[v12,4/7] riscv: Add __riscv_hwprobe pointer to ifunc calls

Message ID 20240214143159.2951158-5-evan@rivosinc.com
State Committed
Commit 78308ce77ad55191d2e578bbcd19bb55c68926cb
Delegated to: Palmer Dabbelt
Series RISC-V: ifunced memcpy using new kernel hwprobe interface |


Context Check Description
redhat-pt-bot/TryBot-apply_patch success Patch applied to master at the time it was sent
linaro-tcwg-bot/tcwg_glibc_build--master-aarch64 success Testing passed
linaro-tcwg-bot/tcwg_glibc_check--master-aarch64 success Testing passed
linaro-tcwg-bot/tcwg_glibc_build--master-arm success Testing passed
linaro-tcwg-bot/tcwg_glibc_check--master-arm success Testing passed

Commit Message

Evan Green Feb. 14, 2024, 2:31 p.m. UTC
  The new __riscv_hwprobe() function is designed to be used by ifunc
selector functions. This presents a challenge for applications and
libraries, as ifunc selectors are invoked before all relocations have
been performed, so an external call to __riscv_hwprobe() from an ifunc
selector won't work. To address this, pass a pointer to the
__riscv_hwprobe() function into ifunc selectors as the second
argument (alongside dl_hwcap, which was already being passed).

Include a typedef as well for convenience, so that ifunc users don't
have to go through contortions to call this routine. Users will need to
remember to check the second argument for NULL, to account for older
glibcs that don't pass the function.

Signed-off-by: Evan Green <evan@rivosinc.com>


(no changes since v10)

Changes in v10:
 - Hand in pointer to __riscv_hwprobe(), not vDSO function

Changes in v7:
 - Remove __THROW from function pointer type, as it creates warnings
   together with __fortified_attr_access.

 sysdeps/riscv/dl-irel.h                     |  9 +++++----
 sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h | 10 ++++++++++
 2 files changed, 15 insertions(+), 4 deletions(-)


diff --git a/sysdeps/riscv/dl-irel.h b/sysdeps/riscv/dl-irel.h
index e6ab51ccd4..61b3511c96 100644
--- a/sysdeps/riscv/dl-irel.h
+++ b/sysdeps/riscv/dl-irel.h
@@ -24,6 +24,7 @@ 
 #include <unistd.h>
 #include <ldsodefs.h>
 #include <sysdep.h>
+#include <sys/hwprobe.h>
@@ -31,10 +32,10 @@  static inline ElfW(Addr)
 __attribute ((always_inline))
 elf_ifunc_invoke (ElfW(Addr) addr)
-  /* The second argument is a void pointer to preserve the extension
-     fexibility.  */
-  return ((ElfW(Addr) (*) (uint64_t, void *)) (addr))
-	 (GLRO(dl_hwcap), NULL);
+  /* The third argument is a void pointer to preserve the extension
+     flexibility.  */
+  return ((ElfW(Addr) (*) (uint64_t, void *, void *)) (addr))
+	 (GLRO(dl_hwcap), __riscv_hwprobe, NULL);
 static inline void
diff --git a/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
index 5592b9e100..34a2e3dbc2 100644
--- a/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
+++ b/sysdeps/unix/sysv/linux/riscv/sys/hwprobe.h
@@ -69,6 +69,16 @@  extern int __riscv_hwprobe (struct riscv_hwprobe *__pairs, size_t __pair_count,
      __fortified_attr_access (__read_write__, 1, 2)
      __fortified_attr_access (__read_only__, 4, 3);
+/* A pointer to the __riscv_hwprobe vDSO function is passed as the second
+   argument to ifunc selector routines. Include a function pointer type for
+   convenience in calling the function in those settings. */
+typedef int (*__riscv_hwprobe_t) (struct riscv_hwprobe *__pairs, size_t __pair_count,
+				  size_t __cpu_count, unsigned long int *__cpus,
+				  unsigned int __flags)
+     __nonnull ((1)) __wur
+     __fortified_attr_access (__read_write__, 1, 2)
+     __fortified_attr_access (__read_only__, 4, 3);
 #endif /* sys/hwprobe.h */