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Commit 814d83c5 authored by Xianting Tian's avatar Xianting Tian Committed by Greg Kroah-Hartman
Browse files

RISC-V: Add fast call path of crash_kexec() 



[ Upstream commit 3f1901110a89b0e2e13adb2ac8d1a7102879ea98 ]

Currently, almost all archs (x86, arm64, mips...) support fast call
of crash_kexec() when "regs && kexec_should_crash()" is true. But
RISC-V not, it can only enter crash system via panic(). However panic()
doesn't pass the regs of the real accident scene to crash_kexec(),
it caused we can't get accurate backtrace via gdb,
	$ riscv64-linux-gnu-gdb vmlinux vmcore
	Reading symbols from vmlinux...
	[New LWP 95]
	#0  console_unlock () at kernel/printk/printk.c:2557
	2557                    if (do_cond_resched)
	(gdb) bt
	#0  console_unlock () at kernel/printk/printk.c:2557
	#1  0x0000000000000000 in ?? ()

With the patch we can get the accurate backtrace,
	$ riscv64-linux-gnu-gdb vmlinux vmcore
	Reading symbols from vmlinux...
	[New LWP 95]
	#0  0xffffffe00063a4e0 in test_thread (data=<optimized out>) at drivers/test_crash.c:81
	81             *(int *)p = 0xdead;
	(gdb)
	(gdb) bt
	#0  0xffffffe00064d5c0 in test_thread (data=<optimized out>) at drivers/test_crash.c:81
	#1  0x0000000000000000 in ?? ()

Test code to produce NULL address dereference in test_crash.c,
	void *p = NULL;
	*(int *)p = 0xdead;

Reviewed-by: default avatarGuo Ren <guoren@kernel.org>
Tested-by: default avatarXianting Tian <xianting.tian@linux.alibaba.com>
Signed-off-by: default avatarXianting Tian <xianting.tian@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220606082308.2883458-1-xianting.tian@linux.alibaba.com


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 812cb212

arch/riscv/kernel/traps.c

+4 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <linux/mm.h>

#include <linux/module.h>

#include <linux/irq.h>

#include <linux/kexec.h>



#include <asm/processor.h>

#include <asm/ptrace.h>
@@ -43,6 +44,9 @@ void die(struct pt_regs *regs, const char *str) 


	ret = notify_die(DIE_OOPS, str, regs, 0, regs->scause, SIGSEGV);



	if (regs && kexec_should_crash(current))

		crash_kexec(regs);



	bust_spinlocks(0);

	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);

	spin_unlock_irq(&die_lock);