eal/unix: make stack dump signal safe

rte_dump_stack() needs to be usable in situations when a bug is
encountered and from signal handlers (such as SEGV).

Glibc backtrace_symbols() calls malloc which makes it
dangerous in a signal handler that is handling errors that maybe
due to memory corruption. Additionally, rte_log() is unsafe because
syslog() is not signal safe; printf() is also documented as
not being safe.

This version formats message and uses writev for each line in a manner
similar to what glibc version of backtrace_symbols_fd() does. The
FreeBSD version of backtrace_symbols_fd() is not signal safe.

Sample output:

0: ./build/app/dpdk-testpmd (rte_dump_stack+0x2b) [560a6e9c002b]
1: ./build/app/dpdk-testpmd (main+0xad) [560a6decd5ad]
2: /lib/x86_64-linux-gnu/libc.so.6 (__libc_start_main+0xcd) [7fd43d3e27fd]
3: ./build/app/dpdk-testpmd (_start+0x2a) [560a6e83628a]

Bugzilla ID: 929

Acked-by: Morten Brørup <mb@smartsharesystems.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Reviewed-by: David Marchand <david.marchand@redhat.com>

diff --git a/lib/eal/freebsd/eal_debug.c b/lib/eal/freebsd/eal_debug.c
deleted file mode 100644 (file)
index 64dab4e..0000000
--- a/lib/eal/freebsd/eal_debug.c
+++ /dev/null
@@ -1,43 +0,0 @@
-/* SPDX-License-Identifier: BSD-3-Clause
- * Copyright(c) 2010-2014 Intel Corporation
- */
-
-#ifdef RTE_BACKTRACE
-#include <execinfo.h>
-#endif
-#include <stdarg.h>
-#include <signal.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <stdint.h>
-
-#include <rte_log.h>
-#include <rte_debug.h>
-#include <rte_common.h>
-#include <rte_eal.h>
-
-#define BACKTRACE_SIZE 256
-
-/* dump the stack of the calling core */
-void rte_dump_stack(void)
-{
-#ifdef RTE_BACKTRACE
-       void *func[BACKTRACE_SIZE];
-       char **symb = NULL;
-       int size;
-
-       size = backtrace(func, BACKTRACE_SIZE);
-       symb = backtrace_symbols(func, size);
-
-       if (symb == NULL)
-               return;
-
-       while (size > 0) {
-               rte_log(RTE_LOG_ERR, RTE_LOGTYPE_EAL,
-                       "%d: [%s]\n", size, symb[size - 1]);
-               size --;
-       }
-
-       free(symb);
-#endif /* RTE_BACKTRACE */
-}

diff --git a/lib/eal/freebsd/meson.build b/lib/eal/freebsd/meson.build
index fe9097303ac5888eb61c3cdba4504819363efe0a..a9588be70f584928ca481e821dab5ff8a0b76c6b 100644 (file)
--- a/lib/eal/freebsd/meson.build
+++ b/lib/eal/freebsd/meson.build
@@ -7,7 +7,6 @@ sources += files(
         'eal.c',
         'eal_alarm.c',
         'eal_cpuflags.c',
-        'eal_debug.c',
         'eal_dev.c',
         'eal_hugepage_info.c',
         'eal_interrupts.c',

diff --git a/lib/eal/include/rte_debug.h b/lib/eal/include/rte_debug.h
index c4bc71ce28f52518f9b92b34f463df8d087f439e..2c4b94a7c9bfeedf46dbf984d65cacc2da2a4fa5 100644 (file)
--- a/lib/eal/include/rte_debug.h
+++ b/lib/eal/include/rte_debug.h
@@ -22,7 +22,7 @@ extern "C" {
 #endif
 
 /**
- * Dump the stack of the calling core to the console.
+ * Dump the stack of the calling core to the standard error.
  */
 void rte_dump_stack(void);
 

diff --git a/lib/eal/linux/eal_debug.c b/lib/eal/linux/eal_debug.c
deleted file mode 100644 (file)
index b0ecf5a..0000000
--- a/lib/eal/linux/eal_debug.c
+++ /dev/null
@@ -1,38 +0,0 @@
-/* SPDX-License-Identifier: BSD-3-Clause
- * Copyright(c) 2010-2014 Intel Corporation
- */
-
-#ifdef RTE_BACKTRACE
-#include <execinfo.h>
-#endif
-#include <stdlib.h>
-#include <stdio.h>
-
-#include <rte_log.h>
-#include <rte_debug.h>
-
-#define BACKTRACE_SIZE 256
-
-/* dump the stack of the calling core */
-void rte_dump_stack(void)
-{
-#ifdef RTE_BACKTRACE
-       void *func[BACKTRACE_SIZE];
-       char **symb = NULL;
-       int size;
-
-       size = backtrace(func, BACKTRACE_SIZE);
-       symb = backtrace_symbols(func, size);
-
-       if (symb == NULL)
-               return;
-
-       while (size > 0) {
-               rte_log(RTE_LOG_ERR, RTE_LOGTYPE_EAL,
-                       "%d: [%s]\n", size, symb[size - 1]);
-               size --;
-       }
-
-       free(symb);
-#endif /* RTE_BACKTRACE */
-}

diff --git a/lib/eal/linux/meson.build b/lib/eal/linux/meson.build
index 65f2ac6b4798a399aac7436a72080f9f53788329..3cccfa36c0a491ba54f6a890d12af38ce7acb315 100644 (file)
--- a/lib/eal/linux/meson.build
+++ b/lib/eal/linux/meson.build
@@ -7,7 +7,6 @@ sources += files(
         'eal.c',
         'eal_alarm.c',
         'eal_cpuflags.c',
-        'eal_debug.c',
         'eal_dev.c',
         'eal_hugepage_info.c',
         'eal_interrupts.c',

diff --git a/lib/eal/unix/eal_debug.c b/lib/eal/unix/eal_debug.c
new file mode 100644 (file)
index 0000000..69ba375
--- /dev/null
+++ b/lib/eal/unix/eal_debug.c
@@ -0,0 +1,127 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright(c) 2010-2014 Intel Corporation
+ */
+
+#include <rte_debug.h>
+
+#ifdef RTE_BACKTRACE
+
+#include <dlfcn.h>
+#include <execinfo.h>
+#include <string.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+#define BACKTRACE_SIZE 256
+
+/*
+ * Convert number to string and return start of string.
+ * Note: string does not start at beginning of buffer.
+ */
+static char *safe_itoa(long val, char *buf, size_t len, unsigned int radix)
+{
+       char *bp = buf + len;
+       static const char hexdigit[] = "0123456789abcdef";
+
+       *--bp = '\0'; /* Null terminate the string */
+       do {
+               /* if buffer is not big enough, then truncate */
+               if (bp == buf)
+                       return bp;
+
+               *--bp = hexdigit[val % radix];
+               val /= radix;
+       } while (val != 0);
+
+       return bp;
+}
+
+/*
+ * Dump the stack of the calling core
+ *
+ * To be safe in signal handler requires limiting what functions are
+ * used in this code since may be called from inside libc or
+ * when malloc poll is corrupt.
+ *
+ * Most of libc is therefore not safe, include RTE_LOG (calls syslog);
+ * backtrace_symbols (calls malloc), etc.
+ */
+void rte_dump_stack(void)
+{
+       void *func[BACKTRACE_SIZE];
+       Dl_info info;
+       char buf1[8], buf2[32], buf3[32], buf4[32];
+       struct iovec iov[10];
+       int i, size;
+
+       size = backtrace(func, BACKTRACE_SIZE);
+
+       for (i = 0; i < size; i++) {
+               struct iovec *io = iov;
+               char *str;
+               uintptr_t base;
+               long offset;
+               void *pc = func[i];
+
+/*
+ * Macro to put string onto set of iovecs.
+ * cast is to suppress warnings about lose of const qualifier.
+ */
+#define PUSH_IOV(io, str) {                                    \
+               (io)->iov_base = (char *)(uintptr_t)str;        \
+               (io)->iov_len = strlen(str);                    \
+               ++io; }
+
+               /* output stack frame number */
+               str = safe_itoa(i, buf1, sizeof(buf1), 10);
+               PUSH_IOV(io, str);      /* iov[0] */
+               PUSH_IOV(io, ": ");     /* iov[1] */
+
+               /* Lookup the symbol information */
+               if (dladdr(pc, &info) == 0) {
+                       PUSH_IOV(io, "?? [");
+               } else {
+                       const char *fname;
+
+                       if (info.dli_fname && *info.dli_fname)
+                               fname = info.dli_fname;
+                       else
+                               fname = "(vdso)";
+                       PUSH_IOV(io, fname);    /* iov[2] */
+                       PUSH_IOV(io, " (");     /* iov[3] */
+
+                       if (info.dli_saddr != NULL) {
+                               PUSH_IOV(io, info.dli_sname);   /* iov[4] */
+                               base = (uintptr_t)info.dli_saddr;
+                       } else {
+                               str = safe_itoa((unsigned long)info.dli_fbase,
+                                       buf3, sizeof(buf3), 16);
+                               PUSH_IOV(io, str);
+                               base = (uintptr_t)info.dli_fbase;
+                       }
+
+                       PUSH_IOV(io, "+0x");    /* iov[5] */
+
+                       offset = (uintptr_t)pc - base;
+                       str = safe_itoa(offset, buf4, sizeof(buf4), 16);
+                       PUSH_IOV(io, str);      /* iov[6] */
+
+                       PUSH_IOV(io, ") [");    /* iov[7] */
+               }
+
+               str = safe_itoa((unsigned long)pc, buf2, sizeof(buf2), 16);
+               PUSH_IOV(io, str);      /* iov[8] */
+               PUSH_IOV(io, "]\n");    /* iov[9] */
+
+               if (writev(STDERR_FILENO, iov, io - iov) < 0)
+                       break;
+#undef PUSH_IOV
+       }
+}
+
+#else /* !RTE_BACKTRACE */
+
+/* stub if not enabled */
+void rte_dump_stack(void) { }
+
+#endif /* RTE_BACKTRACE */

diff --git a/lib/eal/unix/meson.build b/lib/eal/unix/meson.build
index 781505ca90612093383a83ebadf6ffb1e9beb85c..cc7d67dd321d806192051fa47c9ea505fd7227fa 100644 (file)
--- a/lib/eal/unix/meson.build
+++ b/lib/eal/unix/meson.build
@@ -2,6 +2,7 @@
 # Copyright(c) 2020 Dmitry Kozlyuk
 
 sources += files(
+        'eal_debug.c',
         'eal_file.c',
         'eal_filesystem.c',
         'eal_firmware.c',