diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c index 9fe8102..6d835b4 100644 --- a/kpatch-build/create-diff-object.c +++ b/kpatch-build/create-diff-object.c @@ -649,17 +649,118 @@ out: log_debug("section %s has changed\n", sec->name); } +/* + * Determine if a section has changed only due to a WARN* macro call's + * embedding of the line number into an instruction operand. + * + * Warning: Hackery lies herein. It's hopefully justified by the fact that + * this issue is very common. + * + * base object: + * + * 28e: be de 10 00 00 mov $0x10de,%esi + * 293: 48 c7 c7 00 00 00 00 mov $0x0,%rdi + * 29a: e8 00 00 00 00 callq 29f + * + * patched object: + * + * 28e: be df 10 00 00 mov $0x10df,%esi + * 293: 48 c7 c7 00 00 00 00 mov $0x0,%rdi + * 29a: e8 00 00 00 00 callq 29f + */ +static int kpatch_warn_only_change(struct section *sec) +{ + struct insn insn1, insn2; + unsigned long start1, start2, size, offset, length; + struct rela *rela; + int warnonly = 0, found; + + if (sec->status != CHANGED || + is_rela_section(sec) || + !is_text_section(sec) || + sec->sh.sh_size != sec->twin->sh.sh_size || + !sec->rela || + sec->rela->status != SAME) + return 0; + + start1 = (unsigned long)sec->twin->data->d_buf; + start2 = (unsigned long)sec->data->d_buf; + size = sec->sh.sh_size; + for (offset = 0; offset < size; offset += length) { + insn_init(&insn1, (void *)(start1 + offset), 1); + insn_init(&insn2, (void *)(start2 + offset), 1); + insn_get_length(&insn1); + insn_get_length(&insn2); + length = insn1.length; + + if (!insn1.length || !insn2.length) + ERROR("can't decode instruction in section %s at offset 0x%lx", + sec->name, offset); + + if (insn1.length != insn2.length) + return 0; + + if (!memcmp((void *)start1 + offset, (void *)start2 + offset, + length)) + continue; + + /* verify it's a mov immediate to %esi */ + insn_get_opcode(&insn1); + insn_get_opcode(&insn2); + if (insn1.opcode.value != 0xbe || insn2.opcode.value != 0xbe) + return 0; + + /* verify the next instruction is mov $0x0,%rdi */ + if (*(unsigned int *)(start1 + offset + length) != 0xc7c748) + return 0; + + /* verify the instruction after that is callq */ + if (*(unsigned int *)(start1 + offset + length + 7) != 0xe8) + return 0; + + /* verify the callq's rela is for warn_slowpath_null */ + found = 0; + list_for_each_entry(rela, &sec->rela->relas, list) { + if (rela->offset == offset + length + 8 && + !strcmp(rela->sym->name, "warn_slowpath_null")) { + found = 1; + break; + } + } + if (!found) + return 0; + + warnonly = 1; + } + + if (!warnonly) + ERROR("no instruction changes detected for changed section %s", sec->name); + + return 1; +} + void kpatch_compare_sections(struct list_head *seclist) { struct section *sec; + /* compare all sections */ list_for_each_entry(sec, seclist, list) { if (sec->twin) kpatch_compare_correlated_section(sec); else sec->status = NEW; + } - /* sync symbol status */ + /* exclude WARN-only changes */ + list_for_each_entry(sec, seclist, list) + if (kpatch_warn_only_change(sec)) { + log_debug("reverting WARN-only section %s status to SAME\n", + sec->name); + sec->status = SAME; + } + + /* sync symbol status */ + list_for_each_entry(sec, seclist, list) { if (is_rela_section(sec)) { if (sec->base->sym && sec->base->sym->status != CHANGED) sec->base->sym->status = sec->status; diff --git a/test/integration/replace-section-references.patch b/test/integration/replace-section-references.patch index 24ccc4e..178c9d7 100644 --- a/test/integration/replace-section-references.patch +++ b/test/integration/replace-section-references.patch @@ -11,19 +11,3 @@ Index: src/arch/x86/kvm/x86.c if (slot >= shared_msrs_global.nr) shared_msrs_global.nr = slot + 1; shared_msrs_global.msrs[slot] = msr; -@@ -6307,6 +6309,7 @@ static int complete_emulated_mmio(struct - } - - -+#include "kpatch-macros.h" - int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run) - { - int r; -@@ -6352,6 +6355,7 @@ out: - - return r; - } -+KPATCH_IGNORE_FUNCTION(kvm_arch_vcpu_ioctl_run); - - int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs) - { diff --git a/test/integration/warn-detect-FAIL.patch b/test/integration/warn-detect-FAIL.patch new file mode 100644 index 0000000..f0e4a19 --- /dev/null +++ b/test/integration/warn-detect-FAIL.patch @@ -0,0 +1,9 @@ +Index: src/arch/x86/kvm/x86.c +=================================================================== +--- src.orig/arch/x86/kvm/x86.c ++++ src/arch/x86/kvm/x86.c +@@ -1,3 +1,4 @@ ++ + /* + * Kernel-based Virtual Machine driver for Linux + *