From ea78d2fb11cc745874c93fb41ce29c2aa37e6a6c Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Wed, 12 Jan 2022 22:42:18 +0900
Subject: [PATCH 1/3] meson: require bpftool version >= 5.6

Closes #22051.
---
 meson.build | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index 910862ed36..a0ce462f31 100644
--- a/meson.build
+++ b/meson.build
@@ -1005,7 +1005,11 @@ else
 
         # Debian installs this in /usr/sbin/ which is not in $PATH.
         # We check for 'bpftool' first, honouring $PATH, and in /usr/sbin/ for Debian.
-        bpftool = find_program('bpftool', '/usr/sbin/bpftool', required : bpf_framework_required)
+        # We use 'bpftool gen' subcommand, it was added by 985ead416df39d6fe8e89580cc1db6aa273e0175 (v5.6).
+        bpftool = find_program('bpftool',
+                               '/usr/sbin/bpftool',
+                               required : bpf_framework_required,
+                               version : '>= 5.6')
 
         deps_found = libbpf.found() and clang.found() and llvm_strip.found() and bpftool.found()
         # Can build BPF program from source code in restricted C

From a6ac8b5a4da379d959bfccba255db65b0da0c821 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Thu, 13 Jan 2022 15:33:46 +0900
Subject: [PATCH 2/3] meson: check if clang supports bpf

---
 meson.build | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/meson.build b/meson.build
index a0ce462f31..073667ef6c 100644
--- a/meson.build
+++ b/meson.build
@@ -995,6 +995,14 @@ else
                 clang_bin = 'clang'
         endif
         clang = find_program(clang_bin, required : bpf_framework_required)
+
+        if clang.found()
+                # Check if 'clang -target bpf' is supported.
+                clang_supports_bpf = run_command(clang, '-target', 'bpf', '--print-supported-cpus', check : false).returncode() == 0
+        else
+                clang_supports_bpf = false
+        endif
+
         if not meson.is_cross_build() and clang.found()
                 llvm_strip_bin = run_command(clang, '--print-prog-name', 'llvm-strip',
                                              check : true).stdout().strip()
@@ -1011,7 +1019,7 @@ else
                                required : bpf_framework_required,
                                version : '>= 5.6')
 
-        deps_found = libbpf.found() and clang.found() and llvm_strip.found() and bpftool.found()
+        deps_found = libbpf.found() and clang.found() and clang_supports_bpf and llvm_strip.found() and bpftool.found()
         # Can build BPF program from source code in restricted C
         conf.set10('BPF_FRAMEWORK', deps_found)
 endif

From dc7e9c1bc4236f17049112ffaa766f3a5b749171 Mon Sep 17 00:00:00 2001
From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Thu, 13 Jan 2022 15:43:24 +0900
Subject: [PATCH 3/3] meson: use the compiler command array as is

Also check if the flags used when building bpf are supported by clang.
---
 meson.build | 27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/meson.build b/meson.build
index 073667ef6c..648f47b56c 100644
--- a/meson.build
+++ b/meson.build
@@ -990,20 +990,32 @@ if want_bpf_framework == 'false'
 else
         # Support 'versioned' clang/llvm-strip binaries, as seen on Debian/Ubuntu
         # (like clang-10/llvm-strip-10)
-        clang_bin = cc.get_id() == 'clang' ? cc.cmd_array()[0] : 'clang'
-        if meson.is_cross_build() or clang_bin.contains('afl-clang') or clang_bin.contains('hfuzz-clang')
-                clang_bin = 'clang'
+        if meson.is_cross_build() or cc.get_id() != 'clang' or cc.cmd_array()[0].contains('afl-clang') or cc.cmd_array()[0].contains('hfuzz-clang')
+                r = find_program('clang', required : bpf_framework_required)
+                clang_found = r.found()
+                if clang_found
+                        if meson.version().version_compare('>= 0.55')
+                                clang = [r.full_path()]
+                        else
+                                clang = [r.path()]
+                        endif
+                endif
+                # Assume that the required flags are supported by the found clang.
+                clang_supports_flags = clang_found
+        else
+                clang_found = true
+                clang = cc.cmd_array()
+                clang_supports_flags = cc.has_argument('-Wno-compare-distinct-pointer-types')
         endif
-        clang = find_program(clang_bin, required : bpf_framework_required)
 
-        if clang.found()
+        if clang_found
                 # Check if 'clang -target bpf' is supported.
                 clang_supports_bpf = run_command(clang, '-target', 'bpf', '--print-supported-cpus', check : false).returncode() == 0
         else
                 clang_supports_bpf = false
         endif
 
-        if not meson.is_cross_build() and clang.found()
+        if not meson.is_cross_build() and clang_found
                 llvm_strip_bin = run_command(clang, '--print-prog-name', 'llvm-strip',
                                              check : true).stdout().strip()
         else
@@ -1019,7 +1031,8 @@ else
                                required : bpf_framework_required,
                                version : '>= 5.6')
 
-        deps_found = libbpf.found() and clang.found() and clang_supports_bpf and llvm_strip.found() and bpftool.found()
+        deps_found = libbpf.found() and clang_found and clang_supports_bpf and clang_supports_flags and llvm_strip.found() and bpftool.found()
+
         # Can build BPF program from source code in restricted C
         conf.set10('BPF_FRAMEWORK', deps_found)
 endif