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command -x: tweak args list size detection (re: 9ddb45b1)

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src/cmd/ksh93/features/externs: ARG_EXTRA_BYTES detection:
- Improve detection of extra bytes per argument: on every loop
  iteration, recalculate the size of the environment while taking
  the amount extra bytes we're currently trying into account. Also
  count arguments (argv[]) as they are stored in the same buffer.
  On 64-bit Linux with glibc, this now detects 9 extra bytes per
  argument instead of 8. An odd number (literally and figuratively)
  but apparently it needs it; I do think my method is correct now.
  On 64-bit Solaris and macOS, this still detects 8 extra bytes.
  (On 64-bit Linux with musl C library, it detects 0 bytes. Nice.)

src/cmd/ksh93/sh/path.c: path_xargs():
- Remove the kludge subtracting twice the size of the environment.
  With the feature test fixed, this should no longer fail on Linux.
- Take into account the size of the final null element in the
  argument and environment lists.

src/cmd/ksh93/tests/path.sh:
- Do not use awk for the test due to breakage in the system awks
  on Solaris/Illumos (hangs) and AIX & UnixWare (drops arguments).
  Instead, use (wait for it...) ksh. It's a bit slower, but works.
This commit is contained in:
Martijn Dekker 2021-02-12 23:59:57 +00:00
parent 8c1e9971a7
commit 6f6b22016a
3 changed files with 31 additions and 22 deletions
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29
src/cmd/ksh93/features/externs
View file

@ -17,8 +17,8 @@ tst note{ determining extra bytes per argument for arguments list }end output{
* Figure out if this OS requires extra bytes per argument
* in the arguments list of a process.
* Outputs an appropriate #define ARG_EXTRA_BYTES.
* Without this, 'command -x' failed with E2BIG on macOS and Linux even
* if all the arguments should fit in ARG_MAX based on their length.
* Without this, 'command -x' failed with E2BIG on macOS, Linux and Solaris
* even if all the arguments should fit in ARG_MAX based on their length.
*/
/* AST includes */
@ -43,20 +43,25 @@ tst note{ determining extra bytes per argument for arguments list }end output{
int main(int argc,char *argv[])
{
int extra_bytes = 0, envlen = 0, argmax, i;
int extra_bytes = 0, envlen, argmax, i;
pid_t childpid;
error_info.id="ARG_EXTRA_BYTES test (parent)";
for(i=0; environ[i]; i++)
envlen += strlen(environ[i]) + 1;
argmax = strtoimax(astconf("ARG_MAX",NiL,NiL),NiL,0) - 2 * envlen;
if (argmax < 2048)
{
error(ERROR_ERROR|2, "argmax too small");
return 1;
}
while(1)
{
envlen = 0;
for(i=0; argv[i]; i++)
envlen += strlen(argv[i]) + 1 + extra_bytes;
envlen += 1 + extra_bytes; /* final null element */
for(i=0; environ[i]; i++)
envlen += strlen(environ[i]) + 1 + extra_bytes;
envlen += 1 + extra_bytes; /* final null element */
argmax = strtoimax(astconf("ARG_MAX",NiL,NiL),NiL,0) - envlen;
if (argmax < 2048)
{
error(ERROR_ERROR|2, "argmax too small");
return 1;
}
if(!(childpid = fork()))
{
/* child */
@ -122,5 +127,5 @@ tst note{ determining extra bytes per argument for arguments list }end output{
return 0;
}
}end fail{
echo "#define ARG_EXTRA_BYTES 8 /* BUG: test failed; assuming 8 */"
echo "#define ARG_EXTRA_BYTES 16 /* BUG: test failed; assuming 16 */"
}end

3
src/cmd/ksh93/sh/path.c
View file

@ -164,11 +164,12 @@ static pid_t path_xargs(Shell_t *shp,const char *path, char *argv[],char *const
return((pid_t)-1);
size = shp->gd->lim.arg_max - (ARG_EXTRA_BYTES > 2 ? 1024*ARG_EXTRA_BYTES : 2048);
for(ev=envp; cp= *ev; ev++)
size -= 2 * (strlen(cp) + 1 + ARG_EXTRA_BYTES);
size -= strlen(cp) + 1 + ARG_EXTRA_BYTES;
for(av=argv; (cp= *av) && av< &argv[shp->xargmin]; av++)
size -= strlen(cp) + 1 + ARG_EXTRA_BYTES;
for(av=avlast; cp= *av; av++,nlast++)
size -= strlen(cp) + 1 + ARG_EXTRA_BYTES;
size -= 2 + 2 * ARG_EXTRA_BYTES; /* final null env and arg elements */
av = &argv[shp->xargmin];
if(!spawn)
job_clear();

21
src/cmd/ksh93/tests/path.sh
View file

@ -542,7 +542,7 @@ fi
ofile=$tmp/command_x_chunks.sh
trap 'sleep_pid=; while kill -9 $pid; do :; done 2>/dev/null; err_exit "'\''command -x'\'' hung"' TERM
trap 'kill $sleep_pid; while kill -9 $pid; do :; done 2>/dev/null; trap - INT; kill -s INT $$"' INT
{ sleep 15; kill $$; } &
{ sleep 60; kill $$; } &
sleep_pid=$!
(
export LC_ALL=C
@ -558,14 +558,17 @@ sleep_pid=$!
done
print "chunks=0 expargs=$# args=0 expsize=$((${#args}+1)) size=0"
unset args
command -px awk 'BEGIN {
ARGC -= 2; # final static args
for (i=1; i<ARGC; i++)
size += length(ARGV[i]) + 1;
print ("let chunks++ args+=")(ARGC - 1)(" size+=")(size);
if(ARGV[ARGC] != "static_arg_1" || ARGV[ARGC+1] != "final_static_arg_2")
print "err_exit \"'\''command -x'\'': static final arguments for chunk $chunks incorrect\"";
}' "$@" static_arg_1 final_static_arg_2
command -x "$SHELL" -c '
integer i size=0 numargs=${#}-2
for ((i=numargs; i; i--))
do let "size += ${#1} + 1"
shift
done
print "let chunks++ args+=$numargs size+=$size"
if [[ $0 != static_argzero || $1 != final_static_arg_1 || $2 != final_static_arg_2 ]]
then print "err_exit \"'\''command -x'\'': static arguments for chunk \$chunks incorrect\""
fi
' static_argzero "$@" final_static_arg_1 final_static_arg_2
) >$ofile &
pid=$!
wait $pid