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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
Download Patch File Download Diff File Expand all files Collapse all files

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