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[ACTIVITY] (Anton Vorontsov) 2012-09-17 - 2012-09-21

by Anton Vorontsov

== Highlights == * Performed some proof-of-concept tests on the Mel Gorman's idea of using nr_scanned/(nr_reclaimed+1) ratio for memory pressure detection -- and the idea seems to work great. Didn't have time to implement it in the vmevent API, but hopefully this week I'll have something to show; * Addressed Jason Wessel's comments on KDB FIQ debugger patches, i.e. now we only register ttyNMI interface and disable_nmi command on arches that actually support NMI rerouting, plus reworked enable_nmi callback; * Got a bunch of new ideas from Android folks on KDB FIQ debugger, cpufreq, low memory handling, and more. Lots of things to investigate and implement; * Some power supply and pstore maintenance activity, reviewed over 90 patches in total.

12 years, 9 months

[PATCH v8 0/11] KGDB/KDB FIQ (NMI) debugger

by Anton Vorontsov

Hi all, In v8, addressed Jason's comments: - Changed kgdb_enable_nmi() weak function to kgdb_arch callbck; - We no longer register disable_nmi command if arch does not register KGDB NMI handling (i.e. not filling kgdb_arch.enable_nmi callback); - The same is for ttyNMI: if architecure does not provide us with enable_nmi call, we don't need the tty device. Of course, there is no way to tell wether a specific serial device can be used for NMI debugging, as it is not serial-device specific, but specific to whether IRQ can be rerouted to an NMI (for most our cases, pretty much every IRQ can be rerouted, e.g. a hot-pluggable serial device on a PCI bus). - Rebased on the latest and greatest tty-next, just in case. These patches can be found in the following repo (based on tty-next): git://git.infradead.org/users/cbou/linux-nmi-kdb.git master Old changelogs and rationale for these patches can be found here: v1-v5, rationale: http://lkml.org/lkml/2012/9/10/2 v6: http://lkml.org/lkml/2012/9/10/2 v7: http://lkml.org/lkml/2012/9/13/367 Thanks, -- arch/arm/Kconfig | 19 ++ arch/arm/common/vic.c | 28 +++ arch/arm/include/asm/hardware/vic.h | 2 + arch/arm/include/asm/kgdb.h | 8 + arch/arm/kernel/Makefile | 1 + arch/arm/kernel/entry-armv.S | 167 +------------ arch/arm/kernel/entry-header.S | 170 +++++++++++++ arch/arm/kernel/kgdb_fiq.c | 124 +++++++++ arch/arm/kernel/kgdb_fiq_entry.S | 87 +++++++ arch/arm/mach-versatile/Makefile | 1 + arch/arm/mach-versatile/kgdb_fiq.c | 31 +++ drivers/tty/serial/Kconfig | 19 ++ drivers/tty/serial/Makefile | 1 + drivers/tty/serial/amba-pl011.c | 73 +++++- drivers/tty/serial/kgdb_nmi.c | 402 ++++++++++++++++++++++++++++++ drivers/tty/serial/kgdboc.c | 9 + drivers/tty/serial/serial_core.c | 17 ++ include/linux/kdb.h | 29 ++- include/linux/kgdb.h | 13 + include/linux/serial_core.h | 1 + kernel/debug/debug_core.c | 14 +- kernel/debug/kdb/kdb_main.c | 31 +++ 22 files changed, 1054 insertions(+), 193 deletions(-)

12 years, 9 months

[PATCH] arm: add SDIV/UDIV emulation for ARMv7 processors

by Vladimir Murzin

The Virtualization Extensions introduce the requirement for an ARMv7-A implementation to include SDIV and UDIV. Any implementation of the Virtualization Extensions must include the SDIV and UDIV instructions in the Thumb and ARM instruction sets. In an ARMv7-A implementation that does not include the Virtualization Extensions, it is IMPLEMENTATION DEFINED whether: * SDIV and UDIV are not implemented * SDIV and UDIV are implemented only in the Thumb instruction set * SDIV and UDIV are implemented in the Thumb and ARM instruction sets. This patch adds a handler to trap and emulate unimplemented SDIV and UDIV instructions in ARM and Thumb modes. Also some basic statistic is exported via /proc/cpu/idiv_emulation Signed-off-by: Vladimir Murzin <murzin.v(a)gmail.com> --- arch/arm/kernel/Makefile | 1 + arch/arm/kernel/idiv_emulate.c | 194 ++++++++++++++++++++++++++++++++++++++++ arch/arm/mm/Kconfig | 26 ++++++ 3 files changed, 221 insertions(+), 0 deletions(-) create mode 100644 arch/arm/kernel/idiv_emulate.c diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 7ad2d5c..057a630 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -62,6 +62,7 @@ obj-$(CONFIG_OF) += devtree.o obj-$(CONFIG_CRASH_DUMP) += crash_dump.o obj-$(CONFIG_SWP_EMULATE) += swp_emulate.o CFLAGS_swp_emulate.o := -Wa,-march=armv7-a +obj-$(CONFIG_IDIV_EMULATE) += idiv_emulate.o obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o obj-$(CONFIG_CPU_XSCALE) += xscale-cp0.o diff --git a/arch/arm/kernel/idiv_emulate.c b/arch/arm/kernel/idiv_emulate.c new file mode 100644 index 0000000..f021d0e --- /dev/null +++ b/arch/arm/kernel/idiv_emulate.c @@ -0,0 +1,195 @@ +/* + * linux/arch/arm/kernel/idiv_emulate.c + * + * This code is based on swp_emulate.c + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * Implements emulation of the SDIV/UDIV instructions. They are defined for + * ARMv7-R and ARMv7-M profiles (in Thumb state only) and are UNDEFINED in the + * ARMv7-A profile. SDIV/UDIV are present by default on Cortex-A15. + * + * This emulation allow using integer divide instructions in case hardware is + * not presented + * + * Syntax of SDIV/UDIV instructions: SDIV/UDIV<c> <Rd>,<Rn>,<Rm> + * Where: Rd = the destination register. + * Rn = the register that contains the dividend. + * Rm = the register that contains the divisor. + */ + +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/proc_fs.h> +#include <linux/sched.h> +#include <linux/syscalls.h> +#include <linux/perf_event.h> + +#include <asm/opcodes.h> +#include <asm/traps.h> +#include <asm/uaccess.h> + +/* + * Macros/defines for extracting register numbers from instruction. + */ +#define EXTRACT_REG_NUM(instruction, offset) \ + (((instruction) & (0xf << (offset))) >> (offset)) + +/* + * Offsets for ARM mode + */ +#define RD_OFFSET 16 +#define RN_OFFSET 0 +#define RM_OFFSET 8 + +/* + * Offsets for Thumb mode + */ +#define RD_T_OFFSET 8 +#define RN_T_OFFSET 16 +#define RM_T_OFFSET 0 + +#define TYPE_OF_DIV (1 << 21) + +static unsigned long sdivcounter; +static unsigned long udivcounter; +static pid_t previous_pid; + +#ifdef CONFIG_PROC_FS +static int proc_read_status(char *page, char **start, off_t off, int count, + int *eof, void *data) +{ + char *p = page; + int len; + + p += sprintf(p, "Emulated UDIV:\t\t%lu\n", udivcounter); + p += sprintf(p, "Emulated SDIV:\t\t%lu\n", sdivcounter); + if (previous_pid != 0) + p += sprintf(p, "Last process:\t\t%d\n", previous_pid); + + len = (p - page) - off; + if (len < 0) + len = 0; + + *eof = (len <= count) ? 1 : 0; + *start = page + off; + + return len; +} +#endif + +static u32 emulate_udiv(u32 n, u32 base) +{ + udivcounter++; + + return n/base; +} + +static s32 emulate_sdiv(s32 n, s32 base) +{ + sdivcounter++; + + return n/base; +} + +static int idiv_handler(struct pt_regs *regs, unsigned int instr) +{ + long dividend, divisor, dest, res; + + perf_sw_event(PERF_COUNT_SW_EMULATION_FAULTS, 1, regs, regs->ARM_pc); + + res = arm_check_condition(instr, regs->ARM_cpsr); + + switch (res) { + case ARM_OPCODE_CONDTEST_PASS: + break; + case ARM_OPCODE_CONDTEST_FAIL: + /* Condition failed - return to next instruction */ + regs->ARM_pc += 4; + return 0; + case ARM_OPCODE_CONDTEST_UNCOND: + if (!thumb_mode(regs)) + return -EFAULT; + break; + default: + return -EINVAL; + } + + if (current->pid != previous_pid) { + pr_debug("\"%s\" (%ld) uses idiv instruction\n", + current->comm, (unsigned long)current->pid); + previous_pid = current->pid; + } + + if (!thumb_mode(regs)) { + dividend = regs->uregs[EXTRACT_REG_NUM(instr, RN_OFFSET)]; + divisor = regs->uregs[EXTRACT_REG_NUM(instr, RM_OFFSET)]; + dest = EXTRACT_REG_NUM(instr, RD_OFFSET); + } else { + dividend = regs->uregs[EXTRACT_REG_NUM(instr, RN_T_OFFSET)]; + divisor = regs->uregs[EXTRACT_REG_NUM(instr, RM_T_OFFSET)]; + dest = EXTRACT_REG_NUM(instr, RD_T_OFFSET); + } + +/* + * In an ARMv7-A profile implementation that supports the SDIV and UDIV + * instructions, divide-by-zero always returns a zero result. + * In fact, integer division emulation provided by gcc lib has already handle + * division by zero case sending the signal to the caused process. Emulate this + * behavior here as well. + */ + if (!divisor) { + siginfo_t info; + + info.si_code = FPE_INTDIV; + info.si_signo = SIGFPE; + info.si_errno = 0; + + arm_notify_die("Division by zero", regs, &info, 0, 0); + + goto out; + } + + if (instr & TYPE_OF_DIV) + res = emulate_udiv((u32)dividend, (u32)divisor); + else + res = emulate_sdiv((s32)dividend, (s32)divisor); + + regs->ARM_pc += 4; + regs->uregs[dest] = res; + +out: + return 0; +} + +static struct undef_hook idiv_hook = { + .instr_mask = 0x0310f010, + .instr_val = 0x0310f010, + .cpsr_mask = MODE_MASK, + .cpsr_val = USR_MODE, + .fn = idiv_handler +}; + +static int __init idiv_emulation_init(void) +{ +#ifdef CONFIG_PROC_FS + struct proc_dir_entry *res; + + res = create_proc_entry("cpu/idiv_emulation", S_IRUGO, NULL); + + if (!res) + return -ENOMEM; + + res->read_proc = proc_read_status; +#endif /* CONFIG_PROC_FS */ + + pr_notice("Registering SDIV/UDIV emulation handler\n"); + + register_undef_hook(&idiv_hook); + + return 0; +} + +late_initcall(idiv_emulation_init); diff --git a/arch/arm/mm/Kconfig b/arch/arm/mm/Kconfig index 101b968..8e2fa94 100644 --- a/arch/arm/mm/Kconfig +++ b/arch/arm/mm/Kconfig @@ -651,6 +651,32 @@ config SWP_EMULATE If unsure, say Y. +config IDIV_EMULATE + bool "Emulate SDIV/UDIV instructions" + depends on !CPU_USE_DOMAINS && CPU_V7 + select HAVE_PROC_CPU if PROC_FS + default y if SMP + help + + The Virtualization Extensions introduce the requirement for an + ARMv7-A implementation to include SDIV and UDIV. Any + implementation of the Virtualization Extensions must include + the SDIV and UDIV instructions in the Thumb and ARM + instruction sets. + + In an ARMv7-A implementation that does not include the + Virtualization Extensions, it is IMPLEMENTATION DEFINED whether: + * SDIV and UDIV are not implemented + * SDIV and UDIV are implemented only in the Thumb instruction set + * SDIV and UDIV are implemented in the Thumb and ARM + instruction sets. + + This option allows to handle exeptions due to unimplemented + SDIV and UDIV instructions in ARM and Thumb modes. + + If unsure, say Y. + + config CPU_BIG_ENDIAN bool "Build big-endian kernel" depends on ARCH_SUPPORTS_BIG_ENDIAN -- 1.7.8.6

12 years, 9 months

[PATCH v7 0/11] KGDB/KDB FIQ (NMI) debugger

by Anton Vorontsov

Hi all, Here comes the lucky v7: - Per Alan Cox's suggestion added hangup method and removed a small leftover; - Per Colin Cross' suggestion moved IRQ quiescing logic into poll_get_char routine. IIUC, Alan is less unhappy about it. As a result, clear_irq() callback dropped. These patches can be found in the following repo (based on tty-next): git://git.infradead.org/users/cbou/linux-nmi-kdb.git master Old changelogs and rationale for these patches can be found here: v1-v5, rationale: http://lkml.org/lkml/2012/9/10/2 v6: http://lkml.org/lkml/2012/9/10/2 Thanks, -- arch/arm/Kconfig | 19 ++ arch/arm/common/vic.c | 28 ++ arch/arm/include/asm/hardware/vic.h | 2 + arch/arm/include/asm/kgdb.h | 8 + arch/arm/kernel/Makefile | 1 + arch/arm/kernel/entry-armv.S | 167 +----------- arch/arm/kernel/entry-header.S | 170 +++++++++++++ arch/arm/kernel/kgdb_fiq.c | 99 ++++++++ arch/arm/kernel/kgdb_fiq_entry.S | 87 +++++++ arch/arm/mach-versatile/Makefile | 1 + arch/arm/mach-versatile/kgdb_fiq.c | 31 +++ drivers/tty/serial/Kconfig | 19 ++ drivers/tty/serial/Makefile | 1 + drivers/tty/serial/amba-pl011.c | 73 +++++- drivers/tty/serial/kgdb_nmi.c | 396 +++++++++++++++++++++++++++++ drivers/tty/serial/kgdboc.c | 6 + drivers/tty/serial/serial_core.c | 17 ++ include/linux/kdb.h | 29 ++- include/linux/kgdb.h | 33 +++ include/linux/serial_core.h | 1 + kernel/debug/debug_core.c | 36 ++- kernel/debug/kdb/kdb_main.c | 29 +++ 22 files changed, 1060 insertions(+), 193 deletions(-)

12 years, 9 months

[ACTIVITY] (John Stultz) Sept 10-14

by John Stultz

Whoops. Sorry this is late. === Highlights === * Attended a connect planning meeting * Sent out first pass of refinied jiffies patch (help kill CLOCK_TICK_RATE for unified-zImage) * Sent out half of the -stable backports * Debugged and fixed a 32bit time regression in 3.6-rc, got it merged in tip for upstream. * Arve pinged me on an issue they were seeing with the upstream alarmtimer code. Implemented a solution and will be sending it out for discussion shortly. * Discussed with Mel Gorman on his approach to low-memory notification * Emailed Colin Cross and AntonV to get a coffee meeting scheduled. === Plans === * Make first pass at sending SIGBUS on accessing purged volatile pages * Send out alarmtimer fix for discussion * Send out vsyscall update patches for discussion * Finish testing and sending -stable backports === Issues === * NA

12 years, 10 months

(no subject)

by Deepak Saxena

== Deepak Saxena <dsaxena> == === Highlights === * Got mostly caught up on all email, minus upstream mailing lists * Had initial discussions with Jakub on project management * OPSCOM roadmap card review === Plans === * Update roadmap cards as per OPSCOM review * Go through all old blueprints and clean them up * Create BPs for currently untracked work (single zImage, aarch64) * Catch up on Linux Plumber's Conf and Kernel Summit presentations * Write up blueprint process for project status tracking * Get caught up on linux-arm-kernel list === Issues === === Travel/Time Off === * Travelling to NYC for 1 week,Sept 22nd - 28th, will be working half time * Copenhagen Connect

12 years, 10 months

[Activity] (Omar Ramirez) Sep 10 - Sep 16 2012

by Omar Ramirez Luna

=== omarrmz === === Highlights === * Reworked and resubmitted iommu series: DONE. * Submitted mailbox DT series: DONE. * AARCH64: - Setup git.linaro.org credentials: DONE - Hosted a mirror branch of aarch64-linux with versatile code: DONE === Plans === * Track iommu and mailbox patches into upstream. * Submit bootctrl patch to tidspbridge. * Continue Aarch64 work. Regards, Omar

12 years, 10 months

[ACTIVITY] (Thomas Abraham) Sept-10

by Thomas Abraham

== Status == * Started working on common clock support for Exynos4 platforms. == Next Week == * Complete initial implementation of the common clock support for Exynos4 platforms. == Misc == * Was on leave from Sept-11 to Sept-14.

12 years, 10 months

[ACTIVITY] (Dong Aisheng) Sept-10-Sept-14

by Dong Aisheng

=== Highlights === * Setup kvm development environment. 1) build Cortex A15x1 fast model simulator 2) Successfully ran A15x1 simulator on ubuntu PC 3) Ran A15 kernel via qemu-system-arm within simulator environment * Research kvm subsystem and qemu (read doc and code) * Research big.LITTLE tech, read ARM doc on it and some online technical articles on switcher and bit.LITTLE MP scheduler, started to read ARM reference switcher code from: http://git.linaro.org/gitweb?p=arm/big.LITTLE/switcher.git;a=summary

12 years, 10 months

[ACTIVITY] (Anton Vorontsov) 2012-09-03 - 2012-09-14

by Anton Vorontsov

== Highlights == * Lots of work for KDB FIQ/NMI debugger, sent out v5, v6 and v7. Switched NMI console driver to tty_port infrastructure, discussed the ways to handle serial interrupts quiescing, made magic sequence configurable. TTY patches got Alan Cox's ack. * Looked into timer slack support for cgroups. While it's indeed somewhat close to deferrable timers, it's still not exactly what we need. Timer slack let us group wakeups, but there is still no way to tell that the timer/poll/select itself should not cause wakeups. As for deferrable timers, there are still no comments. * Looked into ideas on early OOM detection from the userland. There are a lot of inspirational thoughts on measuring memory stress levels, and I definitely need to perform some tests. I'll prepare a detailed answer to the ideas, but the most interesting part is that the ideas are based on vmstat monitoring, which is important: if we're going to use vmstat, we'll eventually get beaten by vmstat downsides: slow/expensive updates (so the latency if the pre-OOM detection would be equal to vmstat_update_time). And for Android low memory killer use case, pre-OOM condition is important, but not the main problem: the main "problem" is to monitor memory level when there is no stress at all (but deferrable timers would solve this). * Rebased and applied pstore/ftrace debugfs rework, this is now in linux-next. Also reviewed/fixed FDT support for pstore, by Bryan Freed @ Chromium.org.

12 years, 10 months

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