On Mon, 28 Aug 2023 21:09:53 +0900 Takashi Yano wrote: > On Mon, 28 Aug 2023 12:57:19 +0200 > Corinna Vinschen wrote: > > On Aug 28 18:46, Takashi Yano wrote: > > > Previously, the number of command line args was not checked for > > > cygwin process. Due to this, segmentation fault was caused if too > > > many command line args are specified. > > > https://cygwin.com/pipermail/cygwin/2023-August/254333.html > > > > > > Since char *argv[argc + 1] is placed on the stack in dll_crt0_1(), > > > STATUS_STACK_OVERFLOW occurs if the stack does not have enough > > > space. > > > > > > With this patch, the total length of the arguments and the size of > > > argv[] is restricted to 1/4 of total stack size for the process, and > > > spawnve() returns E2BIG if the size exceeds the limit. > > > [...] > > > +static size_t > > > +get_stack_size (const WCHAR *filename) > > > +{ > > > + HANDLE h; > > > + h = CreateFileW (filename, GENERIC_READ, FILE_SHARE_READ, > > > + NULL, OPEN_EXISTING, 0, NULL); > > > + char buf[1024]; > > > + DWORD n; > > > + ReadFile (h, buf, sizeof (buf), &n, 0); > > > + CloseHandle (h); > > > + IMAGE_NT_HEADERS32 *p = (IMAGE_NT_HEADERS32 *) memmem (buf, n, > > > "PE\0\0", 4); > > > + if (!p) > > > + return 0; > > > + if ((char *) &p->OptionalHeader.SizeOfStackCommit > buf + n) > > > + return 0; /* buf[] is not enough */ > > > + if (p->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR32_MAGIC) > > > + return p->OptionalHeader.SizeOfStackReserve; > > > + IMAGE_NT_HEADERS64 *p64 = (IMAGE_NT_HEADERS64 *) p; > > > + if ((char *) &p64->OptionalHeader.SizeOfStackCommit > buf + n) > > > + return 0; /* buf[] is not enough */ > > > + return p64->OptionalHeader.SizeOfStackReserve; > > > +} > > > > Sorry, but this proposal is too complicated, IMHO. > > > > Checking the stacksize in the file header for each single execve > > is quite a bit time consuming, isn't it? > > I did this because the stack size of an executable can vary by > peflags -x command or -Wl,--stack=xxxxx option. > > > The question is rather, why storing argv on the stack at all? I guess > > the original idea was that argv is always a rather overseeable number. > > But it doesn't have to stay on the stack. > > > > I tried this simple patch: > > > > diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc > > index 49b7a44aeb15..961dea4ab993 100644 > > --- a/winsup/cygwin/dcrt0.cc > > +++ b/winsup/cygwin/dcrt0.cc > > @@ -978,11 +978,8 @@ dll_crt0_1 (void *) > > a change to an element of argv[] it does not affect Cygwin's argv. > > Changing the the contents of what argv[n] points to will still > > affect Cygwin. This is similar (but not exactly like) Linux. */ > > - char *newargv[__argc + 1]; > > - char **nav = newargv; > > - char **oav = __argv; > > - while ((*nav++ = *oav++) != NULL) > > - continue; > > + char **newargv = (char **) malloc ((__argc + 1) * sizeof (char **)); > > + memcpy (newargv, __argv, (__argc + 1) * sizeof (char **)); > > /* Handle any signals which may have arrived */ > > sig_dispatch_pending (false); > > _my_tls.call_signal_handler (); > > > > and the testcase `LC_ALL=C sed 's/x/y/' $(seq 1000000)' simply ran > > as desired. Combined with a bit of error checking... > > > > > diff --git a/winsup/cygwin/sysconf.cc b/winsup/cygwin/sysconf.cc > > > index 2db92e4de..6cb2aecd0 100644 > > > --- a/winsup/cygwin/sysconf.cc > > > +++ b/winsup/cygwin/sysconf.cc > > > @@ -21,6 +21,13 @@ details. */ > > > #include "cpuid.h" > > > #include "clock.h" > > > > > > +#define DEFAULT_STACKGUARD (wincap.def_guard_page_size() + > > > wincap.page_size ()) > > > +static long > > > +get_arg_max (int in) > > > +{ > > > + return (long) (get_rlimit_stack () + DEFAULT_STACKGUARD) / 4; > > > +} > > > + > > > static long > > > get_page_size (int in) > > > { > > > @@ -485,7 +492,7 @@ static struct > > > }; > > > } sca[] = > > > { > > > - {cons, {c:ARG_MAX}}, /* 0, _SC_ARG_MAX */ > > > + {func, {f:get_arg_max}}, /* 0, _SC_ARG_MAX */ > > > {cons, {c:CHILD_MAX}}, /* 1, _SC_CHILD_MAX */ > > > {cons, {c:CLOCKS_PER_SEC}}, /* 2, _SC_CLK_TCK */ > > > {cons, {c:NGROUPS_MAX}}, /* 3, _SC_NGROUPS_MAX */ > > > -- > > > 2.39.0 > > > > Along these lines, there's no reason to couple SC_ARG_MAX to the > > size of the stack. I'd propose to return the value 2097152. It's > > the default value returned by getconf ARG_MAX on LInx as well. > > The default value of 2097152 in Linux comes from 1/4 of the stack > size. It varies by ulimit -s command. So I tried to imitate it.
The value 2097152 is too large for default stack size of cygwin. It is whole of the stack size. -- Takashi Yano <takashi.y...@nifty.ne.jp>
