From d1d7f01f7cd35e16c6bcef5a0e31988b5c9980f9 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 10 Feb 2025 17:09:25 +0100 Subject: um: mark rodata read-only and implement _nofault accesses Mark read-only data actually read-only (simple mprotect), and to be able to test it also implement _nofault accesses. This works by setting up a new "segv_continue" pointer in current, and then when we hit a segfault we change the signal return context so that we continue at that address. The code using this sets it up so that it jumps to a label and then aborts the access that way, returning -EFAULT. It's possible to optimize the ___backtrack_faulted() thing by using asm goto (compiler version dependent) and/or gcc's (not sure if clang has it) &&label extension, but at least in one attempt I made the && caused the compiler to not load -EFAULT into the register in case of jumping to the &&label from the fault handler. So leave it like this for now. Signed-off-by: Johannes Berg Co-developed-by: Benjamin Berg Signed-off-by: Benjamin Berg Link: https://patch.msgid.link/20250210160926.420133-2-benjamin@sipsolutions.net Signed-off-by: Johannes Berg --- arch/um/include/shared/kern_util.h | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'arch/um/include/shared/kern_util.h') diff --git a/arch/um/include/shared/kern_util.h b/arch/um/include/shared/kern_util.h index f21dc8517538..00ca3e12fd9a 100644 --- a/arch/um/include/shared/kern_util.h +++ b/arch/um/include/shared/kern_util.h @@ -24,10 +24,12 @@ extern void free_stack(unsigned long stack, int order); struct pt_regs; extern void do_signal(struct pt_regs *regs); extern void interrupt_end(void); -extern void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs); +extern void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs, + void *mc); extern unsigned long segv(struct faultinfo fi, unsigned long ip, - int is_user, struct uml_pt_regs *regs); + int is_user, struct uml_pt_regs *regs, + void *mc); extern int handle_page_fault(unsigned long address, unsigned long ip, int is_write, int is_user, int *code_out); @@ -59,8 +61,10 @@ extern unsigned long from_irq_stack(int nested); extern int singlestepping(void); -extern void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs); -extern void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs); +extern void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs, + void *mc); +extern void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs, + void *mc); extern void fatal_sigsegv(void) __attribute__ ((noreturn)); void um_idle_sleep(void); -- cgit v1.2.3