diff options
Diffstat (limited to 'arch/x86/net/bpf_jit_comp32.c')
| -rw-r--r-- | arch/x86/net/bpf_jit_comp32.c | 198 |
1 files changed, 198 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index d17b67c69f89..0a7a2870f111 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -1390,6 +1390,19 @@ static inline void emit_push_r64(const u8 src[], u8 **pprog) *pprog = prog; } +static void emit_push_r32(const u8 src[], u8 **pprog) +{ + u8 *prog = *pprog; + int cnt = 0; + + /* mov ecx,dword ptr [ebp+off] */ + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, IA32_ECX), STACK_VAR(src_lo)); + /* push ecx */ + EMIT1(0x51); + + *pprog = prog; +} + static u8 get_cond_jmp_opcode(const u8 op, bool is_cmp_lo) { u8 jmp_cond; @@ -1459,6 +1472,174 @@ static u8 get_cond_jmp_opcode(const u8 op, bool is_cmp_lo) return jmp_cond; } +/* i386 kernel compiles with "-mregparm=3". From gcc document: + * + * ==== snippet ==== + * regparm (number) + * On x86-32 targets, the regparm attribute causes the compiler + * to pass arguments number one to (number) if they are of integral + * type in registers EAX, EDX, and ECX instead of on the stack. + * Functions that take a variable number of arguments continue + * to be passed all of their arguments on the stack. + * ==== snippet ==== + * + * The first three args of a function will be considered for + * putting into the 32bit register EAX, EDX, and ECX. + * + * Two 32bit registers are used to pass a 64bit arg. + * + * For example, + * void foo(u32 a, u32 b, u32 c, u32 d): + * u32 a: EAX + * u32 b: EDX + * u32 c: ECX + * u32 d: stack + * + * void foo(u64 a, u32 b, u32 c): + * u64 a: EAX (lo32) EDX (hi32) + * u32 b: ECX + * u32 c: stack + * + * void foo(u32 a, u64 b, u32 c): + * u32 a: EAX + * u64 b: EDX (lo32) ECX (hi32) + * u32 c: stack + * + * void foo(u32 a, u32 b, u64 c): + * u32 a: EAX + * u32 b: EDX + * u64 c: stack + * + * The return value will be stored in the EAX (and EDX for 64bit value). + * + * For example, + * u32 foo(u32 a, u32 b, u32 c): + * return value: EAX + * + * u64 foo(u32 a, u32 b, u32 c): + * return value: EAX (lo32) EDX (hi32) + * + * Notes: + * The verifier only accepts function having integer and pointers + * as its args and return value, so it does not have + * struct-by-value. + * + * emit_kfunc_call() finds out the btf_func_model by calling + * bpf_jit_find_kfunc_model(). A btf_func_model + * has the details about the number of args, size of each arg, + * and the size of the return value. + * + * It first decides how many args can be passed by EAX, EDX, and ECX. + * That will decide what args should be pushed to the stack: + * [first_stack_regno, last_stack_regno] are the bpf regnos + * that should be pushed to the stack. + * + * It will first push all args to the stack because the push + * will need to use ECX. Then, it moves + * [BPF_REG_1, first_stack_regno) to EAX, EDX, and ECX. + * + * When emitting a call (0xE8), it needs to figure out + * the jmp_offset relative to the jit-insn address immediately + * following the call (0xE8) instruction. At this point, it knows + * the end of the jit-insn address after completely translated the + * current (BPF_JMP | BPF_CALL) bpf-insn. It is passed as "end_addr" + * to the emit_kfunc_call(). Thus, it can learn the "immediate-follow-call" + * address by figuring out how many jit-insn is generated between + * the call (0xE8) and the end_addr: + * - 0-1 jit-insn (3 bytes each) to restore the esp pointer if there + * is arg pushed to the stack. + * - 0-2 jit-insns (3 bytes each) to handle the return value. + */ +static int emit_kfunc_call(const struct bpf_prog *bpf_prog, u8 *end_addr, + const struct bpf_insn *insn, u8 **pprog) +{ + const u8 arg_regs[] = { IA32_EAX, IA32_EDX, IA32_ECX }; + int i, cnt = 0, first_stack_regno, last_stack_regno; + int free_arg_regs = ARRAY_SIZE(arg_regs); + const struct btf_func_model *fm; + int bytes_in_stack = 0; + const u8 *cur_arg_reg; + u8 *prog = *pprog; + s64 jmp_offset; + + fm = bpf_jit_find_kfunc_model(bpf_prog, insn); + if (!fm) + return -EINVAL; + + first_stack_regno = BPF_REG_1; + for (i = 0; i < fm->nr_args; i++) { + int regs_needed = fm->arg_size[i] > sizeof(u32) ? 2 : 1; + + if (regs_needed > free_arg_regs) + break; + + free_arg_regs -= regs_needed; + first_stack_regno++; + } + + /* Push the args to the stack */ + last_stack_regno = BPF_REG_0 + fm->nr_args; + for (i = last_stack_regno; i >= first_stack_regno; i--) { + if (fm->arg_size[i - 1] > sizeof(u32)) { + emit_push_r64(bpf2ia32[i], &prog); + bytes_in_stack += 8; + } else { + emit_push_r32(bpf2ia32[i], &prog); + bytes_in_stack += 4; + } + } + + cur_arg_reg = &arg_regs[0]; + for (i = BPF_REG_1; i < first_stack_regno; i++) { + /* mov e[adc]x,dword ptr [ebp+off] */ + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, *cur_arg_reg++), + STACK_VAR(bpf2ia32[i][0])); + if (fm->arg_size[i - 1] > sizeof(u32)) + /* mov e[adc]x,dword ptr [ebp+off] */ + EMIT3(0x8B, add_2reg(0x40, IA32_EBP, *cur_arg_reg++), + STACK_VAR(bpf2ia32[i][1])); + } + + if (bytes_in_stack) + /* add esp,"bytes_in_stack" */ + end_addr -= 3; + + /* mov dword ptr [ebp+off],edx */ + if (fm->ret_size > sizeof(u32)) + end_addr -= 3; + + /* mov dword ptr [ebp+off],eax */ + if (fm->ret_size) + end_addr -= 3; + + jmp_offset = (u8 *)__bpf_call_base + insn->imm - end_addr; + if (!is_simm32(jmp_offset)) { + pr_err("unsupported BPF kernel function jmp_offset:%lld\n", + jmp_offset); + return -EINVAL; + } + + EMIT1_off32(0xE8, jmp_offset); + + if (fm->ret_size) + /* mov dword ptr [ebp+off],eax */ + EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EAX), + STACK_VAR(bpf2ia32[BPF_REG_0][0])); + + if (fm->ret_size > sizeof(u32)) + /* mov dword ptr [ebp+off],edx */ + EMIT3(0x89, add_2reg(0x40, IA32_EBP, IA32_EDX), + STACK_VAR(bpf2ia32[BPF_REG_0][1])); + + if (bytes_in_stack) + /* add esp,"bytes_in_stack" */ + EMIT3(0x83, add_1reg(0xC0, IA32_ESP), bytes_in_stack); + + *pprog = prog; + + return 0; +} + static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, int oldproglen, struct jit_context *ctx) { @@ -1888,6 +2069,18 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, if (insn->src_reg == BPF_PSEUDO_CALL) goto notyet; + if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) { + int err; + + err = emit_kfunc_call(bpf_prog, + image + addrs[i], + insn, &prog); + + if (err) + return err; + break; + } + func = (u8 *) __bpf_call_base + imm32; jmp_offset = func - (image + addrs[i]); @@ -2393,3 +2586,8 @@ out: tmp : orig_prog); return prog; } + +bool bpf_jit_supports_kfunc_call(void) +{ + return true; +} |