Hi, Vicentiu! Looks mostly ok. Does it mean, it will replace my changes in 10.0+ related to calculating the offset? struct link_map *lm = (struct link_map*) dlopen(0, RTLD_NOW); etc As far as LIBDL and dependencies are concerned... 1. Don't add LIBDL to the link list. The server has it and clients should not link with my_addr_resove (and it's good to get a linker error, if by some mistake they do) 2. Check for dladdr in configure.cmake: CHECK_FUNCTION_EXISTS (dladdr HAVE_DLADDR) 3. handle dladdr in my_global.h (search for dlopen or dlerror) But, I think, you won't need any ifdefs in my_addr_resolve.c, because my_global.h will take care of that. Ok to push after that, thanks! On Jan 16, vicentiu@mariadb.org wrote:

revision-id: 6ffd535e415028f414b9d1c9e9efbfb81bf25798 (mariadb-5.5.58-42-g6ffd535e415) parent(s): 6267be460ab5147e3bc0fffd03e690b3650f2fe2 author: Vicențiu Ciorbaru committer: Vicențiu Ciorbaru timestamp: 2018-01-16 22:57:52 +0200 message:

MDEV-14229: Stack trace is not resolved for shared objects

Resolving a stacktrace including functions in dynamic libraries requires us to look inside the libraries for the symbols. Addr2line needs to be started with the correct binary for each address on the stack. To do this, figure out which library it is using dladdr, then if the addr2line binary was started with a different binary, fork it again with the correct one.

We only have one addr2line process running at any point during the stacktrace resolving step. The maximum number of forks for addr2line should generally be around 6.

One for server stacktrace code, one for plugin code, one when going back into server code, one for pthread library, one for libc, one for the _start function in the server. More can come up if plugin calls server function which goes back to a plugin, etc.

--- mysys/CMakeLists.txt | 2 +- mysys/my_addr_resolve.c | 97 +++++++++++++++++++++++++++++++++---------------- 2 files changed, 67 insertions(+), 32 deletions(-)

diff --git a/mysys/CMakeLists.txt b/mysys/CMakeLists.txt index cb86850c2de..15f3fbad9bf 100644 --- a/mysys/CMakeLists.txt +++ b/mysys/CMakeLists.txt @@ -67,7 +67,7 @@ ENDIF()

ADD_CONVENIENCE_LIBRARY(mysys ${MYSYS_SOURCES}) TARGET_LINK_LIBRARIES(mysys dbug strings ${ZLIB_LIBRARY} - ${LIBNSL} ${LIBM} ${LIBRT} ${LIBSOCKET} ${LIBEXECINFO}) + ${LIBNSL} ${LIBM} ${LIBRT} ${LIBSOCKET} ${LIBEXECINFO} ${LIBDL}) DTRACE_INSTRUMENT(mysys)

IF(HAVE_BFD_H) diff --git a/mysys/my_addr_resolve.c b/mysys/my_addr_resolve.c index 90e6f43f390..f831ad5121f 100644 --- a/mysys/my_addr_resolve.c +++ b/mysys/my_addr_resolve.c @@ -132,15 +132,79 @@ const char *my_addr_resolve_init()

#include #include + +#include + static int in[2], out[2]; -static int initialized= 0; +static pid_t pid; +static char addr2line_binary[1024]; static char output[1024]; + +int start_addr2line_fork(const char *binary_path) +{ + + if (pid > 0) + { + /* Don't leak FDs */ + close(in[1]); + close(out[0]); + /* Don't create zombie processes. */ + waitpid(pid, NULL, 0); + } + + if (pipe(in) < 0) + return 1; + if (pipe(out) < 0) + return 1; + + pid = fork(); + if (pid == -1) + return 1; + + if (!pid) /* child */ + { + dup2(in[0], 0); + dup2(out[1], 1); + close(in[0]); + close(in[1]); + close(out[0]); + close(out[1]); + execlp("addr2line", "addr2line", "-C", "-f", "-e", binary_path, NULL); + exit(1); + } + + close(in[0]); + close(out[1]); + + return 0; +} + int my_addr_resolve(void *ptr, my_addr_loc *loc) { char input[32], *s; size_t len;

- len= my_snprintf(input, sizeof(input), "%p\n", ptr); + Dl_info info; + void *offset; + + if (!dladdr(ptr, &info)) + return 1; + + if (strcmp(addr2line_binary, info.dli_fname)) + { + /* We use dli_fname in case the path is longer than the length of our static + string. We don't want to allocate anything dynamicaly here as we are in + a "crashed" state. */ + if (start_addr2line_fork(info.dli_fname)) + { + addr2line_binary[0] = '\0'; + return 1; + } + /* Save result for future comparisons. */ + strnmov(addr2line_binary, info.dli_fname, sizeof(addr2line_binary)); + } + offset = info.dli_fbase; + len= my_snprintf(input, sizeof(input), "%p\n", ptr - offset); if (write(in[1], input, len) <= 0) return 1; if (read(out[0], output, sizeof(output)) <= 0) @@ -168,35 +232,6 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)

const char *my_addr_resolve_init() { - if (!initialized) - { - pid_t pid; - - if (pipe(in) < 0) - return "pipe(in)"; - if (pipe(out) < 0) - return "pipe(out)"; - - pid = fork(); - if (pid == -1) - return "fork"; - - if (!pid) /* child */ - { - dup2(in[0], 0); - dup2(out[1], 1); - close(in[0]); - close(in[1]); - close(out[0]); - close(out[1]); - execlp("addr2line", "addr2line", "-C", "-f", "-e", my_progname, NULL); - exit(1); - } - - close(in[0]); - close(out[1]); - initialized= 1; - } return 0; } #endif

Regards, Sergei Chief Architect MariaDB and security@mariadb.org