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bpf: Introduce bpf register BPF_REG_PARAMS

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Introduce BPF_REG_PARAMS as a dedicated BPF register for stack
argument accesses. It occupies the BPF register number 11 (R11),
which is used as the base pointer for the stack argument area,
keeping it separate from the R10-based (BPF_REG_FP) program stack.

The kernel-internal hidden register BPF_REG_AX previously occupied
slot 11 (MAX_BPF_REG). With BPF_REG_PARAMS taking that slot,
BPF_REG_AX moves to slot 12 and MAX_BPF_EXT_REG increases
accordingly.

Acked-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20260423033506.2542005-1-yonghong.song@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yonghong Song 2026-04-22 20:35:06 -07:00 committed by Alexei Starovoitov
parent 9b9f0b4270
commit 246ad6e5ee
6 changed files with 62 additions and 61 deletions
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5
include/linux/filter.h
View File

@ -58,8 +58,9 @@ struct ctl_table_header;
#define BPF_REG_H BPF_REG_9 /* hlen, callee-saved */
/* Kernel hidden auxiliary/helper register. */
#define BPF_REG_AX MAX_BPF_REG
#define MAX_BPF_EXT_REG (MAX_BPF_REG + 1)
#define BPF_REG_PARAMS MAX_BPF_REG
#define BPF_REG_AX (MAX_BPF_REG + 1)
#define MAX_BPF_EXT_REG (MAX_BPF_REG + 2)
#define MAX_BPF_JIT_REG MAX_BPF_EXT_REG
/* unused opcode to mark special call to bpf_tail_call() helper */

4
kernel/bpf/core.c
View File

@ -1299,8 +1299,8 @@ static int bpf_jit_blind_insn(const struct bpf_insn *from,
u32 imm_rnd = get_random_u32();
s16 off;
BUILD_BUG_ON(BPF_REG_AX + 1 != MAX_BPF_JIT_REG);
BUILD_BUG_ON(MAX_BPF_REG + 1 != MAX_BPF_JIT_REG);
BUILD_BUG_ON(BPF_REG_PARAMS + 2 != MAX_BPF_JIT_REG);
BUILD_BUG_ON(BPF_REG_AX + 1 != MAX_BPF_JIT_REG);
/* Constraints on AX register:
*

14
tools/testing/selftests/bpf/prog_tests/ctx_rewrite.c
View File

@ -69,19 +69,19 @@ static struct test_case test_cases[] = {
#if defined(__x86_64__) || defined(__aarch64__)
{
N(SCHED_CLS, struct __sk_buff, tstamp),
.read = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
"if w11 & 0x4 goto pc+1;"
.read = "r12 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
"if w12 & 0x4 goto pc+1;"
"goto pc+4;"
"if w11 & 0x3 goto pc+1;"
"if w12 & 0x3 goto pc+1;"
"goto pc+2;"
"$dst = 0;"
"goto pc+1;"
"$dst = *(u64 *)($ctx + sk_buff::tstamp);",
.write = "r11 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
"if w11 & 0x4 goto pc+1;"
.write = "r12 = *(u8 *)($ctx + sk_buff::__mono_tc_offset);"
"if w12 & 0x4 goto pc+1;"
"goto pc+2;"
"w11 &= -4;"
"*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r11;"
"w12 &= -4;"
"*(u8 *)($ctx + sk_buff::__mono_tc_offset) = r12;"
"*(u64 *)($ctx + sk_buff::tstamp) = $src;",
},
#endif

24
tools/testing/selftests/bpf/progs/verifier_bpf_fastcall.c
View File

@ -630,13 +630,13 @@ __xlated("...")
__xlated("4: r0 = &(void __percpu *)(r0)")
__xlated("...")
/* may_goto expansion starts */
__xlated("6: r11 = *(u64 *)(r10 -24)")
__xlated("7: if r11 == 0x0 goto pc+6")
__xlated("8: r11 -= 1")
__xlated("9: if r11 != 0x0 goto pc+2")
__xlated("10: r11 = -24")
__xlated("6: r12 = *(u64 *)(r10 -24)")
__xlated("7: if r12 == 0x0 goto pc+6")
__xlated("8: r12 -= 1")
__xlated("9: if r12 != 0x0 goto pc+2")
__xlated("10: r12 = -24")
__xlated("11: call unknown")
__xlated("12: *(u64 *)(r10 -24) = r11")
__xlated("12: *(u64 *)(r10 -24) = r12")
/* may_goto expansion ends */
__xlated("13: *(u64 *)(r10 -8) = r1")
__xlated("14: exit")
@ -668,13 +668,13 @@ __xlated("1: *(u64 *)(r10 -16) =")
__xlated("2: r1 = 1")
__xlated("3: call bpf_get_smp_processor_id")
/* may_goto expansion starts */
__xlated("4: r11 = *(u64 *)(r10 -24)")
__xlated("5: if r11 == 0x0 goto pc+6")
__xlated("6: r11 -= 1")
__xlated("7: if r11 != 0x0 goto pc+2")
__xlated("8: r11 = -24")
__xlated("4: r12 = *(u64 *)(r10 -24)")
__xlated("5: if r12 == 0x0 goto pc+6")
__xlated("6: r12 -= 1")
__xlated("7: if r12 != 0x0 goto pc+2")
__xlated("8: r12 = -24")
__xlated("9: call unknown")
__xlated("10: *(u64 *)(r10 -24) = r11")
__xlated("10: *(u64 *)(r10 -24) = r12")
/* may_goto expansion ends */
__xlated("11: *(u64 *)(r10 -8) = r1")
__xlated("12: exit")

12
tools/testing/selftests/bpf/progs/verifier_may_goto_1.c
View File

@ -81,13 +81,13 @@ __arch_s390x
__arch_arm64
__xlated("0: *(u64 *)(r10 -16) = 65535")
__xlated("1: *(u64 *)(r10 -8) = 0")
__xlated("2: r11 = *(u64 *)(r10 -16)")
__xlated("3: if r11 == 0x0 goto pc+6")
__xlated("4: r11 -= 1")
__xlated("5: if r11 != 0x0 goto pc+2")
__xlated("6: r11 = -16")
__xlated("2: r12 = *(u64 *)(r10 -16)")
__xlated("3: if r12 == 0x0 goto pc+6")
__xlated("4: r12 -= 1")
__xlated("5: if r12 != 0x0 goto pc+2")
__xlated("6: r12 = -16")
__xlated("7: call unknown")
__xlated("8: *(u64 *)(r10 -16) = r11")
__xlated("8: *(u64 *)(r10 -16) = r12")
__xlated("9: r0 = 1")
__xlated("10: r0 = 2")
__xlated("11: exit")

64
tools/testing/selftests/bpf/progs/verifier_sdiv.c
View File

@ -778,10 +778,10 @@ __arch_x86_64
__xlated("0: r2 = 0x8000000000000000")
__xlated("2: r3 = -1")
__xlated("3: r4 = r2")
__xlated("4: r11 = r3")
__xlated("5: r11 += 1")
__xlated("6: if r11 > 0x1 goto pc+4")
__xlated("7: if r11 == 0x0 goto pc+1")
__xlated("4: r12 = r3")
__xlated("5: r12 += 1")
__xlated("6: if r12 > 0x1 goto pc+4")
__xlated("7: if r12 == 0x0 goto pc+1")
__xlated("8: r2 = 0")
__xlated("9: r2 = -r2")
__xlated("10: goto pc+1")
@ -812,10 +812,10 @@ __success __retval(-5)
__arch_x86_64
__xlated("0: r2 = 5")
__xlated("1: r3 = -1")
__xlated("2: r11 = r3")
__xlated("3: r11 += 1")
__xlated("4: if r11 > 0x1 goto pc+4")
__xlated("5: if r11 == 0x0 goto pc+1")
__xlated("2: r12 = r3")
__xlated("3: r12 += 1")
__xlated("4: if r12 > 0x1 goto pc+4")
__xlated("5: if r12 == 0x0 goto pc+1")
__xlated("6: r2 = 0")
__xlated("7: r2 = -r2")
__xlated("8: goto pc+1")
@ -890,10 +890,10 @@ __arch_x86_64
__xlated("0: w2 = -2147483648")
__xlated("1: w3 = -1")
__xlated("2: w4 = w2")
__xlated("3: r11 = r3")
__xlated("4: w11 += 1")
__xlated("5: if w11 > 0x1 goto pc+4")
__xlated("6: if w11 == 0x0 goto pc+1")
__xlated("3: r12 = r3")
__xlated("4: w12 += 1")
__xlated("5: if w12 > 0x1 goto pc+4")
__xlated("6: if w12 == 0x0 goto pc+1")
__xlated("7: w2 = 0")
__xlated("8: w2 = -w2")
__xlated("9: goto pc+1")
@ -925,10 +925,10 @@ __arch_x86_64
__xlated("0: w2 = -5")
__xlated("1: w3 = -1")
__xlated("2: w4 = w2")
__xlated("3: r11 = r3")
__xlated("4: w11 += 1")
__xlated("5: if w11 > 0x1 goto pc+4")
__xlated("6: if w11 == 0x0 goto pc+1")
__xlated("3: r12 = r3")
__xlated("4: w12 += 1")
__xlated("5: if w12 > 0x1 goto pc+4")
__xlated("6: if w12 == 0x0 goto pc+1")
__xlated("7: w2 = 0")
__xlated("8: w2 = -w2")
__xlated("9: goto pc+1")
@ -1004,10 +1004,10 @@ __arch_x86_64
__xlated("0: r2 = 0x8000000000000000")
__xlated("2: r3 = -1")
__xlated("3: r4 = r2")
__xlated("4: r11 = r3")
__xlated("5: r11 += 1")
__xlated("6: if r11 > 0x1 goto pc+3")
__xlated("7: if r11 == 0x1 goto pc+3")
__xlated("4: r12 = r3")
__xlated("5: r12 += 1")
__xlated("6: if r12 > 0x1 goto pc+3")
__xlated("7: if r12 == 0x1 goto pc+3")
__xlated("8: w2 = 0")
__xlated("9: goto pc+1")
__xlated("10: r2 s%= r3")
@ -1034,10 +1034,10 @@ __arch_x86_64
__xlated("0: r2 = 5")
__xlated("1: r3 = -1")
__xlated("2: r4 = r2")
__xlated("3: r11 = r3")
__xlated("4: r11 += 1")
__xlated("5: if r11 > 0x1 goto pc+3")
__xlated("6: if r11 == 0x1 goto pc+3")
__xlated("3: r12 = r3")
__xlated("4: r12 += 1")
__xlated("5: if r12 > 0x1 goto pc+3")
__xlated("6: if r12 == 0x1 goto pc+3")
__xlated("7: w2 = 0")
__xlated("8: goto pc+1")
__xlated("9: r2 s%= r3")
@ -1108,10 +1108,10 @@ __arch_x86_64
__xlated("0: w2 = -2147483648")
__xlated("1: w3 = -1")
__xlated("2: w4 = w2")
__xlated("3: r11 = r3")
__xlated("4: w11 += 1")
__xlated("5: if w11 > 0x1 goto pc+3")
__xlated("6: if w11 == 0x1 goto pc+4")
__xlated("3: r12 = r3")
__xlated("4: w12 += 1")
__xlated("5: if w12 > 0x1 goto pc+3")
__xlated("6: if w12 == 0x1 goto pc+4")
__xlated("7: w2 = 0")
__xlated("8: goto pc+1")
__xlated("9: w2 s%= w3")
@ -1140,10 +1140,10 @@ __arch_x86_64
__xlated("0: w2 = -5")
__xlated("1: w3 = -1")
__xlated("2: w4 = w2")
__xlated("3: r11 = r3")
__xlated("4: w11 += 1")
__xlated("5: if w11 > 0x1 goto pc+3")
__xlated("6: if w11 == 0x1 goto pc+4")
__xlated("3: r12 = r3")
__xlated("4: w12 += 1")
__xlated("5: if w12 > 0x1 goto pc+3")
__xlated("6: if w12 == 0x1 goto pc+4")
__xlated("7: w2 = 0")
__xlated("8: goto pc+1")
__xlated("9: w2 s%= w3")