[RFC PATCH bpf-next v2 11/16] bpf: allow tailcalls in subprograms for MIPS64/MIPS32
From: Tony Ambardar <hidden>
Date: 2021-10-05 08:31:58
Also in:
bpf, netdev
Subsystem:
bpf jit for mips (32-bit and 64-bit), bpf jit for x86 64-bit, bpf [core], bpf [general] (safe dynamic programs and tools), mips, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Johan Almbladh, Paul Burton, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Thomas Bogendoerfer, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
The BPF core/verifier is hard-coded to permit mixing bpf2bpf and tail calls for only x86-64. Change the logic to instead rely on a new weak function 'bool bpf_jit_supports_subprog_tailcalls(void)', which a capable JIT backend can override. Update the x86-64 eBPF JIT to reflect this, and also enable the feature for the MIPS64/MIPS32 JIT. Signed-off-by: Tony Ambardar <redacted> --- arch/mips/net/ebpf_jit.c | 6 ++++++ arch/x86/net/bpf_jit_comp.c | 6 ++++++ include/linux/filter.h | 1 + kernel/bpf/core.c | 6 ++++++ kernel/bpf/verifier.c | 3 ++- 5 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c
index 7d8ed8bb19ab..501c1d532be6 100644
--- a/arch/mips/net/ebpf_jit.c
+++ b/arch/mips/net/ebpf_jit.c@@ -2416,3 +2416,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) bpf_jit_binary_free(header); goto out_ctx; } + +/* Indicate the JIT backend supports mixing bpf2bpf and tailcalls. */ +bool bpf_jit_supports_subprog_tailcalls(void) +{ + return true; +}
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 3ae729bb2475..2d78588fb5b5 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c@@ -2367,3 +2367,9 @@ bool bpf_jit_supports_kfunc_call(void) { return true; } + +/* Indicate the JIT backend supports mixing bpf2bpf and tailcalls. */ +bool bpf_jit_supports_subprog_tailcalls(void) +{ + return true; +}
diff --git a/include/linux/filter.h b/include/linux/filter.h
index 16e5cebea82c..50b50fb271b5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h@@ -933,6 +933,7 @@ u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog); void bpf_jit_compile(struct bpf_prog *prog); bool bpf_jit_needs_zext(void); +bool bpf_jit_supports_subprog_tailcalls(void); bool bpf_jit_supports_kfunc_call(void); bool bpf_helper_changes_pkt_data(void *func);
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 189934d2a3f2..c82b48ed0005 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c@@ -2366,6 +2366,12 @@ bool __weak bpf_jit_needs_zext(void) return false; } +/* Return TRUE if the JIT backend supports mixing bpf2bpf and tailcalls. */ +bool __weak bpf_jit_supports_subprog_tailcalls(void) +{ + return false; +} + bool __weak bpf_jit_supports_kfunc_call(void) { return false;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6e2ebcb0d66f..267de5428fad 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c@@ -5144,7 +5144,8 @@ static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id) static bool allow_tail_call_in_subprogs(struct bpf_verifier_env *env) { - return env->prog->jit_requested && IS_ENABLED(CONFIG_X86_64); + return env->prog->jit_requested && + bpf_jit_supports_subprog_tailcalls(); } static int check_map_func_compatibility(struct bpf_verifier_env *env,
--
2.25.1