[PATCH V2 0/2] staging: slicoss: fix checksum computation

[PATCH V2 0/2] staging: slicoss: fix checksum computation

[David Matlack]

This patchset fixes a broken checksum function and removes a struct
that was being used to ignore bad checksum values.

V2 Changes:
  * Change subject to make clear this patchset fixes a bug.
  * Explicitly comment that the checksum algorithm is RFC 1071.
  * Remove byte swapping code.
  * Add detail in the changelog of each patch describing the effects
    on the user.

David Matlack (2):
  staging: slicoss: fix eeprom checksum code
  staging: slicoss: fail on corrupt eeprom

 drivers/staging/slicoss/slic.h    |   7 ---
 drivers/staging/slicoss/slicoss.c | 113 ++++++--------------------------------
 2 files changed, 16 insertions(+), 104 deletions(-)

-- 
1.9.2

[PATCH V2 1/2] staging: slicoss: fix eeprom checksum code

[David Matlack]

Rewrite slic_eeprom_cksum() to fix bugs and make readable. This patch
technically has no effect on the user as failed eeprom checksums are
ignored anyway.

The original implementation had the following issues:

  1. 2 of the 3 unrolled loops had the following bug:

       while ((len -= 32) >= 0) {
               [...]
               sum += w[15];
               w = (u16 *)((ulong) w + 16);    /* verify */
       }

     This processes 32-bytes of data but only increments the word
     pointer by 16 bytes. Fixing both of these bugs seems to fix
     slic_eeprom_cksum().

  2. Non-descriptive variable names, use of unions, and macros that
     change local state make the code difficult to read.

  3. The checksum loop is unrolled which makes the code harder to
     reason about while providing small performance improvement:
      - max eeprom length is 0x80 bytes (MAX_EECODE_SIZE), that's
        only 0x40 iterations
      - checksum is only computed during pci probe(), so not very
        often

Tested on Mojave card

Signed-off-by: David Matlack <matlackdavid@gmail.com>
---
 drivers/staging/slicoss/slicoss.c | 110 ++++++--------------------------------
 1 file changed, 15 insertions(+), 95 deletions(-)

diff --git a/drivers/staging/slicoss/slicoss.c b/drivers/staging/slicoss/slicoss.c
index dba6a00..9eb2434 100644
--- a/drivers/staging/slicoss/slicoss.c
+++ b/drivers/staging/slicoss/slicoss.c
@@ -1138,105 +1138,26 @@ static int slic_config_get(struct adapter *adapter, u32 config, u32 config_h)
 }
 
 /*
- *  this is here to checksum the eeprom, there is some ucode bug
- *  which prevens us from using the ucode result.
- *  remove this once ucode is fixed.
+ * Compute a checksum of the EEPROM according to RFC 1071.
  */
-static ushort slic_eeprom_cksum(char *m, int len)
+static u16 slic_eeprom_cksum(void *eeprom, unsigned len)
 {
-#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
-#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);\
-		}
+	u16 *wp = eeprom;
+	u32 checksum = 0;
 
-	u16 *w;
-	u32 sum = 0;
-	u32 byte_swapped = 0;
-	u32 w_int;
-
-	union {
-		char c[2];
-		ushort s;
-	} s_util;
-
-	union {
-		ushort s[2];
-		int l;
-	} l_util;
-
-	l_util.l = 0;
-	s_util.s = 0;
-
-	w = (u16 *)m;
-#if BITS_PER_LONG == 64
-	w_int = (u32) ((ulong) w & 0x00000000FFFFFFFF);
-#else
-	w_int = (u32) (w);
-#endif
-	if ((1 & w_int) && (len > 0)) {
-		REDUCE;
-		sum <<= 8;
-		s_util.c[0] = *(unsigned char *)w;
-		w = (u16 *)((char *)w + 1);
-		len--;
-		byte_swapped = 1;
+	while (len > 1) {
+		checksum += *(wp++);
+		len -= 2;
 	}
 
-	/* Unroll the loop to make overhead from branches &c small. */
-	while ((len -= 32) >= 0) {
-		sum += w[0];
-		sum += w[1];
-		sum += w[2];
-		sum += w[3];
-		sum += w[4];
-		sum += w[5];
-		sum += w[6];
-		sum += w[7];
-		sum += w[8];
-		sum += w[9];
-		sum += w[10];
-		sum += w[11];
-		sum += w[12];
-		sum += w[13];
-		sum += w[14];
-		sum += w[15];
-		w = (u16 *)((ulong) w + 16);	/* verify */
-	}
-	len += 32;
-	while ((len -= 8) >= 0) {
-		sum += w[0];
-		sum += w[1];
-		sum += w[2];
-		sum += w[3];
-		w = (u16 *)((ulong) w + 4);	/* verify */
-	}
-	len += 8;
-	if (len != 0 || byte_swapped != 0) {
-		REDUCE;
-		while ((len -= 2) >= 0)
-			sum += *w++;	/* verify */
-		if (byte_swapped) {
-			REDUCE;
-			sum <<= 8;
-			byte_swapped = 0;
-			if (len == -1) {
-				s_util.c[1] = *(char *) w;
-				sum += s_util.s;
-				len = 0;
-			} else {
-				len = -1;
-			}
+	if (len > 0)
+		checksum += *(u8 *) wp;
 
-		} else if (len == -1) {
-			s_util.c[0] = *(char *) w;
-		}
 
-		if (len == -1) {
-			s_util.c[1] = 0;
-			sum += s_util.s;
-		}
-	}
-	REDUCE;
-	return (ushort) sum;
+	while (checksum >> 16)
+		checksum = (checksum & 0xFFFF) + ((checksum >> 16) & 0xFFFF);
+
+	return ~checksum;
 }
 
 static void slic_rspqueue_free(struct adapter *adapter)
@@ -2893,9 +2814,8 @@ static int slic_card_init(struct sliccard *card, struct adapter *adapter)
 			/*
 			    calculate the EEPROM checksum
 			*/
-			calc_chksum =
-			    ~slic_eeprom_cksum((char *) peeprom,
-					       (eecodesize - 2));
+			calc_chksum = slic_eeprom_cksum(peeprom,
+							eecodesize - 2);
 			/*
 			    if the ucdoe chksum flag bit worked,
 			    we wouldn't need this
-- 
1.9.2

[PATCH V2 2/2] staging: slicoss: fail on corrupt eeprom

[David Matlack]

Remove fail_on_bad_eeprom, which was always 0 and thus being used
to ignore incorrect checksumming. This means devices with corrupt
eeprom will now cause the driver to fail.

Since fail_on_bad_eeprom was the last member in use of struct
slic_reg_params, remove that struct altogether.

Signed-off-by: David Matlack <matlackdavid@gmail.com>
---
 drivers/staging/slicoss/slic.h    | 7 -------
 drivers/staging/slicoss/slicoss.c | 3 +--
 2 files changed, 1 insertion(+), 9 deletions(-)

diff --git a/drivers/staging/slicoss/slic.h b/drivers/staging/slicoss/slic.h
index 0dc73d5..3a5aa88 100644
--- a/drivers/staging/slicoss/slic.h
+++ b/drivers/staging/slicoss/slic.h
@@ -362,12 +362,6 @@ struct slic_shmem {
 	volatile struct slic_stats     inicstats;
 };
 
-struct slic_reg_params {
-	u32       linkspeed;
-	u32       linkduplex;
-	u32       fail_on_bad_eeprom;
-};
-
 struct slic_upr {
 	uint               adapter;
 	u32            upr_request;
@@ -492,7 +486,6 @@ struct adapter {
 	u32             intagg_period;
 	struct inicpm_state    *inicpm_info;
 	void *pinicpm_info;
-	struct slic_reg_params   reg_params;
 	struct slic_ifevents  if_events;
 	struct slic_stats        inicstats_prev;
 	struct slicnet_stats     slic_stats;
diff --git a/drivers/staging/slicoss/slicoss.c b/drivers/staging/slicoss/slicoss.c
index 9eb2434..b9fd94f 100644
--- a/drivers/staging/slicoss/slicoss.c
+++ b/drivers/staging/slicoss/slicoss.c
@@ -2841,8 +2841,7 @@ static int slic_card_init(struct sliccard *card, struct adapter *adapter)
 				    sizeof(struct slic_eeprom),
 				    peeprom, phys_config);
 
-		if ((!card->config.EepromValid) &&
-		    (adapter->reg_params.fail_on_bad_eeprom)) {
+		if (!card->config.EepromValid) {
 			slic_reg64_write(adapter, &slic_regs->slic_isp, 0,
 					 &slic_regs->slic_addr_upper,
 					 0, FLUSH);
-- 
1.9.2

Re: [PATCH V2 2/2] staging: slicoss: fail on corrupt eeprom

[Dan Carpenter]

Now, those are some beautiful changelogs.  ;)  Thanks so much.

regards,
dan carpenter

Re: [PATCH V2 2/2] staging: slicoss: fail on corrupt eeprom

[David Matlack]

Thanks for the reviews!