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Fix freeing stack when guard pages are disabled #716

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merged 2 commits into from
Jul 19, 2023
Merged

Fix freeing stack when guard pages are disabled #716

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fdb18a9
Free a correctly-sized stack when guard pages are disabled
msimberg Jul 17, 2023
8750022
Add error checking to stack munmap/mprotect/madvise calls
msimberg Jul 17, 2023
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110 changes: 80 additions & 30 deletions libs/pika/coroutines/include/pika/coroutines/detail/posix_utility.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@

#include <pika/config.hpp>
#include <pika/assert.hpp>
#include <pika/type_support/unused.hpp>

// include unist.d conditionally to check for POSIX version. Not all OSs have the
// unistd header...
Expand All @@ -47,7 +48,9 @@
# include <cerrno>
# include <cstddef>
# include <cstdlib>
# include <cstring>
# include <stdexcept>
# include <string>

# if defined(_POSIX_MAPPED_FILES) && _POSIX_MAPPED_FILES > 0
# include <errno.h>
Expand Down Expand Up @@ -75,9 +78,60 @@ namespace pika::threads::coroutines::detail::posix {

# if defined(PIKA_HAVE_THREAD_STACK_MMAP) && defined(_POSIX_MAPPED_FILES) && _POSIX_MAPPED_FILES > 0

inline void* to_stack_with_guard_page(void* stack)
{
# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (use_guard_pages)
{
return static_cast<void*>(static_cast<void**>(stack) - (EXEC_PAGESIZE / sizeof(void*)));
}
# endif
return stack;
}

inline void* to_stack_without_guard_page(void* stack)
{
# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (use_guard_pages)
{
return static_cast<void*>(static_cast<void**>(stack) + (EXEC_PAGESIZE / sizeof(void*)));
}
# endif
return stack;
}

inline void add_guard_page(void* stack)
{
# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (use_guard_pages)
{
int r = ::mprotect(stack, EXEC_PAGESIZE, PROT_NONE);
if (r != 0)
{
std::string error_message = "mprotect on a stack allocation failed with errno " +
std::to_string(errno) + " (" + std::strerror(errno) + ")";
throw std::runtime_error(error_message);
}
}
# else
PIKA_UNUSED(stack);
# endif
}

inline std::size_t stack_size_with_guard_page(std::size_t size)
{
# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (use_guard_pages)
{
return size + EXEC_PAGESIZE;
}
# endif
return size;
}

inline void* alloc_stack(std::size_t size)
{
void* real_stack = ::mmap(nullptr, size + EXEC_PAGESIZE, PROT_READ | PROT_WRITE,
void* real_stack = ::mmap(nullptr, stack_size_with_guard_page(size), PROT_READ | PROT_WRITE,
# if defined(__APPLE__)
MAP_PRIVATE | MAP_ANON | MAP_NORESERVE,
# elif defined(__FreeBSD__)
Expand All @@ -89,29 +143,25 @@ namespace pika::threads::coroutines::detail::posix {

if (real_stack == MAP_FAILED)
{
char const* error_message = "mmap() failed to allocate thread stack";
# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (ENOMEM == errno && use_guard_pages)
{
error_message = "mmap() failed to allocate thread stack due to insufficient "
"resources, increase /proc/sys/vm/max_map_count or add "
"-Ipika.stacks.use_guard_pages=0 to the command line";
char const* error_message =
"mmap failed to allocate thread stack due to insufficient resources. "
"Increasing /proc/sys/vm/max_map_count or disabling guard pages with the "
"configuration option pika.stacks.use_guard_pages=0 may reduce memory "
"consumption.";
throw std::runtime_error(error_message);
}
# endif

std::string error_message = "mmap failed to allocate thread stack with errno " +
std::to_string(errno) + " (" + std::strerror(errno) + ")";
throw std::runtime_error(error_message);
}

# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (use_guard_pages)
{
// Add a guard page.
::mprotect(real_stack, EXEC_PAGESIZE, PROT_NONE);

void** stack = static_cast<void**>(real_stack) + (EXEC_PAGESIZE / sizeof(void*));
return static_cast<void*>(stack);
}
return real_stack;
# else
return real_stack;
# endif
add_guard_page(real_stack);
return to_stack_without_guard_page(real_stack);
}

inline void watermark_stack(void* stack, std::size_t size)
Expand All @@ -133,7 +183,13 @@ namespace pika::threads::coroutines::detail::posix {
{
// We never free up the first page, as it's initialized only when the
// stack is created.
::madvise(stack, size - EXEC_PAGESIZE, MADV_DONTNEED);
int r = ::madvise(stack, size - EXEC_PAGESIZE, MADV_DONTNEED);
if (r != 0)
{
std::string error_message = "madvise on a stack allocation failed with errno " +
std::to_string(errno) + " (" + std::strerror(errno) + ")";
throw std::runtime_error(error_message);
}
return true;
}

Expand All @@ -142,19 +198,13 @@ namespace pika::threads::coroutines::detail::posix {

inline void free_stack(void* stack, std::size_t size)
{
# if defined(PIKA_HAVE_THREAD_GUARD_PAGE)
if (use_guard_pages)
{
void** real_stack = static_cast<void**>(stack) - (EXEC_PAGESIZE / sizeof(void*));
::munmap(static_cast<void*>(real_stack), size + EXEC_PAGESIZE);
}
else
int r = ::munmap(to_stack_with_guard_page(stack), stack_size_with_guard_page(size));
if (r != 0)
{
::munmap(stack, size);
std::string error_message = "munmap failed to deallocate thread stack with errno " +
std::to_string(errno) + " (" + std::strerror(errno) + ")";
throw std::runtime_error(error_message);
}
# else
::munmap(stack, size);
# endif
}

# else // non-mmap()
Expand Down