linux /proc/<pid>/exe & valgrind - linux

Question

As per the man page /proc/pid/exe is a symlink containing the actual path of the executed command..
when I run valgrind on my program, I see that /proc/pid/exe points to /usr/lib64/valgrind/amd64-linux/memcheck
lnx-host> which valgrind
/usr/bin/valgrind
Any idea why /proc/pid/exe points to usr/lib64/valgrind/amd64-linux/memcheck when I am invoking it as valgrind ?
In my code I am trying to get the executable name from the pid, and in this case expecting to see valgrind.

Answer 1

memcheck is the default tool used by Valgrind, unless you tell it to use another of the tools, such as callgrind.
Use --tool=<name> to specify the tool you want to invoke.
Side-note: is your /usr/bin/valgrind also a script just like it is by default? Why not play with that to do what you want to achieve? On my system that invokes first of all /usr/bin/valgrind.bin and then the respective (backend) tool (/usr/lib/valgrind/memcheck-amd64-linux).
Relevant output from strace:
execve("/usr/bin/valgrind", ["valgrind", "./myprog"], [/* 35 vars */]) = 0
stat("/home/user/HEAD/myprog", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
execve("/usr/bin/valgrind.bin", ["/usr/bin/valgrind.bin", "./myprog"], [/* 39 vars */]) = 0
open("./myprog", O_RDONLY) = 3
execve("/usr/lib/valgrind/memcheck-amd64-linux", ["/usr/bin/valgrind.bin", "./myprog"], [/* 40 vars */]) = 0
getcwd("/home/user/HEAD/myprog", 4095) = 25
open("./myprog", O_RDONLY) = 3
stat("./myprog", {st_mode=S_IFREG|0755, st_size=1886240, ...}) = 0
readlink("/proc/self/fd/3", "/home/user/HEAD/myprog/myprog", 4096) = 31
readlink("/proc/self/fd/3", "/home/user/HEAD/myprog/myprog", 4096) = 31
open("./myprog", O_RDONLY) = 3
write(1015, "./myprog", 8) = 8
write(1016, "==23547== Command: ./myprog\n", 28==23547== Command: ./myprog
stat("/home/user/HEAD/myprog/myprog", {st_mode=S_IFREG|0755, st_size=1886240, ...}) = 0
open("/home/user/HEAD/myprog/myprog", O_RDONLY) = 3
stat("/home/user/HEAD/myprog/myprog", {st_mode=S_IFREG|0755, st_size=1886240, ...}) = 0
open("/home/user/HEAD/myprog/myprog", O_RDONLY) = 3
open("/home/user/HEAD/myprog/myprog", O_RDONLY) = 3
readlink("/proc/self/fd/3", "/home/user/HEAD/myprog/myprog", 4096) = 31
getcwd("/home/user/HEAD/myprog", 4096) = 25
lstat("/home/user/HEAD/myprog/myprog", {st_mode=S_IFREG|0755, st_size=1886240, ...}) = 0
open("/home/user/HEAD/myprog/datafile", O_RDONLY) = 3
access("/home/user/HEAD/myprog/datafile", F_OK) = 0
open("/home/user/HEAD/myprog/datafile", O_RDONLY) = 3
open("/home/user/HEAD/myprog/datafile", O_RDONLY) = 4
You'll notice that all execve calls are not referring to ./myprog but instead to the Valgrind wrapper script, the binary and then the backend tool:
execve("/usr/bin/valgrind", ["valgrind", "./myprog"], [/* 35 vars */]) = 0
execve("/usr/bin/valgrind.bin", ["/usr/bin/valgrind.bin", "./myprog"], [/* 39 vars */]) = 0
execve("/usr/lib/valgrind/memcheck-amd64-linux", ["/usr/bin/valgrind.bin", "./myprog"], [/* 40 vars */]) = 0