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| author | Tiezhu Yang <yangtiezhu@loongson.cn> | 2022-08-29 11:05:09 +0800 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2022-08-29 15:38:14 +0200 |
| commit | bbcf0f55e57841e532ab395596db9197e8d53e8d (patch) | |
| tree | 064f8ae5f1073140956797ba0d93b8a0ed9843ed | |
| parent | aa75622c3be4d5819ce69c714acbcbd67bba5d65 (diff) | |
| download | linux-bbcf0f55e57841e532ab395596db9197e8d53e8d.tar.gz linux-bbcf0f55e57841e532ab395596db9197e8d53e8d.tar.bz2 linux-bbcf0f55e57841e532ab395596db9197e8d53e8d.zip | |
bpf, mips: No need to use min() to get MAX_TAIL_CALL_CNT
MAX_TAIL_CALL_CNT is 33, so min(MAX_TAIL_CALL_CNT, 0xffff) is always
MAX_TAIL_CALL_CNT, it is better to use MAX_TAIL_CALL_CNT directly.
At the same time, add BUILD_BUG_ON(MAX_TAIL_CALL_CNT > 0xffff) with a
comment on why the assertion is there.
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Suggested-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/1661742309-2320-1-git-send-email-yangtiezhu@loongson.cn
| -rw-r--r-- | arch/mips/net/bpf_jit_comp32.c | 10 | ||||
| -rw-r--r-- | arch/mips/net/bpf_jit_comp64.c | 10 |
2 files changed, 18 insertions, 2 deletions
diff --git a/arch/mips/net/bpf_jit_comp32.c b/arch/mips/net/bpf_jit_comp32.c index 83c975d5cca2..ace5db3fbd17 100644 --- a/arch/mips/net/bpf_jit_comp32.c +++ b/arch/mips/net/bpf_jit_comp32.c @@ -1377,11 +1377,19 @@ void build_prologue(struct jit_context *ctx) int stack, saved, locals, reserved; /* + * In the unlikely event that the TCC limit is raised to more + * than 16 bits, it is clamped to the maximum value allowed for + * the generated code (0xffff). It is better fail to compile + * instead of degrading gracefully. + */ + BUILD_BUG_ON(MAX_TAIL_CALL_CNT > 0xffff); + + /* * The first two instructions initialize TCC in the reserved (for us) * 16-byte area in the parent's stack frame. On a tail call, the * calling function jumps into the prologue after these instructions. */ - emit(ctx, ori, MIPS_R_T9, MIPS_R_ZERO, min(MAX_TAIL_CALL_CNT, 0xffff)); + emit(ctx, ori, MIPS_R_T9, MIPS_R_ZERO, MAX_TAIL_CALL_CNT); emit(ctx, sw, MIPS_R_T9, 0, MIPS_R_SP); /* diff --git a/arch/mips/net/bpf_jit_comp64.c b/arch/mips/net/bpf_jit_comp64.c index 6475828ffb36..0e7c1bdcf914 100644 --- a/arch/mips/net/bpf_jit_comp64.c +++ b/arch/mips/net/bpf_jit_comp64.c @@ -548,11 +548,19 @@ void build_prologue(struct jit_context *ctx) int stack, saved, locals, reserved; /* + * In the unlikely event that the TCC limit is raised to more + * than 16 bits, it is clamped to the maximum value allowed for + * the generated code (0xffff). It is better fail to compile + * instead of degrading gracefully. + */ + BUILD_BUG_ON(MAX_TAIL_CALL_CNT > 0xffff); + + /* * The first instruction initializes the tail call count register. * On a tail call, the calling function jumps into the prologue * after this instruction. */ - emit(ctx, ori, tc, MIPS_R_ZERO, min(MAX_TAIL_CALL_CNT, 0xffff)); + emit(ctx, ori, tc, MIPS_R_ZERO, MAX_TAIL_CALL_CNT); /* === Entry-point for tail calls === */ |