@ -17,6 +17,7 @@
 #define sv_pc	r6
 #define mask	r7
 #define sv_lr	r8
+#define loglvl	r9
 
 ENTRY(c_backtrace)
 
@@ -99,6 +100,7 @@ ENDPROC(c_backtrace)
 						@ to ensure 8 byte alignment
 		movs	frame, r0		@ if frame pointer is zero
 		beq	no_frame		@ we have no stack frames
+		mov	loglvl, r2
 		tst	r1, #0x10		@ 26 or 32-bit mode?
 		moveq	mask, #0xfc000003
 		movne	mask, #0		@ mask for 32-bit
@@ -167,6 +169,7 @@ finished_setup:
 		mov	r1, sv_lr
 		mov	r2, frame
 		bic	r1, r1, mask		@ mask PC/LR for the mode
+		mov	r3, loglvl
 		bl	dump_backtrace_entry
 
 /*
@@ -183,6 +186,7 @@ finished_setup:
 		ldr	r0, [frame]		@ locals are stored in
 						@ the preceding frame
 		subeq	r0, r0, #4
+		mov	r2, loglvl
 		bleq	dump_backtrace_stm	@ dump saved registers
 
 /*
@@ -196,7 +200,8 @@ finished_setup:
 		bhi	for_each_frame
 
 1006:		adr	r0, .Lbad
-		mov	r1, frame
+		mov	r1, loglvl
+		mov	r2, frame
 		bl	printk
 no_frame:	ldmfd	sp!, {r4 - r9, fp, pc}
 ENDPROC(c_backtrace)
@@ -209,7 +214,7 @@ ENDPROC(c_backtrace)
 		.long   1005b, 1006b
 		.popsection
 
-.Lbad:		.asciz	"Backtrace aborted due to bad frame pointer <%p>\n"
+.Lbad:		.asciz	"%sBacktrace aborted due to bad frame pointer <%p>\n"
 		.align
 .Lopcode:	.word	0xe92d4800 >> 11	@ stmfd sp!, {... fp, lr}
 		.word	0x0b000000		@ bl if these bits are set
diff --git a/arch/arm/lib/backtrace.S b/arch/arm/lib/backtrace.S
index 582925238d65..872f658638d9 100644
--- a/arch/arm/lib/backtrace.S
+++ b/arch/arm/lib/backtrace.S
@@ -18,6 +18,7 @@
 #define sv_pc	r6
 #define mask	r7
 #define offset	r8
+#define loglvl	r9
 
 ENTRY(c_backtrace)
 
@@ -25,9 +26,10 @@ ENTRY(c_backtrace)
 		ret	lr
 ENDPROC(c_backtrace)
 #else
-		stmfd	sp!, {r4 - r8, lr}	@ Save an extra register so we have a location...
+		stmfd	sp!, {r4 - r9, lr}	@ Save an extra register so we have a location...
 		movs	frame, r0		@ if frame pointer is zero
 		beq	no_frame		@ we have no stack frames
+		mov	loglvl, r2
 
 		tst	r1, #0x10		@ 26 or 32-bit mode?
  ARM(		moveq	mask, #0xfc000003	)
@@ -73,6 +75,7 @@ for_each_frame:	tst	frame, mask		@ Check for address exceptions
 		ldr	r1, [frame, #-4]	@ get saved lr
 		mov	r2, frame
 		bic	r1, r1, mask		@ mask PC/LR for the mode
+		mov	r3, loglvl
 		bl	dump_backtrace_entry
 
 		ldr	r1, [sv_pc, #-4]	@ if stmfd sp!, {args} exists,
@@ -80,12 +83,14 @@ for_each_frame:	tst	frame, mask		@ Check for address exceptions
 		teq	r3, r1, lsr #11
 		ldreq	r0, [frame, #-8]	@ get sp
 		subeq	r0, r0, #4		@ point at the last arg
+		mov	r2, loglvl
 		bleq	dump_backtrace_stm	@ dump saved registers
 
 1004:		ldr	r1, [sv_pc, #0]		@ if stmfd sp!, {..., fp, ip, lr, pc}
 		ldr	r3, .Ldsi		@ instruction exists,
 		teq	r3, r1, lsr #11
 		subeq	r0, frame, #16
+		mov	r2, loglvl
 		bleq	dump_backtrace_stm	@ dump saved registers
 
 		teq	sv_fp, #0		@ zero saved fp means
@@ -96,9 +101,10 @@ for_each_frame:	tst	frame, mask		@ Check for address exceptions
 		bhi	for_each_frame
 
 1006:		adr	r0, .Lbad
-		mov	r1, frame
+		mov	r1, loglvl
+		mov	r2, frame
 		bl	printk
-no_frame:	ldmfd	sp!, {r4 - r8, pc}
+no_frame:	ldmfd	sp!, {r4 - r9, pc}
 ENDPROC(c_backtrace)
 		
 		.pushsection __ex_table,"a"
@@ -109,7 +115,7 @@ ENDPROC(c_backtrace)
 		.long	1004b, 1006b
 		.popsection
 
-.Lbad:		.asciz	"Backtrace aborted due to bad frame pointer <%p>\n"
+.Lbad:		.asciz	"%sBacktrace aborted due to bad frame pointer <%p>\n"
 		.align
 .Ldsi:		.word	0xe92dd800 >> 11	@ stmfd sp!, {... fp, ip, lr, pc}
 		.word	0xe92d0000 >> 11	@ stmfd sp!, {}
-- 
2.23.0


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[PATCH 05/50] arm: Add loglvl to unwind_backtrace()

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Add log level argument to unwind_backtrace() as a preparation for
introducing show_stack_loglvl().

As a good side-effect arm_syscall() is now printing errors with the same
log level as the backtrace.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: clang-built-linux@googlegroups.com
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm/include/asm/unwind.h | 3 ++-
 arch/arm/kernel/traps.c       | 6 +++---
 arch/arm/kernel/unwind.c      | 7 ++++---
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/arm/include/asm/unwind.h b/arch/arm/include/asm/unwind.h
index 6e282c33126b..0f8a3439902d 100644
--- a/arch/arm/include/asm/unwind.h
+++ b/arch/arm/include/asm/unwind.h
@@ -36,7 +36,8 @@ extern struct unwind_table *unwind_table_add(unsigned long start,
 					     unsigned long text_addr,
 					     unsigned long text_size);
 extern void unwind_table_del(struct unwind_table *tab);
-extern void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk);
+extern void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+			     const char *loglvl);
 
 #endif	/* !__ASSEMBLY__ */
 
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 7c3f32b26585..69e35462c9e9 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -202,7 +202,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
 #ifdef CONFIG_ARM_UNWIND
 static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 {
-	unwind_backtrace(regs, tsk);
+	unwind_backtrace(regs, tsk, KERN_DEBUG);
 }
 #else
 static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
@@ -660,10 +660,10 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
 	if (user_debug & UDBG_SYSCALL) {
 		pr_err("[%d] %s: arm syscall %d\n",
 		       task_pid_nr(current), current->comm, no);
-		dump_instr("", regs);
+		dump_instr(KERN_ERR, regs);
 		if (user_mode(regs)) {
 			__show_regs(regs);
-			c_backtrace(frame_pointer(regs), processor_mode(regs), NULL);
+			c_backtrace(frame_pointer(regs), processor_mode(regs), KERN_ERR);
 		}
 	}
 #endif
diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
index 0a65005e10f0..caaae1b6f721 100644
--- a/arch/arm/kernel/unwind.c
+++ b/arch/arm/kernel/unwind.c
@@ -455,11 +455,12 @@ int unwind_frame(struct stackframe *frame)
 	return URC_OK;
 }
 
-void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+		      const char *loglvl)
 {
 	struct stackframe frame;
 
-	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);
 
 	if (!tsk)
 		tsk = current;
@@ -493,7 +494,7 @@ void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 		urc = unwind_frame(&frame);
 		if (urc < 0)
 			break;
-		dump_backtrace_entry(where, frame.pc, frame.sp - 4, NULL);
+		dump_backtrace_entry(where, frame.pc, frame.sp - 4, loglvl);
 	}
 }
 
-- 
2.23.0


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Re: [PATCH 05/50] arm: Add loglvl to unwind_backtrace()

[Russell King - ARM Linux admin]

On Wed, Nov 06, 2019 at 03:04:56AM +0000, Dmitry Safonov wrote:
> Currently, the log-level of show_stack() depends on a platform
> realization. It creates situations where the headers are printed with
> lower log level or higher than the stacktrace (depending on
> a platform or user).
> 
> Furthermore, it forces the logic decision from user to an architecture
> side. In result, some users as sysrq/kdb/etc are doing tricks with
> temporary rising console_loglevel while printing their messages.
> And in result it not only may print unwanted messages from other CPUs,
> but also omit printing at all in the unlucky case where the printk()
> was deferred.
> 
> Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
> an easier approach than introducing more printk buffers.
> Also, it will consolidate printings with headers.
> 
> Add log level argument to unwind_backtrace() as a preparation for
> introducing show_stack_loglvl().
> 
> As a good side-effect arm_syscall() is now printing errors with the same
> log level as the backtrace.
> 
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Will Deacon <will@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: clang-built-linux@googlegroups.com
> [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> ---
>  arch/arm/include/asm/unwind.h | 3 ++-
>  arch/arm/kernel/traps.c       | 6 +++---
>  arch/arm/kernel/unwind.c      | 7 ++++---
>  3 files changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm/include/asm/unwind.h b/arch/arm/include/asm/unwind.h
> index 6e282c33126b..0f8a3439902d 100644
> --- a/arch/arm/include/asm/unwind.h
> +++ b/arch/arm/include/asm/unwind.h
> @@ -36,7 +36,8 @@ extern struct unwind_table *unwind_table_add(unsigned long start,
>  					     unsigned long text_addr,
>  					     unsigned long text_size);
>  extern void unwind_table_del(struct unwind_table *tab);
> -extern void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk);
> +extern void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
> +			     const char *loglvl);
>  
>  #endif	/* !__ASSEMBLY__ */
>  
> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
> index 7c3f32b26585..69e35462c9e9 100644
> --- a/arch/arm/kernel/traps.c
> +++ b/arch/arm/kernel/traps.c
> @@ -202,7 +202,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
>  #ifdef CONFIG_ARM_UNWIND
>  static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>  {
> -	unwind_backtrace(regs, tsk);
> +	unwind_backtrace(regs, tsk, KERN_DEBUG);

Why demote this to debug level?  This is used as part of the kernel
panic message, surely we don't want this at debug level?  What about
the non-unwind version?

>  }
>  #else
>  static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
> @@ -660,10 +660,10 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
>  	if (user_debug & UDBG_SYSCALL) {
>  		pr_err("[%d] %s: arm syscall %d\n",
>  		       task_pid_nr(current), current->comm, no);
> -		dump_instr("", regs);
> +		dump_instr(KERN_ERR, regs);
>  		if (user_mode(regs)) {
>  			__show_regs(regs);
> -			c_backtrace(frame_pointer(regs), processor_mode(regs), NULL);
> +			c_backtrace(frame_pointer(regs), processor_mode(regs), KERN_ERR);
>  		}
>  	}
>  #endif
> diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
> index 0a65005e10f0..caaae1b6f721 100644
> --- a/arch/arm/kernel/unwind.c
> +++ b/arch/arm/kernel/unwind.c
> @@ -455,11 +455,12 @@ int unwind_frame(struct stackframe *frame)
>  	return URC_OK;
>  }
>  
> -void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
> +void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
> +		      const char *loglvl)
>  {
>  	struct stackframe frame;
>  
> -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
> +	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);

Clearly, this isn't supposed to be part of the normal backtrace output...

Overall impression at this point is really not good.

-- 
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Re: [PATCH 05/50] arm: Add loglvl to unwind_backtrace()

[Dmitry Safonov]

On 11/6/19 9:12 AM, Russell King - ARM Linux admin wrote:
> On Wed, Nov 06, 2019 at 03:04:56AM +0000, Dmitry Safonov wrote:
>> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
>> index 7c3f32b26585..69e35462c9e9 100644
>> --- a/arch/arm/kernel/traps.c
>> +++ b/arch/arm/kernel/traps.c
>> @@ -202,7 +202,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
>>  #ifdef CONFIG_ARM_UNWIND
>>  static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>>  {
>> -	unwind_backtrace(regs, tsk);
>> +	unwind_backtrace(regs, tsk, KERN_DEBUG);
> 
> Why demote this to debug level?  This is used as part of the kernel
> panic message, surely we don't want this at debug level?  What about
> the non-unwind version?

Right, I wanted to keep the old loglevel in this patch - KERN_DEFAULT.
But got confused with log level in unwind_backtrace().
Will fix.

[..]
>> diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
>> index 0a65005e10f0..caaae1b6f721 100644
>> --- a/arch/arm/kernel/unwind.c
>> +++ b/arch/arm/kernel/unwind.c
>> @@ -455,11 +455,12 @@ int unwind_frame(struct stackframe *frame)
>>  	return URC_OK;
>>  }
>>  
>> -void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>> +void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
>> +		      const char *loglvl)
>>  {
>>  	struct stackframe frame;
>>  
>> -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
>> +	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);
> 
> Clearly, this isn't supposed to be part of the normal backtrace output...

Yes, sorry it's debug for a backtrace - will return pr_debug() for the
message.

Thanks,
          Dmitry

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[PATCH 06/50] arm: Add loglvl to dump_backtrace()

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Add log level argument to dump_backtrace() as a preparation for
introducing show_stack_loglvl().

As a good side-effect __die() now prints not only "Stack:" header with
KERN_EMERG, but the backtrace itself.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: clang-built-linux@googlegroups.com
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm/kernel/traps.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 69e35462c9e9..e4f4ec8a1899 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -200,17 +200,19 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
 }
 
 #ifdef CONFIG_ARM_UNWIND
-static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+				  const char *loglvl)
 {
-	unwind_backtrace(regs, tsk, KERN_DEBUG);
+	unwind_backtrace(regs, tsk, loglvl);
 }
 #else
-static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+			   const char *loglvl)
 {
 	unsigned int fp, mode;
 	int ok = 1;
 
-	printk("Backtrace: ");
+	printk("%sBacktrace: ", loglvl);
 
 	if (!tsk)
 		tsk = current;
@@ -237,13 +239,13 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	pr_cont("\n");
 
 	if (ok)
-		c_backtrace(fp, mode, NULL);
+		c_backtrace(fp, mode, loglvl);
 }
 #endif
 
 void show_stack(struct task_struct *tsk, unsigned long *sp)
 {
-	dump_backtrace(NULL, tsk);
+	dump_backtrace(NULL, tsk, KERN_DEFAULT);
 	barrier();
 }
 
@@ -285,7 +287,7 @@ static int __die(const char *str, int err, struct pt_regs *regs)
 	if (!user_mode(regs) || in_interrupt()) {
 		dump_mem(KERN_EMERG, "Stack: ", regs->ARM_sp,
 			 THREAD_SIZE + (unsigned long)task_stack_page(tsk));
-		dump_backtrace(regs, tsk);
+		dump_backtrace(regs, tsk, KERN_EMERG);
 		dump_instr(KERN_EMERG, regs);
 	}
 
-- 
2.23.0


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[PATCH 07/50] arm: Wire up dump_backtrace_{entry,stm}

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Now that c_backtrace() always emits correct loglvl, use it for printing.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: clang-built-linux@googlegroups.com
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm/kernel/traps.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index e4f4ec8a1899..16022b75a72f 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -66,13 +66,16 @@ void dump_backtrace_entry(unsigned long where, unsigned long from,
 			  unsigned long frame, const char *loglvl)
 {
 #ifdef CONFIG_KALLSYMS
-	printk("[<%08lx>] (%ps) from [<%08lx>] (%pS)\n", where, (void *)where, from, (void *)from);
+	printk("%s[<%08lx>] (%ps) from [<%08lx>] (%pS)\n",
+		loglvl, where, (void *)where, from, (void *)from);
 #else
-	printk("Function entered at [<%08lx>] from [<%08lx>]\n", where, from);
+	printk("%sFunction entered at [<%08lx>] from [<%08lx>]\n",
+		loglvl, where, from);
 #endif
 
 	if (in_entry_text(from))
-		dump_mem("", "Exception stack", frame + 4, frame + 4 + sizeof(struct pt_regs));
+		dump_mem(loglvl, "Exception stack",
+			frame + 4, frame + 4 + sizeof(struct pt_regs));
 }
 
 void dump_backtrace_stm(u32 *stack, u32 instruction, const char *loglvl)
@@ -87,12 +90,12 @@ void dump_backtrace_stm(u32 *stack, u32 instruction, const char *loglvl)
 			if (++x == 6) {
 				x = 0;
 				p = str;
-				printk("%s\n", str);
+				printk("%s%s\n", loglvl, str);
 			}
 		}
 	}
 	if (p != str)
-		printk("%s\n", str);
+		printk("%s%s\n", loglvl, str);
 }
 
 #ifndef CONFIG_ARM_UNWIND
-- 
2.23.0


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[PATCH 08/50] arm: Add show_stack_loglvl()

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Introduce show_stack_loglvl(), that eventually will substitute
show_stack().

Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: clang-built-linux@googlegroups.com
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm/kernel/traps.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 16022b75a72f..f999a0e4bab8 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -246,12 +246,18 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
 }
 #endif
 
-void show_stack(struct task_struct *tsk, unsigned long *sp)
+void show_stack_loglvl(struct task_struct *tsk, unsigned long *sp,
+		       const char *loglvl)
 {
-	dump_backtrace(NULL, tsk, KERN_DEFAULT);
+	dump_backtrace(NULL, tsk, loglvl);
 	barrier();
 }
 
+void show_stack(struct task_struct *tsk, unsigned long *sp)
+{
+	show_stack_loglvl(tsk, sp, KERN_DEFAULT);
+}
+
 #ifdef CONFIG_PREEMPT
 #define S_PREEMPT " PREEMPT"
 #else
-- 
2.23.0


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[PATCH 09/50] arm64: Add loglvl to dump_backtrace()

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Add log level argument to dump_backtrace() as a preparation for
introducing show_stack_loglvl().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm64/include/asm/stacktrace.h |  3 ++-
 arch/arm64/kernel/process.c         |  2 +-
 arch/arm64/kernel/traps.c           | 17 +++++++++--------
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/include/asm/stacktrace.h b/arch/arm64/include/asm/stacktrace.h
index 4d9b1f48dc39..fdb913cc0bcb 100644
--- a/arch/arm64/include/asm/stacktrace.h
+++ b/arch/arm64/include/asm/stacktrace.h
@@ -64,7 +64,8 @@ struct stackframe {
 extern int unwind_frame(struct task_struct *tsk, struct stackframe *frame);
 extern void walk_stackframe(struct task_struct *tsk, struct stackframe *frame,
 			    int (*fn)(struct stackframe *, void *), void *data);
-extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk);
+extern void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+			   const char *loglvl);
 
 DECLARE_PER_CPU(unsigned long *, irq_stack_ptr);
 
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 71f788cd2b18..1a6b58b1be2c 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -291,7 +291,7 @@ void __show_regs(struct pt_regs *regs)
 void show_regs(struct pt_regs * regs)
 {
 	__show_regs(regs);
-	dump_backtrace(regs, NULL);
+	dump_backtrace(regs, NULL, KERN_DEFAULT);
 }
 
 static void tls_thread_flush(void)
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 34739e80211b..59072c7b9fb4 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -52,9 +52,9 @@ static const char *handler[]= {
 
 int show_unhandled_signals = 0;
 
-static void dump_backtrace_entry(unsigned long where)
+static void dump_backtrace_entry(unsigned long where, const char *loglvl)
 {
-	printk(" %pS\n", (void *)where);
+	printk("%s %pS\n", loglvl, (void *)where);
 }
 
 static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
@@ -82,12 +82,13 @@ static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
 	printk("%sCode: %s\n", lvl, str);
 }
 
-void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
+void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
+		    const char *loglvl)
 {
 	struct stackframe frame;
 	int skip = 0;
 
-	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);
 
 	if (regs) {
 		if (user_mode(regs))
@@ -114,11 +115,11 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 				thread_saved_pc(tsk));
 	}
 
-	printk("Call trace:\n");
+	printk("%sCall trace:\n", loglvl);
 	do {
 		/* skip until specified stack frame */
 		if (!skip) {
-			dump_backtrace_entry(frame.pc);
+			dump_backtrace_entry(frame.pc, loglvl);
 		} else if (frame.fp == regs->regs[29]) {
 			skip = 0;
 			/*
@@ -128,7 +129,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 			 * at which an exception has taken place, use regs->pc
 			 * instead.
 			 */
-			dump_backtrace_entry(regs->pc);
+			dump_backtrace_entry(regs->pc, loglvl);
 		}
 	} while (!unwind_frame(tsk, &frame));
 
@@ -137,7 +138,7 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 
 void show_stack(struct task_struct *tsk, unsigned long *sp)
 {
-	dump_backtrace(NULL, tsk);
+	dump_backtrace(NULL, tsk, KERN_DEFAULT);
 	barrier();
 }
 
-- 
2.23.0


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Re: [PATCH 09/50] arm64: Add loglvl to dump_backtrace()

[Will Deacon]

On Wed, Nov 06, 2019 at 03:05:00AM +0000, Dmitry Safonov wrote:
> Currently, the log-level of show_stack() depends on a platform
> realization. It creates situations where the headers are printed with
> lower log level or higher than the stacktrace (depending on
> a platform or user).
> 
> Furthermore, it forces the logic decision from user to an architecture
> side. In result, some users as sysrq/kdb/etc are doing tricks with
> temporary rising console_loglevel while printing their messages.
> And in result it not only may print unwanted messages from other CPUs,
> but also omit printing at all in the unlucky case where the printk()
> was deferred.
> 
> Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
> an easier approach than introducing more printk buffers.
> Also, it will consolidate printings with headers.
> 
> Add log level argument to dump_backtrace() as a preparation for
> introducing show_stack_loglvl().
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Russell King <linux@armlinux.org.uk>
> Cc: Will Deacon <will@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
> Signed-off-by: Dmitry Safonov <dima@arista.com>
> ---
>  arch/arm64/include/asm/stacktrace.h |  3 ++-
>  arch/arm64/kernel/process.c         |  2 +-
>  arch/arm64/kernel/traps.c           | 17 +++++++++--------
>  3 files changed, 12 insertions(+), 10 deletions(-)

[...]

> diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
> index 34739e80211b..59072c7b9fb4 100644
> --- a/arch/arm64/kernel/traps.c
> +++ b/arch/arm64/kernel/traps.c
> @@ -52,9 +52,9 @@ static const char *handler[]= {
>  
>  int show_unhandled_signals = 0;
>  
> -static void dump_backtrace_entry(unsigned long where)
> +static void dump_backtrace_entry(unsigned long where, const char *loglvl)
>  {
> -	printk(" %pS\n", (void *)where);
> +	printk("%s %pS\n", loglvl, (void *)where);
>  }
>  
>  static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
> @@ -82,12 +82,13 @@ static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
>  	printk("%sCode: %s\n", lvl, str);
>  }
>  
> -void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
> +void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
> +		    const char *loglvl)
>  {
>  	struct stackframe frame;
>  	int skip = 0;
>  
> -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
> +	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);

This one needs to stay as pr_debug().

Will

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Re: [PATCH 09/50] arm64: Add loglvl to dump_backtrace()

[Dmitry Safonov]

On 11/6/19 1:25 PM, Will Deacon wrote:
> On Wed, Nov 06, 2019 at 03:05:00AM +0000, Dmitry Safonov wrote:
[..]
>> @@ -82,12 +82,13 @@ static void dump_kernel_instr(const char *lvl, struct pt_regs *regs)
>>  	printk("%sCode: %s\n", lvl, str);
>>  }
>>  
>> -void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>> +void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
>> +		    const char *loglvl)
>>  {
>>  	struct stackframe frame;
>>  	int skip = 0;
>>  
>> -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
>> +	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);
> 
> This one needs to stay as pr_debug().

Makes sense, it's debug rather part of backtrace, will fix.

Thanks,
          Dmitry

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[PATCH 10/50] arm64: Add show_stack_loglvl()

[Dmitry Safonov]

Currently, the log-level of show_stack() depends on a platform
realization. It creates situations where the headers are printed with
lower log level or higher than the stacktrace (depending on
a platform or user).

Furthermore, it forces the logic decision from user to an architecture
side. In result, some users as sysrq/kdb/etc are doing tricks with
temporary rising console_loglevel while printing their messages.
And in result it not only may print unwanted messages from other CPUs,
but also omit printing at all in the unlucky case where the printk()
was deferred.

Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
an easier approach than introducing more printk buffers.
Also, it will consolidate printings with headers.

Introduce show_stack_loglvl(), that eventually will substitute
show_stack().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
 arch/arm64/kernel/traps.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 59072c7b9fb4..5b3ae8ed33fd 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -136,12 +136,18 @@ void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk,
 	put_task_stack(tsk);
 }
 
-void show_stack(struct task_struct *tsk, unsigned long *sp)
+void show_stack_loglvl(struct task_struct *tsk, unsigned long *sp,
+		       const char *loglvl)
 {
-	dump_backtrace(NULL, tsk, KERN_DEFAULT);
+	dump_backtrace(NULL, tsk, loglvl);
 	barrier();
 }
 
+void show_stack(struct task_struct *tsk, unsigned long *sp)
+{
+	show_stack_loglvl(tsk, sp, KERN_DEFAULT);
+}
+
 #ifdef CONFIG_PREEMPT
 #define S_PREEMPT " PREEMPT"
 #else
-- 
2.23.0


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