On 10/20/24 3:01 PM, Jiri Olsa wrote:
On Sun, Oct 20, 2024 at 12:14:05PM -0700, Yonghong Song wrote:
Three private stack modes are used to direct jit action:
NO_PRIV_STACK: do not use private stack
PRIV_STACK_SUB_PROG: adjust frame pointer address (similar to normal stack)
PRIV_STACK_ROOT_PROG: set the frame pointer
Note that for subtree root prog (main prog or callback fn), even if the
bpf_prog stack size is 0, PRIV_STACK_ROOT_PROG mode is still used.
This is for bpf exception handling. More details can be found in
subsequent jit support and selftest patches.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
include/linux/bpf.h | 9 +++++++++
kernel/bpf/core.c | 19 +++++++++++++++++++
kernel/bpf/verifier.c | 29 +++++++++++++++++++++++++++++
3 files changed, 57 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 376e43fc72b9..27430e9dcfe3 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1456,6 +1456,12 @@ struct btf_mod_pair {
struct bpf_kfunc_desc_tab;
+enum bpf_priv_stack_mode {
+ NO_PRIV_STACK,
+ PRIV_STACK_SUB_PROG,
+ PRIV_STACK_ROOT_PROG,
+};
+
struct bpf_prog_aux {
atomic64_t refcnt;
u32 used_map_cnt;
@@ -1472,6 +1478,9 @@ struct bpf_prog_aux {
u32 ctx_arg_info_size;
u32 max_rdonly_access;
u32 max_rdwr_access;
+ enum bpf_priv_stack_mode priv_stack_mode;
+ u16 subtree_stack_depth; /* Subtree stack depth if PRIV_STACK_ROOT_PROG, 0 otherwise */
+ void __percpu *priv_stack_ptr;
struct btf *attach_btf;
const struct bpf_ctx_arg_aux *ctx_arg_info;
struct mutex dst_mutex; /* protects dst_* pointers below, *after* prog becomes visible */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 14d9288441f2..aee0055def4f 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1240,6 +1240,7 @@ void __weak bpf_jit_free(struct bpf_prog *fp)
struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
bpf_jit_binary_free(hdr);
+ free_percpu(fp->aux->priv_stack_ptr);
this should be also put to the x86 version of the bpf_jit_free ?
Thanks for spotting this! Indeed, the x86 version of bpf_jit_free should
be used. Will fix in the next revision.
jirka
WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(fp));
}
[...]
