bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 57 insertions, 0 deletions

diff --git a/arch/powerpc/math-emu/fdiv.c b/arch/powerpc/math-emu/fdiv.c
new file mode 100644
index 000000000..6e64ece2d
--- /dev/null
+++ b/arch/powerpc/math-emu/fdiv.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/uaccess.h>
+
+#include <asm/sfp-machine.h>
+#include <math-emu/soft-fp.h>
+#include <math-emu/double.h>
+
+int
+fdiv(void *frD, void *frA, void *frB)
+{
+	FP_DECL_D(A);
+	FP_DECL_D(B);
+	FP_DECL_D(R);
+	FP_DECL_EX;
+
+#ifdef DEBUG
+	printk("%s: %p %p %p\n", __func__, frD, frA, frB);
+#endif
+
+	FP_UNPACK_DP(A, frA);
+	FP_UNPACK_DP(B, frB);
+
+#ifdef DEBUG
+	printk("A: %ld %lu %lu %ld (%ld)\n", A_s, A_f1, A_f0, A_e, A_c);
+	printk("B: %ld %lu %lu %ld (%ld)\n", B_s, B_f1, B_f0, B_e, B_c);
+#endif
+
+	if (A_c == FP_CLS_ZERO && B_c == FP_CLS_ZERO) {
+		FP_SET_EXCEPTION(EFLAG_VXZDZ);
+#ifdef DEBUG
+		printk("%s: FPSCR_VXZDZ raised\n", __func__);
+#endif
+	}
+	if (A_c == FP_CLS_INF && B_c == FP_CLS_INF) {
+		FP_SET_EXCEPTION(EFLAG_VXIDI);
+#ifdef DEBUG
+		printk("%s: FPSCR_VXIDI raised\n", __func__);
+#endif
+	}
+
+	if (B_c == FP_CLS_ZERO && A_c != FP_CLS_ZERO) {
+		FP_SET_EXCEPTION(EFLAG_DIVZERO);
+		if (__FPU_TRAP_P(EFLAG_DIVZERO))
+			return FP_CUR_EXCEPTIONS;
+	}
+	FP_DIV_D(R, A, B);
+
+#ifdef DEBUG
+	printk("D: %ld %lu %lu %ld (%ld)\n", R_s, R_f1, R_f0, R_e, R_c);
+#endif
+
+	__FP_PACK_D(frD, R);
+
+	return FP_CUR_EXCEPTIONS;
+}