[tip:x86/mpx] x86/mpx: Simplify handling of errors when computing linear addresses

[tip-bot for Ricardo Neri]

Commit-ID:  b15d70df6e685912be8bbcb7557d277d48aa942c
Gitweb:     https://git.kernel.org/tip/b15d70df6e685912be8bbcb7557d277d48aa942c
Author:     Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 27 Oct 2017 13:25:32 -0700
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 1 Nov 2017 21:50:08 +0100

x86/mpx: Simplify handling of errors when computing linear addresses

When errors occur in the computation of the linear address, -1L is
returned. Rather than having a separate return path for errors, the
variable used to return the computed linear address can be initialized
with the error value. Hence, only one return path is needed. This makes
the function easier to read.

While here, ensure that the error value is -1L, a 64-bit value, rather
than -1, a 32-bit value.

Suggested-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Cc: Adan Hawthorn <adanhawthorn@xxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: ricardo.neri@xxxxxxxxx
Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxx>
Cc: Nathan Howard <liverlint@xxxxxxxxx>
Cc: "Ravi V. Shankar" <ravi.v.shankar@xxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Colin Ian King <colin.king@xxxxxxxxxxxxx>
Cc: Chen Yucong <slaoub@xxxxxxxxx>
Cc: Adam Buchbinder <adam.buchbinder@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/1509135945-13762-6-git-send-email-ricardo.neri-calderon@xxxxxxxxxxxxxxx

---
 arch/x86/mm/mpx.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 9ceaa95..f4c48a0 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -138,7 +138,7 @@ static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
  */
 static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
 {
-	unsigned long addr, base, indx;
+	unsigned long addr = -1L, base, indx;
 	int addr_offset, base_offset, indx_offset;
 	insn_byte_t sib;
 
@@ -149,17 +149,17 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
 	if (X86_MODRM_MOD(insn->modrm.value) == 3) {
 		addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
 		if (addr_offset < 0)
-			goto out_err;
+			goto out;
 		addr = regs_get_register(regs, addr_offset);
 	} else {
 		if (insn->sib.nbytes) {
 			base_offset = get_reg_offset(insn, regs, REG_TYPE_BASE);
 			if (base_offset < 0)
-				goto out_err;
+				goto out;
 
 			indx_offset = get_reg_offset(insn, regs, REG_TYPE_INDEX);
 			if (indx_offset < 0)
-				goto out_err;
+				goto out;
 
 			base = regs_get_register(regs, base_offset);
 			indx = regs_get_register(regs, indx_offset);
@@ -167,14 +167,13 @@ static void __user *mpx_get_addr_ref(struct insn *insn, struct pt_regs *regs)
 		} else {
 			addr_offset = get_reg_offset(insn, regs, REG_TYPE_RM);
 			if (addr_offset < 0)
-				goto out_err;
+				goto out;
 			addr = regs_get_register(regs, addr_offset);
 		}
 		addr += insn->displacement.value;
 	}
+out:
 	return (void __user *)addr;
-out_err:
-	return (void __user *)-1;
 }
 
 static int mpx_insn_decode(struct insn *insn,