January 2026 - SeaBIOS - mail.coreboot.org

[PATCH] Implement semantic OFW path matching and unit address parsing
by Glenn Griffin May 12, 2026

May 12, 2026

Introduce a robust semantic matcher for Open Firmware (OFW) device paths to replace the previous prefix-based string matching logic. This change enables SeaBIOS to accurately correlate bootorder entries with concrete hardware devices by understanding the topological structure and addressing scheme of IEEE 1275-compliant paths. Key changes: - Implement parse_hex to handle standard and relaxed unit addresses (e.g., treating "@1,0" and "@1" as equivalent for function 0). - Implement fw_path_match to perform node-by-node comparisons, supporting wildcards ('*') for both node names and unit addresses. - Incorporate a generic name fallback mechanism where nodes match based solely on unit addresses if names differ, essential for Broadcom/standard PCI addressing compatibility. - Update find_prio and boot_lchs_find to utilize the new semantic matcher, ensuring consistent behavior across boot priority and disk geometry selection. These improvements ensure that boot ordering remains predictable and flexible even when host-side tools use generic labels or when controller driver names vary within the guest. Signed-off-by: Glenn Griffin <glenng(a)google.com> --- src/boot.c | 142 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 126 insertions(+), 16 deletions(-) diff --git a/src/boot.c b/src/boot.c index 5c37dafd..d60950c1 100644 --- a/src/boot.c +++ b/src/boot.c @@ -29,24 +29,134 @@ // See if 'str' starts with 'glob' - if glob contains an '*' character // it will match any number of characters in str that aren't a '/' or // the next glob character. -static char * -glob_prefix(const char *glob, const char *str) +// Parse a hex number from a string. +static int +parse_hex(const char **ptr) { - for (;;) { - if (!*glob && (!*str || *str == '/')) - return (char*)str; - if (*glob == '*') { - if (!*str || *str == '/' || *str == glob[1]) - glob++; - else - str++; + const char *p = *ptr; + int val = 0; + while (1) { + char c = *p; + if (c >= '0' && c <= '9') + val = (val << 4) | (c - '0'); + else if (c >= 'a' && c <= 'f') + val = (val << 4) | (c - 'a' + 10); + else if (c >= 'A' && c <= 'F') + val = (val << 4) | (c - 'A' + 10); + else + break; + p++; + } + *ptr = p; + return val; +} + +// Perform semantic matching of an Open Firmware path glob against a concrete path. +// Supports: +// - '*' wildcard for node names (e.g., /pci@* matches /pci@i0cf8) +// - Generic fallback: if addresses match, node name is ignored (e.g. /disk@3,0 matches /nvme@3) +// - Relaxed unit address matching (e.g., @3,0 matches @3) +static int +fw_path_match(const char *glob, const char *path) +{ + while (*glob && *path) { + // match separators + if (*glob == '/') { + if (*path != '/') + return 0; + glob++; + path++; continue; } - if (*glob != *str) - return NULL; - glob++; - str++; + + // parse node name + const char *glob_end = strchr(glob, '@'); + const char *path_end = strchr(path, '@'); + // Handle cases where @ is missing (malformed or root?) or next char is / + const char *glob_slash = strchr(glob, '/'); + const char *path_slash = strchr(path, '/'); + + if (!glob_end || (glob_slash && glob_slash < glob_end)) + glob_end = glob_slash ? glob_slash : glob + strlen(glob); + if (!path_end || (path_slash && path_slash < path_end)) + path_end = path_slash ? path_slash : path + strlen(path); + + int glob_len = glob_end - glob; + int path_len = path_end - path; + + // Check Name Match + int name_match = 0; + if (glob[0] == '*') + name_match = 1; // Wildcard matches anything + else if (glob_len == path_len && memcmp(glob, path, glob_len) == 0) + name_match = 1; // Exact match + + glob = glob_end; + path = path_end; + + // Check Address Match + int glob_has_addr = (*glob == '@'); + int path_has_addr = (*path == '@'); + + if (glob_has_addr != path_has_addr) + return 0; // Structure mismatch + + if (glob_has_addr) { + glob++; + path++; + + // Check for wildcard in address + if (glob[0] == '*') { + // Wildcard address matches any path address + // But we still require structure match (both had @) + // We advance pointers past address + // Consume glob address until / or end + while (*glob && *glob != '/') glob++; + // Consume path address until / or end + while (*path && *path != '/') path++; + + // If name matched (or was *) AND address is *, then match. + if (!name_match) return 0; + continue; + } + + // Parse Address + // Format: N[,M] + int glob_val1 = parse_hex(&glob); + int path_val1 = parse_hex(&path); + + if (glob_val1 != path_val1) + return 0; + + int glob_val2 = 0; + int path_val2 = 0; + + if (*glob == ',') { + glob++; + glob_val2 = parse_hex(&glob); + } + if (*path == ',') { + path++; + path_val2 = parse_hex(&path); + } + + // Semantic Address Match: Treat missing secondary address as 0 + // If addresses match, we consider the node a match even if names differed! + // (Generic PCI fallback logic: /ethernet@3 == /scsi@3 if address is 3) + if (glob_val2 != path_val2) + return 0; + + // If we are here, addresses matched. + // We ignore 'name_match' result (allow mismatch/alias) + } else { + // No addresses. Strict name match required (or wildcard) + if (!name_match) + return 0; + } } + + // Both must end or have matched fully + return (*glob == '\0' && *path == '\0'); } #define FW_PCI_DOMAIN "/pci@i0cf8" @@ -177,7 +287,7 @@ boot_lchs_find(const char *glob) dprintf(1, "Searching bios-geometry for: %s\n", glob); int i; for (i = 0; i < BiosGeometryCount; i++) - if (glob_prefix(glob, BiosGeometry[i].name)) + if (fw_path_match(glob, BiosGeometry[i].name)) return &BiosGeometry[i]; return NULL; } @@ -290,7 +400,7 @@ find_prio(const char *glob) dprintf(1, "Searching bootorder for: %s\n", glob); int i; for (i = 0; i < BootorderCount; i++) - if (glob_prefix(glob, Bootorder[i])) + if (fw_path_match(glob, Bootorder[i])) return i+1; return -1; } -- 2.52.0.457.g6b5491de43-goog

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[PATCH v3] boot: Add boot failure catch-all handler to prevent VM crashes
by Alexander Graf Jan. 21, 2026

Jan. 21, 2026

Implement catch-all mechanism to handle invalid boot loaders that execute random instructions and reach the VGA hole at 0xa0000, which would lead to VM crashes with KVM_INTERNAL_ERROR. When a BIOS boot loader gets corrupted, it can end up jumping across address space and execute stray code. The typical symptom of that is that it executes 0x0 (addw) instructions until the code reaches an MMIO region, such as the VGA window. When running in KVM, attempting to execute code from the MMIO window results in KVM_INTERNAL_ERROR exits which crash the VM. To prevent VM crashes before we reach such an MMIO window, place trampoline code into a special panic handler at strategic locations that should never get executed in the first place. When we now have stray code executing, the trampoline jumps to the panic handler which causes an emergency print of "BIOS failed to boot volume" and cleanly shuts down the machine. This is a nicer experience for users as it prints out why their system broke and in addition it avoids KVM_INTERNAL_ERROR calls when a virtual machine attempts to execute from MMIO because of a broken boot loader. Signed-off-by: Alexander Graf <graf(a)amazon.com> --- v1 -> v2: - Clarify error message - Move 32bit handler entry to similar other interrupt code v2 -> v3: - Replace int logic with a ljmp trampoline - Use assembler instead of hard coding opcodes - Make naming more consistent - Simplify installation logic --- src/boot.c | 25 +++++++++++++++++++++++++ src/post.c | 1 + src/romlayout.S | 11 +++++++++++ src/util.h | 1 + 4 files changed, 38 insertions(+) diff --git a/src/boot.c b/src/boot.c index 5c37dafd..5c0c8f4c 100644 --- a/src/boot.c +++ b/src/boot.c @@ -1044,3 +1044,28 @@ handle_19(void) BootSequence = 0; do_boot(0); } + +void VISIBLE32FLAT +panic_bootfail_catchall(void) +{ + printf("\n\nBIOS failed to boot volume. The boot loader may be corrupted.\n\n "); + + /* Try to shut down. Will busy loop on failure to shut down. */ + apm_shutdown(); +} + +/* + * Install the catch-all trampoline just before VGA hole at 0xa0000 and at the end + * of the PMM zero region. + */ +void +install_bootfail_catchall(void) +{ + extern u8 bootfail_catchall_trampoline[], bootfail_catchall_trampoline_end[]; + int len = (long)bootfail_catchall_trampoline_end - (long)bootfail_catchall_trampoline; + + /* Install just before the VGA hole */ + memcpy((u8*)BUILD_LOWRAM_END - len, bootfail_catchall_trampoline, len); + /* and after the PMM zero region */ + memcpy((u8*)BUILD_EBDA_MINIMUM, bootfail_catchall_trampoline, len); +} diff --git a/src/post.c b/src/post.c index f93106a1..026e2cd9 100644 --- a/src/post.c +++ b/src/post.c @@ -115,6 +115,7 @@ interface_init(void) // Other interfaces boot_init(); + install_bootfail_catchall(); bios32_init(); pmm_init(); pnp_init(); diff --git a/src/romlayout.S b/src/romlayout.S index c4a4635e..d37ffbd4 100644 --- a/src/romlayout.S +++ b/src/romlayout.S @@ -580,6 +580,17 @@ entry_19: entry_18: ENTRY_INTO32 _cfunc32flat_handle_18 + // We jump here with ljmp from the catch-all trampoline code + DECLFUNC bootfail_catchall_16 +bootfail_catchall_16: + ENTRY_INTO32 _cfunc32flat_panic_bootfail_catchall + + // This code gets copied into the respective target locations + DECLFUNC bootfail_catchall_trampoline +bootfail_catchall_trampoline: + ljmpw $SEG_BIOS, $bootfail_catchall_16 +.global bootfail_catchall_trampoline_end +bootfail_catchall_trampoline_end: /**************************************************************** * Fixed position entry points diff --git a/src/util.h b/src/util.h index aff8e888..3c5d075c 100644 --- a/src/util.h +++ b/src/util.h @@ -47,6 +47,7 @@ int boot_lchs_find_scsi_device(struct pci_device *pci, int target, int lun, struct chs_s *chs); int boot_lchs_find_ata_device(struct pci_device *pci, int chanid, int slave, struct chs_s *chs); +void install_bootfail_catchall(void); // bootsplash.c void enable_vga_console(void); -- 2.47.1 Amazon Web Services Development Center Germany GmbH Tamara-Danz-Str. 13 10243 Berlin Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597

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[PATCH v2] boot: Add boot failure catch-all handler to prevent VM crashes
by Alexander Graf Jan. 21, 2026

Jan. 21, 2026

Implement catch-all mechanism to handle invalid boot loaders that execute random instructions and reach the VGA hole at 0xa0000, which would lead to VM crashes with KVM_INTERNAL_ERROR. When a BIOS boot loader gets corrupted, it can end up jumping across address space and execute stray code. The typical symptom of that is that it executes 0x0 (addw) instructions until the code reaches an MMIO region, such as the VGA window. When running in KVM, attempting to execute code from the MMIO window results in KVM_INTERNAL_ERROR exits which crash the VM. To prevent VM crashes before we reach such an MMIO window, introduce an internal int 0xf0 handler and call it at strategic locations that should never get executed in the first place. When we now have stray code executing, these int calls cause an emergency print of "BIOS failed to boot volume" and cleanly shut down the machine. This is a nicer experience for users as it prints out why their system broke and in addition it avoids KVM_INTERNAL_ERROR calls when a virtual machine attempts to execute from MMIO because of a broken boot loader. Signed-off-by: Alexander Graf <graf(a)amazon.com> --- v1 -> v2: - Clarify error message - Move 32bit handler entry to similar other interrupt code --- src/boot.c | 36 ++++++++++++++++++++++++++++++++++++ src/post.c | 4 ++++ src/romlayout.S | 4 ++++ src/util.h | 1 + 4 files changed, 45 insertions(+) diff --git a/src/boot.c b/src/boot.c index 5c37dafd..fd8bdf01 100644 --- a/src/boot.c +++ b/src/boot.c @@ -1044,3 +1044,39 @@ handle_19(void) BootSequence = 0; do_boot(0); } + +// INT f0h Boot Failure Service Entry Point +void VISIBLE32FLAT +handle_f0(void) +{ + printf("\n\nBIOS failed to boot volume. The boot loader may be corrupted.\n\n "); + + /* Try to shut down. Will busy loop on failure to shut down. */ + apm_shutdown(); +} + +static const u8 catchall[0x10] = { + 0xcd, // INT + 0xf0, // interrupt number 0xF0 + 0xeb, // JMP short + 0xfc, // -3 (jump back to INT) +}; + +static void +install_bootfail_catchall_one(u8 *catchall_addr) +{ + memcpy(catchall_addr, catchall, sizeof(catchall)); +} + +/* + * Install the catch-all code just before VGA hole at 0xa0000 and at the end + * of the PMM zero region. + */ +void +install_bootfail_catchall(void) +{ + /* Install just before the VGA hole */ + install_bootfail_catchall_one((u8*)BUILD_LOWRAM_END - sizeof(catchall)); + /* and after the PMM zero region */ + install_bootfail_catchall_one((u8*)BUILD_EBDA_MINIMUM); +} diff --git a/src/post.c b/src/post.c index f93106a1..bdacbdb8 100644 --- a/src/post.c +++ b/src/post.c @@ -68,6 +68,9 @@ ivt_init(void) // set vector 0x79 to zero // this is used by 'gardian angel' protection system SET_IVT(0x79, SEGOFF(0, 0)); + + // Boot failure catch-all interrupt (INT 0xF0) + SET_IVT(0xf0, FUNC16(entry_f0)); } static void @@ -115,6 +118,7 @@ interface_init(void) // Other interfaces boot_init(); + install_bootfail_catchall(); bios32_init(); pmm_init(); pnp_init(); diff --git a/src/romlayout.S b/src/romlayout.S index c4a4635e..e8feae9c 100644 --- a/src/romlayout.S +++ b/src/romlayout.S @@ -580,6 +580,10 @@ entry_19: entry_18: ENTRY_INTO32 _cfunc32flat_handle_18 + // int f0 is SeaBIOS specific and used to handle early boot breakage +entry_f0: + ENTRY_INTO32 _cfunc32flat_handle_f0 + /**************************************************************** * Fixed position entry points diff --git a/src/util.h b/src/util.h index aff8e888..3c5d075c 100644 --- a/src/util.h +++ b/src/util.h @@ -47,6 +47,7 @@ int boot_lchs_find_scsi_device(struct pci_device *pci, int target, int lun, struct chs_s *chs); int boot_lchs_find_ata_device(struct pci_device *pci, int chanid, int slave, struct chs_s *chs); +void install_bootfail_catchall(void); // bootsplash.c void enable_vga_console(void); -- 2.47.1 Amazon Web Services Development Center Germany GmbH Tamara-Danz-Str. 13 10243 Berlin Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597

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[PATCH v3 0/9] Build system improvements
by Jiaxun Yang Jan. 20, 2026

Jan. 20, 2026

Hi all, This series improved SeaBIOS build system in various aspects. Most notably, it makes cross compiling on MacOS Arm64 with x86_64-elf- toolchain possible. It also fixed various issues exposed when I was trying to clang build work. Although I eventually give up. Thanks Signed-off-by: Jiaxun Yang <jiaxun.yang(a)flygoat.com> --- Changes in v3: - Fix typo/style issues. - Link to v2: https://lore.kernel.org/r/20250903-build-v2-0-8e8916974f9c@flygoat.com --- Jiaxun Yang (9): Remove remaining ACPI tooling bits Makefile: Don't use $(CC) as default $(HOSTCC) Makefile: Invoke preprocessor and assembler with CC Makefile: Allow more linux style knobs asm-offset: Refresh definitions from Linux scripts: Use python3 as python LegacyBios.h: Import from edk2-stable202311 virtio-blk: Fix indentation for vring_get_buf call usb-ohci: Fix logical condition in start_ohci function Makefile | 24 +- scripts/acpi_extract.py | 366 ------- scripts/acpi_extract_preprocess.py | 41 - scripts/buildrom.py | 2 +- scripts/buildversion.py | 2 +- scripts/checkrom.py | 2 +- scripts/checkstack.py | 2 +- scripts/checksum.py | 2 +- scripts/encodeint.py | 2 +- scripts/gen-offsets.sh | 7 +- scripts/kconfig/Makefile | 6 +- scripts/layoutrom.py | 2 +- scripts/ldnoexec.py | 2 +- scripts/readserial.py | 2 +- scripts/transdump.py | 2 +- scripts/vgafixup.py | 2 +- src/gen-defs.h | 8 +- src/hw/usb-ohci.c | 2 +- src/hw/virtio-blk.c | 2 +- src/std/LegacyBios.h | 1972 ++++++++++++++++++------------------ 20 files changed, 1024 insertions(+), 1426 deletions(-) --- base-commit: 0026c353eb4e220af29750fcf000d48faf8d4ab3 change-id: 20250903-build-d57c47407e58 Best regards, -- Jiaxun Yang <jiaxun.yang(a)flygoat.com>

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[PATCH] boot: Add boot failure catch-all handler to prevent VM crashes
by Alexander Graf Jan. 15, 2026

Jan. 15, 2026

Implement catch-all mechanism to handle invalid boot loaders that execute random instructions and reach the VGA hole at 0xa0000, which would lead to VM crashes with KVM_INTERNAL_ERROR. When a BIOS boot loader gets corrupted, it can end up jumping across address space and execute stray code. The typical symptom of that is that it executes 0x0 (addw) instructions until the code reaches an MMIO region, such as the VGA window. When running in KVM, attempting to execute code from the MMIO window results in KVM_INTERNAL_ERROR exits which crash the VM. To prevent VM crashes before we reach such an MMIO window, introduce an internal int 0xf0 handler and call it at strategic locations that should never get executed in the first place. When we now have stray code executing, these int calls cause an emergency print of "BIOS failed to boot volume" and cleanly shut down the machine. This is a nicer experience for users as it prints out why their system broke and in addition it avoids KVM_INTERNAL_ERROR calls when a virtual machine attempts to execute from MMIO because of a broken boot loader. Signed-off-by: Alexander Graf <graf(a)amazon.com> --- src/boot.c | 36 ++++++++++++++++++++++++++++++++++++ src/post.c | 4 ++++ src/romlayout.S | 5 +++++ src/util.h | 1 + 4 files changed, 46 insertions(+) diff --git a/src/boot.c b/src/boot.c index 5c37dafd..39a4f9a7 100644 --- a/src/boot.c +++ b/src/boot.c @@ -1044,3 +1044,39 @@ handle_19(void) BootSequence = 0; do_boot(0); } + +// INT f0h Boot Failure Service Entry Point +void VISIBLE32FLAT +handle_f0(void) +{ + printf("\n\nBIOS failed to boot volume\n\n "); + + /* Try to shut down. Will busy loop on failure to shut down. */ + apm_shutdown(); +} + +static const u8 catchall[0x10] = { + 0xcd, // INT + 0xf0, // interrupt number 0xF0 + 0xeb, // JMP short + 0xfc, // -3 (jump back to INT) +}; + +static void +install_bootfail_catchall_one(u8 *catchall_addr) +{ + memcpy(catchall_addr, catchall, sizeof(catchall)); +} + +/* + * Install the catch-all code just before VGA hole at 0xa0000 and at the end + * of the PMM zero region. + */ +void +install_bootfail_catchall(void) +{ + /* Install just before the VGA hole */ + install_bootfail_catchall_one((u8*)BUILD_LOWRAM_END - sizeof(catchall)); + /* and after the PMM zero region */ + install_bootfail_catchall_one((u8*)BUILD_EBDA_MINIMUM); +} diff --git a/src/post.c b/src/post.c index f93106a1..bdacbdb8 100644 --- a/src/post.c +++ b/src/post.c @@ -68,6 +68,9 @@ ivt_init(void) // set vector 0x79 to zero // this is used by 'gardian angel' protection system SET_IVT(0x79, SEGOFF(0, 0)); + + // Boot failure catch-all interrupt (INT 0xF0) + SET_IVT(0xf0, FUNC16(entry_f0)); } static void @@ -115,6 +118,7 @@ interface_init(void) // Other interfaces boot_init(); + install_bootfail_catchall(); bios32_init(); pmm_init(); pnp_init(); diff --git a/src/romlayout.S b/src/romlayout.S index c4a4635e..283a8f5a 100644 --- a/src/romlayout.S +++ b/src/romlayout.S @@ -684,6 +684,11 @@ entry_iret_official: ORG 0xff54 IRQ_ENTRY_ARG 05 + // Boot failure catch-all interrupt handler (INT 0xF0) + .global entry_f0 +entry_f0: + ENTRY_INTO32 _cfunc32flat_handle_f0 + ORG 0xfff0 // Power-up Entry Point .global reset_vector reset_vector: diff --git a/src/util.h b/src/util.h index aff8e888..3c5d075c 100644 --- a/src/util.h +++ b/src/util.h @@ -47,6 +47,7 @@ int boot_lchs_find_scsi_device(struct pci_device *pci, int target, int lun, struct chs_s *chs); int boot_lchs_find_ata_device(struct pci_device *pci, int chanid, int slave, struct chs_s *chs); +void install_bootfail_catchall(void); // bootsplash.c void enable_vga_console(void); -- 2.47.1 Amazon Web Services Development Center Germany GmbH Tamara-Danz-Str. 13 10243 Berlin Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B Sitz: Berlin Ust-ID: DE 365 538 597

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Now: Cyber Resilience Act Boot Manager Standard Deep Dive
by Carl-Daniel Hailfinger Jan. 15, 2026

Jan. 15, 2026

Hi everyone! If you are interested in the current state of the EU CRA Boot Manager (firmware/bootloader) standard, a deep dive session (video conference with explanations) is starting right now. Time: 15:30-17:00 CET today (now!) https://meet.goto.com/etsicybereusr/deep-dive-sessions Regards, Carl-Daniel

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[PATCH] e820: Add E820_SOFT_RESERVED type support
by fanhuang Jan. 5, 2026

Jan. 5, 2026

Add support for E820 Soft Reserved Memory type which is used by QEMU to expose Specific Purpose Memory (SPM) regions. Changes: - Define E820_SOFT_RESERVED in e820map.h - Handle E820_SOFT_RESERVED in qemu_early_e820() Signed-off-by: FangSheng Huang <FangSheng.Huang(a)amd.com> --- src/e820map.h | 1 + src/fw/paravirt.c | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/src/e820map.h b/src/e820map.h index 07ce16ec..a46fcc42 100644 --- a/src/e820map.h +++ b/src/e820map.h @@ -8,6 +8,7 @@ #define E820_ACPI 3 #define E820_NVS 4 #define E820_UNUSABLE 5 +#define E820_SOFT_RESERVED 0xEFFFFFFF struct e820entry { u64 start; diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c index e5d4eca0..2ec22878 100644 --- a/src/fw/paravirt.c +++ b/src/fw/paravirt.c @@ -768,6 +768,11 @@ static int qemu_early_e820(void) dprintf(1, "qemu/e820: addr 0x%016llx len 0x%016llx [reserved]\n", table.address, table.length); break; + case E820_SOFT_RESERVED: + e820_add(table.address, table.length, table.type); + dprintf(1, "qemu/e820: addr 0x%016llx len 0x%016llx [soft reserved]\n", + table.address, table.length); + break; case E820_RAM: e820_add(table.address, table.length, table.type); dprintf(1, "qemu/e820: addr 0x%016llx len 0x%016llx [RAM]\n", -- 2.34.1

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