Currently the caller-allocated portion of the stack frame is described
using constants, hardcoded values, and an ASCII drawing, making it
harder than necessary to ensure that everything is in sync.
Declare a struct and use offsetof() and offsetofend() macros to refer
to various values stored within the frame.
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
---
arch/s390/net/bpf_jit.h | 55 ----------------------------
arch/s390/net/bpf_jit_comp.c | 69 ++++++++++++++++++++++++------------
2 files changed, 47 insertions(+), 77 deletions(-)
delete mode 100644 arch/s390/net/bpf_jit.h
diff --git a/arch/s390/net/bpf_jit.h b/arch/s390/net/bpf_jit.h
deleted file mode 100644
index 7822ea92e54a..000000000000
--- a/arch/s390/net/bpf_jit.h
+++ /dev/null
@@ -1,55 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * BPF Jit compiler defines
- *
- * Copyright IBM Corp. 2012,2015
- *
- * Author(s): Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
- * Michael Holzheu <holzheu@xxxxxxxxxxxxxxxxxx>
- */
-
-#ifndef __ARCH_S390_NET_BPF_JIT_H
-#define __ARCH_S390_NET_BPF_JIT_H
-
-#ifndef __ASSEMBLY__
-
-#include <linux/filter.h>
-#include <linux/types.h>
-
-#endif /* __ASSEMBLY__ */
-
-/*
- * Stackframe layout (packed stack):
- *
- * ^ high
- * +---------------+ |
- * | old backchain | |
- * +---------------+ |
- * | r15 - r6 | |
- * +---------------+ |
- * | 4 byte align | |
- * | tail_call_cnt | |
- * BFP -> +===============+ |
- * | | |
- * | BPF stack | |
- * | | |
- * R15+160 -> +---------------+ |
- * | new backchain | |
- * R15+152 -> +---------------+ |
- * | + 152 byte SA | |
- * R15 -> +---------------+ + low
- *
- * We get 160 bytes stack space from calling function, but only use
- * 12 * 8 byte for old backchain, r15..r6, and tail_call_cnt.
- *
- * The stack size used by the BPF program ("BPF stack" above) is passed
- * via "aux->stack_depth".
- */
-#define STK_SPACE_ADD (160)
-#define STK_160_UNUSED (160 - 12 * 8)
-#define STK_OFF (STK_SPACE_ADD - STK_160_UNUSED)
-
-#define STK_OFF_R6 (160 - 11 * 8) /* Offset of r6 on stack */
-#define STK_OFF_TCCNT (160 - 12 * 8) /* Offset of tail_call_cnt on stack */
-
-#endif /* __ARCH_S390_NET_BPF_JIT_H */
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 76ad52a24444..8bb738f1b1b6 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -32,7 +32,6 @@
#include <asm/set_memory.h>
#include <asm/text-patching.h>
#include <asm/unwind.h>
-#include "bpf_jit.h"
struct bpf_jit {
u32 seen; /* Flags to remember seen eBPF instructions */
@@ -54,7 +53,7 @@ struct bpf_jit {
int prologue_plt; /* Start of prologue hotpatch PLT */
int kern_arena; /* Pool offset of kernel arena address */
u64 user_arena; /* User arena address */
- u32 frame_off; /* Offset of frame from %r15 */
+ u32 frame_off; /* Offset of struct bpf_prog from %r15 */
};
#define SEEN_MEM BIT(0) /* use mem[] for temporary storage */
@@ -426,12 +425,26 @@ static void jit_fill_hole(void *area, unsigned int size)
memset(area, 0, size);
}
+/*
+ * Caller-allocated part of the frame.
+ * Thanks to packed stack, its otherwise unused initial part can be used for
+ * the BPF stack and for the next frame.
+ */
+struct prog_frame {
+ u64 unused[8];
+ /* BPF stack starts here and grows towards 0 */
+ u32 tail_call_cnt;
+ u32 pad;
+ u64 r6[10]; /* r6 - r15 */
+ u64 backchain;
+} __packed;
+
/*
* Save registers from "rs" (register start) to "re" (register end) on stack
*/
static void save_regs(struct bpf_jit *jit, u32 rs, u32 re)
{
- u32 off = STK_OFF_R6 + (rs - 6) * 8;
+ u32 off = offsetof(struct prog_frame, r6) + (rs - 6) * 8;
if (rs == re)
/* stg %rs,off(%r15) */
@@ -446,7 +459,7 @@ static void save_regs(struct bpf_jit *jit, u32 rs, u32 re)
*/
static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re)
{
- u32 off = jit->frame_off + STK_OFF_R6 + (rs - 6) * 8;
+ u32 off = jit->frame_off + offsetof(struct prog_frame, r6) + (rs - 6) * 8;
if (rs == re)
/* lg %rs,off(%r15) */
@@ -570,10 +583,12 @@ static void bpf_jit_plt(struct bpf_plt *plt, void *ret, void *target)
* Emit function prologue
*
* Save registers and create stack frame if necessary.
- * See stack frame layout description in "bpf_jit.h"!
+ * Stack frame layout is described by struct prog_frame.
*/
static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp)
{
+ BUILD_BUG_ON(sizeof(struct prog_frame) != STACK_FRAME_OVERHEAD);
+
/* No-op for hotpatching */
/* brcl 0,prologue_plt */
EMIT6_PCREL_RILC(0xc0040000, 0, jit->prologue_plt);
@@ -581,8 +596,9 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp)
if (!bpf_is_subprog(fp)) {
/* Initialize the tail call counter in the main program. */
- /* xc STK_OFF_TCCNT(4,%r15),STK_OFF_TCCNT(%r15) */
- _EMIT6(0xd703f000 | STK_OFF_TCCNT, 0xf000 | STK_OFF_TCCNT);
+ /* xc tail_call_cnt(4,%r15),tail_call_cnt(%r15) */
+ _EMIT6(0xd703f000 | offsetof(struct prog_frame, tail_call_cnt),
+ 0xf000 | offsetof(struct prog_frame, tail_call_cnt));
} else {
/*
* Skip the tail call counter initialization in subprograms.
@@ -625,13 +641,15 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp)
if (is_first_pass(jit) || (jit->seen & SEEN_STACK)) {
/* lgr %w1,%r15 (backchain) */
EMIT4(0xb9040000, REG_W1, REG_15);
- /* la %bfp,STK_160_UNUSED(%r15) (BPF frame pointer) */
- EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15, STK_160_UNUSED);
+ /* la %bfp,unused_end(%r15) (BPF frame pointer) */
+ EMIT4_DISP(0x41000000, BPF_REG_FP, REG_15,
+ offsetofend(struct prog_frame, unused));
/* aghi %r15,-frame_off */
EMIT4_IMM(0xa70b0000, REG_15, -jit->frame_off);
- /* stg %w1,152(%r15) (backchain) */
+ /* stg %w1,backchain(%r15) */
EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
- REG_15, 152);
+ REG_15,
+ offsetof(struct prog_frame, backchain));
}
}
@@ -1774,9 +1792,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
* Note 2: We assume that the verifier does not let us call the
* main program, which clears the tail call counter on entry.
*/
- /* mvc STK_OFF_TCCNT(4,%r15),frame_off+STK_OFF_TCCNT(%r15) */
- _EMIT6(0xd203f000 | STK_OFF_TCCNT,
- 0xf000 | (jit->frame_off + STK_OFF_TCCNT));
+ /* mvc tail_call_cnt(4,%r15),frame_off+tail_call_cnt(%r15) */
+ _EMIT6(0xd203f000 | offsetof(struct prog_frame, tail_call_cnt),
+ 0xf000 | (jit->frame_off +
+ offsetof(struct prog_frame, tail_call_cnt)));
/* Sign-extend the kfunc arguments. */
if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
@@ -1827,7 +1846,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
* goto out;
*/
- off = jit->frame_off + STK_OFF_TCCNT;
+ off = jit->frame_off +
+ offsetof(struct prog_frame, tail_call_cnt);
/* lhi %w0,1 */
EMIT4_IMM(0xa7080000, REG_W0, 1);
/* laal %w1,%w0,off(%r15) */
@@ -2160,7 +2180,9 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
jit->prg = 0;
jit->excnt = 0;
if (is_first_pass(jit) || (jit->seen & SEEN_STACK))
- jit->frame_off = STK_OFF + round_up(fp->aux->stack_depth, 8);
+ jit->frame_off = sizeof(struct prog_frame) -
+ offsetofend(struct prog_frame, unused) +
+ round_up(fp->aux->stack_depth, 8);
else
jit->frame_off = 0;
@@ -2642,9 +2664,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
/* stg %r1,backchain_off(%r15) */
EMIT6_DISP_LH(0xe3000000, 0x0024, REG_1, REG_0, REG_15,
tjit->backchain_off);
- /* mvc tccnt_off(4,%r15),stack_size+STK_OFF_TCCNT(%r15) */
+ /* mvc tccnt_off(4,%r15),stack_size+tail_call_cnt(%r15) */
_EMIT6(0xd203f000 | tjit->tccnt_off,
- 0xf000 | (tjit->stack_size + STK_OFF_TCCNT));
+ 0xf000 | (tjit->stack_size +
+ offsetof(struct prog_frame, tail_call_cnt)));
/* stmg %r2,%rN,fwd_reg_args_off(%r15) */
if (nr_reg_args)
EMIT6_DISP_LH(0xeb000000, 0x0024, REG_2,
@@ -2781,8 +2804,9 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
(nr_stack_args * sizeof(u64) - 1) << 16 |
tjit->stack_args_off,
0xf000 | tjit->orig_stack_args_off);
- /* mvc STK_OFF_TCCNT(4,%r15),tccnt_off(%r15) */
- _EMIT6(0xd203f000 | STK_OFF_TCCNT, 0xf000 | tjit->tccnt_off);
+ /* mvc tail_call_cnt(4,%r15),tccnt_off(%r15) */
+ _EMIT6(0xd203f000 | offsetof(struct prog_frame, tail_call_cnt),
+ 0xf000 | tjit->tccnt_off);
/* lgr %r1,%r8 */
EMIT4(0xb9040000, REG_1, REG_8);
/* %r1() */
@@ -2839,8 +2863,9 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
if (flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET))
EMIT6_DISP_LH(0xe3000000, 0x0004, REG_2, REG_0, REG_15,
tjit->retval_off);
- /* mvc stack_size+STK_OFF_TCCNT(4,%r15),tccnt_off(%r15) */
- _EMIT6(0xd203f000 | (tjit->stack_size + STK_OFF_TCCNT),
+ /* mvc stack_size+tail_call_cnt(4,%r15),tccnt_off(%r15) */
+ _EMIT6(0xd203f000 | (tjit->stack_size +
+ offsetof(struct prog_frame, tail_call_cnt)),
0xf000 | tjit->tccnt_off);
/* aghi %r15,stack_size */
EMIT4_IMM(0xa70b0000, REG_15, tjit->stack_size);
--
2.49.0
