The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
89d21e259a94 ("powerpc/bpf/32: Fix Oops on tail call tests") 49c3af43e65f ("powerpc/bpf: Simplify bpf_to_ppc() and adopt it for powerpc64") 3a3fc9bf1039 ("powerpc64/bpf: Store temp registers' bpf to ppc mapping") 036d559c0bde ("powerpc/bpf: Use _Rn macros for GPRs") 576a6c3a00c1 ("powerpc/bpf: Move bpf_jit64.h into bpf_jit_comp64.c") 7b187dcdb5d3 ("powerpc/bpf: Cleanup bpf_jit.h") 794abc08d75e ("powerpc64/bpf: Get rid of PPC_BPF_[LL|STL|STLU] macros") 391c271f4deb ("powerpc64/bpf: Convert some of the uses of PPC_BPF_[LL|STL] to PPC_BPF_[LD|STD]") feb6307289d8 ("powerpc64/bpf: Optimize instruction sequence used for function calls") 43d636f8b4fd ("powerpc64/bpf elfv1: Do not load TOC before calling functions") b10cb163c4b3 ("powerpc64/bpf elfv2: Setup kernel TOC in r2 on entry") 1d4866d5652f ("powerpc64/bpf: Use r12 for constant blinding") c2067f7f8883 ("powerpc64/bpf: Do not save/restore LR on each call to bpf_stf_barrier()") 0ffdbce6f4a8 ("powerpc/bpf: Handle large branch ranges with BPF_EXIT") bafb5898de5d ("powerpc/bpf: Emit a single branch instruction for known short branch ranges") a8936569a07b ("powerpc/bpf: Always reallocate BPF_REG_5, BPF_REG_AX and TMP_REG when possible") 3f5f766d5f7f ("powerpc64/bpf: Limit 'ldbrx' to processors compliant with ISA v2.06") f9320c49993c ("powerpc/bpf: Update ldimm64 instructions during extra pass") 29ec39fcf11e ("Merge tag 'powerpc-5.17-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 89d21e259a94f7d5582ec675aa445f5a79f347e4 Mon Sep 17 00:00:00 2001 From: Christophe Leroy christophe.leroy@csgroup.eu Date: Thu, 24 Nov 2022 09:37:27 +0100 Subject: [PATCH] powerpc/bpf/32: Fix Oops on tail call tests
test_bpf tail call tests end up as:
test_bpf: #0 Tail call leaf jited:1 85 PASS test_bpf: #1 Tail call 2 jited:1 111 PASS test_bpf: #2 Tail call 3 jited:1 145 PASS test_bpf: #3 Tail call 4 jited:1 170 PASS test_bpf: #4 Tail call load/store leaf jited:1 190 PASS test_bpf: #5 Tail call load/store jited:1 BUG: Unable to handle kernel data access on write at 0xf1b4e000 Faulting instruction address: 0xbe86b710 Oops: Kernel access of bad area, sig: 11 [#1] BE PAGE_SIZE=4K MMU=Hash PowerMac Modules linked in: test_bpf(+) CPU: 0 PID: 97 Comm: insmod Not tainted 6.1.0-rc4+ #195 Hardware name: PowerMac3,1 750CL 0x87210 PowerMac NIP: be86b710 LR: be857e88 CTR: be86b704 REGS: f1b4df20 TRAP: 0300 Not tainted (6.1.0-rc4+) MSR: 00009032 <EE,ME,IR,DR,RI> CR: 28008242 XER: 00000000 DAR: f1b4e000 DSISR: 42000000 GPR00: 00000001 f1b4dfe0 c11d2280 00000000 00000000 00000000 00000002 00000000 GPR08: f1b4e000 be86b704 f1b4e000 00000000 00000000 100d816a f2440000 fe73baa8 GPR16: f2458000 00000000 c1941ae4 f1fe2248 00000045 c0de0000 f2458030 00000000 GPR24: 000003e8 0000000f f2458000 f1b4dc90 3e584b46 00000000 f24466a0 c1941a00 NIP [be86b710] 0xbe86b710 LR [be857e88] __run_one+0xec/0x264 [test_bpf] Call Trace: [f1b4dfe0] [00000002] 0x2 (unreliable) Instruction dump: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX ---[ end trace 0000000000000000 ]---
This is a tentative to write above the stack. The problem is encoutered with tests added by commit 38608ee7b690 ("bpf, tests: Add load store test case for tail call")
This happens because tail call is done to a BPF prog with a different stack_depth. At the time being, the stack is kept as is when the caller tail calls its callee. But at exit, the callee restores the stack based on its own properties. Therefore here, at each run, r1 is erroneously increased by 32 - 16 = 16 bytes.
This was done that way in order to pass the tail call count from caller to callee through the stack. As powerpc32 doesn't have a red zone in the stack, it was necessary the maintain the stack as is for the tail call. But it was not anticipated that the BPF frame size could be different.
Let's take a new approach. Use register r4 to carry the tail call count during the tail call, and save it into the stack at function entry if required. This means the input parameter must be in r3, which is more correct as it is a 32 bits parameter, then tail call better match with normal BPF function entry, the down side being that we move that input parameter back and forth between r3 and r4. That can be optimised later.
Doing that also has the advantage of maximising the common parts between tail calls and a normal function exit.
With the fix, tail call tests are now successfull:
test_bpf: #0 Tail call leaf jited:1 53 PASS test_bpf: #1 Tail call 2 jited:1 115 PASS test_bpf: #2 Tail call 3 jited:1 154 PASS test_bpf: #3 Tail call 4 jited:1 165 PASS test_bpf: #4 Tail call load/store leaf jited:1 101 PASS test_bpf: #5 Tail call load/store jited:1 141 PASS test_bpf: #6 Tail call error path, max count reached jited:1 994 PASS test_bpf: #7 Tail call count preserved across function calls jited:1 140975 PASS test_bpf: #8 Tail call error path, NULL target jited:1 110 PASS test_bpf: #9 Tail call error path, index out of range jited:1 69 PASS test_bpf: test_tail_calls: Summary: 10 PASSED, 0 FAILED, [10/10 JIT'ed]
Suggested-by: Naveen N. Rao naveen.n.rao@linux.vnet.ibm.com Fixes: 51c66ad849a7 ("powerpc/bpf: Implement extended BPF on PPC32") Cc: stable@vger.kernel.org Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/757acccb7fbfc78efa42dcf3c974b46678198905.166927888...
diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index 43f1c76d48ce..a379b0ce19ff 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -113,23 +113,19 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx) { int i;
- /* First arg comes in as a 32 bits pointer. */ - EMIT(PPC_RAW_MR(bpf_to_ppc(BPF_REG_1), _R3)); - EMIT(PPC_RAW_LI(bpf_to_ppc(BPF_REG_1) - 1, 0)); + /* Initialize tail_call_cnt, to be skipped if we do tail calls. */ + EMIT(PPC_RAW_LI(_R4, 0)); + +#define BPF_TAILCALL_PROLOGUE_SIZE 4 + EMIT(PPC_RAW_STWU(_R1, _R1, -BPF_PPC_STACKFRAME(ctx)));
- /* - * Initialize tail_call_cnt in stack frame if we do tail calls. - * Otherwise, put in NOPs so that it can be skipped when we are - * invoked through a tail call. - */ if (ctx->seen & SEEN_TAILCALL) - EMIT(PPC_RAW_STW(bpf_to_ppc(BPF_REG_1) - 1, _R1, - bpf_jit_stack_offsetof(ctx, BPF_PPC_TC))); - else - EMIT(PPC_RAW_NOP()); + EMIT(PPC_RAW_STW(_R4, _R1, bpf_jit_stack_offsetof(ctx, BPF_PPC_TC)));
-#define BPF_TAILCALL_PROLOGUE_SIZE 16 + /* First arg comes in as a 32 bits pointer. */ + EMIT(PPC_RAW_MR(bpf_to_ppc(BPF_REG_1), _R3)); + EMIT(PPC_RAW_LI(bpf_to_ppc(BPF_REG_1) - 1, 0));
/* * We need a stack frame, but we don't necessarily need to @@ -170,24 +166,24 @@ static void bpf_jit_emit_common_epilogue(u32 *image, struct codegen_context *ctx for (i = BPF_PPC_NVR_MIN; i <= 31; i++) if (bpf_is_seen_register(ctx, i)) EMIT(PPC_RAW_LWZ(i, _R1, bpf_jit_stack_offsetof(ctx, i))); -} - -void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) -{ - EMIT(PPC_RAW_MR(_R3, bpf_to_ppc(BPF_REG_0))); - - bpf_jit_emit_common_epilogue(image, ctx); - - /* Tear down our stack frame */
if (ctx->seen & SEEN_FUNC) EMIT(PPC_RAW_LWZ(_R0, _R1, BPF_PPC_STACKFRAME(ctx) + PPC_LR_STKOFF));
+ /* Tear down our stack frame */ EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_PPC_STACKFRAME(ctx)));
if (ctx->seen & SEEN_FUNC) EMIT(PPC_RAW_MTLR(_R0));
+} + +void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx) +{ + EMIT(PPC_RAW_MR(_R3, bpf_to_ppc(BPF_REG_0))); + + bpf_jit_emit_common_epilogue(image, ctx); + EMIT(PPC_RAW_BLR()); }
@@ -244,7 +240,6 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o EMIT(PPC_RAW_RLWINM(_R3, b2p_index, 2, 0, 29)); EMIT(PPC_RAW_ADD(_R3, _R3, b2p_bpf_array)); EMIT(PPC_RAW_LWZ(_R3, _R3, offsetof(struct bpf_array, ptrs))); - EMIT(PPC_RAW_STW(_R0, _R1, bpf_jit_stack_offsetof(ctx, BPF_PPC_TC)));
/* * if (prog == NULL) @@ -255,19 +250,14 @@ static int bpf_jit_emit_tail_call(u32 *image, struct codegen_context *ctx, u32 o
/* goto *(prog->bpf_func + prologue_size); */ EMIT(PPC_RAW_LWZ(_R3, _R3, offsetof(struct bpf_prog, bpf_func))); - - if (ctx->seen & SEEN_FUNC) - EMIT(PPC_RAW_LWZ(_R0, _R1, BPF_PPC_STACKFRAME(ctx) + PPC_LR_STKOFF)); - EMIT(PPC_RAW_ADDIC(_R3, _R3, BPF_TAILCALL_PROLOGUE_SIZE)); - - if (ctx->seen & SEEN_FUNC) - EMIT(PPC_RAW_MTLR(_R0)); - EMIT(PPC_RAW_MTCTR(_R3));
EMIT(PPC_RAW_MR(_R3, bpf_to_ppc(BPF_REG_1)));
+ /* Put tail_call_cnt in r4 */ + EMIT(PPC_RAW_MR(_R4, _R0)); + /* tear restore NVRs, ... */ bpf_jit_emit_common_epilogue(image, ctx);