This commit implements support for the native-bypass option in linux-user. By utilizing this functionality, the specified shared library can be loaded into the user program. This is achieved by dynamically modifying the /etc/ld.so.preload file, enabling the user program to load the shared library effortlessly.
Signed-off-by: Yeqi Fu <fufuyqqq...@gmail.com> --- include/native/native.h | 7 ++++++ linux-user/main.c | 20 +++++++++++++++ linux-user/syscall.c | 55 +++++++++++++++++++++++++++++++++++++++++ 3 files changed, 82 insertions(+) create mode 100644 include/native/native.h diff --git a/include/native/native.h b/include/native/native.h new file mode 100644 index 0000000000..12462a261e --- /dev/null +++ b/include/native/native.h @@ -0,0 +1,7 @@ +#if defined(CONFIG_USER_ONLY) && defined(CONFIG_NATIVE_CALL) +extern char *native_lib_path; +/* Check if the native-bypass option is enabled. */ +#define native_bypass_enabled() (native_lib_path != NULL) +#else +#define native_bypass_enabled() false +#endif diff --git a/linux-user/main.c b/linux-user/main.c index dba67ffa36..4c1d515944 100644 --- a/linux-user/main.c +++ b/linux-user/main.c @@ -60,6 +60,11 @@ #include "semihosting/semihost.h" #endif +#if defined(CONFIG_NATIVE_CALL) +#include "native/native.h" +char *native_lib_path; +#endif + #ifndef AT_FLAGS_PRESERVE_ARGV0 #define AT_FLAGS_PRESERVE_ARGV0_BIT 0 #define AT_FLAGS_PRESERVE_ARGV0 (1 << AT_FLAGS_PRESERVE_ARGV0_BIT) @@ -293,6 +298,17 @@ static void handle_arg_set_env(const char *arg) free(r); } +#if defined(CONFIG_NATIVE_CALL) +static void handle_arg_native_bypass(const char *arg) +{ + if (!g_file_test(arg, G_FILE_TEST_IS_REGULAR)) { + fprintf(stderr, "native library %s does not exist\n", arg); + exit(EXIT_FAILURE); + } + native_lib_path = g_strdup(arg); +} +#endif + static void handle_arg_unset_env(const char *arg) { char *r, *p, *token; @@ -522,6 +538,10 @@ static const struct qemu_argument arg_table[] = { "", "Generate a /tmp/perf-${pid}.map file for perf"}, {"jitdump", "QEMU_JITDUMP", false, handle_arg_jitdump, "", "Generate a jit-${pid}.dump file for perf"}, +#if defined(CONFIG_NATIVE_CALL) + {"native-bypass", "QEMU_NATIVE_BYPASS", true, handle_arg_native_bypass, + "", "native bypass for library calls"}, +#endif {NULL, NULL, false, NULL, NULL, NULL} }; diff --git a/linux-user/syscall.c b/linux-user/syscall.c index 08162cc966..7034f58373 100644 --- a/linux-user/syscall.c +++ b/linux-user/syscall.c @@ -143,6 +143,7 @@ #include "fd-trans.h" #include "tcg/tcg.h" #include "cpu_loop-common.h" +#include "native/native.h" #ifndef CLONE_IO #define CLONE_IO 0x80000000 /* Clone io context */ @@ -8503,6 +8504,40 @@ static int open_hardware(CPUArchState *cpu_env, int fd) } #endif +#if defined(CONFIG_NATIVE_CALL) +static int is_ld_so_preload(const char *filename, const char *entry) +{ + if (native_bypass_enabled() && !strcmp(filename, entry)) { + return 1; + } + return 0; +} + +/* This function is only called when the "native-bypass" option is provided. */ +static int open_ld_so_preload(CPUArchState *cpu_env, int fd) +{ + FILE *fp; + char *line = NULL; + size_t len = 0; + ssize_t read; + + dprintf(fd, "%s\n", native_lib_path); + fp = fopen("/etc/ld.so.preload", "r"); + if (fp == NULL) { + return 0; + } + + while ((read = getline(&line, &len, fp)) != -1) { + dprintf(fd, "%s", line); + } + + free(line); + fclose(fp); + + return 0; +} +#endif + int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, int flags, mode_t mode, bool safe) { @@ -8527,6 +8562,9 @@ int do_guest_openat(CPUArchState *cpu_env, int dirfd, const char *pathname, #endif #if defined(TARGET_M68K) { "/proc/hardware", open_hardware, is_proc }, +#endif +#if defined(CONFIG_NATIVE_CALL) + { "/etc/ld.so.preload", open_ld_so_preload, is_ld_so_preload }, #endif { NULL, NULL, NULL } }; @@ -9523,6 +9561,11 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1, return -TARGET_EFAULT; } ret = get_errno(access(path(p), arg2)); + if (ret != 0 && native_bypass_enabled()) { + if (strcmp(p, "/etc/ld.so.preload") == 0 && arg2 == R_OK) { + return 0; + } + } unlock_user(p, arg1, 0); return ret; #endif @@ -9532,6 +9575,12 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1, return -TARGET_EFAULT; } ret = get_errno(faccessat(arg1, p, arg3, 0)); + if (ret != 0 && native_bypass_enabled()) { + if (strcmp(p, "/etc/ld.so.preload") == 0 && arg1 == AT_FDCWD && + arg3 == R_OK) { + return 0; + } + } unlock_user(p, arg2, 0); return ret; #endif @@ -9541,6 +9590,12 @@ static abi_long do_syscall1(CPUArchState *cpu_env, int num, abi_long arg1, return -TARGET_EFAULT; } ret = get_errno(faccessat(arg1, p, arg3, arg4)); + if (ret != 0 && native_bypass_enabled()) { + if (strcmp(p, "/etc/ld.so.preload") == 0 && arg1 == AT_FDCWD && + arg3 == R_OK) { + return 0; + } + } unlock_user(p, arg2, 0); return ret; #endif -- 2.34.1