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Subject[PATCH bpf-next v3 2/7] bpf: JIT helpers for fmod_ret progs
Date
From: KP Singh <kpsingh@google.com>

* Split the invoke_bpf program to prepare for special handling of
fmod_ret programs introduced in a subsequent patch.
* Move the definition of emit_cond_near_jump and emit_nops as they are
needed for fmod_ret.
* Refactor branch target alignment into its own generic helper function
i.e. emit_align.

Signed-off-by: KP Singh <kpsingh@google.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
---
arch/x86/net/bpf_jit_comp.c | 148 +++++++++++++++++++++---------------
1 file changed, 85 insertions(+), 63 deletions(-)

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 15c7d28bc05c..d6349e930b06 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1361,35 +1361,95 @@ static void restore_regs(const struct btf_func_model *m, u8 **prog, int nr_args,
-(stack_size - i * 8));
}

+static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
+ struct bpf_prog *p, int stack_size)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ if (emit_call(&prog, __bpf_prog_enter, prog))
+ return -EINVAL;
+ /* remember prog start time returned by __bpf_prog_enter */
+ emit_mov_reg(&prog, true, BPF_REG_6, BPF_REG_0);
+
+ /* arg1: lea rdi, [rbp - stack_size] */
+ EMIT4(0x48, 0x8D, 0x7D, -stack_size);
+ /* arg2: progs[i]->insnsi for interpreter */
+ if (!p->jited)
+ emit_mov_imm64(&prog, BPF_REG_2,
+ (long) p->insnsi >> 32,
+ (u32) (long) p->insnsi);
+ /* call JITed bpf program or interpreter */
+ if (emit_call(&prog, p->bpf_func, prog))
+ return -EINVAL;
+
+ /* arg1: mov rdi, progs[i] */
+ emit_mov_imm64(&prog, BPF_REG_1, (long) p >> 32,
+ (u32) (long) p);
+ /* arg2: mov rsi, rbx <- start time in nsec */
+ emit_mov_reg(&prog, true, BPF_REG_2, BPF_REG_6);
+ if (emit_call(&prog, __bpf_prog_exit, prog))
+ return -EINVAL;
+
+ *pprog = prog;
+ return 0;
+}
+
+static void emit_nops(u8 **pprog, unsigned int len)
+{
+ unsigned int i, noplen;
+ u8 *prog = *pprog;
+ int cnt = 0;
+
+ while (len > 0) {
+ noplen = len;
+
+ if (noplen > ASM_NOP_MAX)
+ noplen = ASM_NOP_MAX;
+
+ for (i = 0; i < noplen; i++)
+ EMIT1(ideal_nops[noplen][i]);
+ len -= noplen;
+ }
+
+ *pprog = prog;
+}
+
+static void emit_align(u8 **pprog, u32 align)
+{
+ u8 *target, *prog = *pprog;
+
+ target = PTR_ALIGN(prog, align);
+ if (target != prog)
+ emit_nops(&prog, target - prog);
+
+ *pprog = prog;
+}
+
+static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond)
+{
+ u8 *prog = *pprog;
+ int cnt = 0;
+ s64 offset;
+
+ offset = func - (ip + 2 + 4);
+ if (!is_simm32(offset)) {
+ pr_err("Target %p is out of range\n", func);
+ return -EINVAL;
+ }
+ EMIT2_off32(0x0F, jmp_cond + 0x10, offset);
+ *pprog = prog;
+ return 0;
+}
+
static int invoke_bpf(const struct btf_func_model *m, u8 **pprog,
struct bpf_tramp_progs *tp, int stack_size)
{
+ int i;
u8 *prog = *pprog;
- int cnt = 0, i;

for (i = 0; i < tp->nr_progs; i++) {
- if (emit_call(&prog, __bpf_prog_enter, prog))
- return -EINVAL;
- /* remember prog start time returned by __bpf_prog_enter */
- emit_mov_reg(&prog, true, BPF_REG_6, BPF_REG_0);
-
- /* arg1: lea rdi, [rbp - stack_size] */
- EMIT4(0x48, 0x8D, 0x7D, -stack_size);
- /* arg2: progs[i]->insnsi for interpreter */
- if (!tp->progs[i]->jited)
- emit_mov_imm64(&prog, BPF_REG_2,
- (long) tp->progs[i]->insnsi >> 32,
- (u32) (long) tp->progs[i]->insnsi);
- /* call JITed bpf program or interpreter */
- if (emit_call(&prog, tp->progs[i]->bpf_func, prog))
- return -EINVAL;
-
- /* arg1: mov rdi, progs[i] */
- emit_mov_imm64(&prog, BPF_REG_1, (long) tp->progs[i] >> 32,
- (u32) (long) tp->progs[i]);
- /* arg2: mov rsi, rbx <- start time in nsec */
- emit_mov_reg(&prog, true, BPF_REG_2, BPF_REG_6);
- if (emit_call(&prog, __bpf_prog_exit, prog))
+ if (invoke_bpf_prog(m, &prog, tp->progs[i], stack_size))
return -EINVAL;
}
*pprog = prog;
@@ -1531,42 +1591,6 @@ int arch_prepare_bpf_trampoline(void *image, void *image_end,
return prog - (u8 *)image;
}

-static int emit_cond_near_jump(u8 **pprog, void *func, void *ip, u8 jmp_cond)
-{
- u8 *prog = *pprog;
- int cnt = 0;
- s64 offset;
-
- offset = func - (ip + 2 + 4);
- if (!is_simm32(offset)) {
- pr_err("Target %p is out of range\n", func);
- return -EINVAL;
- }
- EMIT2_off32(0x0F, jmp_cond + 0x10, offset);
- *pprog = prog;
- return 0;
-}
-
-static void emit_nops(u8 **pprog, unsigned int len)
-{
- unsigned int i, noplen;
- u8 *prog = *pprog;
- int cnt = 0;
-
- while (len > 0) {
- noplen = len;
-
- if (noplen > ASM_NOP_MAX)
- noplen = ASM_NOP_MAX;
-
- for (i = 0; i < noplen; i++)
- EMIT1(ideal_nops[noplen][i]);
- len -= noplen;
- }
-
- *pprog = prog;
-}
-
static int emit_fallback_jump(u8 **pprog)
{
u8 *prog = *pprog;
@@ -1589,7 +1613,7 @@ static int emit_fallback_jump(u8 **pprog)

static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs)
{
- u8 *jg_reloc, *jg_target, *prog = *pprog;
+ u8 *jg_reloc, *prog = *pprog;
int pivot, err, jg_bytes = 1, cnt = 0;
s64 jg_offset;

@@ -1644,9 +1668,7 @@ static int emit_bpf_dispatcher(u8 **pprog, int a, int b, s64 *progs)
* Coding Rule 11: All branch targets should be 16-byte
* aligned.
*/
- jg_target = PTR_ALIGN(prog, 16);
- if (jg_target != prog)
- emit_nops(&prog, jg_target - prog);
+ emit_align(&prog, 16);
jg_offset = prog - jg_reloc;
emit_code(jg_reloc - jg_bytes, jg_offset, jg_bytes);

--
2.20.1
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