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create-diff-object: register patchable child functions #1526

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create-diff-object: register patchable child functions #1526

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36 changes: 30 additions & 6 deletions kpatch-build/create-diff-object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2175,13 +2175,39 @@ static int kpatch_include_changed_functions(struct kpatch_elf *kelf)
return changed_nr;
}

/*
* A compiler-generated child function is independently patchable when it has
* its own profiling call and no changed ancestor already redirects execution
* to the replacement child. Children without a profiling call are carried by
* their changed parent instead.
*/
static bool kpatch_is_patch_func(struct symbol *sym)
{
struct symbol *parent;

if (sym->type != STT_FUNC || sym->status != CHANGED)
return false;

if (!sym->parent)
return true;

if (!sym->has_func_profiling)
return false;

for (parent = sym->parent; parent; parent = parent->parent)
if (parent->status == CHANGED)
return false;

return true;
}

static void kpatch_print_changes(struct kpatch_elf *kelf)
{
struct symbol *sym;

list_for_each_entry(sym, &kelf->symbols, list) {
if (!sym->include || !sym->sec || sym->type != STT_FUNC ||
sym->parent || sym->is_pfx)
if (!sym->include || !sym->sec || !kpatch_is_patch_func(sym) ||
sym->is_pfx)
continue;
if (sym->status == NEW)
log_normal("new function: %s\n", sym->name);
Expand Down Expand Up @@ -3452,8 +3478,7 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
/* count patched functions */
nr = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type != STT_FUNC || sym->status != CHANGED ||
sym->parent)
if (!kpatch_is_patch_func(sym))
continue;
nr++;
}
Expand All @@ -3474,8 +3499,7 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
/* populate sections */
index = 0;
list_for_each_entry(sym, &kelf->symbols, list) {
if (sym->type != STT_FUNC || sym->status != CHANGED ||
sym->parent)
if (!kpatch_is_patch_func(sym))
continue;

if (!lookup_symbol(table, sym, &symbol))
Expand Down