From 304662234dc65961a2b01628e1d4c7a612da9bf5 Mon Sep 17 00:00:00 2001
From: WANG Xuerui <git@xen0n.name>
Date: Mon, 16 Jun 2025 16:16:55 +0800
Subject: [PATCH] RISC-V: [gprofng] Allow building gprofng without
 asm/hwprobe.h

The code is actually able to gracefully fallback if the syscall number
of riscv_hwprobe is not available at build time, but it still depended
on the <asm/hwprobe.h> header unconditionally. In certain environments
such as one of crosstool-NG's Canadian Cross build step (binutils for
host), or one with very outdated kernel headers, the header will not be
present, causing the build to fail.

While the relevant projects/environments should be fixed nevertheless,
a configure-time check for <asm/hwprobe.h> is helpful for fixing gprofng
builds with released versions of ct-ng etc.

Signed-off-by: WANG Xuerui <git@xen0n.name>
---
 gprofng/common/config.h.in |  3 +++
 gprofng/common/cpuid.c     |  6 ++++--
 gprofng/configure          | 15 +++++++++++++++
 gprofng/configure.ac       |  4 ++++
 4 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/gprofng/common/config.h.in b/gprofng/common/config.h.in
index aabb043957a..5f2c1278c95 100644
--- a/gprofng/common/config.h.in
+++ b/gprofng/common/config.h.in
@@ -9,6 +9,9 @@
 /* Enable java profiling */
 #undef GPROFNG_JAVA_PROFILING
 
+/* Define to 1 if you have the <asm/hwprobe.h> header file. */
+#undef HAVE_ASM_HWPROBE_H
+
 /* Define to 1 if you have the `clock_gettime' function. */
 #undef HAVE_CLOCK_GETTIME
 
diff --git a/gprofng/common/cpuid.c b/gprofng/common/cpuid.c
index e40404c645a..f9f90462839 100644
--- a/gprofng/common/cpuid.c
+++ b/gprofng/common/cpuid.c
@@ -48,8 +48,10 @@ __get_cpuid (unsigned int op ATTRIBUTE_UNUSED, unsigned int *eax,
 #include <sched.h>
 #include <sys/syscall.h>
 #include <unistd.h>
+#ifdef HAVE_ASM_HWPROBE_H
 #include <asm/hwprobe.h>
 #endif
+#endif
 
 /*
  * Various routines to handle identification
@@ -188,7 +190,7 @@ get_cpuid_info ()
       break;
     }
 #elif defined(__riscv)
-  #ifndef __riscv_hwprobe
+  #if !defined(__riscv_hwprobe) || !defined(HAVE_ASM_HWPROBE_H)
 	  cpi->cpi_vendor = 0;
 	  cpi->cpi_family = 0;
 	  cpi->cpi_model = 0;
@@ -208,7 +210,7 @@ get_cpuid_info ()
 	cpi->cpi_vendor = res.value;
 	cpi->cpi_family = 0;
 	cpi->cpi_model = 0;
-	#endif
+  #endif
 #endif
   return cpi;
 }
diff --git a/gprofng/configure b/gprofng/configure
index 2edfff107dd..2f4e18c47f6 100755
--- a/gprofng/configure
+++ b/gprofng/configure
@@ -17165,6 +17165,21 @@ fi
 done
 
 
+# For riscv builds inside incomplete environments such as during intermediate
+# steps of cross toolchain building, or with outdated Linux headers.
+for ac_header in asm/hwprobe.h
+do :
+  ac_fn_c_check_header_mongrel "$LINENO" "asm/hwprobe.h" "ac_cv_header_asm_hwprobe_h" "$ac_includes_default"
+if test "x$ac_cv_header_asm_hwprobe_h" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ASM_HWPROBE_H 1
+_ACEOF
+
+fi
+
+done
+
+
 clock_gettime_link=
 # At least for glibc, clock_gettime is in librt.  But don't
 # pull that in if it still doesn't give us the function we want.  This
diff --git a/gprofng/configure.ac b/gprofng/configure.ac
index 1f473b9b583..deb3ed586da 100644
--- a/gprofng/configure.ac
+++ b/gprofng/configure.ac
@@ -245,6 +245,10 @@ AC_SUBST(GPROFNG_CPPFLAGS, [${gprofng_cppflags}])
 AC_CHECK_DECLS([basename])
 AC_CHECK_FUNCS(clock_gettime strsignal)
 
+# For riscv builds inside incomplete environments such as during intermediate
+# steps of cross toolchain building, or with outdated Linux headers.
+AC_CHECK_HEADERS(asm/hwprobe.h)
+
 clock_gettime_link=
 # At least for glibc, clock_gettime is in librt.  But don't
 # pull that in if it still doesn't give us the function we want.  This
-- 
2.47.2