Hi,
The patch below fixes an off-by-one in /arch/amd64/stand/libsa/cmd_i386.c.
The affected code path is handling the machine boot command in the bootloader.
Currently, trying to boot from MBR partition 'a', with a command such as
machine boot hd0a, will in fact boot from whichever partition is flagged as
active, rather than forcing a boot from partition 'a'.
The bug was introduced in revision 1.20 of the original i386 architecture file
over 20 years ago on 19980224.
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--- arch/amd64/stand/libsa/cmd_i386.c.dist Fri May 10 18:20:43 2019
+++ arch/amd64/stand/libsa/cmd_i386.c Sun Aug 15 23:44:45 2021
@@ -107,7 +107,7 @@
dev += (cmd.argv[1][2] - '0');
part = (cmd.argv[1][3] - 'a');
- if (part > 0)
+ if (part >= 0)
printf("[%x,%d]\n", dev, part);
else
printf("[%x]\n", dev);
@@ -119,7 +119,7 @@
goto bad;
/* Frob boot flag in buffer from HD */
- if ((dev & 0x80) && (part > 0)){
+ if ((dev & 0x80) && (part >= 0)){
int i, j;
for (i = 0, j = DOSPARTOFF; i < 4; i++, j += 16)
--- arch/i386/stand/libsa/cmd_i386.c.dist Fri Jun 10 15:36:06 2016
+++ arch/i386/stand/libsa/cmd_i386.c Sun Aug 15 23:44:23 2021
@@ -119,7 +119,7 @@
dev += (cmd.argv[1][2] - '0');
part = (cmd.argv[1][3] - 'a');
- if (part > 0)
+ if (part >= 0)
printf("[%x,%d]\n", dev, part);
else
printf("[%x]\n", dev);
@@ -131,7 +131,7 @@
goto bad;
/* Frob boot flag in buffer from HD */
- if ((dev & 0x80) && (part > 0)){
+ if ((dev & 0x80) && (part >= 0)){
int i, j;
for (i = 0, j = DOSPARTOFF; i < 4; i++, j += 16)
