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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id a11sm1586602wmh.40.2019.10.25.00.33.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Oct 2019 00:33:42 -0700 (PDT) From: Daniel Thompson To: Douglas Anderson , Jason Wessel Cc: Daniel Thompson , kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org, patches@linaro.org Subject: [PATCH v4 1/5] kdb: Tidy up code to handle escape sequences Date: Fri, 25 Oct 2019 08:33:24 +0100 Message-Id: <20191025073328.643-2-daniel.thompson@linaro.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20191025073328.643-1-daniel.thompson@linaro.org> References: <20191025073328.643-1-daniel.thompson@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org kdb_read_get_key() has extremely complex break/continue control flow managed by state variables and is very hard to review or modify. In particular the way the escape sequence handling interacts with the general control flow is hard to follow. Separate out the escape key handling, without changing the control flow. This makes the main body of the code easier to review. Signed-off-by: Daniel Thompson Reviewed-by: Douglas Anderson --- kernel/debug/kdb/kdb_io.c | 128 ++++++++++++++++++++------------------ 1 file changed, 67 insertions(+), 61 deletions(-) diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 3a5184eb6977..cfc054fd8097 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -49,6 +49,65 @@ static int kgdb_transition_check(char *buffer) return 0; } +/** + * kdb_handle_escape() - validity check on an accumulated escape sequence. + * @buf: Accumulated escape characters to be examined. Note that buf + * is not a string, it is an array of characters and need not be + * nil terminated. + * @sz: Number of accumulated escape characters. + * + * Return: -1 if the escape sequence is unwanted, 0 if it is incomplete, + * otherwise it returns a mapped key value to pass to the upper layers. + */ +static int kdb_handle_escape(char *buf, size_t sz) +{ + char *lastkey = buf + sz - 1; + + switch (sz) { + case 1: + if (*lastkey == '\e') + return 0; + break; + + case 2: /* \e */ + if (*lastkey == '[') + return 0; + break; + + case 3: + switch (*lastkey) { + case 'A': /* \e[A, up arrow */ + return 16; + case 'B': /* \e[B, down arrow */ + return 14; + case 'C': /* \e[C, right arrow */ + return 6; + case 'D': /* \e[D, left arrow */ + return 2; + case '1': /* \e[<1,3,4>], may be home, del, end */ + case '3': + case '4': + return 0; + } + break; + + case 4: + if (*lastkey == '~') { + switch (buf[2]) { + case '1': /* \e[1~, home */ + return 1; + case '3': /* \e[3~, del */ + return 4; + case '4': /* \e[4~, end */ + return 5; + } + } + break; + } + + return -1; +} + static int kdb_read_get_key(char *buffer, size_t bufsize) { #define ESCAPE_UDELAY 1000 @@ -102,68 +161,15 @@ static int kdb_read_get_key(char *buffer, size_t bufsize) escape_delay = 2; continue; } - if (ped - escape_data == 1) { - /* \e */ - continue; - } else if (ped - escape_data == 2) { - /* \e */ - if (key != '[') - escape_delay = 2; - continue; - } else if (ped - escape_data == 3) { - /* \e[ */ - int mapkey = 0; - switch (key) { - case 'A': /* \e[A, up arrow */ - mapkey = 16; - break; - case 'B': /* \e[B, down arrow */ - mapkey = 14; - break; - case 'C': /* \e[C, right arrow */ - mapkey = 6; - break; - case 'D': /* \e[D, left arrow */ - mapkey = 2; - break; - case '1': /* dropthrough */ - case '3': /* dropthrough */ - /* \e[<1,3,4>], may be home, del, end */ - case '4': - mapkey = -1; - break; - } - if (mapkey != -1) { - if (mapkey > 0) { - escape_data[0] = mapkey; - escape_data[1] = '\0'; - } - escape_delay = 2; - } - continue; - } else if (ped - escape_data == 4) { - /* \e[<1,3,4> */ - int mapkey = 0; - if (key == '~') { - switch (escape_data[2]) { - case '1': /* \e[1~, home */ - mapkey = 1; - break; - case '3': /* \e[3~, del */ - mapkey = 4; - break; - case '4': /* \e[4~, end */ - mapkey = 5; - break; - } - } - if (mapkey > 0) { - escape_data[0] = mapkey; - escape_data[1] = '\0'; - } - escape_delay = 2; - continue; + + key = kdb_handle_escape(escape_data, ped - escape_data); + if (key > 0) { + escape_data[0] = key; + escape_data[1] = '\0'; } + if (key) + escape_delay = 2; + continue; } break; /* A key to process */ } -- 2.21.0