On 7/24/24 11:18 PM, Hao Peng wrote:
On Sat, Jul 13, 2024 at 12:43 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
On Wed, Jul 10, 2024 at 10:45 PM <flyingpenghao@xxxxxxxxx> wrote:
By tracing the call chain, we found that do_misc_fixups consumed a lot
of stack space. mark it as noinline_for_stack to prevent it from spreading
to bpf_check's stack size.
...
-static int do_misc_fixups(struct bpf_verifier_env *env)
+static noinline_for_stack int do_misc_fixups(struct bpf_verifier_env *env)
Now we're getting somewhere, but this is not a fix.
It may shut up the warn, but it will only increase the total stack usage.
Looking at C code do_misc_fixups() needs ~200 bytes worth of stack
space for insn_buf[16] and spill/fill.
That's far from the artificial 2k limit.
Please figure out what exact variable is causing kasan to consume
so much stack. You may need to analyze compiler internals and
do more homework.
What is before/after stack usage ? with and without kasan?
With gcc try
+CFLAGS_verifier.o += -fstack-usage
I see:
sort -k2 -n kernel/bpf/verifier.su |tail -10
../kernel/bpf/verifier.c:13087:12:adjust_ptr_min_max_vals 240
dynamic,bounded
../kernel/bpf/verifier.c:20804:12:do_check_common 248 dynamic,bounded
../kernel/bpf/verifier.c:19151:12:convert_ctx_accesses 256 static
../kernel/bpf/verifier.c:7450:12:check_mem_reg 256 static
../kernel/bpf/verifier.c:7482:12:check_kfunc_mem_size_reg 256 static
../kernel/bpf/verifier.c:10268:12:check_helper_call.isra 272
dynamic,bounded
../kernel/bpf/verifier.c:21562:5:bpf_check 296 dynamic,bounded
../kernel/bpf/verifier.c:19860:12:do_misc_fixups 320 static
../kernel/bpf/verifier.c:13991:12:adjust_reg_min_max_vals 392 static
../kernel/bpf/verifier.c:12280:12:check_kfunc_call.isra 408
dynamic,bounded
do_misc_fixups() is not the smallest, but not that large either.
If I use gcc, I get the same result as you, but if I use llvm to build
the kernel, the result is like this：
# sort -k2 -n kernel/bpf/verifier.su | tail -10
kernel/bpf/verifier.c:14026:adjust_reg_min_max_vals 440 static
kernel/bpf/verifier.c:7432:check_mem_reg 440 static
kernel/bpf/verifier.c:15955:check_cfg 472 static
kernel/bpf/verifier.c:7464:check_kfunc_mem_size_reg 472 static
kernel/bpf/verifier.c:15104:check_cond_jmp_op 504 static
kernel/bpf/verifier.c:4166:__mark_chain_precision 504 static
kernel/bpf/verifier.c:10239:check_helper_call 536 static
kernel/bpf/verifier.c:17744:do_check 792 static
kernel/bpf/verifier.c:12248:check_kfunc_call 984 static
kernel/bpf/verifier.c:21486:bpf_check 2456 static
Obviously, do_misc_fixups is automatically inlined into bpf_check.
So adding noinline_for_stack to the do_misc_fixups function is a solution.
Looks like you are building your own kernel with KASAN.
You can change config CONFIG_FRAME_WARN value. In your config file you
have CONFIG_FRAME_WARN=2048. You can change it to
CONFIG_FRAME_WARN=4096 which should fix the issue.
Thanks.
Do in-depth analysis instead of silencing the warn.
pw-bot: cr
