linux-kernel - [PATCH] FRV: Arrange things such that BRA can reach from the trap table

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Message-ID: <20071113165336.18722.27037.stgit@warthog.procyon.org.uk>
Date:	Tue, 13 Nov 2007 16:53:36 +0000
From:	David Howells <dhowells@...hat.com>
To:	torvalds@...l.org, akpm@...l.org
Cc:	linux-kernel@...r.kernel.org, dhowells@...hat.com
Subject: [PATCH] FRV: Arrange things such that BRA can reach from the trap
	table

From: David Howells <dhowells@...hat.com>

Arrange the sections in the FRV arch so that a BRA instruction with a 16-bit
displacement can always reach from the trap table to entry.S, tlb-miss.S and
break.S.

The problem otherwise is that the linker can insert sufficient code between
the slots in the trap table and the targets of the branch instructions in
those slots that the displacement field in the instruction isn't sufficiently
large.  This is because the branch targets were in the .text section along
with most of the other code in the kernel.

Signed-off-by: David Howells <dhowells@...hat.com>
---

 arch/frv/kernel/break.S       |    2 +-
 arch/frv/kernel/entry.S       |    2 +-
 arch/frv/kernel/vmlinux.lds.S |   27 +++++++++++++++------------
 arch/frv/mm/tlb-miss.S        |    2 +-
 4 files changed, 18 insertions(+), 15 deletions(-)

diff --git a/arch/frv/kernel/break.S b/arch/frv/kernel/break.S
index dac4a5f..bd0bdf9 100644
--- a/arch/frv/kernel/break.S
+++ b/arch/frv/kernel/break.S
@@ -63,7 +63,7 @@ __break_trace_through_exceptions:
 # entry point for Break Exceptions/Interrupts
 #
 ###############################################################################
-	.text
+	.section	.text.break
 	.balign		4
 	.globl		__entry_break
 __entry_break:
diff --git a/arch/frv/kernel/entry.S b/arch/frv/kernel/entry.S
index 1e74f3c..f926c70 100644
--- a/arch/frv/kernel/entry.S
+++ b/arch/frv/kernel/entry.S
@@ -38,7 +38,7 @@
 
 #define nr_syscalls ((syscall_table_size)/4)
 
-	.text
+	.section	.text.entry
 	.balign		4
 
 .macro LEDS val
diff --git a/arch/frv/kernel/vmlinux.lds.S b/arch/frv/kernel/vmlinux.lds.S
index a62b245..a372e34 100644
--- a/arch/frv/kernel/vmlinux.lds.S
+++ b/arch/frv/kernel/vmlinux.lds.S
@@ -76,6 +76,12 @@ SECTIONS
 	  *(.data.init_task)
   }
 
+  . = ALIGN(4096);
+  .data.page_aligned : { *(.data.idt) }
+
+  . = ALIGN(L1_CACHE_BYTES);
+  .data.cacheline_aligned : { *(.data.cacheline_aligned) }
+
   .trap : {
 	/* trap table management - read entry-table.S before modifying */
 	. = ALIGN(8192);
@@ -86,28 +92,25 @@ SECTIONS
 	*(.trap.break)
   }
 
-  . = ALIGN(4096);
-  .data.page_aligned : { *(.data.idt) }
-
-  . = ALIGN(L1_CACHE_BYTES);
-  .data.cacheline_aligned : { *(.data.cacheline_aligned) }
-
   /* Text and read-only data */
   . = ALIGN(4);
   _text = .;
   _stext = .;
   .text : {
-	*(
-		.text.start .text.*
+	*(.text.start)
+	*(.text.entry)
+	*(.text.break)
+	*(.text.tlbmiss)
+	TEXT_TEXT
+	SCHED_TEXT
+	LOCK_TEXT
 #ifdef CONFIG_DEBUG_INFO
+	*(
 	.init.text
 	.exit.text
 	.exitcall.exit
-#endif
 	)
-	TEXT_TEXT
-	SCHED_TEXT
-	LOCK_TEXT
+#endif
 	*(.fixup)
 	*(.gnu.warning)
 	*(.exitcall.exit)
diff --git a/arch/frv/mm/tlb-miss.S b/arch/frv/mm/tlb-miss.S
index 04da674..0764348 100644
--- a/arch/frv/mm/tlb-miss.S
+++ b/arch/frv/mm/tlb-miss.S
@@ -16,7 +16,7 @@
 #include <asm/highmem.h>
 #include <asm/spr-regs.h>
 
-	.section	.text
+	.section	.text.tlbmiss
 	.balign		4
 
 	.globl		__entry_insn_mmu_miss

-
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