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Groups > linux.kernel > #1268296 > unrolled thread
| Started by | Yang Shi <yang.shi@linaro.org> |
|---|---|
| First post | 2015-11-12 23:20 +0100 |
| Last post | 2015-11-13 04:30 +0100 |
| Articles | 6 — 3 participants |
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[PATCH V2 0/2] arm64: bpf: correct JIT stack setup and make it align with ARM64 AAPCS Yang Shi <yang.shi@linaro.org> - 2015-11-12 23:20 +0100
[PATCH 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS Yang Shi <yang.shi@linaro.org> - 2015-11-12 23:20 +0100
Re: [PATCH 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS Z Lim <zlim.lnx@gmail.com> - 2015-11-13 04:30 +0100
Re: [PATCH 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS "Shi, Yang" <yang.shi@linaro.org> - 2015-11-13 18:30 +0100
[PATCH 1/2] arm64: bpf: fix JIT frame pointer setup Yang Shi <yang.shi@linaro.org> - 2015-11-12 23:20 +0100
Re: [PATCH 1/2] arm64: bpf: fix JIT frame pointer setup Z Lim <zlim.lnx@gmail.com> - 2015-11-13 04:30 +0100
| From | Yang Shi <yang.shi@linaro.org> |
|---|---|
| Date | 2015-11-12 23:20 +0100 |
| Subject | [PATCH V2 0/2] arm64: bpf: correct JIT stack setup and make it align with ARM64 AAPCS |
| Message-ID | <qu8nL-6oo-1@gated-at.bofh.it> |
Changelog in V2:
Split to two patches according to the suggestion from Zi Shen Lim
Show A64_FP in stack layout diagram
Correct "+64" to "-64"
Yang Shi (2):
arm64: bpf: fix JIT frame pointer setup
arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS
arch/arm64/net/bpf_jit_comp.c | 38 +++++++++++++++++++++++++++++++-------
1 file changed, 31 insertions(+), 7 deletions(-)
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| From | Yang Shi <yang.shi@linaro.org> |
|---|---|
| Date | 2015-11-12 23:20 +0100 |
| Subject | [PATCH 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS |
| Message-ID | <qu8nM-6oo-29@gated-at.bofh.it> |
| In reply to | #1268296 |
Save and restore FP/LR in BPF prog prologue and epilogue, save SP to FP
in prologue in order to get the correct stack backtrace.
However, ARM64 JIT used FP (x29) as eBPF fp register, FP is subjected to
change during function call so it may cause the BPF prog stack base address
change too.
Use x25 to replace FP as BPF stack base register (fp). Since x25 is callee
saved register, so it will keep intact during function call.
It is initialized in BPF prog prologue when BPF prog is started to run
everytime. When BPF prog exits, it could be just tossed.
So, the BPF stack layout looks like:
high
original A64_SP => 0:+-----+ BPF prologue
| | FP/LR and callee saved registers
BPF fp register => -64:+-----+
| |
| ... | BPF prog stack
| |
| |
current A64_SP/FP => +-----+
| |
| ... | Function call stack
| |
+-----+
low
CC: Zi Shen Lim <zlim.lnx@gmail.com>
CC: Xi Wang <xi.wang@gmail.com>
Signed-off-by: Yang Shi <yang.shi@linaro.org>
---
arch/arm64/net/bpf_jit_comp.c | 34 +++++++++++++++++++++++++++++-----
1 file changed, 29 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index ac8b548..8753bb7 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -50,7 +50,7 @@ static const int bpf2a64[] = {
[BPF_REG_8] = A64_R(21),
[BPF_REG_9] = A64_R(22),
/* read-only frame pointer to access stack */
- [BPF_REG_FP] = A64_FP,
+ [BPF_REG_FP] = A64_R(25),
/* temporary register for internal BPF JIT */
[TMP_REG_1] = A64_R(23),
[TMP_REG_2] = A64_R(24),
@@ -155,17 +155,41 @@ static void build_prologue(struct jit_ctx *ctx)
stack_size += 4; /* extra for skb_copy_bits buffer */
stack_size = STACK_ALIGN(stack_size);
+ /*
+ * BPF prog stack layout
+ *
+ * high
+ * original A64_SP => 0:+-----+ BPF prologue
+ * | | FP/LR and callee saved registers
+ * BPF fp register => -64:+-----+
+ * | |
+ * | ... | BPF prog stack
+ * | |
+ * | |
+ * current A64_SP/FP => +-----+
+ * | |
+ * | ... | Function call stack
+ * | |
+ * +-----+
+ * low
+ *
+ */
+
+ /* Save FP and LR registers to stay align with ARM64 AAPCS */
+ emit(A64_PUSH(A64_FP, A64_LR, A64_SP), ctx);
+
/* Save callee-saved register */
emit(A64_PUSH(r6, r7, A64_SP), ctx);
emit(A64_PUSH(r8, r9, A64_SP), ctx);
if (ctx->tmp_used)
emit(A64_PUSH(tmp1, tmp2, A64_SP), ctx);
- /* Set up frame pointer */
+ /* Set up BPF prog stack base register (x25) */
emit(A64_MOV(1, fp, A64_SP), ctx);
- /* Set up BPF stack */
+ /* Set up function call stack */
emit(A64_SUB_I(1, A64_SP, A64_SP, stack_size), ctx);
+ emit(A64_MOV(1, A64_FP, A64_SP), ctx);
/* Clear registers A and X */
emit_a64_mov_i64(ra, 0, ctx);
@@ -196,8 +220,8 @@ static void build_epilogue(struct jit_ctx *ctx)
emit(A64_POP(r8, r9, A64_SP), ctx);
emit(A64_POP(r6, r7, A64_SP), ctx);
- /* Restore frame pointer */
- emit(A64_MOV(1, fp, A64_SP), ctx);
+ /* Restore FP/LR registers */
+ emit(A64_POP(A64_FP, A64_LR, A64_SP), ctx);
/* Set return value */
emit(A64_MOV(1, A64_R(0), r0), ctx);
--
2.0.2
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| From | Z Lim <zlim.lnx@gmail.com> |
|---|---|
| Date | 2015-11-13 04:30 +0100 |
| Subject | Re: [PATCH 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS |
| Message-ID | <quddL-11M-3@gated-at.bofh.it> |
| In reply to | #1268301 |
On Thu, Nov 12, 2015 at 1:57 PM, Yang Shi <yang.shi@linaro.org> wrote:
>
> Save and restore FP/LR in BPF prog prologue and epilogue, save SP to FP
> in prologue in order to get the correct stack backtrace.
>
> However, ARM64 JIT used FP (x29) as eBPF fp register, FP is subjected to
> change during function call so it may cause the BPF prog stack base address
> change too.
>
> Use x25 to replace FP as BPF stack base register (fp). Since x25 is callee
> saved register, so it will keep intact during function call.
> It is initialized in BPF prog prologue when BPF prog is started to run
> everytime. When BPF prog exits, it could be just tossed.
>
> So, the BPF stack layout looks like:
>
> high
> original A64_SP => 0:+-----+ BPF prologue
> | | FP/LR and callee saved registers
> BPF fp register => -64:+-----+
> | |
> | ... | BPF prog stack
> | |
> | |
> current A64_SP/FP => +-----+
> | |
> | ... | Function call stack
> | |
> +-----+
> low
>
Yang, for stack unwinding to work, shouldn't it be something like the following?
| LR |
A64_FP => | FP |
| .. |
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| From | "Shi, Yang" <yang.shi@linaro.org> |
|---|---|
| Date | 2015-11-13 18:30 +0100 |
| Subject | Re: [PATCH 2/2] arm64: bpf: make BPF prologue and epilogue align with ARM64 AAPCS |
| Message-ID | <quqkG-UL-17@gated-at.bofh.it> |
| In reply to | #1268562 |
On 11/12/2015 7:28 PM, Z Lim wrote: > On Thu, Nov 12, 2015 at 1:57 PM, Yang Shi <yang.shi@linaro.org> wrote: >> >> Save and restore FP/LR in BPF prog prologue and epilogue, save SP to FP >> in prologue in order to get the correct stack backtrace. >> >> However, ARM64 JIT used FP (x29) as eBPF fp register, FP is subjected to >> change during function call so it may cause the BPF prog stack base address >> change too. >> >> Use x25 to replace FP as BPF stack base register (fp). Since x25 is callee >> saved register, so it will keep intact during function call. >> It is initialized in BPF prog prologue when BPF prog is started to run >> everytime. When BPF prog exits, it could be just tossed. >> >> So, the BPF stack layout looks like: >> >> high >> original A64_SP => 0:+-----+ BPF prologue >> | | FP/LR and callee saved registers >> BPF fp register => -64:+-----+ >> | | >> | ... | BPF prog stack >> | | >> | | >> current A64_SP/FP => +-----+ >> | | >> | ... | Function call stack >> | | >> +-----+ >> low >> > > Yang, for stack unwinding to work, shouldn't it be something like the following? Yes, thanks for catching this. v3 will be post soon. Yang > > | LR | > A64_FP => | FP | > | .. | > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Yang Shi <yang.shi@linaro.org> |
|---|---|
| Date | 2015-11-12 23:20 +0100 |
| Subject | [PATCH 1/2] arm64: bpf: fix JIT frame pointer setup |
| Message-ID | <qu8nM-6oo-37@gated-at.bofh.it> |
| In reply to | #1268296 |
BPF fp should point to the top of the BPF prog stack. The original implementation made it point to the bottom incorrectly. Move A64_SP to fp before reserve BPF prog stack space. CC: Zi Shen Lim <zlim.lnx@gmail.com> CC: Xi Wang <xi.wang@gmail.com> Signed-off-by: Yang Shi <yang.shi@linaro.org> --- arch/arm64/net/bpf_jit_comp.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index a44e529..ac8b548 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -161,12 +161,12 @@ static void build_prologue(struct jit_ctx *ctx) if (ctx->tmp_used) emit(A64_PUSH(tmp1, tmp2, A64_SP), ctx); - /* Set up BPF stack */ - emit(A64_SUB_I(1, A64_SP, A64_SP, stack_size), ctx); - /* Set up frame pointer */ emit(A64_MOV(1, fp, A64_SP), ctx); + /* Set up BPF stack */ + emit(A64_SUB_I(1, A64_SP, A64_SP, stack_size), ctx); + /* Clear registers A and X */ emit_a64_mov_i64(ra, 0, ctx); emit_a64_mov_i64(rx, 0, ctx); -- 2.0.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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| From | Z Lim <zlim.lnx@gmail.com> |
|---|---|
| Date | 2015-11-13 04:30 +0100 |
| Subject | Re: [PATCH 1/2] arm64: bpf: fix JIT frame pointer setup |
| Message-ID | <quddM-11M-13@gated-at.bofh.it> |
| In reply to | #1268304 |
On Thu, Nov 12, 2015 at 1:57 PM, Yang Shi <yang.shi@linaro.org> wrote:
> BPF fp should point to the top of the BPF prog stack. The original
> implementation made it point to the bottom incorrectly.
> Move A64_SP to fp before reserve BPF prog stack space.
>
> CC: Zi Shen Lim <zlim.lnx@gmail.com>
> CC: Xi Wang <xi.wang@gmail.com>
> Signed-off-by: Yang Shi <yang.shi@linaro.org>
> ---
Reviewed-by: Zi Shen Lim <zlim.lnx@gmail.com>
Also,
Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler")
Cc: <stable@vger.kernel.org> # 3.18+
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