linux-kernel - [PATCH] x86: Fix kprobes build with non-gawk awk

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Message-ID: <20091213220437.GA27718@progeny.tock>
Date:	Sun, 13 Dec 2009 16:04:38 -0600
From:	Jonathan Nieder <jrnieder@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Masami Hiramatsu <mhiramat@...hat.com>,
	Jim Keniston <jkenisto@...ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>, x86@...nel.org
Subject: [PATCH] x86: Fix kprobes build with non-gawk awk

The instruction attribute table generator fails when run by mawk
or original-awk:

 $ mawk -f arch/x86/tools/gen-insn-attr-x86.awk \
	arch/x86/lib/x86-opcode-map.txt > /dev/null
 Semantic error at 240: Second IMM error
 $ echo $?
 1

Line 240 contains "c8: ENTER Iw,Ib", which indicates that this
instruction has two immediate operands, the second of which is
one byte.  The script loops through the immediate operands using
a for loop.

Unfortunately, there is no guarantee in awk that a for (variable
in array) loop will return the indices in increasing order.
Internally, both original-awk and mawk iterate over a hash table
for this purpose, and both implementations happen to produce the
index 2 before 1.  The supposed second immediate operand is more
than one byte wide, producing the error.

So loop over the indices in increasing order instead.  As a
side-effect, with mawk this means the silly two-entry hash table
never has to be built.

Cc: Masami Hiramatsu <mhiramat@...hat.com>
Cc: Jim Keniston <jkenisto@...ibm.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: x86@...nel.org
Signed-off-by: Jonathan Nieder <jrnieder@...il.com>
---
 arch/x86/tools/gen-insn-attr-x86.awk |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/tools/gen-insn-attr-x86.awk b/arch/x86/tools/gen-insn-attr-x86.awk
index e34e92a..7a68506 100644
--- a/arch/x86/tools/gen-insn-attr-x86.awk
+++ b/arch/x86/tools/gen-insn-attr-x86.awk
@@ -226,12 +226,12 @@ function add_flags(old,new) {
 }
 
 # convert operands to flags.
-function convert_operands(opnd,       i,imm,mod)
+function convert_operands(count,opnd,       i,j,imm,mod)
 {
 	imm = null
 	mod = null
-	for (i in opnd) {
-		i  = opnd[i]
+	for (j = 1; j <= count; j++) {
+		i = opnd[j]
 		if (match(i, imm_expr) == 1) {
 			if (!imm_flag[i])
 				semantic_error("Unknown imm opnd: " i)
@@ -282,8 +282,8 @@ function convert_operands(opnd,       i,imm,mod)
 		# parse one opcode
 		if (match($i, opnd_expr)) {
 			opnd = $i
-			split($(i++), opnds, ",")
-			flags = convert_operands(opnds)
+			count = split($(i++), opnds, ",")
+			flags = convert_operands(count, opnds)
 		}
 		if (match($i, ext_expr))
 			ext = $(i++)
-- 
1.6.5.4

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