File gcc7-pfe-0020-Backport-varasm-Fix-up-__patchabl... of Package cross-epiphany-gcc7-bootstrap.21370

Overview Repositories Revisions Requests Users Attributes Meta

File gcc7-pfe-0020-Backport-varasm-Fix-up-__patchable_function_entries-.patch of Package cross-epiphany-gcc7-bootstrap.21370

From 686af21802e691f3b08cc45a5cb2c961b9676675 Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 16 Dec 2020 16:15:35 +0100
Subject: [PATCH 20/22] Backport varasm: Fix up __patchable_function_entries
 handling

The SECTION_LINK_ORDER changes don't seem to work properly.

If I compile:
static inline __attribute__((__gnu_inline__)) __attribute__((__unused__)) __attribute__((patchable_function_entry(0, 0))) int foo (int x)
{
  return x + 1;
}

static inline __attribute__((__gnu_inline__)) __attribute__((__unused__)) __attribute__((patchable_function_entry(0, 0))) int bar (int x)
{
  return x + 2;
}

int
baz (int x)
{
  return foo (x) + 1;
}

int
qux (int x)
{
  return bar (x) + 2;
}
(distilled from aarch64 Linux kernel) with
-O2 -fpatchable-function-entry=2 on aarch64 compiler configured against
latest binutils, I get:
...
	.section	__patchable_function_entries,"awo",@progbits,baz
...
	.section	__patchable_function_entries
...
in the assembly, but when it is assembled, one gets:
  [ 4] __patchable_function_entries PROGBITS        0000000000000000 000060 000008 00 WAL  1   0  8
  [ 5] .rela__patchable_function_entries RELA            0000000000000000 000280 000018 18   I 12   4  8
  [ 6] __patchable_function_entries PROGBITS        0000000000000000 000068 000008 00      0   0  8
  [ 7] .rela__patchable_function_entries RELA            0000000000000000 000298 000018 18   I 12   6  8
i.e. one writable allocated section with SHF_LINK_ORDER and another
non-allocated non-writable without link order.  In the kernel case there is
always one entry in the WAL section and then dozens or more in the
non-allocated one.
The kernel then fails to link:
WARNING: modpost: vmlinux.o (__patchable_function_entries): unexpected non-allocatable section.
Did you forget to use "ax"/"aw" in a .S file?
Note that for example <linux/init.h> contains
section definitions for use in .S files.
ld: .init.data has both ordered [`__patchable_function_entries' in init/main.o] and unordered [`.init.data' in
+./drivers/firmware/efi/libstub/vsprintf.stub.o] sections
ld: final link failed: bad value
make: *** [Makefile:1175: vmlinux] Error 1

The following patch fixes it by always forcing full section flags for
SECTION_LINK_ORDER sections.

2020-12-16  Jakub Jelinek  <jakub@redhat.com>

* varasm.c (default_elf_asm_named_section): Always force
	section flags even for sections with SECTION_LINK_ORDER flag.
---
 gcc/varasm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/gcc/varasm.c b/gcc/varasm.c
index 7b0792ddaed..9e0e7c0976f 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -6363,9 +6363,10 @@ default_elf_asm_named_section (const char *name, unsigned int flags,
 
   /* If we have already declared this section, we can use an
      abbreviated form to switch back to it -- unless this section is
-     part of a COMDAT groups, in which case GAS requires the full
-     declaration every time.  */
+     part of a COMDAT groups or with SHF_GNU_RETAIN or with SHF_LINK_ORDER,
+     in which case GAS requires the full declaration every time.  */
   if (!(HAVE_COMDAT_GROUP && (flags & SECTION_LINKONCE))
+      && !(flags & (SECTION_RETAIN | SECTION_LINK_ORDER))
       && (flags & SECTION_DECLARED))
     {
       fprintf (asm_out_file, "\t.section\t%s\n", name);
-- 
2.33.1

Places

File gcc7-pfe-0020-Backport-varasm-Fix-up-__patchable_function_entries-.patch of Package cross-epiphany-gcc7-bootstrap.21370

Places