Use "p->sum -= checksum()" style for setting checksums.

Some code cleared the original checksum and then calculated a new one,
    others manipulated the checksum range to not include the old
    checksum.  However, this was error prone - use the "-=" syntax
    consistently to reduce possible errors.

8 files changed, 11 insertions, 16 deletions

diff --git a/src/acpi.c b/src/acpi.c
index f140f1ac..72977b12 100644
--- a/src/acpi.c
+++ b/src/acpi.c
@@ -236,7 +236,7 @@ static void acpi_build_table_header(struct acpi_table_header *h,
     memcpy(h->oem_table_id + 4, (void*)&sig, 4);
     h->oem_revision = cpu_to_le32(1);
     h->asl_compiler_revision = cpu_to_le32(1);
-    h->checksum = -checksum(h, len);
+    h->checksum -= checksum(h, len);
 }
 
 #define SSDT_SIGNATURE 0x54445353// SSDT
@@ -369,7 +369,7 @@ void acpi_bios_init(void)
     rsdp->signature = RSDP_SIGNATURE;
     memcpy(rsdp->oem_id, CONFIG_APPNAME6, 6);
     rsdp->rsdt_physical_address = cpu_to_le32(rsdt_addr);
-    rsdp->checksum = -checksum(rsdp, 20);
+    rsdp->checksum -= checksum(rsdp, 20);
     RsdpAddr = rsdp;
 
     /* RSDT */
diff --git a/src/ata.c b/src/ata.c
index 3b609c5b..699eecd4 100644
--- a/src/ata.c
+++ b/src/ata.c
@@ -951,8 +951,7 @@ fill_fdpt(int driveid)
     fdpt->a0h_signature = 0xa0;
 
     // Checksum structure.
-    u8 sum = checksum(fdpt, sizeof(*fdpt)-1);
-    fdpt->checksum = -sum;
+    fdpt->checksum -= checksum(fdpt, sizeof(*fdpt));
 }
 
 // Map a drive (that was registered via add_bcv_hd)
diff --git a/src/coreboot.c b/src/coreboot.c
index 859928f9..b8479c5b 100644
--- a/src/coreboot.c
+++ b/src/coreboot.c
@@ -62,8 +62,7 @@ copy_mptable(void *pos)
     memcpy((void*)bios_table_cur_addr, pos, length);
     struct mptable_floating_s *newp = (void*)bios_table_cur_addr;
     newp->physaddr = bios_table_cur_addr + length;
-    newp->checksum = 0;
-    newp->checksum = -checksum(newp, sizeof(*newp));
+    newp->checksum -= checksum(newp, sizeof(*newp));
     memcpy((void*)bios_table_cur_addr + length, (void*)p->physaddr, mpclength);
     bios_table_cur_addr += length + mpclength;
 }
diff --git a/src/mptable.c b/src/mptable.c
index 47aee24b..e81bd62c 100644
--- a/src/mptable.c
+++ b/src/mptable.c
@@ -44,7 +44,7 @@ mptable_init(void)
     floating->physaddr = (u32)config;
     floating->length = 1;
     floating->spec_rev = 4;
-    floating->checksum = -checksum(floating, sizeof(*floating));
+    floating->checksum -= checksum(floating, sizeof(*floating));
 
     // Config structure.
     memset(config, 0, sizeof(*config));
@@ -106,7 +106,7 @@ mptable_init(void)
     }
 
     // Set checksum.
-    config->checksum = -checksum(config, config->length);
+    config->checksum -= checksum(config, config->length);
 
     dprintf(1, "MP table addr=0x%x MPC table addr=0x%x size=0x%x\n",
             (u32)floating, (u32)config, length);
diff --git a/src/pirtable.c b/src/pirtable.c
index a96ffbc6..a83d4f7e 100644
--- a/src/pirtable.c
+++ b/src/pirtable.c
@@ -100,6 +100,6 @@ create_pirtable()
     dprintf(3, "init PIR table\n");
 
     PIR_TABLE.pir.signature = PIR_SIGNATURE;
-    PIR_TABLE.pir.checksum = -checksum(&PIR_TABLE, sizeof(PIR_TABLE));
+    PIR_TABLE.pir.checksum -= checksum(&PIR_TABLE, sizeof(PIR_TABLE));
     PirOffset = (u32)&PIR_TABLE.pir - BUILD_BIOS_ADDR;
 }
diff --git a/src/pnpbios.c b/src/pnpbios.c
index cf78f007..7d9ece50 100644
--- a/src/pnpbios.c
+++ b/src/pnpbios.c
@@ -99,5 +99,5 @@ pnp_setup()
 
     PNPHEADER.real_ip = (u32)entry_pnp_real - BUILD_BIOS_ADDR;
     PNPHEADER.prot_ip = (u32)entry_pnp_prot - BUILD_BIOS_ADDR;
-    PNPHEADER.checksum = -checksum(&PNPHEADER, sizeof(PNPHEADER));
+    PNPHEADER.checksum -= checksum(&PNPHEADER, sizeof(PNPHEADER));
 }
diff --git a/src/post.c b/src/post.c
index 638f95a8..b0189356 100644
--- a/src/post.c
+++ b/src/post.c
@@ -209,7 +209,7 @@ _start()
     boot_prep();
 
     // Setup bios checksum.
-    BiosChecksum = -checksum((u8*)BUILD_BIOS_ADDR, BUILD_BIOS_SIZE - 1);
+    BiosChecksum -= checksum((u8*)BUILD_BIOS_ADDR, BUILD_BIOS_SIZE);
 
     // Prep for boot process.
     make_bios_readonly();
diff --git a/src/smbios.c b/src/smbios.c
index 40812e3b..e9a4b31b 100644
--- a/src/smbios.c
+++ b/src/smbios.c
@@ -244,12 +244,9 @@ smbios_entry_point_init(void *start,
     ep->number_of_structures = number_of_structures;
     ep->smbios_bcd_revision = 0x24;
 
-    ep->checksum = 0;
-    ep->intermediate_checksum = 0;
+    ep->checksum -= checksum(start, 0x10);
 
-    ep->checksum = -checksum(start, 0x10);
-
-    ep->intermediate_checksum = -checksum(start + 0x10, ep->length - 0x10);
+    ep->intermediate_checksum -= checksum(start + 0x10, ep->length - 0x10);
 }
 
 /* Type 0 -- BIOS Information */