Expose the kernel's build-ID through sysctl
After our migration (of certain architectures) to lld the kernel is built with a unique build-ID. Make it available via a sysctl and uname(1) to allow the user to identify their running kernel. Submitted by: Ali Mashtizadeh <ali_mashtizadeh.com> MFC after: 2 weeks Relnotes: Yes Event: Waterloo Hackathon 2019 Differential Revision: https://reviews.freebsd.org/D20326
This commit is contained in:
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01b5874679
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@ -74,6 +74,11 @@ SECTIONS
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PROVIDE (etext = .);
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.rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.eh_frame_hdr : { *(.eh_frame_hdr) }
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.eh_frame : ONLY_IF_RO { KEEP (*(.eh_frame)) }
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.gcc_except_table : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }
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@ -27,6 +27,11 @@ SECTIONS
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.gnu.version : { *(.gnu.version) }
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.gnu.version_d : { *(.gnu.version_d) }
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.gnu.version_r : { *(.gnu.version_r) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.rel.text :
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{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
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.rela.text :
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@ -27,6 +27,11 @@ SECTIONS
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.gnu.version : { *(.gnu.version) }
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.gnu.version_d : { *(.gnu.version_d) }
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.gnu.version_r : { *(.gnu.version_r) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.rel.text :
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{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
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.rela.text :
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@ -62,6 +62,11 @@ SECTIONS
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PROVIDE (etext = .);
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.rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.eh_frame_hdr : { *(.eh_frame_hdr) }
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.eh_frame : ONLY_IF_RO { KEEP (*(.eh_frame)) }
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.gcc_except_table : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }
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@ -63,6 +63,11 @@ SECTIONS
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.gnu.version : { *(.gnu.version) }
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.gnu.version_d : { *(.gnu.version_d) }
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.gnu.version_r : { *(.gnu.version_r) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.rel.init : { *(.rel.init) }
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.rela.init : { *(.rela.init) }
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.rel.text :
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@ -192,6 +192,11 @@ SECTIONS
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PROVIDE (etext = .);
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.rodata : { *(.rodata) *(.rodata.*) *(.gnu.linkonce.r.*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.reginfo : { *(.reginfo) }
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.sdata2 : { *(.sdata2) *(.sdata2.*) *(.gnu.linkonce.s2.*) }
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.sbss2 : { *(.sbss2) *(.sbss2.*) *(.gnu.linkonce.sb2.*) }
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@ -176,6 +176,11 @@ SECTIONS
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PROVIDE (etext = .);
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.rodata : { *(.rodata) *(.rodata.*) *(.gnu.linkonce.r.*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.reginfo : { *(.reginfo) }
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.sdata2 : { *(.sdata2) *(.sdata2.*) *(.gnu.linkonce.s2.*) }
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.sbss2 : { *(.sbss2) *(.sbss2.*) *(.gnu.linkonce.sb2.*) }
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@ -24,6 +24,12 @@ SECTIONS {
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. = ALIGN(32);
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}
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.data : {
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_rwdata = .;
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*(.data)
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@ -55,6 +55,11 @@ SECTIONS
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.fini : { *(.fini) } =0
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.rodata : { *(.rodata) *(.gnu.linkonce.r*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.sdata2 : { *(.sdata2) }
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.sbss2 : { *(.sbss2) }
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/* Adjust the address for the data segment to the next page up. */
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@ -46,6 +46,11 @@ SECTIONS
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.gnu.version : { *(.gnu.version) }
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.gnu.version_d : { *(.gnu.version_d) }
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.gnu.version_r : { *(.gnu.version_r) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.rela.text :
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{ *(.rela.text) *(.rela.gnu.linkonce.t*) }
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.rela.data :
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@ -55,6 +55,11 @@ SECTIONS
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.fini : { *(.fini) } =0
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.rodata : { *(.rodata) *(.gnu.linkonce.r*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.sdata2 : { *(.sdata2) }
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.sbss2 : { *(.sbss2) }
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/* Adjust the address for the data segment to the next page up. */
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@ -27,6 +27,11 @@ SECTIONS
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.gnu.version : { *(.gnu.version) }
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.gnu.version_d : { *(.gnu.version_d) }
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.gnu.version_r : { *(.gnu.version_r) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.rel.text :
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{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
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.rela.text :
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@ -146,6 +146,11 @@ SECTIONS
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PROVIDE (etext = .);
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.rodata : { *(.rodata) *(.rodata.*) *(.gnu.linkonce.r.*) }
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.rodata1 : { *(.rodata1) }
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.note.gnu.build-id : {
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PROVIDE (__build_id_start = .);
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*(.note.gnu.build-id)
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PROVIDE (__build_id_end = .);
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}
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.sdata2 : { *(.sdata2) *(.sdata2.*) *(.gnu.linkonce.s2.*) }
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.sbss2 : { *(.sbss2) *(.sbss2.*) *(.gnu.linkonce.sb2.*) }
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. = ALIGN(0x2000) + (. & (0x2000 - 1));
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@ -481,6 +481,54 @@ SYSCTL_PROC(_kern, KERN_OSRELDATE, osreldate,
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CTLTYPE_INT | CTLFLAG_CAPRD | CTLFLAG_RD | CTLFLAG_MPSAFE,
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NULL, 0, sysctl_osreldate, "I", "Kernel release date");
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/*
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* The build-id is copied from the ELF section .note.gnu.build-id. The linker
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* script defines two variables to expose the beginning and end. LLVM
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* currently uses a SHA-1 hash, but other formats can be supported by checking
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* the length of the section.
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*/
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extern char __build_id_start[];
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extern char __build_id_end[];
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#define BUILD_ID_HEADER_LEN 0x10
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#define BUILD_ID_HASH_MAXLEN 0x14
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static int
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sysctl_build_id(SYSCTL_HANDLER_ARGS)
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{
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uintptr_t sectionlen = (uintptr_t)(__build_id_end - __build_id_start);
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int hashlen;
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char buf[2*BUILD_ID_HASH_MAXLEN+1];
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/*
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* The ELF note section has a four byte length for the vendor name,
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* four byte length for the value, and a four byte vendor specific
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* type. The name for the build id is "GNU\0". We skip the first 16
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* bytes to read the build hash. We will return the remaining bytes up
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* to 20 (SHA-1) hash size. If the hash happens to be a custom number
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* of bytes we will pad the value with zeros, as the section should be
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* four byte aligned.
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*/
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if (sectionlen <= BUILD_ID_HEADER_LEN ||
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sectionlen > (BUILD_ID_HEADER_LEN + BUILD_ID_HASH_MAXLEN)) {
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return (ENOENT);
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}
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hashlen = sectionlen - BUILD_ID_HEADER_LEN;
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for (int i = 0; i < hashlen; i++) {
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uint8_t c = __build_id_start[i+BUILD_ID_HEADER_LEN];
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snprintf(&buf[2*i], 3, "%02x", c);
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}
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return (SYSCTL_OUT(req, buf, strlen(buf) + 1));
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}
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SYSCTL_PROC(_kern, OID_AUTO, build_id,
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CTLTYPE_STRING | CTLFLAG_CAPRD | CTLFLAG_RD | CTLFLAG_MPSAFE,
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NULL, 0, sysctl_build_id, "A", "Operating system build-id");
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SYSCTL_NODE(_kern, OID_AUTO, features, CTLFLAG_RD, 0, "Kernel Features");
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#ifdef COMPAT_FREEBSD4
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