diff options
Diffstat (limited to 'patches/musl/1.0.3/0002-fix_mips_linker_regression.patch')
| -rw-r--r-- | patches/musl/1.0.3/0002-fix_mips_linker_regression.patch | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/patches/musl/1.0.3/0002-fix_mips_linker_regression.patch b/patches/musl/1.0.3/0002-fix_mips_linker_regression.patch new file mode 100644 index 0000000..4891b4f --- /dev/null +++ b/patches/musl/1.0.3/0002-fix_mips_linker_regression.patch @@ -0,0 +1,88 @@ +From 2d8cc92a7cb4a3256ed07d86843388ffd8a882b1 Mon Sep 17 00:00:00 2001 +From: Rich Felker <dalias@aerifal.cx> +Date: Mon, 30 Jun 2014 05:18:14 +0000 +Subject: fix regression in mips dynamic linker + +this issue caused the address of functions in shared libraries to +resolve to their PLT thunks in the main program rather than their +correct addresses. it was observed causing crashes, though the +mechanism of the crash was not thoroughly investigated. since the +issue is very subtle, it calls for some explanation: + +on all well-behaved archs, GOT entries that belong to the PLT use a +special relocation type, typically called JMP_SLOT, so that the +dynamic linker can avoid having the jump destinations for the PLT +resolve to PLT thunks themselves (they also provide a definition for +the symbol, which must be used whenever the address of the function is +taken so that all DSOs see the same address). + +however, the traditional mips PIC ABI lacked such a JMP_SLOT +relocation type, presumably because, due to the way PIC works, the +address of the PLT thunk was never needed and could always be ignored. + +prior to commit adf94c19666e687a728bbf398f9a88ea4ea19996, the mips +version of reloc.h contained a hack that caused all symbol lookups to +be treated like JMP_SLOT, inhibiting undefined symbols from ever being +used to resolve symbolic relocations. this hack goes all the way back +to commit babf820180368f00742ec65b2050a82380d7c542, when the mips +dynamic linker was first made usable. + +during the recent refactoring to eliminate arch-specific relocation +processing (commit adf94c19666e687a728bbf398f9a88ea4ea19996), this +hack was overlooked and no equivalent functionality was provided in +the new code. + +fixing the problem is not as simple as adding back an equivalent hack, +since there is now also a "non-PIC ABI" that can be used for the main +executable, which actually does use a PLT. the closest thing to +official documentation I could find for this ABI is nonpic.txt, +attached to Message-ID: 20080701202236.GA1534@caradoc.them.org, which +can be found in the gcc mailing list archives and elsewhere. per this +document, undefined symbols corresponding to PLT thunks have the +STO_MIPS_PLT bit set in the symbol's st_other field. thus, I have +added an arch-specific rule for mips, applied at the find_sym level +rather than the relocation level, to reject undefined symbols with the +STO_MIPS_PLT bit clear. + +the previous hack of treating all mips relocations as JMP_SLOT-like, +rather than rejecting the unwanted symbols in find_sym, probably also +caused dlsym to wrongly return PLT thunks in place of the correct +address of a function under at least some conditions. this should now +be fixed, at least for global-scope symbol lookups. +--- +diff --git a/arch/mips/reloc.h b/arch/mips/reloc.h +index 91fa097..4b81d32 100644 +--- a/arch/mips/reloc.h ++++ b/arch/mips/reloc.h +@@ -86,3 +86,4 @@ static void do_arch_relocs(struct dso *this, struct dso *head) + + #define NEED_ARCH_RELOCS 1 + #define DYNAMIC_IS_RO 1 ++#define ARCH_SYM_REJECT_UND(s) (!((s)->st_other & STO_MIPS_PLT)) +diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c +index a08300d..55124ff 100644 +--- a/src/ldso/dynlink.c ++++ b/src/ldso/dynlink.c +@@ -233,6 +233,10 @@ static Sym *gnu_lookup(const char *s, uint32_t h1, struct dso *dso) + #define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON | 1<<STT_TLS) + #define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE) + ++#ifndef ARCH_SYM_REJECT_UND ++#define ARCH_SYM_REJECT_UND(s) 0 ++#endif ++ + static struct symdef find_sym(struct dso *dso, const char *s, int need_def) + { + uint32_t h = 0, gh = 0; +@@ -249,7 +253,8 @@ static struct symdef find_sym(struct dso *dso, const char *s, int need_def) + } + if (!sym) continue; + if (!sym->st_shndx) +- if (need_def || (sym->st_info&0xf) == STT_TLS) ++ if (need_def || (sym->st_info&0xf) == STT_TLS ++ || ARCH_SYM_REJECT_UND(sym)) + continue; + if (!sym->st_value) + if ((sym->st_info&0xf) != STT_TLS) +-- +cgit v0.9.0.3-65-g4555 |