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Fix build with _FILE_OFFSET_BITS=64

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This commit is contained in:
Cameron Gutman
2022-09-05 22:04:24 -05:00
parent ad3ed97472
commit ab6b88073c
3 changed files with 95 additions and 76 deletions
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2
app/app.pro
View File

@@ -271,7 +271,7 @@ libdrm {
linux {
message(Master hooks enabled)
SOURCES += masterhook.c
SOURCES += masterhook.c masterhook_internal.c
LIBS += -ldl
}
}

79
app/masterhook.c
View File

@@ -11,9 +11,12 @@
#define _GNU_SOURCE
// NOTE: This file MUST NOT include fcntl.h due to open() -> open64()
// redirection that happens when _FILE_OFFSET_BITS=64!
// See masterhook_internal.c for details.
#include <SDL.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
@@ -21,16 +24,6 @@
#include <xf86drm.h>
#include <xf86drmMode.h>
// __OPEN_NEEDS_MODE is a glibc-ism, so define it ourselves for other libc
#ifndef __OPEN_NEEDS_MODE
#ifdef __O_TMPFILE
# define __OPEN_NEEDS_MODE(oflag) \
(((oflag) & O_CREAT) != 0 || ((oflag) & __O_TMPFILE) == __O_TMPFILE)
#else
# define __OPEN_NEEDS_MODE(oflag) (((oflag) & O_CREAT) != 0)
#endif
#endif
// We require SDL 2.0.15+ to hook because it supports sharing
// the DRM FD with our code. This avoids having multiple DRM FDs
// in flight at the same time which would significantly complicate
@@ -96,12 +89,6 @@ int drmModeAtomicCommit(int fd, drmModeAtomicReqPtr req,
// master on the Qt FD to allow the new FD to have master.
int openHook(const char *funcname, const char *pathname, int flags, va_list va);
// fcntl.h may define open to open64 which will cause us to define open64 twice.
// Remove this redirection to allow our hooks to build properly with _FILE_OFFSET_BITS=64.
#ifdef open
#undef open
#endif
int open(const char *pathname, int flags, ...)
{
va_list va;
@@ -120,64 +107,6 @@ int open64(const char *pathname, int flags, ...)
return fd;
}
int openHook(const char *funcname, const char *pathname, int flags, va_list va)
{
int fd;
mode_t mode;
// Call the real thing to do the open operation
if (__OPEN_NEEDS_MODE(flags)) {
mode = va_arg(va, mode_t);
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
}
else {
mode = 0;
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
}
// If the file was successfully opened and we have a DRM master FD,
// check if the FD we just opened is a DRM device.
if (fd >= 0 && g_QtDrmMasterFd != -1) {
if (strncmp(pathname, "/dev/dri/card", 13) == 0) {
// It's a DRM device, but is it _our_ DRM device?
struct stat64 fdstat;
fstat64(fd, &fdstat);
if (g_DrmMasterStat.st_dev == fdstat.st_dev &&
g_DrmMasterStat.st_ino == fdstat.st_ino) {
// It is our device. Time to do the magic!
// This code assumes SDL only ever opens a single FD
// for a given DRM device.
SDL_assert(g_SdlDrmMasterFd == -1);
// Drop master on Qt's FD so we can pick it up for SDL.
if (drmDropMaster(g_QtDrmMasterFd) < 0) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"Failed to drop master on Qt DRM FD: %d",
errno);
// Hope for the best
return fd;
}
// We are not allowed to call drmSetMaster() without CAP_SYS_ADMIN,
// but since we just dropped the master, we can become master by
// simply creating a new FD. Let's do it.
close(fd);
if (__OPEN_NEEDS_MODE(flags)) {
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
}
else {
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
}
g_SdlDrmMasterFd = fd;
}
}
}
return fd;
}
// Our close() hook handles restoring DRM master to the Qt FD
// after SDL closes its DRM FD.
int close(int fd)

90
app/masterhook_internal.c Normal file
View File

@@ -0,0 +1,90 @@
// This file contains the private implementation of the open() hook
// which must be in a separate compilation unit due to fcntl.h doing
// unwanted redirection of open() to open64().
#define _GNU_SOURCE
#include <SDL.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <xf86drm.h>
#include <xf86drmMode.h>
// __OPEN_NEEDS_MODE is a glibc-ism, so define it ourselves for other libc
#ifndef __OPEN_NEEDS_MODE
#ifdef __O_TMPFILE
# define __OPEN_NEEDS_MODE(oflag) \
(((oflag) & O_CREAT) != 0 || ((oflag) & __O_TMPFILE) == __O_TMPFILE)
#else
# define __OPEN_NEEDS_MODE(oflag) (((oflag) & O_CREAT) != 0)
#endif
#endif
#if SDL_VERSION_ATLEAST(2, 0, 15)
extern int g_QtDrmMasterFd;
extern struct stat64 g_DrmMasterStat;
extern int g_SdlDrmMasterFd;
int openHook(const char *funcname, const char *pathname, int flags, va_list va)
{
int fd;
mode_t mode;
// Call the real thing to do the open operation
if (__OPEN_NEEDS_MODE(flags)) {
mode = va_arg(va, mode_t);
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
}
else {
mode = 0;
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
}
// If the file was successfully opened and we have a DRM master FD,
// check if the FD we just opened is a DRM device.
if (fd >= 0 && g_QtDrmMasterFd != -1) {
if (strncmp(pathname, "/dev/dri/card", 13) == 0) {
// It's a DRM device, but is it _our_ DRM device?
struct stat64 fdstat;
fstat64(fd, &fdstat);
if (g_DrmMasterStat.st_dev == fdstat.st_dev &&
g_DrmMasterStat.st_ino == fdstat.st_ino) {
// It is our device. Time to do the magic!
// This code assumes SDL only ever opens a single FD
// for a given DRM device.
SDL_assert(g_SdlDrmMasterFd == -1);
// Drop master on Qt's FD so we can pick it up for SDL.
if (drmDropMaster(g_QtDrmMasterFd) < 0) {
SDL_LogError(SDL_LOG_CATEGORY_APPLICATION,
"Failed to drop master on Qt DRM FD: %d",
errno);
// Hope for the best
return fd;
}
// We are not allowed to call drmSetMaster() without CAP_SYS_ADMIN,
// but since we just dropped the master, we can become master by
// simply creating a new FD. Let's do it.
close(fd);
if (__OPEN_NEEDS_MODE(flags)) {
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags, mode);
}
else {
fd = ((typeof(open)*)dlsym(RTLD_NEXT, funcname))(pathname, flags);
}
g_SdlDrmMasterFd = fd;
}
}
}
return fd;
}
#endif