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([2a0b:e7c0:0:107::70f]) by smtp.gmail.com with ESMTPSA id d9sm755726edt.20.2020.08.12.04.45.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 12 Aug 2020 04:45:45 -0700 (PDT) Subject: Re: [PATCH 2/2] tty/sysrq: Add configurable handler to execute a compound action To: Andrzej Pietrasiewicz , linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , Dmitry Torokhov , linux-input@vger.kernel.org, kernel@collabora.com References: <20200804162402.2087-1-andrzej.p@collabora.com> <20200804162402.2087-3-andrzej.p@collabora.com> From: Jiri Slaby Message-ID: <0280e30a-2e70-7d21-68a9-5a2c22d7f316@kernel.org> Date: Wed, 12 Aug 2020 13:45:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200804162402.2087-3-andrzej.p@collabora.com> Content-Type: text/plain; charset=iso-8859-2 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-input-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-input@vger.kernel.org On 04. 08. 20, 18:24, Andrzej Pietrasiewicz wrote: > Userland might want to execute e.g. 'w' (show blocked tasks), followed > by 's' (sync), followed by 1000 ms delay and then followed by 'c' (crash) > upon a single magic SysRq. Or one might want to execute the famous "Raising > Elephants Is So Utterly Boring" action. This patch adds a configurable > handler, triggered with 'C', for this exact purpose. The user specifies the > composition of the compound action using syntax similar to getopt, where > each letter corresponds to an individual action and a colon followed by a > number corresponds to a delay of that many milliseconds, e.g.: > > ws:1000c > > or > > r:100eis:1000ub I think I miss what's that good for, given I can do it one-by-one without setting such strings anywhere (I usually want to do different things on different kinds of crashes)? > Signed-off-by: Andrzej Pietrasiewicz > --- > Documentation/admin-guide/sysrq.rst | 9 ++++ > drivers/tty/sysrq.c | 81 ++++++++++++++++++++++++++++- > include/linux/sysrq.h | 1 + > 3 files changed, 90 insertions(+), 1 deletion(-) > > diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst > index 67dfa4c29093..80bdd8bf9636 100644 > --- a/Documentation/admin-guide/sysrq.rst > +++ b/Documentation/admin-guide/sysrq.rst > @@ -32,6 +32,7 @@ to 1. Here is the list of possible values in /proc/sys/kernel/sysrq: > 64 = 0x40 - enable signalling of processes (term, kill, oom-kill) > 128 = 0x80 - allow reboot/poweroff > 256 = 0x100 - allow nicing of all RT tasks > + 512 = 0x200 - allow compound action > > You can set the value in the file by the following command:: > > @@ -148,6 +149,14 @@ Command Function > > ``z`` Dump the ftrace buffer > > +``C`` Execute a predefined, compound action. The action is defined with > + sysrq.sysrq_compound_action module parameter, whose value contains known > + command keys (except ``C`` to prevent recursion). The command keys can > + be optionally followed by a colon and a number of milliseconds to wait > + after executing the last action. For example: > + > + sysrq.sysrq_compound_action=r:100eis:1000ub > + > ``0``-``9`` Sets the console log level, controlling which kernel messages > will be printed to your console. (``0``, for example would make > it so that only emergency messages like PANICs or OOPSes would > diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c > index 52e344bfe8c0..ffcda1316675 100644 > --- a/drivers/tty/sysrq.c > +++ b/drivers/tty/sysrq.c > @@ -19,6 +19,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -439,6 +440,15 @@ static const struct sysrq_key_op sysrq_unrt_op = { > .enable_mask = SYSRQ_ENABLE_RTNICE, > }; > > +static void sysrq_action_compound(int key); > + > +static struct sysrq_key_op sysrq_action_compound_op = { > + .handler = sysrq_action_compound, > + .help_msg = "execute-compound-action(C)", > + .action_msg = "Execute compound action", > + .enable_mask = SYSRQ_ENABLE_COMPOUND, > +}; > + > /* Key Operations table and lock */ > static DEFINE_SPINLOCK(sysrq_key_table_lock); > > @@ -501,7 +511,7 @@ static const struct sysrq_key_op *sysrq_key_table[62] = { > &sysrq_ftrace_dump_op, /* z */ > NULL, /* A */ > NULL, /* B */ > - NULL, /* C */ > + &sysrq_action_compound_op, /* C */ > NULL, /* D */ > NULL, /* E */ > NULL, /* F */ > @@ -634,6 +644,7 @@ EXPORT_SYMBOL(handle_sysrq); > > #ifdef CONFIG_INPUT > static int sysrq_reset_downtime_ms; > +static char *sysrq_compound_action; > > /* Simple translation table for the SysRq keys */ > static const unsigned char sysrq_xlate[KEY_CNT] = > @@ -787,6 +798,61 @@ static void sysrq_of_get_keyreset_config(void) > { > } > #endif > +#define SYSRQ_COMPOUND_ACTION_VALIDATE 0 > +#define SYSRQ_COMPOUND_ACTION_RUN 1 > + > +static int sysrq_process_compound_action(int pass) > +{ > + const char *action = sysrq_compound_action; > + const struct sysrq_key_op *op_p; > + int ret, delay; > + > + while (*action) { > + op_p = __sysrq_get_key_op(*action); > + if (!op_p) > + return -EINVAL; > + > + /* Don't allow calling ourselves recursively */ > + if (op_p == &sysrq_action_compound_op) > + return -EINVAL; > + > + if (pass == SYSRQ_COMPOUND_ACTION_RUN) > + __handle_sysrq(*action, false); > + > + if (*++action == ':') { > + ret = sscanf(action++, ":%d", &delay); You likely want %u and unsigned int. No negative delays. > + if (ret < 1) /* we want at least ":[0-9]" => 1 item */ > + return -EINVAL; > + > + while (*action >= '0' && *action <= '9') > + ++action; > + if (pass == SYSRQ_COMPOUND_ACTION_RUN) > + mdelay(delay); > + } > + } > + > + return 0; > +} > + > +static void sysrq_action_compound(int key) > +{ > + if (!sysrq_compound_action) { > + pr_err("Unconfigured compound action for %s", > + sysrq_action_compound_op.help_msg); Missing \n. > + return; > + } > + > + if (sysrq_process_compound_action(SYSRQ_COMPOUND_ACTION_VALIDATE)) { > + pr_err("Incorrect compound action %s for %s", The same. > + sysrq_compound_action, > + sysrq_action_compound_op.help_msg); > + > + return; > + } > + > + sysrq_process_compound_action(SYSRQ_COMPOUND_ACTION_RUN); > +} > > static void sysrq_reinject_alt_sysrq(struct work_struct *work) > { > @@ -1079,8 +1145,21 @@ module_param_array_named(reset_seq, sysrq_reset_seq, sysrq_reset_seq, > > module_param_named(sysrq_downtime_ms, sysrq_reset_downtime_ms, int, 0644); > > +module_param(sysrq_compound_action, charp, 0644); > +MODULE_PARM_DESC(sysrq_compound_action, > + "Compound sysrq action to be executed on Alt-Shift-SysRq-C\n" > + "The compound action definition consists of known SysRq action letters except 'C',\n" > + "each letter can be optionally followed by a colon and a number of milliseconds to wait\n" > + "after executing the last action.\n" > + "Example:\n" > + "To unRaw, wait 100ms, tErminate, kIll, Sync, wait 1000ms, Unmount, Boot\n" > + "sysrq.sysrq_compound_action=r:100eis:1000ub"); This looks bad in the output, use at least one \t at the start of a new line inside the string. -- js suse labs