Add scat program to cat logs on obmc

devnotes/scat/Makefile

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+export PATH := $(PWD)/.build/armv6-obmc-linux-gnueabi/buildtools/bin/:$(PATH)
+CROSS := armv6-obmc-linux-gnueabi-
+
+CC := $(CROSS)gcc
+STRIP := $(CROSS)strip
+CFLAGS := -march=armv6zk -mcpu=arm1176jz-s
+
+scat: scat.c
+ $(CC) -o $@ $^ $(CFLAGS)
+ $(STRIP) -S $@
+
+clean:
+ $(RM) scat

devnotes/scat/README.md

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+## cat for obmc-console
+
+Server of [obmc-console] used by Talos 2 communicates with its client using
+Unix socket with abstract address (see `man 7 unix`). BMC doesn't have much
+tools installed and it's not clear if there are any for sockets with abstract
+addresses, so here's a tiny C program to get the output (socket name is
+hard-coded at the moment).
+
+It's purpose is to collect logs without a tty, so that termination of ssh
+connection wouldn't interrupt anything.
+
+### Prebuilt binary
+
+For convenience, binary is provided right here to avoid building toolchain.
+
+### Building from sources
+
+Target system uses armv6 which is not supported by popular prebuilt toolchains
+for years, so `crosstool-ng` configuration for building required toolchain is
+provided, skip below if you have a suitable one already.
+
+Prerequisites:
+ * [crosstool-ng]
+ * regular build environment with GCC, GNU make and binutils
+
+Preparation:
+```bash
+# build toolchain for armv6
+ct-ng armv6-obmc-linux-gnueabi
+ct-ng build
+```
+
+Build `scat` binary:
+```bash
+make
+```
+
+With your own toolchain, proceed as usual:
+```bash
+CROSS=armv6-linux-gnueabi- make
+```
+
+### Usage
+
+```
+$ scp scat root@talos:/tmp
+$ ssh root@talos
+# /tmp/scat | gzip > /tmp/boot-log &
+```
+
+[crosstool-ng]: https://crosstool-ng.github.io/
+[obmc-console]: https://github.com/openbmc/obmc-console

devnotes/scat/samples/armv6-obmc-linux-gnueabi/crosstool.config

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+CT_CONFIG_VERSION="3"
+# CT_REMOVE_DOCS is not set
+CT_ARCH_ARM=y
+CT_ARCH_ARCH="armv6"
+CT_ARCH_FLOAT_SW=y
+CT_KERNEL_LINUX=y
+CT_LINUX_V_4_18=y
+# CT_CC_GCC_USE_GRAPHITE is not set
+# CT_CC_GCC_USE_LTO is not set
+# CT_CC_GCC_SJLJ_EXCEPTIONS is not set

devnotes/scat/samples/armv6-obmc-linux-gnueabi/reported.by

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+reporter_name=""
+reporter_url=""
+reporter_comment=""

devnotes/scat/scat.c

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+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+#include <signal.h>
+
+#define BUFFER_SIZE 128
+
+#define SOCKET_NAME "\0obmc-console"
+#define SOCKET_NAME_LEN (sizeof(SOCKET_NAME) - 1)
+
+void signal_noop(int s)
+{
+}
+
+int main(int argc, char *argv[])
+{
+ struct sockaddr_un addr;
+ int ret;
+ int sock;
+ char buffer[BUFFER_SIZE];
+ struct sigaction action;
+
+ // Make Ctrl+C cause read() to return EINTR
+ action.sa_handler = &signal_noop;
+ sigemptyset(&action.sa_mask);
+ action.sa_flags = 0;
+ sigaction(SIGINT, &action, NULL);
+
+ sock = socket(AF_UNIX, SOCK_STREAM, 0);
+ if (sock == -1) {
+ perror("socket");
+ exit(EXIT_FAILURE);
+ }
+
+ memset(&addr, 0, sizeof(addr));
+ addr.sun_family = AF_UNIX;
+ memcpy(addr.sun_path, SOCKET_NAME, SOCKET_NAME_LEN);
+
+ ret = connect(sock,
+ (const struct sockaddr *)&addr,
+ sizeof(addr) - sizeof(addr.sun_path) + SOCKET_NAME_LEN);
+ if (ret == -1) {
+ fprintf(stderr, "Can't connect: %s\n", strerror(errno));
+ exit(EXIT_FAILURE);
+ }
+
+ while (1) {
+ ret = read(sock, buffer, sizeof(buffer) - 1);
+ if (ret == 0)
+ break;
+ if (ret == -1) {
+ if (errno == EINTR) {
+ // Do an async read() to get last portion of data or we won't
+ // miss anything anyway?
+ break;
+ }
+
+ perror("read");
+ exit(EXIT_FAILURE);
+ }
+
+ buffer[ret - 1] = '\0';
+ fputs(buffer, stdout);
+ }
+
+ close(sock);
+ return EXIT_SUCCESS;
+}