diff options
authorArnd Bergmann <>2016-11-10 17:44:46 +0100
committerLinus Torvalds <>2016-11-11 08:45:08 -0800
commit3a6d867612dce2035ca50cb02e7871d27c86aa72 (patch)
parente84efa32b9d2763fb92e73c8942100d8f55ad4ed (diff)
x86: apm: avoid uninitialized data
apm_bios_call() can fail, and return a status in its argument structure. If that status however is zero during a call from apm_get_power_status(), we end up using data that may have never been set, as reported by "gcc -Wmaybe-uninitialized": arch/x86/kernel/apm_32.c: In function ‘apm’: arch/x86/kernel/apm_32.c:1729:17: error: ‘bx’ may be used uninitialized in this function [-Werror=maybe-uninitialized] arch/x86/kernel/apm_32.c:1835:5: error: ‘cx’ may be used uninitialized in this function [-Werror=maybe-uninitialized] arch/x86/kernel/apm_32.c:1730:17: note: ‘cx’ was declared here arch/x86/kernel/apm_32.c:1842:27: error: ‘dx’ may be used uninitialized in this function [-Werror=maybe-uninitialized] arch/x86/kernel/apm_32.c:1731:17: note: ‘dx’ was declared here This changes the function to return "APM_NO_ERROR" here, which makes the code more robust to broken BIOS versions, and avoids the warning. Signed-off-by: Arnd Bergmann <> Reviewed-by: Jiri Kosina <> Reviewed-by: Luis R. Rodriguez <> Signed-off-by: Linus Torvalds <>
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/kernel/apm_32.c b/arch/x86/kernel/apm_32.c
index c7364bd633e1..51287cd90bf6 100644
--- a/arch/x86/kernel/apm_32.c
+++ b/arch/x86/kernel/apm_32.c
@@ -1042,8 +1042,11 @@ static int apm_get_power_status(u_short *status, u_short *bat, u_short *life)
if (apm_info.get_power_status_broken)
- if (apm_bios_call(&call))
+ if (apm_bios_call(&call)) {
+ if (!call.err)
+ return APM_NO_ERROR;
return call.err;
+ }
*status = call.ebx;
*bat = call.ecx;
if (apm_info.get_power_status_swabinminutes) {