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Merge "linker: Set VMA name for bss sections"

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Treehugger Robot 2019-08-15 00:50:49 +00:00 committed by Gerrit Code Review
commit a40a1442a8
1 changed files with 32 additions and 0 deletions
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32
linker/linker_main.cpp
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@ -63,6 +63,8 @@ static ElfW(Addr) get_elf_exec_load_bias(const ElfW(Ehdr)* elf);
static void get_elf_base_from_phdr(const ElfW(Phdr)* phdr_table, size_t phdr_count,
ElfW(Addr)* base, ElfW(Addr)* load_bias);
static void set_bss_vma_name(soinfo* si);
// These should be preserved static to avoid emitting
// RELATIVE relocations for the part of the code running
// before linker links itself.
@ -366,6 +368,8 @@ static ElfW(Addr) linker_main(KernelArgumentBlock& args, const char* exe_to_load
si->set_main_executable();
init_link_map_head(*si);
set_bss_vma_name(si);
// Use the executable's PT_INTERP string as the solinker filename in the
// dynamic linker's module list. gdb reads both PT_INTERP and the module list,
// and if the paths for the linker are different, gdb will report that the
@ -570,6 +574,31 @@ static void get_elf_base_from_phdr(const ElfW(Phdr)* phdr_table, size_t phdr_cou
async_safe_fatal("Could not find a PHDR: broken executable?");
}
/*
* Set anonymous VMA name for .bss section. For DSOs loaded by the linker, this
* is done by ElfReader. This function is here for DSOs loaded by the kernel,
* namely the linker itself and the main executable.
*/
static void set_bss_vma_name(soinfo* si) {
for (size_t i = 0; i < si->phnum; ++i) {
auto phdr = &si->phdr[i];
if (phdr->p_type != PT_LOAD) {
continue;
}
ElfW(Addr) seg_start = phdr->p_vaddr + si->load_bias;
ElfW(Addr) seg_page_end = PAGE_END(seg_start + phdr->p_memsz);
ElfW(Addr) seg_file_end = PAGE_END(seg_start + phdr->p_filesz);
if (seg_page_end > seg_file_end) {
prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME,
reinterpret_cast<void*>(seg_file_end), seg_page_end - seg_file_end,
".bss");
}
}
}
// Detect an attempt to run the linker on itself. e.g.:
// /system/bin/linker64 /system/bin/linker64
// Use priority-1 to run this constructor before other constructors.
@ -660,6 +689,9 @@ __linker_init_post_relocation(KernelArgumentBlock& args, soinfo& tmp_linker_so)
// couldn't make system calls on x86 at that point, but we can now...
if (!tmp_linker_so.protect_relro()) __linker_cannot_link(args.argv[0]);
// And we can set VMA name for the bss section now
set_bss_vma_name(&tmp_linker_so);
// Initialize the linker's static libc's globals
__libc_init_globals();