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Matt Redfearn a0ae2b0833 MIPS: microMIPS: Fix decoding of addiusp instruction Commit `34c2f668d0` ("MIPS: microMIPS: Add unaligned access support.") added handling of microMIPS instructions to manipulate the stack pointer. Unfortunately the decoding of the addiusp instruction was incorrect, and performed a left shift by 2 bits to the raw immediate, rather than decoding the immediate and then performing the shift, as documented in the ISA. This led to incomplete stack traces, due to incorrect frame sizes being calculated. For example the instruction: 801faee0 <do_sys_poll>: 801faee0: 4e25 addiu sp,sp,-952 As decoded by objdump, would be interpreted by the existing code as having manipulated the stack pointer by +1096. Fix this by changing the order of decoding the immediate and applying the left shift. Also change to accessing the instuction through the union to avoid the endianness problem of accesing halfword[0], which will fail on big endian systems. Cope with the special behaviour of immediates 0x0, 0x1, 0x1fe and 0x1ff by XORing with 0x100 again if mod(immediate) < 4. This logic was tested with the following test code: int main(int argc, char **argv) { unsigned int enc; int imm; for (enc = 0; enc < 512; ++enc) { int tmp = enc << 2; imm = -(signed short)(tmp \| ((tmp & 0x100) ? 0xfe00 : 0)); unsigned short tmp = enc; tmp = (tmp ^ 0x100) - 0x100; if ((unsigned short)(tmp + 2) < 4) tmp ^= 0x100; imm = -(signed short)(tmp << 2); printf("%#x\t%d\t->\t(%#x\t%d)\t%#x\t%d\n", enc, enc, (short)tmp, (short)tmp, imm, imm); } return EXIT_SUCCESS; } Which generates the table: input encoding -> tmp (matching manual) frame size ----------------------------------------------------------------------- 0 0 -> (0x100 256) 0xfffffc00 -1024 0x1 1 -> (0x101 257) 0xfffffbfc -1028 0x2 2 -> (0x2 2) 0xfffffff8 -8 0x3 3 -> (0x3 3) 0xfffffff4 -12 ... 0xfe 254 -> (0xfe 254) 0xfffffc08 -1016 0xff 255 -> (0xff 255) 0xfffffc04 -1020 0x100 256 -> (0xffffff00 -256) 0x400 1024 0x101 257 -> (0xffffff01 -255) 0x3fc 1020 ... 0x1fc 508 -> (0xfffffffc -4) 0x10 16 0x1fd 509 -> (0xfffffffd -3) 0xc 12 0x1fe 510 -> (0xfffffefe -258) 0x408 1032 0x1ff 511 -> (0xfffffeff -257) 0x404 1028 Thanks to James Hogan for the test code & verifying the logic. Fixes: `34c2f668d0` ("MIPS: microMIPS: Add unaligned access support.") Suggested-by: James Hogan <james.hogan@imgtec.com> Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com> Cc: Marcin Nowakowski <marcin.nowakowski@imgtec.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Paul Burton <paul.burton@imgtec.com> Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16955/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>		2017-09-06 13:19:49 +02:00
arch	MIPS: microMIPS: Fix decoding of addiusp instruction	2017-09-06 13:19:49 +02:00
block	blk-mq-debugfs: Add names for recently added flags	2017-08-25 08:07:44 -06:00
certs	modsign: add markers to endif-statements in certs/Makefile	2017-07-14 11:01:37 +10:00
crypto	crypto: authencesn - Fix digest_null crash	2017-07-18 17:01:11 +08:00
Documentation	phy: Add an USB PHY driver for the Lantiq SoCs using the RCU module	2017-09-04 21:19:02 +02:00
drivers	watchdog: octeon-wdt: Add support for 78XX SOCs.	2017-09-04 21:19:03 +02:00
firmware	firmware/Makefile: force recompilation if makefile changes	2017-05-08 17:15:10 -07:00
fs	Merge branch 'akpm' (patches from Andrew)	2017-08-25 18:02:27 -07:00
include	MIPS: lantiq: Add a GPHY driver which uses the RCU syscon-mfd	2017-09-04 21:19:02 +02:00
init	random: do not ignore early device randomness	2017-07-12 16:26:00 -07:00
ipc	ipc: add missing container_of()s for randstruct	2017-08-02 17:16:12 -07:00
kernel	Minor page waitqueue cleanups	2017-08-27 13:55:12 -07:00
lib	kernel/watchdog: Prevent false positives with turbo modes	2017-08-18 12:35:02 +02:00
mm	Avoid page waitqueue race leaving possible page locker waiting	2017-08-27 16:25:09 -07:00
net	Two nfsd bugfixes, neither 4.13 regressions, but both potentially	2017-08-25 17:27:26 -07:00
samples	samples/bpf: fix bpf tunnel cleanup	2017-07-31 22:02:47 -07:00
scripts	Kbuild fixes for v4.13	2017-08-24 14:22:27 -07:00
security	Now that IPC and other changes have landed, enable manual markings for	2017-07-19 08:55:18 -07:00
sound	ASoC: rt5677: Reintroduce I2C device IDs	2017-08-24 18:04:29 +02:00
tools	NTB bug fixes to address an incorrect ntb_mw_count reference in the NTB	2017-08-27 17:01:54 -07:00
usr	ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk.	2017-07-06 16:24:30 -07:00
virt	KVM/ARM Fixes for v4.13-rc4	2017-08-03 17:59:58 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes	.gitattributes: set git diff driver for C source code files	2016-10-07 18:46:30 -07:00
.gitignore	kbuild: Add support to generate LLVM assembly files	2017-04-25 08:13:52 +09:00
.mailmap	power supply and reset changes for the v4.12 series (part 2)	2017-05-12 12:02:21 -07:00
COPYING
CREDITS	avr32: remove support for AVR32 architecture	2017-05-01 09:27:15 +02:00
Kbuild	kbuild: Consolidate header generation from ASM offset information	2017-04-13 05:43:37 +09:00
Kconfig
MAINTAINERS	MIPS: lantiq: Convert the fpi bus driver to a platform_driver	2017-09-04 21:19:02 +02:00
Makefile	Linux 4.13-rc7	2017-08-27 17:20:40 -07:00
README	README: add a new README file, pointing to the Documentation/	2016-10-24 08:12:35 -02:00

README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.