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openbios@openbios.org

August 2026

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[PATCH 0/6] ppc: Boot OpenBSD/macppc from disk
by Kirill A. Korinsky Aug. 27, 2026

Aug. 27, 2026

Greetings, OpenBSD/macppc MBR installations store ofwboot on an MSDOS partition; ofwboot then reopens the block device as raw partition 0 to locate the OpenBSD disklabel and kernel. OpenBIOS cannot complete this sequence: the PPC build omits FAT; the inherited GRUB FAT reader interprets little endian, potentially unaligned metadata through host integer loads; GRUBFS mishandles device failures and filesystem instance ownership; partition dispatch can interpret partition 0 as an MBR entry rather than the raw disk required by PowerPC bindings. This series corrects GRUBFS read status, descriptor ownership, and seek semantics; decodes FAT metadata independently of host byte order and alignment; implements the PowerPC partition 0 rule; and enables FAT for PPC. Testing with qemu-system-ppc mac99 confirmed that the resulting firmware loaded ofwboot from an installed OpenBSD/macppc disk; OpenBSD then mounted wd0a as root. To actually boot OpenBSD/macppc in QEMU you need this patch series: https://patchew.org/QEMU/20260827155310.7223-1-kirill@korins.ky/

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[PATCH] elf: clear PT_LOAD BSS during init-program
by Kirill A. Korinsky Aug. 18, 2026

Aug. 18, 2026

elf_init_program() copies only MIN(p_filesz, p_memsz) bytes into a claimed PT_LOAD segment; unlike load_segments(), it neither clears the remaining memory nor handles a segment containing only BSS. Clients therefore inherit stale firmware data where ELF requires zeroes. Restrict the loop to PT_LOAD headers, retain segments with nonzero p_memsz, copy their available file image, and erase the remaining memory. This preserves the existing malformed segment truncation and PPC cache flushing behavior while restoring the ELF loading contract. The issue was found by using OpenBSD sparc64 ofwboot with -Oz/-Os/-O1 when -O1 produces by clang + lld large enough code to be immune, it reduces image and moved freelist into the uncleared segment tail; alloc() read the stale value as a pointer and raised T_ALIGN on its first dereference. --- libopenbios/elf_load.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/libopenbios/elf_load.c b/libopenbios/elf_load.c index f09ccf6..c7bde82 100644 --- a/libopenbios/elf_load.c +++ b/libopenbios/elf_load.c @@ -494,6 +494,8 @@ elf_init_program(void) phdr = (Elf_phdr *)(base + ehdr->e_phoff); for (i = 0; i < ehdr->e_phnum; i++) { + if (phdr[i].p_type != PT_LOAD) + continue; #if DEBUG debug("filesz: %08lX memsz: %08lX p_offset: %08lX " @@ -503,7 +505,7 @@ elf_init_program(void) #endif size = MIN(phdr[i].p_filesz, phdr[i].p_memsz); - if (!size) + if (!phdr[i].p_memsz) continue; #if !defined(CONFIG_SPARC32) && !defined(CONFIG_X86) if( ofmem_claim( phdr[i].p_vaddr, phdr[i].p_memsz, 0 ) == -1 ) { @@ -516,12 +518,16 @@ elf_init_program(void) tmp = phdr[i].p_vaddr; addr = (char *)tmp; - memcpy(addr, base + phdr[i].p_offset, size); + if (size) + memcpy(addr, base + phdr[i].p_offset, size); + if (phdr[i].p_memsz > size) + memset(addr + size, 0, phdr[i].p_memsz - size); total_size += size; #ifdef CONFIG_PPC - flush_icache_range( addr, addr + size ); + if (size) + flush_icache_range( addr, addr + size ); #endif } -- 2.55.0

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