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Change stack field to a pointer in fiber context

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The variable size of zend_fiber_stack results in the offset of other fields to be variable, which causes compatiblity issues with extensions when php-src is compiled with ASan enabled. This solution was prefered over moving the stack field to be the last member, as inclusion of ZEND_FIBER_CONTEXT_FIELDS into other structs may still result in field offset errors.

The definition of zend_fiber_stack was removed from the header to hide it from the ABI.

Renamed prior_pointer and prior_size to asan_pointer and asan_size to reflect their current use.

Changed context flags type to uint8_t.

Renamed valgrind stack id field to valgrind_stack_id and fixed the type to unsigned int.
This commit is contained in:
Aaron Piotrowski 2021-06-11 16:00:09 -05:00
parent d0c43e108e
commit 7df3fd9d55
No known key found for this signature in database
GPG Key ID: ADD1EF783EDE9EEB
2 changed files with 55 additions and 45 deletions
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80
Zend/zend_fibers.c
View File

@ -59,6 +59,21 @@
# include <sanitizer/common_interface_defs.h>
#endif
/* Encapsulates the fiber C stack with extension for debugging tools. */
struct _zend_fiber_stack {
void *pointer;
size_t size;
#ifdef HAVE_VALGRIND
unsigned int valgrind_stack_id;
#endif
#ifdef __SANITIZE_ADDRESS__
const void *asan_pointer;
size_t asan_size;
#endif
};
/* boost_context_data is our customized definition of struct transfer_t as
* provided by boost.context in fcontext.hpp:
*
@ -102,25 +117,25 @@ static size_t zend_fiber_get_page_size(void)
return page_size;
}
static bool zend_fiber_stack_allocate(zend_fiber_stack *stack, size_t size)
static zend_fiber_stack *zend_fiber_stack_allocate(size_t size)
{
void *pointer;
const size_t page_size = zend_fiber_get_page_size();
ZEND_ASSERT(size >= page_size + ZEND_FIBER_GUARD_PAGES * page_size);
stack->size = (size + page_size - 1) / page_size * page_size;
const size_t msize = stack->size + ZEND_FIBER_GUARD_PAGES * page_size;
const size_t stack_size = (size + page_size - 1) / page_size * page_size;
const size_t alloc_size = stack_size + ZEND_FIBER_GUARD_PAGES * page_size;
#ifdef ZEND_WIN32
pointer = VirtualAlloc(0, msize, MEM_COMMIT, PAGE_READWRITE);
pointer = VirtualAlloc(0, alloc_size, MEM_COMMIT, PAGE_READWRITE);
if (!pointer) {
DWORD err = GetLastError();
char *errmsg = php_win32_error_to_msg(err);
zend_throw_exception_ex(NULL, 0, "Fiber make context failed: VirtualAlloc failed: [0x%08lx] %s", err, errmsg[0] ? errmsg : "Unknown");
php_win32_error_msg_free(errmsg);
return false;
return NULL;
}
# if ZEND_FIBER_GUARD_PAGES
@ -132,49 +147,48 @@ static bool zend_fiber_stack_allocate(zend_fiber_stack *stack, size_t size)
zend_throw_exception_ex(NULL, 0, "Fiber protect stack failed: VirtualProtect failed: [0x%08lx] %s", err, errmsg[0] ? errmsg : "Unknown");
php_win32_error_msg_free(errmsg);
VirtualFree(pointer, 0, MEM_RELEASE);
return false;
return NULL;
}
# endif
#else
pointer = mmap(NULL, msize, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
pointer = mmap(NULL, alloc_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (pointer == MAP_FAILED) {
zend_throw_exception_ex(NULL, 0, "Fiber make context failed: mmap failed: %s (%d)", strerror(errno), errno);
return false;
return NULL;
}
# if ZEND_FIBER_GUARD_PAGES
if (mprotect(pointer, ZEND_FIBER_GUARD_PAGES * page_size, PROT_NONE) < 0) {
zend_throw_exception_ex(NULL, 0, "Fiber protect stack failed: mmap failed: %s (%d)", strerror(errno), errno);
munmap(pointer, msize);
return false;
munmap(pointer, alloc_size);
return NULL;
}
# endif
#endif
zend_fiber_stack *stack = emalloc(sizeof(zend_fiber_stack));
stack->pointer = (void *) ((uintptr_t) pointer + ZEND_FIBER_GUARD_PAGES * page_size);
stack->size = stack_size;
#ifdef VALGRIND_STACK_REGISTER
uintptr_t base = (uintptr_t) stack->pointer;
stack->valgrind = VALGRIND_STACK_REGISTER(base, base + stack->size);
stack->valgrind_stack_id = VALGRIND_STACK_REGISTER(base, base + stack->size);
#endif
#ifdef __SANITIZE_ADDRESS__
stack->prior_pointer = stack->pointer;
stack->prior_size = stack->size;
stack->asan_pointer = stack->pointer;
stack->asan_size = stack->size;
#endif
return true;
return stack;
}
static void zend_fiber_stack_free(zend_fiber_stack *stack)
{
if (!stack->pointer) {
return;
}
#ifdef VALGRIND_STACK_DEREGISTER
VALGRIND_STACK_DEREGISTER(stack->valgrind);
VALGRIND_STACK_DEREGISTER(stack->valgrind_stack_id);
#endif
const size_t page_size = zend_fiber_get_page_size();
@ -187,7 +201,7 @@ static void zend_fiber_stack_free(zend_fiber_stack *stack)
munmap(pointer, stack->size + ZEND_FIBER_GUARD_PAGES * page_size);
#endif
stack->pointer = NULL;
efree(stack);
}
static ZEND_NORETURN void zend_fiber_trampoline(boost_context_data data)
@ -195,7 +209,7 @@ static ZEND_NORETURN void zend_fiber_trampoline(boost_context_data data)
zend_fiber_context *from = data.transfer->context;
#ifdef __SANITIZE_ADDRESS__
__sanitizer_finish_switch_fiber(NULL, &from->stack.prior_pointer, &from->stack.prior_size);
__sanitizer_finish_switch_fiber(NULL, &from->stack->asan_pointer, &from->stack->asan_size);
#endif
/* Get a hold of the context that resumed us and update it's handle to allow for symmetric coroutines. */
@ -218,14 +232,16 @@ static ZEND_NORETURN void zend_fiber_trampoline(boost_context_data data)
ZEND_API bool zend_fiber_init_context(zend_fiber_context *context, void *kind, zend_fiber_coroutine coroutine, size_t stack_size)
{
if (UNEXPECTED(!zend_fiber_stack_allocate(&context->stack, stack_size))) {
context->stack = zend_fiber_stack_allocate(stack_size);
if (UNEXPECTED(!context->stack)) {
return false;
}
// Stack grows down, calculate the top of the stack. make_fcontext then shifts pointer to lower 16-byte boundary.
void *stack = (void *) ((uintptr_t) context->stack.pointer + context->stack.size);
void *stack = (void *) ((uintptr_t) context->stack->pointer + context->stack->size);
context->handle = make_fcontext(stack, context->stack.size, zend_fiber_trampoline);
context->handle = make_fcontext(stack, context->stack->size, zend_fiber_trampoline);
ZEND_ASSERT(context->handle != NULL && "make_fcontext() never returns NULL");
context->kind = kind;
@ -236,7 +252,7 @@ ZEND_API bool zend_fiber_init_context(zend_fiber_context *context, void *kind, z
ZEND_API void zend_fiber_destroy_context(zend_fiber_context *context)
{
zend_fiber_stack_free(&context->stack);
zend_fiber_stack_free(context->stack);
}
ZEND_API void zend_fiber_switch_context(zend_fiber_transfer *transfer)
@ -278,8 +294,8 @@ ZEND_API void zend_fiber_switch_context(zend_fiber_transfer *transfer)
void *fake_stack = NULL;
__sanitizer_start_switch_fiber(
from->status != ZEND_FIBER_STATUS_DEAD ? &fake_stack : NULL,
to->stack.prior_pointer,
to->stack.prior_size);
to->stack->asan_pointer,
to->stack->asan_size);
#endif
boost_context_data data = jump_fcontext(to->handle, transfer);
@ -292,7 +308,7 @@ ZEND_API void zend_fiber_switch_context(zend_fiber_transfer *transfer)
to->handle = data.handle;
#ifdef __SANITIZE_ADDRESS__
__sanitizer_finish_switch_fiber(fake_stack, &to->stack.prior_pointer, &to->stack.prior_size);
__sanitizer_finish_switch_fiber(fake_stack, &to->stack->asan_pointer, &to->stack->asan_size);
#endif
EG(current_fiber_context) = from;
@ -741,6 +757,11 @@ void zend_fiber_init(void)
{
zend_fiber_context *context = ecalloc(1, sizeof(zend_fiber_context));
#ifdef __SANITIZE_ADDRESS__
// Main fiber context stack is only accessed if ASan is enabled.
context->stack = emalloc(sizeof(zend_fiber_stack));
#endif
context->status = ZEND_FIBER_STATUS_RUNNING;
EG(main_fiber_context) = context;
@ -750,5 +771,8 @@ void zend_fiber_init(void)
void zend_fiber_shutdown(void)
{
#ifdef __SANITIZE_ADDRESS__
efree(EG(main_fiber_context)->stack);
#endif
efree(EG(main_fiber_context));
}

20
Zend/zend_fibers.h
View File

@ -53,23 +53,9 @@ void zend_fiber_shutdown(void);
extern ZEND_API zend_class_entry *zend_ce_fiber;
/* Encapsulates the fiber C stack with extension for debugging tools. */
typedef struct _zend_fiber_stack {
void *pointer;
size_t size;
#ifdef HAVE_VALGRIND
int valgrind;
#endif
#ifdef __SANITIZE_ADDRESS__
const void *prior_pointer;
size_t prior_size;
#endif
} zend_fiber_stack;
typedef struct _zend_fiber zend_fiber;
typedef struct _zend_fiber_context zend_fiber_context;
typedef struct _zend_fiber_stack zend_fiber_stack;
/* Encapsulates data needed for a context switch. */
typedef struct _zend_fiber_transfer {
@ -92,9 +78,9 @@ typedef void (*zend_fiber_coroutine)(zend_fiber_transfer *transfer);
/* Pointer that identifies the fiber type. */ \
void *kind; \
zend_fiber_coroutine function; \
zend_fiber_stack stack; \
zend_fiber_stack *stack; \
zend_fiber_status status; \
zend_uchar flags
uint8_t flags
/* Standalone context (used primarily as pointer type). */
struct _zend_fiber_context {