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musl/arch/i386/reloc.h

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make the dynamic linker find its path file relative to its own location prior to this change, using a non-default syslibdir was impractical on systems where the ordinary library paths contain musl-incompatible library files. the file containing search paths was always taken from /etc, which would either correspond to a system-wide musl installation, or fail to exist at all, resulting in searching of the default library path. the new search strategy is safe even for suid programs because the pathname used comes from the PT_INTERP header of the program being run, rather than any external input. as part of this change, I have also begun differentiating the names of arch variants that differ by endianness or floating point calling convention. the corresponding changes in the build system and and gcc wrapper script (to use an alternate dynamic linker name) for these configurations have not yet been made.
2013-07-18 23:29:44 +00:00
#define LDSO_ARCH "i386"
proper path searching for dynamic linker first, use $LD_LIBRARY_PATH unless suid. if that fails, read path from /etc/ld-musl-$ARCH.path and fallback to a builtin default.
2011-06-25 05:56:34 +00:00
dynamic linker bootstrap overhaul this overhaul further reduces the amount of arch-specific code needed by the dynamic linker and removes a number of assumptions, including: - that symbolic function references inside libc are bound at link time via the linker option -Bsymbolic-functions. - that libc functions used by the dynamic linker do not require access to data symbols. - that static/internal function calls and data accesses can be made without performing any relocations, or that arch-specific startup code handled any such relocations needed. removing these assumptions paves the way for allowing libc.so itself to be built with stack protector (among other things), and is achieved by a three-stage bootstrap process: 1. relative relocations are processed with a flat function. 2. symbolic relocations are processed with no external calls/data. 3. main program and dependency libs are processed with a fully-functional libc/ldso. reduction in arch-specific code is achived through the following: - crt_arch.h, used for generating crt1.o, now provides the entry point for the dynamic linker too. - asm is no longer responsible for skipping the beginning of argv[] when ldso is invoked as a command. - the functionality previously provided by __reloc_self for heavily GOT-dependent RISC archs is now the arch-agnostic stage-1. - arch-specific relocation type codes are mapped directly as macros rather than via an inline translation function/switch statement.
2015-04-13 06:56:26 +00:00
#define REL_SYMBOLIC R_386_32
#define REL_OFFSET R_386_PC32
#define REL_GOT R_386_GLOB_DAT
#define REL_PLT R_386_JMP_SLOT
#define REL_RELATIVE R_386_RELATIVE
#define REL_COPY R_386_COPY
#define REL_DTPMOD R_386_TLS_DTPMOD32
#define REL_DTPOFF R_386_TLS_DTPOFF32
#define REL_TPOFF R_386_TLS_TPOFF
#define REL_TPOFF_NEG R_386_TLS_TPOFF32
#define REL_TLSDESC R_386_TLS_DESC
#define CRTJMP(pc,sp) __asm__ __volatile__( \
"mov %1,%%esp ; jmp *%0" : : "r"(pc), "r"(sp) : "memory" )
introduce new symbol-lookup-free rcrt1/dlstart stage chaining previously, the call into stage 2 was made by looking up the symbol name "__dls2" (which was chosen short to be easy to look up) from the dynamic symbol table. this was no problem for the dynamic linker, since it always exports all its symbols. in the case of the static pie entry point, however, the dynamic symbol table does not contain the necessary symbol unless -rdynamic/-E was used when linking. this linking requirement is a major obstacle both to practical use of static-pie as a nommu binary format (since it greatly enlarges the file) and to upstream toolchain support for static-pie (adding -E to default linking specs is not reasonable). this patch replaces the runtime symbolic lookup with a link-time lookup via an inline asm fragment, which reloc.h is responsible for providing. in this initial commit, the asm is provided only for i386, and the old lookup code is left in place as a fallback for archs that have not yet transitioned. modifying crt_arch.h to pass the stage-2 function pointer as an argument was considered as an alternative, but such an approach would not be compatible with fdpic, where it's impossible to compute function pointers without already having performed relocations. it was also deemed desirable to keep crt_arch.h as simple/minimal as possible. in principle, archs with pc-relative or got-relative addressing of static variables could instead load the stage-2 function pointer from a static volatile object. that does not work for fdpic, and is not safe against reordering on mips-like archs that use got slots even for static functions, but it's a valid on i386 and many others, and could provide a reasonable default implementation in the future.
2015-09-17 06:30:55 +00:00
#define GETFUNCSYM(fp, sym, got) __asm__ ( \
".hidden " #sym "\n" \
" call 1f\n" \
"1: addl $" #sym "-.,(%%esp)\n" \
" pop %0" \
: "=r"(*fp) : : "memory" )