diff options
| author | Brian Gerst <brgerst@gmail.com> | 2023-06-23 18:55:29 -0400 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2023-07-10 09:52:25 +0200 |
| commit | 3aec4ecb3d1f313a8ab985df7cab07c4af81f478 (patch) | |
| tree | b7866bb1960211cf8f1b4f2cbd1263fa309fc661 /arch/x86/kernel/process.c | |
| parent | 81f755d561f365f544795fad92f05a085ea4f292 (diff) | |
x86: Rewrite ret_from_fork() in C
When kCFI is enabled, special handling is needed for the indirect call
to the kernel thread function. Rewrite the ret_from_fork() function in
C so that the compiler can properly handle the indirect call.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lkml.kernel.org/r/20230623225529.34590-3-brgerst@gmail.com
Diffstat (limited to 'arch/x86/kernel/process.c')
| -rw-r--r-- | arch/x86/kernel/process.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index ff9b80a0e3e3..72015dba72ab 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -28,6 +28,7 @@ #include <linux/static_call.h> #include <trace/events/power.h> #include <linux/hw_breakpoint.h> +#include <linux/entry-common.h> #include <asm/cpu.h> #include <asm/apic.h> #include <linux/uaccess.h> @@ -134,6 +135,25 @@ static int set_new_tls(struct task_struct *p, unsigned long tls) return do_set_thread_area_64(p, ARCH_SET_FS, tls); } +__visible void ret_from_fork(struct task_struct *prev, struct pt_regs *regs, + int (*fn)(void *), void *fn_arg) +{ + schedule_tail(prev); + + /* Is this a kernel thread? */ + if (unlikely(fn)) { + fn(fn_arg); + /* + * A kernel thread is allowed to return here after successfully + * calling kernel_execve(). Exit to userspace to complete the + * execve() syscall. + */ + regs->ax = 0; + } + + syscall_exit_to_user_mode(regs); +} + int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) { unsigned long clone_flags = args->flags; @@ -149,7 +169,7 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) frame = &fork_frame->frame; frame->bp = encode_frame_pointer(childregs); - frame->ret_addr = (unsigned long) ret_from_fork; + frame->ret_addr = (unsigned long) ret_from_fork_asm; p->thread.sp = (unsigned long) fork_frame; p->thread.io_bitmap = NULL; p->thread.iopl_warn = 0; |