Merge branch 'bpf-prepare-to-support-stack-arguments'

Yonghong Song says:

====================
bpf: Prepare to support stack arguments

The patch set prepares to support stack arguments for bpf functions
and kfuncs. The major changes include:
  - Avoid redundant calculation of bpf_reg_state. For stack
    arguments, there exists no corresponding register number.
  - Refactor check_kfunc_mem_size_reg() to have bpf_reg_state's
    for both mem_reg and size_reg.
  - Allow verifier logs to print stack arguments if there is no
    corresponding register.

Please see individual patches for details.

Changelogs:
  v2 -> v3:
    - v2: https://lore.kernel.org/bpf/20260422054149.3124342-1-yonghong.song@linux.dev/
    - Fix a mark_chain_precision issue by rewriting helper reg_from_argno().
  v1 -> v2:
    - v1: https://lore.kernel.org/bpf/20260421171927.3507554-1-yonghong.song@linux.dev/
    - Major change to patch 7. In v1, the argno has type u32 to
      represent registers and arguments. This works but error prone
      as u32 is too easy to mess and leak. This version uses a struct
      type to represent argno which makes things more explicit and easy
      to reason.
====================

Link: https://patch.msgid.link/20260423033425.2536883-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 9 insertions, 2 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d3aea3931b85..715b6df9c403 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1151,6 +1151,11 @@ struct bpf_prog_offload {
 
 /* The longest tracepoint has 12 args.
  * See include/trace/bpf_probe.h
+ *
+ * Also reuse this macro for maximum number of arguments a BPF function
+ * or a kfunc can have. Args 1-5 are passed in registers, args 6-12 via
+ * stack arg slots. The JIT may map some stack arg slots to registers based
+ * on the native calling convention (e.g., arg 6 to R9 on x86-64).
  */
 #define MAX_BPF_FUNC_ARGS 12
 
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index b148f816f25b..d5b4303315dd 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -913,6 +913,7 @@ struct bpf_verifier_env {
 	 * e.g., in reg_type_str() to generate reg_type string
 	 */
 	char tmp_str_buf[TMP_STR_BUF_LEN];
+	char tmp_arg_name[32];
 	struct bpf_insn insn_buf[INSN_BUF_SIZE];
 	struct bpf_insn epilogue_buf[INSN_BUF_SIZE];
 	struct bpf_scc_callchain callchain_buf;
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 1ec6d5ba64cc..b77d0b06db6e 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -58,8 +58,9 @@ struct ctl_table_header;
 #define BPF_REG_H	BPF_REG_9	/* hlen, callee-saved */
 
 /* Kernel hidden auxiliary/helper register. */
-#define BPF_REG_AX		MAX_BPF_REG
-#define MAX_BPF_EXT_REG		(MAX_BPF_REG + 1)
+#define BPF_REG_PARAMS		MAX_BPF_REG
+#define BPF_REG_AX		(MAX_BPF_REG + 1)
+#define MAX_BPF_EXT_REG		(MAX_BPF_REG + 2)
 #define MAX_BPF_JIT_REG		MAX_BPF_EXT_REG
 
 /* unused opcode to mark special call to bpf_tail_call() helper */