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, 25 insertions, 0 deletions

diff --git a/arch/alpha/boot/bootloader.lds b/arch/alpha/boot/bootloader.lds
new file mode 100644
index 000000000..8cdff54c6
--- /dev/null
+++ b/arch/alpha/boot/bootloader.lds
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+OUTPUT_FORMAT("elf64-alpha")
+ENTRY(__start)
+printk = srm_printk;
+SECTIONS
+{
+  . = 0x20000000;
+  .text : { *(.text) }
+  _etext = .;
+  PROVIDE (etext = .);
+  .rodata : { *(.rodata) *(.rodata.*) }
+  .data : { *(.data) CONSTRUCTORS }
+  .got : { *(.got) }
+  .sdata : { *(.sdata) }
+  _edata = .;
+  PROVIDE (edata = .);
+  .sbss : { *(.sbss) *(.scommon) }
+  .bss : { *(.bss) *(COMMON) }
+  _end = . ;
+  PROVIDE (end = .);
+
+  .mdebug 0 : { *(.mdebug) }
+  .note 0 : { *(.note) }
+  .comment 0 : { *(.comment) }
+}