unwind: Implement compat fp unwind

It is important to be able to unwind compat tasks too.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250924080119.613695709@infradead.org

diff --git a/include/linux/unwind_user_types.h b/include/linux/unwind_user_types.h
index a449f15be8902b52367cc547ea12ee0d3913e9f2..938f7e6233327d2488dba7830584fc7774ca309e 100644 (file)
--- a/include/linux/unwind_user_types.h
+++ b/include/linux/unwind_user_types.h
@@ -36,6 +36,7 @@ struct unwind_user_state {
        unsigned long                           ip;
        unsigned long                           sp;
        unsigned long                           fp;
+       unsigned int                            ws;
        enum unwind_user_type                   current_type;
        unsigned int                            available_types;
        bool                                    done;

diff --git a/kernel/unwind/user.c b/kernel/unwind/user.c
index 9dcde797b5d93f11f71c391cee325420ae621c83..642871527a1320c85a293691856ca6fd03d44d44 100644 (file)
--- a/kernel/unwind/user.c
+++ b/kernel/unwind/user.c
@@ -8,19 +8,32 @@
 #include <linux/unwind_user.h>
 #include <linux/uaccess.h>
 
-static const struct unwind_user_frame fp_frame = {
-       ARCH_INIT_USER_FP_FRAME
-};
-
 #define for_each_user_frame(state) \
        for (unwind_user_start(state); !(state)->done; unwind_user_next(state))
 
+static inline int
+get_user_word(unsigned long *word, unsigned long base, int off, unsigned int ws)
+{
+       unsigned long __user *addr = (void __user *)base + off;
+#ifdef CONFIG_COMPAT
+       if (ws == sizeof(int)) {
+               unsigned int data;
+               int ret = get_user(data, (unsigned int __user *)addr);
+               *word = data;
+               return ret;
+       }
+#endif
+       return get_user(*word, addr);
+}
+
 static int unwind_user_next_fp(struct unwind_user_state *state)
 {
-       const struct unwind_user_frame *frame = &fp_frame;
+       const struct unwind_user_frame frame = {
+               ARCH_INIT_USER_FP_FRAME(state->ws)
+       };
        unsigned long cfa, fp, ra;
 
-       if (frame->use_fp) {
+       if (frame.use_fp) {
                if (state->fp < state->sp)
                        return -EINVAL;
                cfa = state->fp;
@@ -29,26 +42,26 @@ static int unwind_user_next_fp(struct unwind_user_state *state)
        }
 
        /* Get the Canonical Frame Address (CFA) */
-       cfa += frame->cfa_off;
+       cfa += frame.cfa_off;
 
        /* stack going in wrong direction? */
        if (cfa <= state->sp)
                return -EINVAL;
 
        /* Make sure that the address is word aligned */
-       if (cfa & (sizeof(long) - 1))
+       if (cfa & (state->ws - 1))
                return -EINVAL;
 
        /* Find the Return Address (RA) */
-       if (get_user(ra, (unsigned long *)(cfa + frame->ra_off)))
+       if (get_user_word(&ra, cfa, frame.ra_off, state->ws))
                return -EINVAL;
 
-       if (frame->fp_off && get_user(fp, (unsigned long __user *)(cfa + frame->fp_off)))
+       if (frame.fp_off && get_user_word(&fp, cfa, frame.fp_off, state->ws))
                return -EINVAL;
 
        state->ip = ra;
        state->sp = cfa;
-       if (frame->fp_off)
+       if (frame.fp_off)
                state->fp = fp;
        return 0;
 }
@@ -100,6 +113,11 @@ static int unwind_user_start(struct unwind_user_state *state)
        state->ip = instruction_pointer(regs);
        state->sp = user_stack_pointer(regs);
        state->fp = frame_pointer(regs);
+       state->ws = unwind_user_word_size(regs);
+       if (!state->ws) {
+               state->done = true;
+               return -EINVAL;
+       }
 
        return 0;
 }