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arm64: Add user_debug command line option

PATCH New Laura Abbott 2 participants 3 messages Apr 9, 2014 arm64

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Laura Abbott

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#0 lore raw

PATCH 1/1 arm64: Add user_debug command line option

arm had a useful command line option to print out debug information on user signals. This is somewhat like a more verbose version of show_unhandled_signals. Add the user_debug command line option to print out more information in a similar manner to arm.

Signed-off-by Laura Abbott <[email protected]>
---
 arch/arm64/include/asm/system_misc.h | 25 +++++++++++++++++++++++++
 arch/arm64/kernel/traps.c            | 13 ++++++++++---
 arch/arm64/mm/fault.c                |  3 +--
 3 files changed, 36 insertions(+), 5 deletions(-)
arch/arm64/include/asm/system_misc.h +25 -0
index 7a18fab..2f95589 100644
@@ -50,6 +50,31 @@ extern void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 #define UDBG_SEGV	(1 << 3)
 #define UDBG_BUS	(1 << 4)
 
+extern unsigned int user_debug;
+extern int show_unhandled_signals;
+
+static inline bool print_user_debug(unsigned int signum, unsigned int mask)
+{
+	int ret = 0;
+	bool sig_assert = false;
+
+	ret |= show_unhandled_signals &&
+		(signum ? unhandled_signal(current, signum) : 1);
+	if (mask & UDBG_SEGV) {
+		sig_assert = true;
+		ret |= (user_debug & mask) && signum == SIGSEGV;
+	}
+	if (mask & UDBG_BUS) {
+		sig_assert = true;
+		ret |= (user_debug & mask) && signum == SIGBUS;
+	}
+	if (sig_assert)
+		ret |= (user_debug & mask);
+
+	return ret ? printk_ratelimit() : false;
+}
+
+
 #endif	/* __ASSEMBLY__ */
 
 #endif	/* __ASM_SYSTEM_MISC_H */
arch/arm64/kernel/traps.c +10 -3
index a6740d0..5519ef1 100644
@@ -48,6 +48,14 @@ static const char *handler[]= {
 };
 
 int show_unhandled_signals = 1;
+unsigned int user_debug;
+
+static int __init user_debug_setup(char *str)
+{
+	get_option(&str, &user_debug);
+	return 1;
+}
+__setup("user_debug=", user_debug_setup);
 
 /*
  * Dump out the contents of some memory nicely...

@@ -270,8 +278,7 @@ asmlinkage void __exception do_undefinstr(struct pt_regs *regs)
 
 	trace_undef_instr(regs, (void *)pc);
 
-	if (show_unhandled_signals && unhandled_signal(current, SIGILL) &&
-	    printk_ratelimit()) {
+	if (print_user_debug(SIGILL, UDBG_UNDEFINED)) {
 		pr_info("%s[%d]: undefined instruction: pc=%p\n",
 			current->comm, task_pid_nr(current), pc);
 		dump_instr(KERN_INFO, regs);

@@ -298,7 +305,7 @@ asmlinkage long do_ni_syscall(struct pt_regs *regs)
 	}
 #endif
 
-	if (show_unhandled_signals && printk_ratelimit()) {
+	if (print_user_debug(0, UDBG_SYSCALL)) {
 		pr_info("%s[%d]: syscall %d\n", current->comm,
 			task_pid_nr(current), (int)regs->syscallno);
 		dump_instr("", regs);
arch/arm64/mm/fault.c +1 -2
index 8e783eb..bbef0b5 100644
@@ -117,8 +117,7 @@ static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
 
 	trace_user_fault(tsk, addr, esr);
 
-	if (show_unhandled_signals && unhandled_signal(tsk, sig) &&
-	    printk_ratelimit()) {
+	if (print_user_debug(sig, UDBG_BUS | UDBG_SEGV)) {
 		pr_info("%s[%d]: unhandled %s (%d) at 0x%08lx, esr 0x%03x\n",
 			tsk->comm, task_pid_nr(tsk), fault_name(esr), sig,
 			addr, esr);
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#1 lore raw

PATCH 1/1 arm64: Add user_debug command line option

Quoted 5 lines · Laura Abbott

arm had a useful command line option to print out debug information on user signals. This is somewhat like a more verbose version of show_unhandled_signals. Add the user_debug command line option to print out more information in a similar manner to arm.

Is this because you want to print information for handled signals as well? What is the use case? (there are alternatives like ptrace as well).

Signature · 1 line
Catalin
author
#2 lore raw

PATCH 1/1 arm64: Add user_debug command line option

Quoted 11 lines · Catalin Marinas
Quoted 5 lines · Laura Abbott

arm had a useful command line option to print out debug information on user signals. This is somewhat like a more verbose version of show_unhandled_signals. Add the user_debug command line option to print out more information in a similar manner to arm.

Is this because you want to print information for handled signals as well? What is the use case? (there are alternatives like ptrace as well).

Yes. We've found user_debug to be helpful in correlating userspace crashes to other events that are spewed in the system log. Example from last week: userspace program crashes, bad page state and panic happens soon after. Some kernel driver was not cleaning up after itself properly after the crash. Without seeing the userspace crash logs it would have been much more difficult to correlate the bad page state to anything.

Laura

Signature · 2 lines
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation