Hi,
Arm64 kernel dmesg will print out a multiline message if any user binary segfaults. We get "unhandled level X translation fault" with pr_info, show_pte() with pr_alert and show_regs with default kernel level:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/ar...
Contrast to arm32 version, where it is only done if CONFIG_DEBUG_USER is selected and user_debug=N is passed down from kernel command line:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/ar...
The verboseness was useful in early platform bringup, but now it is now a more source of confusion (people google for unhandled level translation fault and find old linaro bugs..) . For end users pov, the x86 version with single line on INFO level would probably be good:
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/x8...
example:
test[8901]: segfault at 0 ip 00007fe456a4621f sp 00007ffffd465a90 error 6 in libc-2.19.so[7fe4569db000+19f000]
Could the arm64 behavior be changed to match arm or x86 printouts?
Riku
On Fri, Jul 25, 2014 at 01:22:49PM +0100, Riku Voipio wrote:
Arm64 kernel dmesg will print out a multiline message if any user binary segfaults. We get "unhandled level X translation fault" with pr_info, show_pte() with pr_alert and show_regs with default kernel level:
I agree show_pte() is not useful for user debugging but I'm not sure about show_regs(), it may come in handy when debugging some user application.
We could hide the extra information like show_pte behind a CONFIG_DEBUG_USER while keeping the short reporting as it currently is (based on show_unhandled_signals).
linaro-kernel@lists.linaro.org
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Catalin Marinas -
Riku Voipio