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LoongArch: Use generic BUG() handler

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Inspired by commit 9fb7410f955("arm64/BUG: Use BRK instruction for
generic BUG traps"), do similar for LoongArch to use generic BUG()
handler.

This patch uses the BREAK software breakpoint instruction to generate
a trap instead, similarly to most other arches, with the generic BUG
code generating the dmesg boilerplate.

This allows bug metadata to be moved to a separate table and reduces
the amount of inline code at BUG() and WARN() sites. This also avoids
clobbering any registers before they can be dumped.

To mitigate the size of the bug table further, this patch makes use of
the existing infrastructure for encoding addresses within the bug table
as 32-bit relative pointers instead of absolute pointers.

(Note: this limits the max kernel size to 2GB.)

Before patch:
[ 3018.338013] lkdtm: Performing direct entry BUG
[ 3018.342445] Kernel bug detected[#5]:
[ 3018.345992] CPU: 2 PID: 865 Comm: cat Tainted: G D 6.0.0-rc6+ #35

After patch:
[  125.585985] lkdtm: Performing direct entry BUG
[  125.590433] ------------[ cut here ]------------
[  125.595020] kernel BUG at drivers/misc/lkdtm/bugs.c:78!
[  125.600211] Oops - BUG[#1]:
[  125.602980] CPU: 3 PID: 410 Comm: cat Not tainted 6.0.0-rc6+ #36

Out-of-line file/line data information obtained compared to before.

Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Youling Tang 2022-10-12 16:36:19 +08:00 committed by Huacai Chen
parent dea2df3cc7
commit 2d2c395217
4 changed files with 85 additions and 13 deletions
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8
arch/loongarch/Kconfig
View File

@ -142,6 +142,14 @@ config CPU_HAS_PREFETCH
bool
default y
config GENERIC_BUG
def_bool y
depends on BUG
config GENERIC_BUG_RELATIVE_POINTERS
def_bool y
depends on GENERIC_BUG
config GENERIC_CALIBRATE_DELAY
def_bool y

60
arch/loongarch/include/asm/bug.h
View File

@ -2,22 +2,60 @@
#ifndef __ASM_BUG_H
#define __ASM_BUG_H
#include <linux/compiler.h>
#ifdef CONFIG_BUG
#include <asm/break.h>
#include <linux/stringify.h>
static inline void __noreturn BUG(void)
{
__asm__ __volatile__("break %0" : : "i" (BRK_BUG));
unreachable();
}
#ifndef CONFIG_DEBUG_BUGVERBOSE
#define _BUGVERBOSE_LOCATION(file, line)
#else
#define __BUGVERBOSE_LOCATION(file, line) \
.pushsection .rodata.str, "aMS", @progbits, 1; \
10002: .string file; \
.popsection; \
\
.long 10002b - .; \
.short line;
#define _BUGVERBOSE_LOCATION(file, line) __BUGVERBOSE_LOCATION(file, line)
#endif
#ifndef CONFIG_GENERIC_BUG
#define __BUG_ENTRY(flags)
#else
#define __BUG_ENTRY(flags) \
.pushsection __bug_table, "aw"; \
.align 2; \
10000: .long 10001f - .; \
_BUGVERBOSE_LOCATION(__FILE__, __LINE__) \
.short flags; \
.popsection; \
10001:
#endif
#define ASM_BUG_FLAGS(flags) \
__BUG_ENTRY(flags) \
break BRK_BUG
#define ASM_BUG() ASM_BUG_FLAGS(0)
#define __BUG_FLAGS(flags) \
asm_inline volatile (__stringify(ASM_BUG_FLAGS(flags)));
#define __WARN_FLAGS(flags) \
do { \
instrumentation_begin(); \
__BUG_FLAGS(BUGFLAG_WARNING|(flags)); \
instrumentation_end(); \
} while (0)
#define BUG() \
do { \
instrumentation_begin(); \
__BUG_FLAGS(0); \
unreachable(); \
} while (0)
#define HAVE_ARCH_BUG
#endif
#include <asm-generic/bug.h>
#endif /* __ASM_BUG_H */

4
arch/loongarch/kernel/head.S
View File

@ -8,6 +8,7 @@
#include <asm/addrspace.h>
#include <asm/asm.h>
#include <asm/asmmacro.h>
#include <asm/bug.h>
#include <asm/regdef.h>
#include <asm/loongarch.h>
#include <asm/stackframe.h>
@ -85,6 +86,7 @@ SYM_CODE_START(kernel_entry) # kernel entry point
PTR_ADDI sp, sp, -4 * SZREG # init stack pointer
bl start_kernel
ASM_BUG()
SYM_CODE_END(kernel_entry)
@ -116,6 +118,8 @@ SYM_CODE_START(smpboot_entry)
ld.d tp, t0, CPU_BOOT_TINFO
bl start_secondary
ASM_BUG()
SYM_CODE_END(smpboot_entry)
#endif /* CONFIG_SMP */

26
arch/loongarch/kernel/traps.c
View File

@ -374,6 +374,29 @@ asmlinkage void noinstr do_ale(struct pt_regs *regs)
irqentry_exit(regs, state);
}
#ifdef CONFIG_GENERIC_BUG
int is_valid_bugaddr(unsigned long addr)
{
return 1;
}
#endif /* CONFIG_GENERIC_BUG */
static void bug_handler(struct pt_regs *regs)
{
switch (report_bug(regs->csr_era, regs)) {
case BUG_TRAP_TYPE_BUG:
case BUG_TRAP_TYPE_NONE:
die_if_kernel("Oops - BUG", regs);
force_sig(SIGTRAP);
break;
case BUG_TRAP_TYPE_WARN:
/* Skip the BUG instruction and continue */
regs->csr_era += LOONGARCH_INSN_SIZE;
break;
}
}
asmlinkage void noinstr do_bp(struct pt_regs *regs)
{
bool user = user_mode(regs);
@ -427,8 +450,7 @@ asmlinkage void noinstr do_bp(struct pt_regs *regs)
switch (bcode) {
case BRK_BUG:
die_if_kernel("Kernel bug detected", regs);
force_sig(SIGTRAP);
bug_handler(regs);
break;
case BRK_DIVZERO:
die_if_kernel("Break instruction in kernel code", regs);