[PATCH bpf] libbpf: Handle GCC built-in types for Arm NEON

[Jean-Philippe Brucker <jean-philippe@linaro.org>]

When building Arm NEON (SIMD) code, GCC emits built-in types __PolyXX_t,
which are not recognized by Clang. This causes build failures when
including vmlinux.h generated from a kernel built with CONFIG_RAID6_PQ=y
and CONFIG_KERNEL_MODE_NEON. Emit typedefs for these built-in types,
based on the Clang definitions. poly64_t is unsigned long because it's
only defined for 64-bit Arm.

Including linux/kernel.h to use ARRAY_SIZE() incidentally redefined
max(), causing a build bug due to different types, hence the seemingly
unrelated change.

Reported-by: Jakov Petrina <jakov.petrina@sartura.hr>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
 tools/lib/bpf/btf_dump.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index cf711168d34a..3162d7b1880c 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -13,6 +13,7 @@
 #include <errno.h>
 #include <linux/err.h>
 #include <linux/btf.h>
+#include <linux/kernel.h>
 #include "btf.h"
 #include "hashmap.h"
 #include "libbpf.h"
@@ -549,6 +550,9 @@ static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
 	}
 }
 
+static void btf_dump_emit_int_def(struct btf_dump *d, __u32 id,
+				  const struct btf_type *t);
+
 static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
 				     const struct btf_type *t);
 static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
@@ -671,6 +675,9 @@ static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
 
 	switch (kind) {
 	case BTF_KIND_INT:
+		/* Emit type alias definitions if necessary */
+		btf_dump_emit_int_def(d, id, t);
+
 		tstate->emit_state = EMITTED;
 		break;
 	case BTF_KIND_ENUM:
@@ -870,7 +877,7 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
 			btf_dump_printf(d, ": %d", m_sz);
 			off = m_off + m_sz;
 		} else {
-			m_sz = max(0, btf__resolve_size(d->btf, m->type));
+			m_sz = max(0LL, btf__resolve_size(d->btf, m->type));
 			off = m_off + m_sz * 8;
 		}
 		btf_dump_printf(d, ";");
@@ -890,6 +897,32 @@ static void btf_dump_emit_struct_def(struct btf_dump *d,
 		btf_dump_printf(d, " __attribute__((packed))");
 }
 
+static const char *builtin_types[][2] = {
+	/*
+	 * GCC emits typedefs to its internal __PolyXX_t types when compiling
+	 * Arm SIMD intrinsics. Alias them to the same standard types as Clang.
+	 */
+	{ "__Poly8_t",		"unsigned char" },
+	{ "__Poly16_t",		"unsigned short" },
+	{ "__Poly64_t",		"unsigned long" },
+	{ "__Poly128_t",	"unsigned __int128" },
+};
+
+static void btf_dump_emit_int_def(struct btf_dump *d, __u32 id,
+				  const struct btf_type *t)
+{
+	const char *name = btf_dump_type_name(d, id);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(builtin_types); i++) {
+		if (strcmp(name, builtin_types[i][0]) == 0) {
+			btf_dump_printf(d, "typedef %s %s;\n\n",
+					builtin_types[i][1], name);
+			break;
+		}
+	}
+}
+
 static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
 				   const struct btf_type *t)
 {
-- 
2.27.0