bpf: Move stack_map_get_build_id into lib

[linux-2.6-microblaze.git] / lib / buildid.c

diff --git a/lib/buildid.c b/lib/buildid.c
new file mode 100644 (file)
index 0000000..4a4f520
--- /dev/null
+++ b/lib/buildid.c
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/buildid.h>
+#include <linux/elf.h>
+#include <linux/pagemap.h>
+
+#define BUILD_ID 3
+/*
+ * Parse build id from the note segment. This logic can be shared between
+ * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are
+ * identical.
+ */
+static inline int parse_build_id(void *page_addr,
+                                unsigned char *build_id,
+                                void *note_start,
+                                Elf32_Word note_size)
+{
+       Elf32_Word note_offs = 0, new_offs;
+
+       /* check for overflow */
+       if (note_start < page_addr || note_start + note_size < note_start)
+               return -EINVAL;
+
+       /* only supports note that fits in the first page */
+       if (note_start + note_size > page_addr + PAGE_SIZE)
+               return -EINVAL;
+
+       while (note_offs + sizeof(Elf32_Nhdr) < note_size) {
+               Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs);
+
+               if (nhdr->n_type == BUILD_ID &&
+                   nhdr->n_namesz == sizeof("GNU") &&
+                   nhdr->n_descsz > 0 &&
+                   nhdr->n_descsz <= BUILD_ID_SIZE_MAX) {
+                       memcpy(build_id,
+                              note_start + note_offs +
+                              ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr),
+                              nhdr->n_descsz);
+                       memset(build_id + nhdr->n_descsz, 0,
+                              BUILD_ID_SIZE_MAX - nhdr->n_descsz);
+                       return 0;
+               }
+               new_offs = note_offs + sizeof(Elf32_Nhdr) +
+                       ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4);
+               if (new_offs <= note_offs)  /* overflow */
+                       break;
+               note_offs = new_offs;
+       }
+       return -EINVAL;
+}
+
+/* Parse build ID from 32-bit ELF */
+static int get_build_id_32(void *page_addr, unsigned char *build_id)
+{
+       Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
+       Elf32_Phdr *phdr;
+       int i;
+
+       /* only supports phdr that fits in one page */
+       if (ehdr->e_phnum >
+           (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr))
+               return -EINVAL;
+
+       phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr));
+
+       for (i = 0; i < ehdr->e_phnum; ++i) {
+               if (phdr[i].p_type == PT_NOTE &&
+                   !parse_build_id(page_addr, build_id,
+                                   page_addr + phdr[i].p_offset,
+                                   phdr[i].p_filesz))
+                       return 0;
+       }
+       return -EINVAL;
+}
+
+/* Parse build ID from 64-bit ELF */
+static int get_build_id_64(void *page_addr, unsigned char *build_id)
+{
+       Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
+       Elf64_Phdr *phdr;
+       int i;
+
+       /* only supports phdr that fits in one page */
+       if (ehdr->e_phnum >
+           (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr))
+               return -EINVAL;
+
+       phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr));
+
+       for (i = 0; i < ehdr->e_phnum; ++i) {
+               if (phdr[i].p_type == PT_NOTE &&
+                   !parse_build_id(page_addr, build_id,
+                                   page_addr + phdr[i].p_offset,
+                                   phdr[i].p_filesz))
+                       return 0;
+       }
+       return -EINVAL;
+}
+
+/* Parse build ID of ELF file mapped to vma */
+int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)
+{
+       Elf32_Ehdr *ehdr;
+       struct page *page;
+       void *page_addr;
+       int ret;
+
+       /* only works for page backed storage  */
+       if (!vma->vm_file)
+               return -EINVAL;
+
+       page = find_get_page(vma->vm_file->f_mapping, 0);
+       if (!page)
+               return -EFAULT; /* page not mapped */
+
+       ret = -EINVAL;
+       page_addr = kmap_atomic(page);
+       ehdr = (Elf32_Ehdr *)page_addr;
+
+       /* compare magic x7f "ELF" */
+       if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
+               goto out;
+
+       /* only support executable file and shared object file */
+       if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN)
+               goto out;
+
+       if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
+               ret = get_build_id_32(page_addr, build_id);
+       else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
+               ret = get_build_id_64(page_addr, build_id);
+out:
+       kunmap_atomic(page_addr);
+       put_page(page);
+       return ret;
+}