netdev - Re: [PATCH -next] iwlwifi: dbg: work around clang bug by marking debug strings static

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Message-ID: <b219cf41933b2f965572af515cf9d3119293bfba.camel@perches.com>
Date:   Thu, 11 Jul 2019 19:01:14 -0700
From:   Joe Perches <joe@...ches.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>, kvalo@...eaurora.org
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Emmanuel Grumbach <emmanuel.grumbach@...el.com>,
        Luca Coelho <luciano.coelho@...el.com>,
        Intel Linux Wireless <linuxwifi@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Shahar S Matityahu <shahar.s.matityahu@...el.com>,
        Sara Sharon <sara.sharon@...el.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: Re: [PATCH -next] iwlwifi: dbg: work around clang bug by marking
 debug strings static

On Thu, 2019-07-11 at 17:17 -0700, Nick Desaulniers wrote:
> Commit r353569 in prerelease Clang-9 is producing a linkage failure:
> 
> ld: drivers/net/wireless/intel/iwlwifi/fw/dbg.o:
> in function `_iwl_fw_dbg_apply_point':
> dbg.c:(.text+0x827a): undefined reference to `__compiletime_assert_2387'
> 
> when the following configs are enabled:
> - CONFIG_IWLWIFI
> - CONFIG_IWLMVM
> - CONFIG_KASAN
> 
> Work around the issue for now by marking the debug strings as `static`,
> which they probably should be any ways.
> 
> Link: https://bugs.llvm.org/show_bug.cgi?id=42580
> Link: https://github.com/ClangBuiltLinux/linux/issues/580
> Reported-by: Arnd Bergmann <arnd@...db.de>
> Reported-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
>  drivers/net/wireless/intel/iwlwifi/fw/dbg.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/fw/dbg.c b/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
> index e411ac98290d..f8c90ea4e9b4 100644
> --- a/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
> +++ b/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
> @@ -2438,7 +2438,7 @@ static void iwl_fw_dbg_info_apply(struct iwl_fw_runtime *fwrt,
>  {
>  	u32 img_name_len = le32_to_cpu(dbg_info->img_name_len);
>  	u32 dbg_cfg_name_len = le32_to_cpu(dbg_info->dbg_cfg_name_len);
> -	const char err_str[] =
> +	static const char err_str[] =
>  		"WRT: ext=%d. Invalid %s name length %d, expected %d\n";

Better still would be to use the format string directly
in both locations instead of trying to deduplicate it
via storing it into a separate pointer.

Let the compiler/linker consolidate the format.
It's smaller object code, allows format/argument verification,
and is simpler for humans to understand.

---
diff --git a/drivers/net/wireless/intel/iwlwifi/fw/dbg.c b/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
index e411ac98290d..25e6712932b8 100644
--- a/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
+++ b/drivers/net/wireless/intel/iwlwifi/fw/dbg.c
@@ -2438,17 +2438,17 @@ static void iwl_fw_dbg_info_apply(struct iwl_fw_runtime *fwrt,
 {
 	u32 img_name_len = le32_to_cpu(dbg_info->img_name_len);
 	u32 dbg_cfg_name_len = le32_to_cpu(dbg_info->dbg_cfg_name_len);
-	const char err_str[] =
-		"WRT: ext=%d. Invalid %s name length %d, expected %d\n";
 
 	if (img_name_len != IWL_FW_INI_MAX_IMG_NAME_LEN) {
-		IWL_WARN(fwrt, err_str, ext, "image", img_name_len,
+		IWL_WARN(fwrt, "WRT: ext=%d. Invalid %s name length %d, expected %d\n",
+			 ext, "image", img_name_len,
 			 IWL_FW_INI_MAX_IMG_NAME_LEN);
 		return;
 	}
 
 	if (dbg_cfg_name_len != IWL_FW_INI_MAX_DBG_CFG_NAME_LEN) {
-		IWL_WARN(fwrt, err_str, ext, "debug cfg", dbg_cfg_name_len,
+		IWL_WARN(fwrt, "WRT: ext=%d. Invalid %s name length %d, expected %d\n",
+			 ext, "debug cfg", dbg_cfg_name_len,
 			 IWL_FW_INI_MAX_DBG_CFG_NAME_LEN);
 		return;
 	}
@@ -2775,8 +2775,6 @@ static void _iwl_fw_dbg_apply_point(struct iwl_fw_runtime *fwrt,
 		struct iwl_ucode_tlv *tlv = iter;
 		void *ini_tlv = (void *)tlv->data;
 		u32 type = le32_to_cpu(tlv->type);
-		const char invalid_ap_str[] =
-			"WRT: ext=%d. Invalid apply point %d for %s\n";
 
 		switch (type) {
 		case IWL_UCODE_TLV_TYPE_DEBUG_INFO:
@@ -2786,8 +2784,8 @@ static void _iwl_fw_dbg_apply_point(struct iwl_fw_runtime *fwrt,
 			struct iwl_fw_ini_allocation_data *buf_alloc = ini_tlv;
 
 			if (pnt != IWL_FW_INI_APPLY_EARLY) {
-				IWL_ERR(fwrt, invalid_ap_str, ext, pnt,
-					"buffer allocation");
+				IWL_ERR(fwrt, "WRT: ext=%d. Invalid apply point %d for %s\n",
+					ext, pnt, "buffer allocation");
 				goto next;
 			}
 
@@ -2797,8 +2795,8 @@ static void _iwl_fw_dbg_apply_point(struct iwl_fw_runtime *fwrt,
 		}
 		case IWL_UCODE_TLV_TYPE_HCMD:
 			if (pnt < IWL_FW_INI_APPLY_AFTER_ALIVE) {
-				IWL_ERR(fwrt, invalid_ap_str, ext, pnt,
-					"host command");
+				IWL_ERR(fwrt, "WRT: ext=%d. Invalid apply point %d for %s\n",
+					ext, pnt, "host command");
 				goto next;
 			}
 			iwl_fw_dbg_send_hcmd(fwrt, tlv, ext);