Re: [PATCH bpf-next] riscv, bpf: Fix RV32 broken build, and silence RV64 warning

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On 11/3/21 12:54 PM, Björn Töpel wrote:
Commit 252c765bd764 ("riscv, bpf: Add BPF exception tables") only
addressed RV64, and broke the RV32 build [1]. Fix by gating the exception
tables code with CONFIG_ARCH_RV64I.

Further, silence a "-Wmissing-prototypes" warning [2] in the RV64 BPF
JIT.

[1] https://lore.kernel.org/llvm/202111020610.9oy9Rr0G-lkp@xxxxxxxxx/
[2] https://lore.kernel.org/llvm/202110290334.2zdMyRq4-lkp@xxxxxxxxx/

Fixes: 252c765bd764 ("riscv, bpf: Add BPF exception tables")
Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxx>
---
Tong/Daniel: The RV32 build has been broken since Thursday. I'll try
to fast-track a bit, and commit a quick-fix for it. Hope that's OK
with you, Tong!

I've verified the build on my machine using riscv32 GCC 9.3.0 and
riscv64 GCC 11.2.0.

Thanks for the fix Bjorn!

arch/riscv/mm/extable.c         | 4 ++--
  arch/riscv/net/bpf_jit_comp64.c | 2 ++
  2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/mm/extable.c b/arch/riscv/mm/extable.c
index 18bf338303b6..ddb7d3b99e89 100644
--- a/arch/riscv/mm/extable.c
+++ b/arch/riscv/mm/extable.c
@@ -11,7 +11,7 @@
  #include <linux/module.h>
  #include <linux/uaccess.h>
-#ifdef CONFIG_BPF_JIT
+#if defined(CONFIG_BPF_JIT) && defined(CONFIG_ARCH_RV64I)
  int rv_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs);
  #endif
@@ -23,7 +23,7 @@ int fixup_exception(struct pt_regs *regs)
  	if (!fixup)
  		return 0;
-#ifdef CONFIG_BPF_JIT
+#if defined(CONFIG_BPF_JIT) && defined(CONFIG_ARCH_RV64I)
  	if (regs->epc >= BPF_JIT_REGION_START && regs->epc < BPF_JIT_REGION_END)
  		return rv_bpf_fixup_exception(fixup, regs);
  #endif
diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c
index 2ca345c7b0bf..f2a779c7e225 100644
--- a/arch/riscv/net/bpf_jit_comp64.c
+++ b/arch/riscv/net/bpf_jit_comp64.c
@@ -459,6 +459,8 @@ static int emit_call(bool fixed, u64 addr, struct rv_jit_context *ctx)
  #define BPF_FIXUP_OFFSET_MASK   GENMASK(26, 0)
  #define BPF_FIXUP_REG_MASK      GENMASK(31, 27)
+int rv_bpf_fixup_exception(const struct exception_table_entry *ex,
+				struct pt_regs *regs);

I'm okay to take this as a quick fix, but if its not too much hassle, could we add a
arch/riscv/include/asm/extable.h in similar fashion like arm64 or x86 where we move
the ex_handler_bpf() signature there, did you have a chance to check?

  int rv_bpf_fixup_exception(const struct exception_table_entry *ex,
  				struct pt_regs *regs)
  {

base-commit: cc0356d6a02e064387c16a83cb96fe43ef33181e


Thanks,
Daniel



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