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arm/asm: add loglvl to c_backtrace()

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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: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrew 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: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dmitry Safonov 2020-06-08 21:30:07 -07:00 committed by Linus Torvalds
parent 8ca4d19932
commit 5489ab50c2
6 changed files with 27 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
arch/arm/include/asm/bug.h
View File

@ -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);

3
arch/arm/include/asm/traps.h
View File

@ -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;

9
arch/arm/kernel/traps.c
View File

@ -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

2
arch/arm/kernel/unwind.c
View File

@ -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);
}
}

9
arch/arm/lib/backtrace-clang.S
View File

@ -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

14
arch/arm/lib/backtrace.S
View File

@ -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!, {}