Commit 5489ab50 authored by Dmitry Safonov's avatar Dmitry Safonov Committed by Linus Torvalds
Browse files

arm/asm: add loglvl to c_backtrace() 

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().

[1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u



Signed-off-by: default avatarDmitry Safonov <dima@arista.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Will Deacon <will@kernel.org>
Link: http://lkml.kernel.org/r/20200418201944.482088-5-dima@arista.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8ca4d199

arch/arm/include/asm/bug.h

+2 −1
Original line number Diff line number Diff line
@@ -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);

arch/arm/include/asm/traps.h

+2 −1
Original line number Diff line number Diff line
@@ -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;

arch/arm/kernel/traps.c

+5 −4
Original line number Diff line number Diff line
@@ -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)

{

	unsigned long end = frame + 4 + sizeof(struct pt_regs);
@@ -76,7 +77,7 @@ void dump_backtrace_entry(unsigned long where, unsigned long from, unsigned long 
		dump_mem("", "Exception stack", frame + 4, end);

}



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;
@@ -238,7 +239,7 @@ 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
@@ -666,7 +667,7 @@ 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

arch/arm/kernel/unwind.c

+1 −1
Original line number Diff line number Diff line
@@ -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);

	}

}

arch/arm/lib/backtrace-clang.S

+7 −2
Original line number Diff line number Diff line
@@ -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

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