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bpf, x86: Use emit_nops to replace memcpy x86_nops

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Move emit_nops() before emit_prologue() and replace
memcpy(prog, x86_nops[5], X86_PATCH_SIZE) with emit_nops(&prog, X86_PATCH_SIZE).

Signed-off-by: Leon Hwang <hffilwlqm@gmail.com>
Link: https://lore.kernel.org/r/20240104142226.87869-2-hffilwlqm@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Leon Hwang 2024-01-04 22:22:23 +08:00 • committed by Alexei Starovoitov
parent 61a40c1249
commit 00bc898880
1 changed files with 22 additions and 25 deletions
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47
arch/x86/net/bpf_jit_comp.c
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@ -307,6 +307,25 @@ static void pop_callee_regs(u8 **pprog, bool *callee_regs_used)
*pprog = prog;
}
static void emit_nops(u8 **pprog, int len)
{
u8 *prog = *pprog;
int i, noplen;
while (len > 0) {
noplen = len;
if (noplen > ASM_NOP_MAX)
noplen = ASM_NOP_MAX;
for (i = 0; i < noplen; i++)
EMIT1(x86_nops[noplen][i]);
len -= noplen;
}
*pprog = prog;
}
/*
* Emit the various CFI preambles, see asm/cfi.h and the comments about FineIBT
* in arch/x86/kernel/alternative.c
@ -385,8 +404,7 @@ static void emit_prologue(u8 **pprog, u32 stack_depth, bool ebpf_from_cbpf,
/* BPF trampoline can be made to work without these nops,
* but let's waste 5 bytes for now and optimize later
*/
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
emit_nops(&prog, X86_PATCH_SIZE);
if (!ebpf_from_cbpf) {
if (tail_call_reachable && !is_subprog)
/* When it's the entry of the whole tailcall context,
@ -692,8 +710,7 @@ static void emit_bpf_tail_call_direct(struct bpf_prog *bpf_prog,
if (stack_depth)
EMIT3_off32(0x48, 0x81, 0xC4, round_up(stack_depth, 8));
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
emit_nops(&prog, X86_PATCH_SIZE);
/* out: */
ctx->tail_call_direct_label = prog - start;
@ -1055,25 +1072,6 @@ static void detect_reg_usage(struct bpf_insn *insn, int insn_cnt,
}
}
static void emit_nops(u8 **pprog, int len)
{
u8 *prog = *pprog;
int i, noplen;
while (len > 0) {
noplen = len;
if (noplen > ASM_NOP_MAX)
noplen = ASM_NOP_MAX;
for (i = 0; i < noplen; i++)
EMIT1(x86_nops[noplen][i]);
len -= noplen;
}
*pprog = prog;
}
/* emit the 3-byte VEX prefix
*
* r: same as rex.r, extra bit for ModRM reg field
@ -2700,8 +2698,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *rw_im
/* remember return value in a stack for bpf prog to access */
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
im->ip_after_call = image + (prog - (u8 *)rw_image);
memcpy(prog, x86_nops[5], X86_PATCH_SIZE);
prog += X86_PATCH_SIZE;
emit_nops(&prog, X86_PATCH_SIZE);
}
if (fmod_ret->nr_links) {