From fa76cfe65c1d748ef418e930a4b631a03b28f04c Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Wed, 6 May 2020 20:51:32 +0100 Subject: arm64: bpf: Annotate JITed code for BTI In order to extend the protection offered by BTI to all code executing in kernel mode we need to annotate JITed BPF code appropriately for BTI. To do this we need to add a landing pad to the start of each BPF function and also immediately after the function prologue if we are emitting a function which can be tail called. Jumps within BPF functions are all to immediate offsets and therefore do not require landing pads. Signed-off-by: Mark Brown Reviewed-by: Catalin Marinas Link: https://lore.kernel.org/r/20200506195138.22086-6-broonie@kernel.org Signed-off-by: Will Deacon --- arch/arm64/net/bpf_jit.h | 8 ++++++++ arch/arm64/net/bpf_jit_comp.c | 12 ++++++++++++ 2 files changed, 20 insertions(+) (limited to 'arch/arm64/net') diff --git a/arch/arm64/net/bpf_jit.h b/arch/arm64/net/bpf_jit.h index eb73f9f72c46..05b477709b5f 100644 --- a/arch/arm64/net/bpf_jit.h +++ b/arch/arm64/net/bpf_jit.h @@ -189,4 +189,12 @@ /* Rn & Rm; set condition flags */ #define A64_TST(sf, Rn, Rm) A64_ANDS(sf, A64_ZR, Rn, Rm) +/* HINTs */ +#define A64_HINT(x) aarch64_insn_gen_hint(x) + +/* BTI */ +#define A64_BTI_C A64_HINT(AARCH64_INSN_HINT_BTIC) +#define A64_BTI_J A64_HINT(AARCH64_INSN_HINT_BTIJ) +#define A64_BTI_JC A64_HINT(AARCH64_INSN_HINT_BTIJC) + #endif /* _BPF_JIT_H */ diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index cdc79de0c794..83fa475c6b42 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -171,7 +171,11 @@ static inline int epilogue_offset(const struct jit_ctx *ctx) #define STACK_ALIGN(sz) (((sz) + 15) & ~15) /* Tail call offset to jump into */ +#if IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) +#define PROLOGUE_OFFSET 8 +#else #define PROLOGUE_OFFSET 7 +#endif static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) { @@ -208,6 +212,10 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) * */ + /* BTI landing pad */ + if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) + emit(A64_BTI_C, ctx); + /* Save FP and LR registers to stay align with ARM64 AAPCS */ emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx); emit(A64_MOV(1, A64_FP, A64_SP), ctx); @@ -230,6 +238,10 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) cur_offset, PROLOGUE_OFFSET); return -1; } + + /* BTI landing pad for the tail call, done with a BR */ + if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL)) + emit(A64_BTI_J, ctx); } ctx->stack_size = STACK_ALIGN(prog->aux->stack_depth); -- cgit