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lwp: use mprotect to catch stack overflows

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This commit is contained in:
Daniel Kochmański 2026-03-15 21:52:43 +01:00
parent c73b2e73d9
commit 7fd467321d
2 changed files with 23 additions and 3 deletions
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24
src/c/lwp.d
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@ -15,6 +15,8 @@
#include <ecl/ecl.h>
#include <ecl/internal.h>
# include <sys/mman.h>
# include <unistd.h>
#include <ucontext.h>
/* -- implementation notes -----------------------------------------------------
@ -47,6 +49,24 @@ ensure_cc(cl_env_ptr the_env)
return cc;
}
#define LWP_STACK_SIZE 8*1024
/* FIXME munmap in the finalizer. */
static void*
make_stack(size_t size)
{
size_t page_size = sysconf(_SC_PAGESIZE);
void *mem = mmap(NULL, size+page_size,
PROT_READ | PROT_WRITE,
MAP_ANON | MAP_PRIVATE, -1, 0);
/* catch overflows. Note that we don't need it normally in ECL, because we do
our own overflow checks, but this helps to illustrate and catch early when
GC goes off rails because it doesn't work well with multiple stakck. */
mprotect(mem, page_size, PROT_NONE);
return mem+page_size;
}
static void
_lwp_entry(void)
{
@ -89,8 +109,8 @@ si_make_continuation(cl_object thread)
o->cont.env = new_env;
/* Create the context. */
getcontext(uc);
uc->uc_stack.ss_sp = stack;
uc->uc_stack.ss_size = 16*1024;
uc->uc_stack.ss_sp = make_stack(LWP_STACK_SIZE);
uc->uc_stack.ss_size = LWP_STACK_SIZE;
uc->uc_link = NULL;
makecontext(uc, (void(*)(void))_lwp_entry, 0);
}

2
src/h/object.h
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@ -1071,7 +1071,7 @@ struct ecl_cont {
_ECL_HDR2(resumed, timed_out);
cl_object thread; /* its thread */
ucontext_t uc;
char stack[16*1024];
void *stack;
cl_env_ptr env;
};