[dpdk-stable] patch 'bpf: fix pseudo calls for program loaded from ELF' has been queued to LTS release 18.11.3

[Kevin Traynor]

Hi,

FYI, your patch has been queued to LTS release 18.11.3

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 06/26/19. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/kevintraynor/dpdk-stable-queue

This queued commit can be viewed at:
https://github.com/kevintraynor/dpdk-stable-queue/commit/12d5f99de0e6e7feb3a46ec847cc18ef63e1dae9

Thanks.

Kevin Traynor

---
>From 12d5f99de0e6e7feb3a46ec847cc18ef63e1dae9 Mon Sep 17 00:00:00 2001
From: Konstantin Ananyev <konstantin.ananyev at intel.com>
Date: Fri, 17 May 2019 15:09:42 +0100
Subject: [PATCH] bpf: fix pseudo calls for program loaded from ELF

[ upstream commit 64ac6feb8291eb0fe74cf965dd3890625f8f3171 ]

clang 6.0 and onwards, for the external function call generates
BPF_PSEUDO_CALL instruction:
call pseudo +-off -> call another bpf function.
More details about that change: https://lwn.net/Articles/741773/
DPDK BPF implementation right now doesn't support multiple BPF
functions per module.
To overcome that problem, and preserve existing functionality
(ability to call allowed by user external functions),
bpf_elf_load() clears EBPF_PSEUDO_CALL value.
For details how to reproduce the issue:
https://bugs.dpdk.org/show_bug.cgi?id=259

Fixes: 5dba93ae5f2d ("bpf: add ability to load eBPF program from ELF object file")

Signed-off-by: Konstantin Ananyev <konstantin.ananyev at intel.com>
---
 lib/librte_bpf/bpf_def.h      |  8 ++++++++
 lib/librte_bpf/bpf_load_elf.c | 15 +++++++++++++--
 lib/librte_bpf/rte_bpf.h      |  3 +++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/lib/librte_bpf/bpf_def.h b/lib/librte_bpf/bpf_def.h
index c10f3aec4..d39992997 100644
--- a/lib/librte_bpf/bpf_def.h
+++ b/lib/librte_bpf/bpf_def.h
@@ -121,4 +121,12 @@ enum {
 };
 
+/*
+ * When EBPF_CALL instruction has src_reg == EBPF_PSEUDO_CALL,
+ * it should be treated as pseudo-call instruction, where
+ * imm value contains pc-relative offset to another EBPF function.
+ * Right now DPDK EBPF library doesn't support it.
+ */
+#define	EBPF_PSEUDO_CALL	EBPF_REG_1
+
 /*
  * eBPF instruction format
diff --git a/lib/librte_bpf/bpf_load_elf.c b/lib/librte_bpf/bpf_load_elf.c
index 96d3630fe..926317b6f 100644
--- a/lib/librte_bpf/bpf_load_elf.c
+++ b/lib/librte_bpf/bpf_load_elf.c
@@ -78,8 +78,19 @@ resolve_xsym(const char *sn, size_t ofs, struct ebpf_insn *ins, size_t ins_sz,
 
 	/* for function we just need an index in our xsym table */
-	if (type == RTE_BPF_XTYPE_FUNC)
+	if (type == RTE_BPF_XTYPE_FUNC) {
+
+		/* we don't support multiple functions per BPF module,
+		 * so treat EBPF_PSEUDO_CALL to extrernal function
+		 * as an ordinary EBPF_CALL.
+		 */
+		if (ins[idx].src_reg == EBPF_PSEUDO_CALL) {
+			RTE_BPF_LOG(INFO, "%s(%u): "
+				"EBPF_PSEUDO_CALL to external function: %s\n",
+				__func__, idx, sn);
+			ins[idx].src_reg = EBPF_REG_0;
+		}
 		ins[idx].imm = fidx;
 	/* for variable we need to store its absolute address */
-	else {
+	} else {
 		ins[idx].imm = (uintptr_t)prm->xsym[fidx].var.val;
 		ins[idx + 1].imm =
diff --git a/lib/librte_bpf/rte_bpf.h b/lib/librte_bpf/rte_bpf.h
index ab92af8fe..c8b960176 100644
--- a/lib/librte_bpf/rte_bpf.h
+++ b/lib/librte_bpf/rte_bpf.h
@@ -135,4 +135,7 @@ rte_bpf_load(const struct rte_bpf_prm *prm);
  * Create a new eBPF execution context and load BPF code from given ELF
  * file into it.
+ * Note that if the function will encounter EBPF_PSEUDO_CALL instruction
+ * that references external symbol, it will treat is as standard BPF_CALL
+ * to the external helper function.
  *
  * @param prm
-- 
2.20.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2019-06-21 17:22:13.143532012 +0100
+++ 0027-bpf-fix-pseudo-calls-for-program-loaded-from-ELF.patch	2019-06-21 17:22:11.736518830 +0100
@@ -1 +1 @@
-From 64ac6feb8291eb0fe74cf965dd3890625f8f3171 Mon Sep 17 00:00:00 2001
+From 12d5f99de0e6e7feb3a46ec847cc18ef63e1dae9 Mon Sep 17 00:00:00 2001
@@ -5,0 +6,2 @@
+[ upstream commit 64ac6feb8291eb0fe74cf965dd3890625f8f3171 ]
+
@@ -19 +20,0 @@
-Cc: stable at dpdk.org