com32/chain: comments, minor adjustment

- add some comments to clarify c{nul,add,max} modes
- use enums instead of defines
- remove unnecessary integer casts
- avoid casts and uninline guid_is0()
- minor handover comment/flow changes
- clean up some old comment-outs
- add -fno-strict-aliasing as it's not picked anymore by default for
  elf.mk

Signed-off-by: Michal Soltys <soltys@ziu.info>

diff --git a/com32/chain/Makefile b/com32/chain/Makefile
index 1bb6d22..c7587ea 100644 (file)
--- a/com32/chain/Makefile
+++ b/com32/chain/Makefile
@@ -19,6 +19,7 @@ MAKEDIR = $(topdir)/mk
 include $(MAKEDIR)/elf.mk
 
 OBJS = chain.o partiter.o utility.o options.o mangle.o
+CFLAGS += -fno-strict-aliasing
 
 all: chain.c32
 

diff --git a/com32/chain/chain.c b/com32/chain/chain.c
index f0ccd97..617e9e3 100644 (file)
--- a/com32/chain/chain.c
+++ b/com32/chain/chain.c
@@ -247,14 +247,14 @@ static void do_boot(struct data_area *data, int ndata)
 
        /* Mapping table; start out with identity mapping everything */
        for (i = 0; i < 256; i++)
-           p[i] = (uint8_t)i;
+           p[i] = i;
 
        /* And the actual swap */
        p[driveno] = swapdrive;
        p[swapdrive] = driveno;
 
        /* Adjust registers */
-       opt.regs.ds = opt.regs.cs = (uint16_t)(endimage >> 4);
+       opt.regs.ds = opt.regs.cs = endimage >> 4;
        opt.regs.esi.l = opt.regs.es = 0;
        opt.regs.ecx.l = sizeof swapstub >> 2;
        opt.regs.ip = 0x10;     /* Installer offset */
@@ -401,13 +401,15 @@ static int setup_handover(const struct part_iter *iter,
                   struct data_area *data)
 {
     struct disk_dos_part_entry *ha;
-    uint32_t synth_size;
-    uint32_t *plen;
+    uint32_t synth_size = sizeof *ha;
 
-    if (!iter->index) { /* implies typeraw or non-iterated */
+    /*
+     * we have to cover both non-iterated but otherwise properly detected
+     * gpt/dos schemes as well as raw disks; checking index for 0 covers both
+     */
+    if (iter->index == 0) {
        uint32_t len;
        /* RAW handover protocol */
-       synth_size = sizeof(struct disk_dos_part_entry);
        ha = malloc(synth_size);
        if (!ha) {
            error("Could not build RAW hand-over record!\n");
@@ -415,24 +417,24 @@ static int setup_handover(const struct part_iter *iter,
        }
        len = ~0u;
        if (iter->length < len)
-           len = (uint32_t)iter->length;
-       lba2chs(&ha->start, &iter->di, 0, l2c_cadd);
-       lba2chs(&ha->end, &iter->di, len - 1, l2c_cadd);
+           len = iter->length;
+       lba2chs(&ha->start, &iter->di, 0, L2C_CADD);
+       lba2chs(&ha->end, &iter->di, len - 1, L2C_CADD);
        ha->active_flag = 0x80;
        ha->ostype = 0xDA;      /* "Non-FS Data", anything is good here though ... */
        ha->start_lba = 0;
        ha->length = len;
     } else if (iter->type == typegpt) {
+       uint32_t *plen;
        /* GPT handover protocol */
-       synth_size = sizeof(struct disk_dos_part_entry) +
-           sizeof(uint32_t) + (uint32_t)iter->sub.gpt.pe_size;
+       synth_size += sizeof *plen + iter->sub.gpt.pe_size;
        ha = malloc(synth_size);
        if (!ha) {
            error("Could not build GPT hand-over record!\n");
            goto bail;
        }
-       lba2chs(&ha->start, &iter->di, iter->start_lba, l2c_cadd);
-       lba2chs(&ha->end, &iter->di, iter->start_lba + iter->length - 1, l2c_cadd);
+       lba2chs(&ha->start, &iter->di, iter->start_lba, L2C_CADD);
+       lba2chs(&ha->end, &iter->di, iter->start_lba + iter->length - 1, L2C_CADD);
        ha->active_flag = 0x80;
        ha->ostype = 0xED;
        /* All bits set by default */
@@ -440,12 +442,12 @@ static int setup_handover(const struct part_iter *iter,
        ha->length = ~0u;
        /* If these fit the precision, pass them on */
        if (iter->start_lba < ha->start_lba)
-           ha->start_lba = (uint32_t)iter->start_lba;
+           ha->start_lba = iter->start_lba;
        if (iter->length < ha->length)
-           ha->length = (uint32_t)iter->length;
+           ha->length = iter->length;
        /* Next comes the GPT partition record length */
-       plen = (uint32_t *) (ha + 1);
-       plen[0] = (uint32_t)iter->sub.gpt.pe_size;
+       plen = (uint32_t *)(ha + 1);
+       plen[0] = iter->sub.gpt.pe_size;
        /* Next comes the GPT partition record copy */
        memcpy(plen + 1, iter->record, plen[0]);
 #ifdef DEBUG
@@ -453,9 +455,9 @@ static int setup_handover(const struct part_iter *iter,
        disk_dos_part_dump(ha);
        disk_gpt_part_dump((struct disk_gpt_part_entry *)(plen + 1));
 #endif
+    /* the only possible case left is dos scheme */
     } else if (iter->type == typedos) {
        /* MBR handover protocol */
-       synth_size = sizeof(struct disk_dos_part_entry);
        ha = malloc(synth_size);
        if (!ha) {
            error("Could not build MBR hand-over record!\n");
@@ -463,10 +465,10 @@ static int setup_handover(const struct part_iter *iter,
        }
        memcpy(ha, iter->record, synth_size);
        /* make sure these match bios imaginations and are ebr agnostic */
-       lba2chs(&ha->start, &iter->di, iter->start_lba, l2c_cadd);
-       lba2chs(&ha->end, &iter->di, iter->start_lba + iter->length - 1, l2c_cadd);
-       ha->start_lba = (uint32_t)iter->start_lba;
-       ha->length = (uint32_t)iter->length;
+       lba2chs(&ha->start, &iter->di, iter->start_lba, L2C_CADD);
+       lba2chs(&ha->end, &iter->di, iter->start_lba + iter->length - 1, L2C_CADD);
+       ha->start_lba = iter->start_lba;
+       ha->length = iter->length;
 
 #ifdef DEBUG
        dprintf("MBR handover:\n");

diff --git a/com32/chain/mangle.c b/com32/chain/mangle.c
index e3c494c..69004b8 100644 (file)
--- a/com32/chain/mangle.c
+++ b/com32/chain/mangle.c
@@ -204,7 +204,7 @@ int manglef_grub(const struct part_iter *iter, struct data_area *data)
      *   0-3:  primary partitions
      *   4-*:  logical partitions
      */
-    stage2->install_partition.part1 = (uint8_t)(iter->index - 1);
+    stage2->install_partition.part1 = iter->index - 1;
 
     /*
      * Grub Legacy reserves 89 bytes (from 0x8217 to 0x826f) for the
@@ -264,9 +264,9 @@ int manglef_drmk(struct data_area *data)
     data->size = tsize;
     /* ds:bp is assumed by DRMK to be the boot sector */
     /* offset 28 is the FAT HiddenSectors value */
-    opt.regs.ds = (uint16_t)((tsize >> 4) + (opt.fseg - 2));
+    opt.regs.ds = (tsize >> 4) + (opt.fseg - 2);
     /* "Patch" into tail of the new space */
-    *(uint32_t *)((char*)data->data + tsize - 4) = (uint32_t)fs_lba;
+    *(uint32_t *)((char*)data->data + tsize - 4) = fs_lba;
 
     return 0;
 bail:
@@ -282,7 +282,7 @@ static int mangle_bpb(const struct part_iter *iter, struct data_area *data, cons
     /* BPB: hidden sectors 32bit*/
     if (type >= bpbV34) {
        if (iter->start_lba < ~0u)
-           *(uint32_t *) ((char *)data->data + 0x1c) = (uint32_t)iter->start_lba;
+           *(uint32_t *) ((char *)data->data + 0x1c) = iter->start_lba;
        else
            /* won't really help much, but ... */
            *(uint32_t *) ((char *)data->data + 0x1c) = ~0u;
@@ -290,7 +290,7 @@ static int mangle_bpb(const struct part_iter *iter, struct data_area *data, cons
     /* BPB: hidden sectors 16bit*/
     if (bpbV30 <= type && type <= bpbV32) {
        if (iter->start_lba < 0xFFFF)
-           *(uint16_t *) ((char *)data->data + 0x1c) = (uint16_t)iter->start_lba;
+           *(uint16_t *) ((char *)data->data + 0x1c) = iter->start_lba;
        else
            /* won't really help much, but ... */
            *(uint16_t *) ((char *)data->data + 0x1c) = (uint16_t)~0u;
@@ -298,7 +298,7 @@ static int mangle_bpb(const struct part_iter *iter, struct data_area *data, cons
     /* BPB: legacy geometry */
     if (type >= bpbV30) {
        if (iter->di.cbios)
-           *(uint32_t *)((char *)data->data + 0x18) = (uint32_t)((iter->di.head << 16) | iter->di.spt);
+           *(uint32_t *)((char *)data->data + 0x18) = (iter->di.head << 16) | iter->di.spt;
        else {
            if (iter->di.disk & 0x80)
                *(uint32_t *)((char *)data->data + 0x18) = 0x00FF003F;
@@ -308,8 +308,7 @@ static int mangle_bpb(const struct part_iter *iter, struct data_area *data, cons
     }
     /* BPB: drive */
     if (drvoff_detect(type, &off)) {
-       *(uint8_t *)((char *)data->data + off) = (uint8_t)
-           (opt.swap ? iter->di.disk & 0x80 : iter->di.disk);
+       *(uint8_t *)((char *)data->data + off) = (opt.swap ? iter->di.disk & 0x80 : iter->di.disk);
     }
 
     return 0;
@@ -427,18 +426,18 @@ int mangler_init(const struct part_iter *iter)
 {
     /* Set initial registry values */
     if (opt.file) {
-       opt.regs.cs = opt.regs.ds = opt.regs.ss = (uint16_t)opt.fseg;
-       opt.regs.ip = (uint16_t)opt.fip;
+       opt.regs.cs = opt.regs.ds = opt.regs.ss = opt.fseg;
+       opt.regs.ip = opt.fip;
     } else {
-       opt.regs.cs = opt.regs.ds = opt.regs.ss = (uint16_t)opt.sseg;
-       opt.regs.ip = (uint16_t)opt.sip;
+       opt.regs.cs = opt.regs.ds = opt.regs.ss = opt.sseg;
+       opt.regs.ip = opt.sip;
     }
 
     if (opt.regs.ip == 0x7C00 && !opt.regs.cs)
        opt.regs.esp.l = 0x7C00;
 
     /* DOS kernels want the drive number in BL instead of DL. Indulge them. */
-    opt.regs.ebx.b[0] = opt.regs.edx.b[0] = (uint8_t)iter->di.disk;
+    opt.regs.ebx.b[0] = opt.regs.edx.b[0] = iter->di.disk;
 
     return 0;
 }
@@ -448,7 +447,7 @@ int mangler_handover(const struct part_iter *iter, const struct data_area *data)
 {
     if (opt.file && opt.maps && !opt.hptr) {
        opt.regs.esi.l = opt.regs.ebp.l = opt.soff;
-       opt.regs.ds = (uint16_t)opt.sseg;
+       opt.regs.ds = opt.sseg;
        opt.regs.eax.l = 0;
     } else if (opt.hand) {
        /* base is really 0x7be */
@@ -472,7 +471,7 @@ int mangler_handover(const struct part_iter *iter, const struct data_area *data)
 int mangler_grldr(const struct part_iter *iter)
 {
     if (opt.grldr)
-       opt.regs.edx.b[1] = (uint8_t)(iter->index - 1);
+       opt.regs.edx.b[1] = iter->index - 1;
 
     return 0;
 }
@@ -502,7 +501,7 @@ static int mpe_sethide(struct part_iter *iter, struct part_iter *miter)
     if ((t <= 0x1f) && ((mask >> (t & ~0x10u)) & 1)) {
        /* It's a hideable partition type */
        if (miter->index == iter->index || opt.hide & 4)
-           t &= (uint8_t)(~0x10u);     /* unhide */
+           t &= ~0x10u;        /* unhide */
        else
            t |= 0x10u; /* hide */
     }
@@ -585,8 +584,8 @@ static int mpe_setchs(const struct disk_info *di,
     ochs1 = *(uint32_t *)dp->start;
     ochs2 = *(uint32_t *)dp->end;
 
-    lba2chs(&dp->start, di, lba1, l2c_cadd);
-    lba2chs(&dp->end, di, lba1 + dp->length - 1, l2c_cadd);
+    lba2chs(&dp->start, di, lba1, L2C_CADD);
+    lba2chs(&dp->end, di, lba1 + dp->length - 1, L2C_CADD);
 
     return
        *(uint32_t *)dp->start != ochs1 ||
@@ -618,7 +617,7 @@ int manglepe_fixchs(struct part_iter *miter)
        ridx = iter->rawindex;
        dp = (struct disk_dos_part_entry *)iter->record;
 
-       wb |= mpe_setchs(&iter->di, dp, (uint32_t)iter->start_lba);
+       wb |= mpe_setchs(&iter->di, dp, iter->start_lba);
        if (ridx > 4)
                wb |= mpe_setchs(&iter->di, dp + 1, iter->sub.dos.nebr_lba);
 

diff --git a/com32/chain/options.c b/com32/chain/options.c
index 5f7433d..b831afa 100644 (file)
--- a/com32/chain/options.c
+++ b/com32/chain/options.c
@@ -166,7 +166,7 @@ void opt_set_defs(void)
 int opt_parse_args(int argc, char *argv[])
 {
     int i;
-    unsigned int v;
+    size_t v;
     char *p;
 
     for (i = 1; i < argc; i++) {
@@ -182,7 +182,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.bss = true;
            opt.maps = false;
            opt.setbpb = true;
-           /* opt.save = true; */
        } else if (!strncmp(argv[i], "bs=", 3)) {
            opt.file = argv[i] + 3;
            opt.sect = false;
@@ -198,7 +197,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.fip = 0;
            opt.file = argv[i] + 6;
            opt.setbpb = true;
-           /* opt.save = true; */
            opt.hand = false;
        } else if (!strncmp(argv[i], "reactos=", 8)) {
            /*
@@ -212,7 +210,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.fip = 0x8100;
            opt.file = argv[i] + 8;
            opt.setbpb = true;
-           /* opt.save = true; */
            opt.hand = false;
        } else if (!strncmp(argv[i], "cmldr=", 6)) {
            opt.fseg = 0x2000;  /* CMLDR wants this address */
@@ -221,7 +218,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.file = argv[i] + 6;
            opt.cmldr = true;
            opt.setbpb = true;
-           /* opt.save = true; */
            opt.hand = false;
        } else if (!strncmp(argv[i], "freedos=", 8)) {
            opt.fseg = 0x60;    /* FREEDOS wants this address */
@@ -230,7 +226,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.sseg = 0x1FE0;
            opt.file = argv[i] + 8;
            opt.setbpb = true;
-           /* opt.save = true; */
            opt.hand = false;
        } else if ( (v = 6, !strncmp(argv[i], "msdos=", v) ||
                     !strncmp(argv[i], "pcdos=", v)) ||
@@ -241,7 +236,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.sseg = 0x8000;
            opt.file = argv[i] + v;
            opt.setbpb = true;
-           /* opt.save = true; */
            opt.hand = false;
        } else if (!strncmp(argv[i], "drmk=", 5)) {
            opt.fseg = 0x70;    /* DRMK wants this address */
@@ -253,7 +247,6 @@ int opt_parse_args(int argc, char *argv[])
            opt.file = argv[i] + 5;
            /* opt.drmk = true; */
            opt.setbpb = true;
-           /* opt.save = true; */
            opt.hand = false;
        } else if (!strncmp(argv[i], "grub=", 5)) {
            opt.fseg = 0x800;   /* stage2 wants this address */
@@ -371,13 +364,6 @@ int opt_parse_args(int argc, char *argv[])
        goto bail;
     }
 
-#if 0
-    if ((!opt.maps || !opt.sect) && !opt.file) {
-       error("You have to load something.\n");
-       goto bail;
-    }
-#endif
-
     if (opt.filebpb && !opt.file) {
        error("Option 'filebpb' requires a file.\n");
        goto bail;

diff --git a/com32/chain/partiter.c b/com32/chain/partiter.c
index 7a6006b..092cca2 100644 (file)
--- a/com32/chain/partiter.c
+++ b/com32/chain/partiter.c
@@ -765,7 +765,7 @@ struct part_iter *pi_begin(const struct disk_info *di, int stepall)
            error("Invalid GPT header's values.\n");
            goto bail;
        }
-       if (!(gptl = disk_read_sectors(di, gpt_loff, (uint8_t)gpt_lcnt))) {
+       if (!(gptl = disk_read_sectors(di, gpt_loff, gpt_lcnt))) {
            error("Couldn't read GPT partition list.\n");
            goto bail;
        }
@@ -774,11 +774,11 @@ struct part_iter *pi_begin(const struct disk_info *di, int stepall)
            error("WARNING: GPT partition list checksum invalid, trying backup.\n");
            free(gptl);
            /* secondary array directly precedes secondary header */
-           if (!(gptl = disk_read_sectors(di, gpth->lba_alt - gpt_lcnt, (uint8_t)gpt_lcnt))) {
+           if (!(gptl = disk_read_sectors(di, gpth->lba_alt - gpt_lcnt, gpt_lcnt))) {
                error("Couldn't read backup GPT partition list.\n");
                goto bail;
            }
-           if (check_crc(gpth->table_chksum, (const uint8_t *)gptl, (unsigned int)gpt_lsiz)) {
+           if (check_crc(gpth->table_chksum, (const uint8_t *)gptl, gpt_lsiz)) {
                error("Backup GPT partition list checksum invalid.\n");
                goto bail;
            }

diff --git a/com32/chain/utility.c b/com32/chain/utility.c
index ea3aa1f..18dbbc6 100644 (file)
--- a/com32/chain/utility.c
+++ b/com32/chain/utility.c
@@ -50,16 +50,6 @@ static const char *bpbtypes[] = {
     [7] =  "7.0",
 };
 
-void error(const char *msg)
-{
-    fputs(msg, stderr);
-}
-
-int guid_is0(const struct guid *guid)
-{
-    return !*(const uint64_t *)guid && !*((const uint64_t *)guid + 1);
-}
-
 void wait_key(void)
 {
     int cnt;
@@ -78,7 +68,29 @@ void wait_key(void)
     } while (!cnt || (cnt < 0 && errno == EAGAIN));
 }
 
-void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, uint32_t mode)
+int guid_is0(const struct guid *guid)
+{
+    return
+       !(guid->data1 ||
+         guid->data2 ||
+         guid->data3 ||
+         guid->data4);
+}
+
+/*
+ * mode explanation:
+ *
+ * cnul - "strict" mode, never returning higher value than obtained from cbios
+ * cadd - if the disk is larger than reported geometry /and/ if the geometry has
+ *        less cylinders than 1024 - it means that the total size is somewhere
+ *        between cs and cs+1; in this particular case, we bump the cs to be able
+ *        to return matching chs triplet
+ * cmax - assume we can use any cylinder value
+ *
+ * by default cadd seems most reasonable, giving consistent results with e.g.
+ * sfdisk's behavior
+ */
+void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, int mode)
 {
     uint32_t c, h, s, t;
     uint32_t cs, hs, ss;
@@ -91,9 +103,10 @@ void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, uint32_t m
        cs = di->cyl;
        hs = di->head;
        ss = di->spt;
-       if (mode == l2c_cadd && cs < 1024 && di->lbacnt > cs*hs*ss)
-           cs++;
-       else if (mode == l2c_cmax)
+       if (mode == L2C_CADD) {
+           if (cs < 1024 && di->lbacnt > cs*hs*ss)
+               cs++;
+       } else if (mode == L2C_CMAX)
            cs = 1024;
     } else {
        if (di->disk & 0x80) {
@@ -112,8 +125,8 @@ void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, uint32_t m
        h = hs - 1;
        c = cs - 1;
     } else {
-       s = ((uint32_t)lba % ss) + 1;
-       t = (uint32_t)lba / ss;
+       s = (lba % ss) + 1;
+       t = lba / ss;
        h = t % hs;
        c = t / hs;
     }

diff --git a/com32/chain/utility.h b/com32/chain/utility.h
index 4e32dcd..769c4d1 100644 (file)
--- a/com32/chain/utility.h
+++ b/com32/chain/utility.h
@@ -32,6 +32,7 @@
 #define COM32_CHAIN_UTILITY_H
 
 #include <stdint.h>
+#include <stdio.h>
 #include <syslinux/disk.h>
 
 #define bpbUNK 0
@@ -43,17 +44,21 @@
 #define bpbVNT 6
 #define bpbV70 7
 
-#define l2c_cnul 0
-#define l2c_cadd 1
-#define l2c_cmax 2
+/* see utility.c for details */
+enum {L2C_CNUL, L2C_CADD, L2C_CMAX};
 
-void error(const char *msg);
-int guid_is0(const struct guid *guid);
 void wait_key(void);
-void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, uint32_t mode);
+void lba2chs(disk_chs *dst, const struct disk_info *di, uint64_t lba, int mode);
 uint32_t get_file_lba(const char *filename);
 int drvoff_detect(int type, unsigned int *off);
 int bpb_detect(const uint8_t *bpb, const char *tag);
+int guid_is0(const struct guid *guid);
+
+static inline
+void error(const char *msg)
+{
+    fputs(msg, stderr);
+}
 
 #endif