1 files changed, 117 insertions, 0 deletions
diff --git a/src/crash-stack/crash-stack-libelf-helpers.c b/src/crash-stack/crash-stack-libelf-helpers.c
new file mode 100644
index 0000000..7dab540
--- /dev/null
+++ b/src/crash-stack/crash-stack-libelf-helpers.c
@@ -0,0 +1,117 @@
+#include "crash-stack.h"
+#include <string.h>
+#include <sys/ptrace.h>
+#include <errno.h>
+
+bool crash_stack_libelf_read_value(Dwfl *dwfl, Elf *core, pid_t pid,
+		Dwarf_Addr a, void *v, size_t size,
+		Mappings *mappings)
+{
+	Dwfl_Module *module = 0;
+	Elf_Data *data = NULL;
+
+	int segment = dwfl_addrsegment(dwfl, a, &module);
+
+	if (module != NULL) {
+		Dwarf_Addr start;
+		dwfl_module_info(module, NULL, &start, NULL, NULL, NULL, NULL, NULL);
+
+		GElf_Addr bias;
+		Elf *elf = dwfl_module_getelf(module, &bias);
+
+		data = elf_getdata_rawchunk(elf, a-start, size, ELF_T_BYTE);
+	}
+	if (NULL == data && segment != -1) {
+		// get data from segment
+		GElf_Phdr mem;
+		GElf_Phdr *phdr = gelf_getphdr(core, segment, &mem);
+		Dwarf_Addr offset_in_segment = a - phdr->p_vaddr;
+		if (offset_in_segment < phdr->p_filesz) {
+			Dwarf_Addr offset_in_file = phdr->p_offset + offset_in_segment;
+
+			data = elf_getdata_rawchunk(core, offset_in_file, size, ELF_T_BYTE);
+		}
+	}
+
+	if (NULL == data && module != NULL) {
+		const char *name = dwfl_module_info(module, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
+		if (name != NULL && name[0] == '[') {
+			int i;
+			// get module from mappings
+			for (i = 0; i < mappings->elems; i++) {
+				if (mappings->tab[i].m_start <= a && a < mappings->tab[i].m_end) {
+					// compute offset relative to the start of the mapping
+					long offset = a - mappings->tab[i].m_start;
+					// read from the file, but also account file offset
+					data = elf_getdata_rawchunk(mappings->tab[i].m_elf,
+							offset + mappings->tab[i].m_offset, size, ELF_T_BYTE);
+					break;
+				}
+			}
+		}
+	}
+
+	if (data != NULL) {
+		memcpy(v, data->d_buf, size);
+		return true;
+	}
+
+	/* Still no data, but we have a process - read memory with ptrace */
+	/* FIXME need to know if we are still in the mapped area */
+	/* Bigger issue is that dwfl does not have modules */
+	if (pid > 1) {
+		long val = ptrace(PTRACE_PEEKDATA, pid, a, NULL);
+		if (-1 == val && errno)
+			return false;
+		memcpy(v, &val, size);
+		return true;
+	}
+
+	return false;
+}
+
+Dwarf_Addr crash_stack_libelf_get_prologue_pc(Dwfl *dwfl, Dwarf_Addr current_pc, Mappings *mappings)
+{
+	Dwarf_Addr result = 0;
+	Dwfl_Module *module = dwfl_addrmodule(dwfl, current_pc);
+	if (module) {
+		GElf_Sym sym;
+		dwfl_module_addrsym(module, current_pc, &sym, NULL);
+		result = sym.st_value;
+	}
+	if (0 == result) {
+		int i;
+		for (i=0; i < mappings->elems; i++) {
+			if (mappings->tab[i].m_start <= current_pc && current_pc < mappings->tab[i].m_end) {
+				/* go through symbols to find the nearest */
+				Elf_Scn *scn = NULL;
+				Elf *elf = mappings->tab[i].m_elf;
+				while ((scn = elf_nextscn(elf, scn)) != NULL) {
+					GElf_Shdr shdr_mem;
+					GElf_Shdr *shdr = gelf_getshdr(scn, &shdr_mem);
+					if (shdr != NULL && (shdr->sh_type == SHT_SYMTAB || shdr->sh_type == SHT_DYNSYM)) {
+						Elf_Data *sdata = elf_getdata(scn, NULL);
+						unsigned int nsyms = sdata->d_size / (gelf_getclass(elf) == ELFCLASS32 ?
+								sizeof(Elf32_Sym) :
+								sizeof(Elf64_Sym));
+						unsigned int cnt;
+						uintptr_t address_offset = current_pc;
+						if (shdr->sh_type == SHT_DYNSYM)
+							address_offset -= mappings->tab[i].m_start;
+						for (cnt = 0; cnt < nsyms; ++cnt) {
+							GElf_Sym sym_mem;
+							Elf32_Word xndx;
+							GElf_Sym *sym = gelf_getsymshndx(sdata, NULL, cnt, &sym_mem, &xndx);
+							if (sym != NULL && sym->st_shndx != SHN_UNDEF) {
+								if (sym->st_value <= address_offset && address_offset < sym->st_value + sym->st_size) {
+									return sym->st_value;
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	return result;
+}