bpf, x86: Simplify the parsing logic of structure parameters
Extra_nregs of structure parameters and nr_args can be added directly at the beginning, and using a flip flag to identifiy structure parameters. Meantime, renaming some variables to make them more sense. Signed-off-by: Pu Lehui <pulehui@huawei.com> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/r/20230105035026.3091988-1-pulehui@huaweicloud.com Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
This commit is contained in:
Pu Lehui
Martin KaFai Lau
parent
129d868ede
commit
7f78804957
@ -1857,62 +1857,59 @@ emit_jmp:
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return proglen;
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}
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static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
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static void save_regs(const struct btf_func_model *m, u8 **prog, int nr_regs,
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int stack_size)
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{
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int i, j, arg_size, nr_regs;
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int i, j, arg_size;
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bool next_same_struct = false;
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/* Store function arguments to stack.
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* For a function that accepts two pointers the sequence will be:
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* mov QWORD PTR [rbp-0x10],rdi
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* mov QWORD PTR [rbp-0x8],rsi
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*/
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for (i = 0, j = 0; i < min(nr_args, 6); i++) {
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if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) {
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nr_regs = (m->arg_size[i] + 7) / 8;
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for (i = 0, j = 0; i < min(nr_regs, 6); i++) {
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/* The arg_size is at most 16 bytes, enforced by the verifier. */
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arg_size = m->arg_size[j];
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if (arg_size > 8) {
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arg_size = 8;
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} else {
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nr_regs = 1;
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arg_size = m->arg_size[i];
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next_same_struct = !next_same_struct;
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}
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while (nr_regs) {
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emit_stx(prog, bytes_to_bpf_size(arg_size),
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BPF_REG_FP,
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j == 5 ? X86_REG_R9 : BPF_REG_1 + j,
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-(stack_size - j * 8));
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nr_regs--;
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j++;
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}
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emit_stx(prog, bytes_to_bpf_size(arg_size),
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BPF_REG_FP,
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i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
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-(stack_size - i * 8));
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j = next_same_struct ? j : j + 1;
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}
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}
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static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
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static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_regs,
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int stack_size)
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{
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int i, j, arg_size, nr_regs;
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int i, j, arg_size;
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bool next_same_struct = false;
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/* Restore function arguments from stack.
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* For a function that accepts two pointers the sequence will be:
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* EMIT4(0x48, 0x8B, 0x7D, 0xF0); mov rdi,QWORD PTR [rbp-0x10]
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* EMIT4(0x48, 0x8B, 0x75, 0xF8); mov rsi,QWORD PTR [rbp-0x8]
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*/
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for (i = 0, j = 0; i < min(nr_args, 6); i++) {
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if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG) {
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nr_regs = (m->arg_size[i] + 7) / 8;
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for (i = 0, j = 0; i < min(nr_regs, 6); i++) {
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/* The arg_size is at most 16 bytes, enforced by the verifier. */
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arg_size = m->arg_size[j];
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if (arg_size > 8) {
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arg_size = 8;
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} else {
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nr_regs = 1;
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arg_size = m->arg_size[i];
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next_same_struct = !next_same_struct;
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}
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while (nr_regs) {
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emit_ldx(prog, bytes_to_bpf_size(arg_size),
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j == 5 ? X86_REG_R9 : BPF_REG_1 + j,
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BPF_REG_FP,
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-(stack_size - j * 8));
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nr_regs--;
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j++;
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}
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emit_ldx(prog, bytes_to_bpf_size(arg_size),
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i == 5 ? X86_REG_R9 : BPF_REG_1 + i,
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BPF_REG_FP,
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-(stack_size - i * 8));
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j = next_same_struct ? j : j + 1;
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}
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}
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@ -2138,8 +2135,8 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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struct bpf_tramp_links *tlinks,
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void *func_addr)
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{
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int ret, i, nr_args = m->nr_args, extra_nregs = 0;
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int regs_off, ip_off, args_off, stack_size = nr_args * 8, run_ctx_off;
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int i, ret, nr_regs = m->nr_args, stack_size = 0;
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int regs_off, nregs_off, ip_off, run_ctx_off;
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struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
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struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
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struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
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@ -2148,17 +2145,14 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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u8 *prog;
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bool save_ret;
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/* x86-64 supports up to 6 arguments. 7+ can be added in the future */
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if (nr_args > 6)
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return -ENOTSUPP;
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for (i = 0; i < MAX_BPF_FUNC_ARGS; i++) {
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/* extra registers for struct arguments */
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for (i = 0; i < m->nr_args; i++)
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if (m->arg_flags[i] & BTF_FMODEL_STRUCT_ARG)
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extra_nregs += (m->arg_size[i] + 7) / 8 - 1;
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}
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if (nr_args + extra_nregs > 6)
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nr_regs += (m->arg_size[i] + 7) / 8 - 1;
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/* x86-64 supports up to 6 arguments. 7+ can be added in the future */
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if (nr_regs > 6)
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return -ENOTSUPP;
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stack_size += extra_nregs * 8;
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/* Generated trampoline stack layout:
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*
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@ -2172,7 +2166,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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* [ ... ]
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* RBP - regs_off [ reg_arg1 ] program's ctx pointer
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*
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* RBP - args_off [ arg regs count ] always
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* RBP - nregs_off [ regs count ] always
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*
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* RBP - ip_off [ traced function ] BPF_TRAMP_F_IP_ARG flag
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*
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@ -2184,11 +2178,12 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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if (save_ret)
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stack_size += 8;
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stack_size += nr_regs * 8;
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regs_off = stack_size;
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/* args count */
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/* regs count */
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stack_size += 8;
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args_off = stack_size;
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nregs_off = stack_size;
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if (flags & BPF_TRAMP_F_IP_ARG)
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stack_size += 8; /* room for IP address argument */
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@ -2221,11 +2216,11 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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EMIT1(0x53); /* push rbx */
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/* Store number of argument registers of the traced function:
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* mov rax, nr_args + extra_nregs
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* mov QWORD PTR [rbp - args_off], rax
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* mov rax, nr_regs
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* mov QWORD PTR [rbp - nregs_off], rax
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*/
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emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_args + extra_nregs);
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emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -args_off);
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emit_mov_imm64(&prog, BPF_REG_0, 0, (u32) nr_regs);
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emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -nregs_off);
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if (flags & BPF_TRAMP_F_IP_ARG) {
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/* Store IP address of the traced function:
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@ -2236,7 +2231,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -ip_off);
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}
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save_regs(m, &prog, nr_args, regs_off);
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save_regs(m, &prog, nr_regs, regs_off);
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if (flags & BPF_TRAMP_F_CALL_ORIG) {
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/* arg1: mov rdi, im */
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@ -2266,7 +2261,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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}
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if (flags & BPF_TRAMP_F_CALL_ORIG) {
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restore_regs(m, &prog, nr_args, regs_off);
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restore_regs(m, &prog, nr_regs, regs_off);
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if (flags & BPF_TRAMP_F_ORIG_STACK) {
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emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
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@ -2307,7 +2302,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
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}
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if (flags & BPF_TRAMP_F_RESTORE_REGS)
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restore_regs(m, &prog, nr_args, regs_off);
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restore_regs(m, &prog, nr_regs, regs_off);
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/* This needs to be done regardless. If there were fmod_ret programs,
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* the return value is only updated on the stack and still needs to be
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