* [PATCH v3 2/6] strip: Adapt src/strip -o -f on mips
@ 2024-03-05 9:51 Ying Huang
0 siblings, 0 replies; only message in thread
From: Ying Huang @ 2024-03-05 9:51 UTC (permalink / raw)
To: elfutils-devel; +Cc: Ying Huang
From: Ying Huang <ying.huang@oss.cipunited.com>
In mips64 little-endian, r_info consists of four byte fields(contains
three reloc types) and a 32-bit symbol index. In order to adapt
GELF_R_SYM and GELF_R_TYPE, need convert raw data to get correct symbol
index and type.
libelf/elf_getdata.c: Some eu-utils use read-mmap method to map file,
so we need to malloc and memcpy raw data to avoid segment fault. After
modification, the correct value are saved in the malloced memory not in
process address space.
libelf/elf_updata.c: Because we converted the relocation info in mips
order when we call elf_getdata.c, so we need to convert the modified data
in original order bits before writing the data to the file.
Signed-off-by: Ying Huang <ying.huang@oss.cipunited.com>
---
libelf/elf_getdata.c | 132 ++++++++++++++++++++++++++++++++++++++++++-
libelf/elf_update.c | 53 +++++++++++++++++
2 files changed, 183 insertions(+), 2 deletions(-)
diff --git a/libelf/elf_getdata.c b/libelf/elf_getdata.c
index 7c3ac043..942ba536 100644
--- a/libelf/elf_getdata.c
+++ b/libelf/elf_getdata.c
@@ -133,6 +133,119 @@ __libelf_data_type (GElf_Ehdr *ehdr, int sh_type, GElf_Xword align)
}
}
+/* Convert the data in the current section. */
+static void
+convert_data_for_mips64el (Elf_Scn *scn, int eclass,
+ int data, size_t size, Elf_Type type)
+{
+ /* Do we need to convert the data and/or adjust for alignment? */
+ if (data == MY_ELFDATA || type == ELF_T_BYTE)
+ {
+ /* In order to adapt macro GELF_R_SYM and GELF_R_TYPE on mips64, need to convert
+ relocation info(raw data). Some eu-utils use read-mmap method to map file, so
+ we need to malloc and memcpy raw data to avoid segment fault. After modification,
+ the correct value are saved in the malloced memory not in process address space. */
+ scn->data_base = malloc (size);
+ if (scn->data_base == NULL)
+ {
+ __libelf_seterrno (ELF_E_NOMEM);
+ return;
+ }
+
+ /* The copy will be appropriately aligned for direct access. */
+ memcpy (scn->data_base, scn->rawdata_base, size);
+ }
+ else
+ {
+ xfct_t fp;
+
+ scn->data_base = malloc (size);
+ if (scn->data_base == NULL)
+ {
+ __libelf_seterrno (ELF_E_NOMEM);
+ return;
+ }
+
+ /* Make sure the source is correctly aligned for the conversion
+ function to directly access the data elements. */
+ char *rawdata_source;
+ /* In order to adapt macro GELF_R_SYM and GELF_R_TYPE on mips64, need to convert
+ relocation info(raw data). Some eu-utils use read-mmap method to map file, so
+ we need to malloc and memcpy raw data to avoid segment fault. After modification,
+ the correct value are saved in the malloced memory not in process address space. */
+ rawdata_source = malloc (size);
+ if (rawdata_source == NULL)
+ {
+ __libelf_seterrno (ELF_E_NOMEM);
+ return;
+ }
+
+ /* The copy will be appropriately aligned for direct access. */
+ memcpy (rawdata_source, scn->rawdata_base, size);
+
+ /* Get the conversion function. */
+ fp = __elf_xfctstom[eclass - 1][type];
+
+ fp (scn->data_base, rawdata_source, size, 0);
+
+ if (rawdata_source != scn->rawdata_base)
+ free (rawdata_source);
+ }
+
+ scn->data_list.data.d.d_buf = scn->data_base;
+ scn->data_list.data.d.d_size = size;
+ scn->data_list.data.d.d_type = type;
+ scn->data_list.data.d.d_off = scn->rawdata.d.d_off;
+ scn->data_list.data.d.d_align = scn->rawdata.d.d_align;
+ scn->data_list.data.d.d_version = scn->rawdata.d.d_version;
+
+ scn->data_list.data.s = scn;
+
+ /* In mips64 little-endian, r_info consists of four byte fields(contains
+ three reloc types) and a 32-bit symbol index. In order to adapt
+ GELF_R_SYM and GELF_R_TYPE, need to convert r_info to get correct symbol
+ index and type. */
+ /* references:
+ https://www.linux-mips.org/pub/linux/mips/doc/ABI/elf64-2.4.pdf
+ Page40 && Page41 */
+ GElf_Shdr shdr_mem;
+ GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
+ if (shdr->sh_type == SHT_REL)
+ {
+ size_t sh_entsize = gelf_fsize (scn->elf, ELF_T_REL, 1, EV_CURRENT);
+ int nentries = shdr->sh_size / sh_entsize;
+ for (int cnt = 0; cnt < nentries; ++cnt)
+ {
+ Elf_Data_Scn *data_scn = (Elf_Data_Scn *) &scn->data_list.data.d;
+ Elf64_Rel *value = &((Elf64_Rel *) data_scn->d.d_buf)[cnt];
+ Elf64_Xword info = value->r_info;
+ value->r_info = (((info & 0xffffffff) << 32)
+ | ((info >> 56) & 0xff)
+ | ((info >> 40) & 0xff00)
+ | ((info >> 24) & 0xff0000)
+ | ((info >> 8) & 0xff000000));
+ ((Elf64_Rel *) data_scn->d.d_buf)[cnt] = *value;
+ }
+ }
+ else if (shdr->sh_type == SHT_RELA)
+ {
+ size_t sh_entsize = gelf_fsize (scn->elf, ELF_T_RELA, 1, EV_CURRENT);
+ int nentries = shdr->sh_size / sh_entsize;
+ for (int cnt = 0; cnt < nentries; cnt++)
+ {
+ Elf_Data_Scn *data_scn = (Elf_Data_Scn *) &scn->data_list.data.d;
+ Elf64_Rela *value = &((Elf64_Rela *) data_scn->d.d_buf)[cnt];
+ Elf64_Xword info = value->r_info;
+ value->r_info = (((info & 0xffffffff) << 32)
+ | ((info >> 56) & 0xff)
+ | ((info >> 40) & 0xff00)
+ | ((info >> 24) & 0xff0000)
+ | ((info >> 8) & 0xff000000));
+ ((Elf64_Rela *) data_scn->d.d_buf)[cnt] = *value;
+ }
+ }
+}
+
/* Convert the data in the current section. */
static void
convert_data (Elf_Scn *scn, int eclass,
@@ -451,8 +564,23 @@ __libelf_set_data_list_rdlock (Elf_Scn *scn, int wrlocked)
return;
}
- /* Convert according to the version and the type. */
- convert_data (scn, elf->class,
+ GElf_Shdr shdr_mem;
+ GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
+ GElf_Ehdr ehdr_mem;
+ GElf_Ehdr *ehdr = gelf_getehdr (scn->elf, &ehdr_mem);
+ if (shdr != NULL && (shdr->sh_type == SHT_RELA || shdr->sh_type == SHT_REL) &&
+ scn->elf->class == ELFCLASS64 && ehdr != NULL &&
+ ehdr->e_machine == EM_MIPS && ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
+ convert_data_for_mips64el (scn, elf->class,
+ (elf->class == ELFCLASS32
+ || (offsetof (struct Elf, state.elf32.ehdr)
+ == offsetof (struct Elf, state.elf64.ehdr))
+ ? elf->state.elf32.ehdr->e_ident[EI_DATA]
+ : elf->state.elf64.ehdr->e_ident[EI_DATA]),
+ scn->rawdata.d.d_size, scn->rawdata.d.d_type);
+ else
+ /* Convert according to the version and the type. */
+ convert_data (scn, elf->class,
(elf->class == ELFCLASS32
|| (offsetof (struct Elf, state.elf32.ehdr)
== offsetof (struct Elf, state.elf64.ehdr))
diff --git a/libelf/elf_update.c b/libelf/elf_update.c
index 56af3a1c..aec19b7c 100644
--- a/libelf/elf_update.c
+++ b/libelf/elf_update.c
@@ -228,7 +228,60 @@ elf_update (Elf *elf, Elf_Cmd cmd)
size = -1;
}
else
+ {
+ /* Because we converted the relocation info in mips order when we call elf_getdata.c,
+ so we need to convert the modified data in original order bits before writing the
+ data to the file. */
+ Elf_Scn *scn = NULL;
+ while ((scn = elf_nextscn (elf, scn)) != NULL)
+ {
+ GElf_Shdr shdr_mem;
+ GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
+ GElf_Ehdr ehdr_mem;
+ GElf_Ehdr *ehdr = gelf_getehdr (scn->elf, &ehdr_mem);
+ if (shdr != NULL && (shdr->sh_type == SHT_RELA || shdr->sh_type == SHT_REL) &&
+ scn->elf->class == ELFCLASS64 &&
+ ehdr != NULL && ehdr->e_machine == EM_MIPS && ehdr->e_ident[EI_DATA] == ELFDATA2LSB)
+ {
+ Elf_Data *d = elf_getdata (scn, NULL);
+ if (shdr->sh_type == SHT_REL)
+ {
+ size_t sh_entsize = gelf_fsize (scn->elf, ELF_T_REL, 1, EV_CURRENT);
+ int nentries = shdr->sh_size / sh_entsize;
+ for (int cnt = 0; cnt < nentries; ++cnt)
+ {
+ Elf_Data_Scn *data_scn = (Elf_Data_Scn *) d;
+ Elf64_Rel *value = &((Elf64_Rel *) data_scn->d.d_buf)[cnt];
+ Elf64_Xword info = value->r_info;
+ value->r_info = (info >> 32
+ | ((info << 56) & 0xff00000000000000)
+ | ((info << 40) & 0xff000000000000)
+ | ((info << 24) & 0xff0000000000)
+ | ((info << 8) & 0xff00000000));
+ ((Elf64_Rel *) data_scn->d.d_buf)[cnt] = *value;
+ }
+ }
+ else if (shdr->sh_type == SHT_RELA)
+ {
+ size_t sh_entsize = gelf_fsize (scn->elf, ELF_T_RELA, 1, EV_CURRENT);
+ int nentries = shdr->sh_size / sh_entsize;
+ for (int cnt = 0; cnt < nentries; cnt++)
+ {
+ Elf_Data_Scn *data_scn = (Elf_Data_Scn *) d;
+ Elf64_Rela *value = &((Elf64_Rela *) data_scn->d.d_buf)[cnt];
+ Elf64_Xword info = value->r_info;
+ value->r_info = (info >> 32
+ | ((info << 56) & 0xff00000000000000)
+ | ((info << 40) & 0xff000000000000)
+ | ((info << 24) & 0xff0000000000)
+ | ((info << 8) & 0xff00000000));
+ ((Elf64_Rela *) data_scn->d.d_buf)[cnt] = *value;
+ }
+ }
+ }
+ }
size = write_file (elf, size, change_bo, shnum);
+ }
}
out:
--
2.39.2
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