From: Ilya Leoshkevich <iii@linux.ibm.com>
To: stable@vger.kernel.org
Cc: Ilya Leoshkevich <iii@linux.ibm.com>,
Alexei Starovoitov <ast@kernel.org>
Subject: [PATCH 6.6.y 2/5] s390/bpf: Centralize frame offset calculations
Date: Thu, 16 Oct 2025 23:51:25 +0200 [thread overview]
Message-ID: <20251016215450.53494-3-iii@linux.ibm.com> (raw)
In-Reply-To: <20251016215450.53494-1-iii@linux.ibm.com>
commit b2268d550d20ff860bddfe3a91b1aec00414689a upstream.
The calculation of the distance from %r15 to the caller-allocated
portion of the stack frame is copy-pasted into multiple places in the
JIT code.
Move it to bpf_jit_prog() and save the result into bpf_jit::frame_off,
so that the other parts of the JIT can use it.
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20250624121501.50536-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
arch/s390/net/bpf_jit_comp.c | 56 +++++++++++++++++-------------------
1 file changed, 26 insertions(+), 30 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index fc61801c0f73c..0137fb579fdb9 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -53,6 +53,7 @@ struct bpf_jit {
int excnt; /* Number of exception table entries */
int prologue_plt_ret; /* Return address for prologue hotpatch PLT */
int prologue_plt; /* Start of prologue hotpatch PLT */
+ u32 frame_off; /* Offset of frame from %r15 */
};
#define SEEN_MEM BIT(0) /* use mem[] for temporary storage */
@@ -416,12 +417,9 @@ static void save_regs(struct bpf_jit *jit, u32 rs, u32 re)
/*
* Restore registers from "rs" (register start) to "re" (register end) on stack
*/
-static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re, u32 stack_depth)
+static void restore_regs(struct bpf_jit *jit, u32 rs, u32 re)
{
- u32 off = STK_OFF_R6 + (rs - 6) * 8;
-
- if (jit->seen & SEEN_STACK)
- off += STK_OFF + stack_depth;
+ u32 off = jit->frame_off + STK_OFF_R6 + (rs - 6) * 8;
if (rs == re)
/* lg %rs,off(%r15) */
@@ -465,8 +463,7 @@ static int get_end(u16 seen_regs, int start)
* Save and restore clobbered registers (6-15) on stack.
* We save/restore registers in chunks with gap >= 2 registers.
*/
-static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth,
- u16 extra_regs)
+static void save_restore_regs(struct bpf_jit *jit, int op, u16 extra_regs)
{
u16 seen_regs = jit->seen_regs | extra_regs;
const int last = 15, save_restore_size = 6;
@@ -489,7 +486,7 @@ static void save_restore_regs(struct bpf_jit *jit, int op, u32 stack_depth,
if (op == REGS_SAVE)
save_regs(jit, rs, re);
else
- restore_regs(jit, rs, re, stack_depth);
+ restore_regs(jit, rs, re);
re++;
} while (re <= last);
}
@@ -556,8 +553,7 @@ static void bpf_jit_plt(struct bpf_plt *plt, void *ret, void *target)
* Save registers and create stack frame if necessary.
* See stack frame layout description in "bpf_jit.h"!
*/
-static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
- u32 stack_depth)
+static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp)
{
/* No-op for hotpatching */
/* brcl 0,prologue_plt */
@@ -579,7 +575,7 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
/* Tail calls have to skip above initialization */
jit->tail_call_start = jit->prg;
/* Save registers */
- save_restore_regs(jit, REGS_SAVE, stack_depth, 0);
+ save_restore_regs(jit, REGS_SAVE, 0);
/* Setup literal pool */
if (is_first_pass(jit) || (jit->seen & SEEN_LITERAL)) {
if (!is_first_pass(jit) &&
@@ -599,8 +595,8 @@ static void bpf_jit_prologue(struct bpf_jit *jit, struct bpf_prog *fp,
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);
- /* aghi %r15,-STK_OFF */
- EMIT4_IMM(0xa70b0000, REG_15, -(STK_OFF + stack_depth));
+ /* aghi %r15,-frame_off */
+ EMIT4_IMM(0xa70b0000, REG_15, -jit->frame_off);
/* stg %w1,152(%r15) (backchain) */
EMIT6_DISP_LH(0xe3000000, 0x0024, REG_W1, REG_0,
REG_15, 152);
@@ -647,13 +643,13 @@ static void call_r1(struct bpf_jit *jit)
/*
* Function epilogue
*/
-static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
+static void bpf_jit_epilogue(struct bpf_jit *jit)
{
jit->exit_ip = jit->prg;
/* Load exit code: lgr %r2,%b0 */
EMIT4(0xb9040000, REG_2, BPF_REG_0);
/* Restore registers */
- save_restore_regs(jit, REGS_RESTORE, stack_depth, 0);
+ save_restore_regs(jit, REGS_RESTORE, 0);
if (nospec_uses_trampoline()) {
jit->r14_thunk_ip = jit->prg;
/* Generate __s390_indirect_jump_r14 thunk */
@@ -779,7 +775,7 @@ static int sign_extend(struct bpf_jit *jit, int r, u8 size, u8 flags)
* stack space for the large switch statement.
*/
static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
- int i, bool extra_pass, u32 stack_depth)
+ int i, bool extra_pass)
{
struct bpf_insn *insn = &fp->insnsi[i];
u32 dst_reg = insn->dst_reg;
@@ -1433,9 +1429,9 @@ 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),N(%r15) */
+ /* mvc STK_OFF_TCCNT(4,%r15),frame_off+STK_OFF_TCCNT(%r15) */
_EMIT6(0xd203f000 | STK_OFF_TCCNT,
- 0xf000 | (STK_OFF_TCCNT + STK_OFF + stack_depth));
+ 0xf000 | (jit->frame_off + STK_OFF_TCCNT));
/* Sign-extend the kfunc arguments. */
if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
@@ -1486,10 +1482,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
* goto out;
*/
- if (jit->seen & SEEN_STACK)
- off = STK_OFF_TCCNT + STK_OFF + stack_depth;
- else
- off = STK_OFF_TCCNT;
+ off = jit->frame_off + STK_OFF_TCCNT;
/* lhi %w0,1 */
EMIT4_IMM(0xa7080000, REG_W0, 1);
/* laal %w1,%w0,off(%r15) */
@@ -1519,7 +1512,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
/*
* Restore registers before calling function
*/
- save_restore_regs(jit, REGS_RESTORE, stack_depth, 0);
+ save_restore_regs(jit, REGS_RESTORE, 0);
/*
* goto *(prog->bpf_func + tail_call_start);
@@ -1822,7 +1815,7 @@ static int bpf_set_addr(struct bpf_jit *jit, int i)
* Compile eBPF program into s390x code
*/
static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
- bool extra_pass, u32 stack_depth)
+ bool extra_pass)
{
int i, insn_count, lit32_size, lit64_size;
@@ -1830,19 +1823,23 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
jit->lit64 = jit->lit64_start;
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);
+ else
+ jit->frame_off = 0;
- bpf_jit_prologue(jit, fp, stack_depth);
+ bpf_jit_prologue(jit, fp);
if (bpf_set_addr(jit, 0) < 0)
return -1;
for (i = 0; i < fp->len; i += insn_count) {
- insn_count = bpf_jit_insn(jit, fp, i, extra_pass, stack_depth);
+ insn_count = bpf_jit_insn(jit, fp, i, extra_pass);
if (insn_count < 0)
return -1;
/* Next instruction address */
if (bpf_set_addr(jit, i + insn_count) < 0)
return -1;
}
- bpf_jit_epilogue(jit, stack_depth);
+ bpf_jit_epilogue(jit);
lit32_size = jit->lit32 - jit->lit32_start;
lit64_size = jit->lit64 - jit->lit64_start;
@@ -1902,7 +1899,6 @@ static struct bpf_binary_header *bpf_jit_alloc(struct bpf_jit *jit,
*/
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
{
- u32 stack_depth = round_up(fp->aux->stack_depth, 8);
struct bpf_prog *tmp, *orig_fp = fp;
struct bpf_binary_header *header;
struct s390_jit_data *jit_data;
@@ -1955,7 +1951,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
* - 3: Calculate program size and addrs array
*/
for (pass = 1; pass <= 3; pass++) {
- if (bpf_jit_prog(&jit, fp, extra_pass, stack_depth)) {
+ if (bpf_jit_prog(&jit, fp, extra_pass)) {
fp = orig_fp;
goto free_addrs;
}
@@ -1969,7 +1965,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
goto free_addrs;
}
skip_init_ctx:
- if (bpf_jit_prog(&jit, fp, extra_pass, stack_depth)) {
+ if (bpf_jit_prog(&jit, fp, extra_pass)) {
bpf_jit_binary_free(header);
fp = orig_fp;
goto free_addrs;
--
2.51.0
next prev parent reply other threads:[~2025-10-16 21:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-16 21:51 [PATCH 6.6.y 0/5] s390/bpf: Tail call counter fixes Ilya Leoshkevich
2025-10-16 21:51 ` [PATCH 6.6.y 1/5] s390/bpf: Change seen_reg to a mask Ilya Leoshkevich
2025-10-16 21:51 ` Ilya Leoshkevich [this message]
2025-10-16 21:51 ` [PATCH 6.6.y 3/5] s390/bpf: Describe the frame using a struct instead of constants Ilya Leoshkevich
2025-10-16 21:51 ` [PATCH 6.6.y 4/5] s390/bpf: Write back tail call counter for BPF_PSEUDO_CALL Ilya Leoshkevich
2025-10-16 21:51 ` [PATCH 6.6.y 5/5] s390/bpf: Write back tail call counter for BPF_TRAMP_F_CALL_ORIG Ilya Leoshkevich
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