x86 allows using up to 6 registers to pass arguments between function calls. This value is hardcoded in multiple places, use a define for this value.
Signed-off-by: Alexis Lothoré (eBPF Foundation) alexis.lothore@bootlin.com --- arch/x86/net/bpf_jit_comp.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 15672cb926fc1817f97d2cd1c55d1575803f6958..9689834de1bb1a90fdc28156e0e2a56ac0ff2076 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -61,6 +61,8 @@ static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len) #define EMIT_ENDBR_POISON() #endif
+#define MAX_REGS_FOR_ARGS 6 + static bool is_imm8(int value) { return value <= 127 && value >= -128; @@ -2710,10 +2712,10 @@ static int get_nr_used_regs(const struct btf_func_model *m)
for (i = 0; i < min_t(int, m->nr_args, MAX_BPF_FUNC_ARGS); i++) { arg_regs = (m->arg_size[i] + 7) / 8; - if (nr_used_regs + arg_regs <= 6) + if (nr_used_regs + arg_regs <= MAX_REGS_FOR_ARGS) nr_used_regs += arg_regs;
- if (nr_used_regs >= 6) + if (nr_used_regs >= MAX_REGS_FOR_ARGS) break; }
@@ -2751,7 +2753,7 @@ static void save_args(const struct btf_func_model *m, u8 **prog, * the arg1-5,arg7 will be passed by regs, and arg6 will * by stack. */ - if (nr_regs + arg_regs > 6) { + if (nr_regs + arg_regs > MAX_REGS_FOR_ARGS) { /* copy function arguments from origin stack frame * into current stack frame. * @@ -2811,7 +2813,7 @@ static void restore_regs(const struct btf_func_model *m, u8 **prog, */ for (i = 0; i < min_t(int, m->nr_args, MAX_BPF_FUNC_ARGS); i++) { arg_regs = (m->arg_size[i] + 7) / 8; - if (nr_regs + arg_regs <= 6) { + if (nr_regs + arg_regs <= MAX_REGS_FOR_ARGS) { for (j = 0; j < arg_regs; j++) { emit_ldx(prog, BPF_DW, nr_regs == 5 ? X86_REG_R9 : BPF_REG_1 + nr_regs, @@ -2824,7 +2826,7 @@ static void restore_regs(const struct btf_func_model *m, u8 **prog, stack_size -= 8 * arg_regs; }
- if (nr_regs >= 6) + if (nr_regs >= MAX_REGS_FOR_ARGS) break; } } @@ -3149,7 +3151,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im stack_size += (sizeof(struct bpf_tramp_run_ctx) + 7) & ~0x7; run_ctx_off = stack_size;
- if (nr_regs > 6 && (flags & BPF_TRAMP_F_CALL_ORIG)) { + if (nr_regs > MAX_REGS_FOR_ARGS && (flags & BPF_TRAMP_F_CALL_ORIG)) { /* the space that used to pass arguments on-stack */ stack_size += (nr_regs - get_nr_used_regs(m)) * 8; /* make sure the stack pointer is 16-byte aligned if we