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a1a371c468
One of Linus' favorite hobbies seems to be looking at OOPSes and decoding the error code in his head. This is not one of my favorite hobbies :) Teach the page fault OOPS hander to decode the error code. If it's a !USER fault from user mode, print an explicit note to that effect and print out the addresses of various tables that might cause such an error. With this patch applied, if I intentionally point the LDT at 0x0 and run the x86 selftests, I get: BUG: unable to handle kernel NULL pointer dereference at 0000000000000000 HW error: normal kernel read fault This was a system access from user code IDT: 0xfffffe0000000000 (limit=0xfff) GDT: 0xfffffe0000001000 (limit=0x7f) LDTR: 0x50 -- base=0x0 limit=0xfff7 TR: 0x40 -- base=0xfffffe0000003000 limit=0x206f PGD 800000000456e067 P4D 800000000456e067 PUD 4623067 PMD 0 SMP PTI CPU: 0 PID: 153 Comm: ldt_gdt_64 Not tainted 4.19.0+ #1317 Hardware name: ... RIP: 0033:0x401454 Signed-off-by: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Yu-cheng Yu <yu-cheng.yu@intel.com> Link: http://lkml.kernel.org/r/11212acb25980cd1b3030875cd9502414fbb214d.1542841400.git.luto@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.