diff mbox series

[bpf,2/2] riscv, bpf: Track both a0 (RISC-V ABI) and a5 (BPF) return values

Message ID 20231004120706.52848-3-bjorn@kernel.org (mailing list archive)
State Accepted
Commit 7112cd26e606c7ba51f9cc5c1905f06039f6f379
Delegated to: BPF
Headers show
Series riscv, bpf: Properly sign-extend return values | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for bpf
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 9 this patch: 9
netdev/cc_maintainers warning 11 maintainers not CCed: paul.walmsley@sifive.com martin.lau@linux.dev jolsa@kernel.org haoluo@google.com sdf@google.com john.fastabend@gmail.com yonghong.song@linux.dev aou@eecs.berkeley.edu palmer@dabbelt.com kpsingh@kernel.org song@kernel.org
netdev/build_clang success Errors and warnings before: 9 this patch: 9
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 9 this patch: 9
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 38 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
bpf/vmtest-bpf-PR success PR summary
bpf/vmtest-bpf-VM_Test-0 success Logs for ShellCheck
bpf/vmtest-bpf-VM_Test-3 success Logs for build for x86_64 with gcc
bpf/vmtest-bpf-VM_Test-1 success Logs for build for aarch64 with gcc
bpf/vmtest-bpf-VM_Test-2 success Logs for build for s390x with gcc
bpf/vmtest-bpf-VM_Test-6 success Logs for test_maps on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-5 success Logs for set-matrix
bpf/vmtest-bpf-VM_Test-4 success Logs for build for x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-9 success Logs for test_maps on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-7 success Logs for test_maps on s390x with gcc
bpf/vmtest-bpf-VM_Test-8 success Logs for test_maps on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-10 success Logs for test_progs on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-12 success Logs for test_progs on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-11 success Logs for test_progs on s390x with gcc
bpf/vmtest-bpf-VM_Test-13 success Logs for test_progs on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-15 success Logs for test_progs_no_alu32 on s390x with gcc
bpf/vmtest-bpf-VM_Test-14 success Logs for test_progs_no_alu32 on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-17 success Logs for test_progs_no_alu32 on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-16 success Logs for test_progs_no_alu32 on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-18 success Logs for test_progs_no_alu32_parallel on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-19 success Logs for test_progs_no_alu32_parallel on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-21 success Logs for test_progs_parallel on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-20 success Logs for test_progs_no_alu32_parallel on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-26 success Logs for test_verifier on x86_64 with gcc
bpf/vmtest-bpf-VM_Test-27 success Logs for test_verifier on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-24 success Logs for test_verifier on aarch64 with gcc
bpf/vmtest-bpf-VM_Test-23 success Logs for test_progs_parallel on x86_64 with llvm-16
bpf/vmtest-bpf-VM_Test-25 success Logs for test_verifier on s390x with gcc
bpf/vmtest-bpf-VM_Test-28 success Logs for veristat
bpf/vmtest-bpf-VM_Test-22 success Logs for test_progs_parallel on x86_64 with gcc

Commit Message

Björn Töpel Oct. 4, 2023, 12:07 p.m. UTC 
From: Björn Töpel <bjorn@rivosinc.com>

The RISC-V BPF uses a5 for BPF return values, which are zero-extended,
whereas the RISC-V ABI uses a0 which is sign-extended. In other words,
a5 and a0 can differ, and are used in different context.

The BPF trampoline are used for both BPF programs, and regular kernel
functions.

Make sure that the RISC-V BPF trampoline saves, and restores both a0
and a5.

Fixes: 49b5e77ae3e2 ("riscv, bpf: Add bpf trampoline support for RV64")
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
---
 arch/riscv/net/bpf_jit_comp64.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index de4c9957d223..8581693e62d3 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -759,8 +759,10 @@  static int invoke_bpf_prog(struct bpf_tramp_link *l, int args_off, int retval_of
 	if (ret)
 		return ret;
 
-	if (save_ret)
-		emit_sd(RV_REG_FP, -retval_off, regmap[BPF_REG_0], ctx);
+	if (save_ret) {
+		emit_sd(RV_REG_FP, -retval_off, RV_REG_A0, ctx);
+		emit_sd(RV_REG_FP, -(retval_off - 8), regmap[BPF_REG_0], ctx);
+	}
 
 	/* update branch with beqz */
 	if (ctx->insns) {
@@ -853,7 +855,7 @@  static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 
 	save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
 	if (save_ret) {
-		stack_size += 8;
+		stack_size += 16; /* Save both A5 (BPF R0) and A0 */
 		retval_off = stack_size;
 	}
 
@@ -957,6 +959,7 @@  static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 		if (ret)
 			goto out;
 		emit_sd(RV_REG_FP, -retval_off, RV_REG_A0, ctx);
+		emit_sd(RV_REG_FP, -(retval_off - 8), regmap[BPF_REG_0], ctx);
 		im->ip_after_call = ctx->insns + ctx->ninsns;
 		/* 2 nops reserved for auipc+jalr pair */
 		emit(rv_nop(), ctx);
@@ -988,8 +991,10 @@  static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 	if (flags & BPF_TRAMP_F_RESTORE_REGS)
 		restore_args(nregs, args_off, ctx);
 
-	if (save_ret)
+	if (save_ret) {
 		emit_ld(RV_REG_A0, -retval_off, RV_REG_FP, ctx);
+		emit_ld(regmap[BPF_REG_0], -(retval_off - 8), RV_REG_FP, ctx);
+	}
 
 	emit_ld(RV_REG_S1, -sreg_off, RV_REG_FP, ctx);