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Fix Intel CET / SHSTK support in fibers #14027

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Fix Intel CET / SHSTK support in fibers #14027

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b7d56ba
Fix map_shadow_stack syscall number
arnaud-lb Apr 21, 2024
2e1771e
Increase SHSTK stack size
arnaud-lb Apr 21, 2024
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14 changes: 7 additions & 7 deletions Zend/zend_fibers.c
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Original file line number Diff line number Diff line change
Expand Up @@ -69,10 +69,14 @@
#endif

# if defined __CET__
# include <sys/syscall.h>
# include <unistd.h>
# include <cet.h>
# define SHSTK_ENABLED (__CET__ & 0x2)
# define BOOST_CONTEXT_SHADOW_STACK (SHSTK_ENABLED && SHADOW_STACK_SYSCALL)
# define __NR_map_shadow_stack 451
# ifndef SYS_map_shadow_stack
# define SYS_map_shadow_stack 453
# endif
# ifndef SHADOW_STACK_SET_TOKEN
# define SHADOW_STACK_SET_TOKEN 0x1
#endif
Expand Down Expand Up @@ -275,15 +279,11 @@ static zend_fiber_stack *zend_fiber_stack_allocate(size_t size)
stack->size = stack_size;

#if !defined(ZEND_FIBER_UCONTEXT) && BOOST_CONTEXT_SHADOW_STACK
/* shadow stack saves ret address only, need less space */
stack->ss_size= stack_size >> 5;

/* align shadow stack to 8 bytes. */
stack->ss_size = (stack->ss_size + 7) & ~7;
stack->ss_size = stack_size;

/* issue syscall to create shadow stack for the new fcontext */
/* SHADOW_STACK_SET_TOKEN option will put "restore token" on the new shadow stack */
stack->ss_base = (void *)syscall(__NR_map_shadow_stack, 0, stack->ss_size, SHADOW_STACK_SET_TOKEN);
stack->ss_base = (void *)syscall(SYS_map_shadow_stack, 0, stack->ss_size, SHADOW_STACK_SET_TOKEN);

if (stack->ss_base == MAP_FAILED) {
zend_throw_exception_ex(NULL, 0, "Fiber shadow stack allocate failed: mmap failed: %s (%d)", strerror(errno), errno);
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11 changes: 9 additions & 2 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -1294,11 +1294,18 @@ fi
AC_CACHE_CHECK([whether syscall to create shadow stack exists],
[php_cv_have_shadow_stack_syscall],
[AC_RUN_IFELSE([AC_LANG_SOURCE([
#include <sys/syscall.h>
#include <unistd.h>
#include <sys/mman.h>
#ifndef SYS_map_shadow_stack
# define SYS_map_shadow_stack 453
#endif
#ifndef SHADOW_STACK_SET_TOKEN
# define SHADOW_STACK_SET_TOKEN 0x1
#endif
int main(void) {
/* test if syscall 451, i.e., map_shadow_stack is available */
void* base = (void *)syscall(451, 0, 0x20000, 0x1);
/* test if map_shadow_stack is available */
void* base = (void *)syscall(SYS_map_shadow_stack, 0, 0x20000, SHADOW_STACK_SET_TOKEN);
if (base != (void*)-1) {
munmap(base, 0x20000);
return 0;
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