From: Roland McGrath Date: Sun, 30 Jul 2006 10:04:06 +0000 (-0700) Subject: [PATCH] vDSO hash-style fix X-Git-Tag: v2.6.18-rc4~91 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0b0bf7a3ccb6f0b38ead71980e79f875046047b7;p=linux-2.6 [PATCH] vDSO hash-style fix The latest toolchains can produce a new ELF section in DSOs and dynamically-linked executables. The new section ".gnu.hash" replaces ".hash", and allows for more efficient runtime symbol lookups by the dynamic linker. The new ld option --hash-style={sysv|gnu|both} controls whether to produce the old ".hash", the new ".gnu.hash", or both. In some new systems such as Fedora Core 6, gcc by default passes --hash-style=gnu to the linker, so that a standard invocation of "gcc -shared" results in producing a DSO with only ".gnu.hash". The new ".gnu.hash" sections need to be dealt with the same way as ".hash" sections in all respects; only the dynamic linker cares about their contents. To work with older dynamic linkers (i.e. preexisting releases of glibc), a binary must have the old ".hash" section. The --hash-style=both option produces binaries that a new dynamic linker can use more efficiently, but an old dynamic linker can still handle. The new section runs afoul of the custom linker scripts used to build vDSO images for the kernel. On ia64, the failure mode for this is a boot-time panic because the vDSO's PT_IA_64_UNWIND segment winds up ill-formed. This patch addresses the problem in two ways. First, it mentions ".gnu.hash" in all the linker scripts alongside ".hash". This produces correct vDSO images with --hash-style=sysv (or old tools), with --hash-style=gnu, or with --hash-style=both. Second, it passes the --hash-style=sysv option when building the vDSO images, so that ".gnu.hash" is not actually produced. This is the most conservative choice for compatibility with any old userland. There is some concern that some ancient glibc builds (though not any known old production system) might choke on --hash-style=both binaries. The optimizations provided by the new style of hash section do not really matter for a DSO with a tiny number of symbols, as the vDSO has. If someone wants to use =gnu or =both for their vDSO builds and worry less about that compatibility, just change the option and the linker script changes will make any choice work fine. Signed-off-by: Roland McGrath Cc: "Luck, Tony" Cc: Kyle McMartin Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Jeff Dike Cc: Andi Kleen Cc: Sam Ravnborg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/Documentation/kbuild/makefiles.txt b/Documentation/kbuild/makefiles.txt index 14ef3868a3..0706699c9d 100644 --- a/Documentation/kbuild/makefiles.txt +++ b/Documentation/kbuild/makefiles.txt @@ -407,6 +407,20 @@ more details, with real examples. The second argument is optional, and if supplied will be used if first argument is not supported. + ld-option + ld-option is used to check if $(CC) when used to link object files + supports the given option. An optional second option may be + specified if first option are not supported. + + Example: + #arch/i386/kernel/Makefile + vsyscall-flags += $(call ld-option, -Wl$(comma)--hash-style=sysv) + + In the above example vsyscall-flags will be assigned the option + -Wl$(comma)--hash-style=sysv if it is supported by $(CC). + The second argument is optional, and if supplied will be used + if first argument is not supported. + cc-option cc-option is used to check if $(CC) support a given option, and not supported to use an optional second option. diff --git a/arch/i386/kernel/Makefile b/arch/i386/kernel/Makefile index 1b452a1665..ab98fc21a5 100644 --- a/arch/i386/kernel/Makefile +++ b/arch/i386/kernel/Makefile @@ -59,7 +59,8 @@ quiet_cmd_syscall = SYSCALL $@ export CPPFLAGS_vsyscall.lds += -P -C -U$(ARCH) -vsyscall-flags = -shared -s -Wl,-soname=linux-gate.so.1 +vsyscall-flags = -shared -s -Wl,-soname=linux-gate.so.1 \ + $(call ld-option, -Wl$(comma)--hash-style=sysv) SYSCFLAGS_vsyscall-sysenter.so = $(vsyscall-flags) SYSCFLAGS_vsyscall-int80.so = $(vsyscall-flags) diff --git a/arch/i386/kernel/vsyscall.lds.S b/arch/i386/kernel/vsyscall.lds.S index e26975fc68..f66cd11adb 100644 --- a/arch/i386/kernel/vsyscall.lds.S +++ b/arch/i386/kernel/vsyscall.lds.S @@ -10,6 +10,7 @@ SECTIONS . = VDSO_PRELINK + SIZEOF_HEADERS; .hash : { *(.hash) } :text + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .gnu.version : { *(.gnu.version) } diff --git a/arch/ia64/kernel/Makefile b/arch/ia64/kernel/Makefile index 0e4553f320..ad8215a3c5 100644 --- a/arch/ia64/kernel/Makefile +++ b/arch/ia64/kernel/Makefile @@ -45,7 +45,8 @@ CPPFLAGS_gate.lds := -P -C -U$(ARCH) quiet_cmd_gate = GATE $@ cmd_gate = $(CC) -nostdlib $(GATECFLAGS_$(@F)) -Wl,-T,$(filter-out FORCE,$^) -o $@ -GATECFLAGS_gate.so = -shared -s -Wl,-soname=linux-gate.so.1 +GATECFLAGS_gate.so = -shared -s -Wl,-soname=linux-gate.so.1 \ + $(call ld-option, -Wl$(comma)--hash-style=sysv) $(obj)/gate.so: $(obj)/gate.lds $(obj)/gate.o FORCE $(call if_changed,gate) diff --git a/arch/ia64/kernel/gate.lds.S b/arch/ia64/kernel/gate.lds.S index cc35cddfd4..6d198339bf 100644 --- a/arch/ia64/kernel/gate.lds.S +++ b/arch/ia64/kernel/gate.lds.S @@ -12,6 +12,7 @@ SECTIONS . = GATE_ADDR + SIZEOF_HEADERS; .hash : { *(.hash) } :readable + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .gnu.version : { *(.gnu.version) } diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S index 9989495a51..b3677fc8ee 100644 --- a/arch/parisc/kernel/vmlinux.lds.S +++ b/arch/parisc/kernel/vmlinux.lds.S @@ -204,6 +204,7 @@ SECTIONS *(.dynstr) *(.dynamic) *(.hash) + *(.gnu.hash) #endif } diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile index 8a3bed5f14..3726358faa 100644 --- a/arch/powerpc/kernel/vdso32/Makefile +++ b/arch/powerpc/kernel/vdso32/Makefile @@ -14,7 +14,8 @@ obj-vdso32 := $(addprefix $(obj)/, $(obj-vdso32)) EXTRA_CFLAGS := -shared -s -fno-common -fno-builtin -EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso32.so.1 +EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso32.so.1 \ + $(call ld-option, -Wl$(comma)--hash-style=sysv) EXTRA_AFLAGS := -D__VDSO32__ -s obj-y += vdso32_wrapper.o diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S index f4bad720cb..6187af2d54 100644 --- a/arch/powerpc/kernel/vdso32/vdso32.lds.S +++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S @@ -14,6 +14,7 @@ SECTIONS { . = VDSO32_LBASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .gnu.version : { *(.gnu.version) } diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile index ab39988452..43af9b2a6f 100644 --- a/arch/powerpc/kernel/vdso64/Makefile +++ b/arch/powerpc/kernel/vdso64/Makefile @@ -8,7 +8,8 @@ targets := $(obj-vdso64) vdso64.so obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64)) EXTRA_CFLAGS := -shared -s -fno-common -fno-builtin -EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso64.so.1 +EXTRA_CFLAGS += -nostdlib -Wl,-soname=linux-vdso64.so.1 \ + $(call ld-option, -Wl$(comma)--hash-style=sysv) EXTRA_AFLAGS := -D__VDSO64__ -s obj-y += vdso64_wrapper.o diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S index 4bdf224464..4a2b6dc096 100644 --- a/arch/powerpc/kernel/vdso64/vdso64.lds.S +++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S @@ -12,6 +12,7 @@ SECTIONS { . = VDSO64_LBASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .gnu.version : { *(.gnu.version) } diff --git a/arch/ppc/kernel/vmlinux.lds.S b/arch/ppc/kernel/vmlinux.lds.S index 09c6525cfa..095fd33233 100644 --- a/arch/ppc/kernel/vmlinux.lds.S +++ b/arch/ppc/kernel/vmlinux.lds.S @@ -8,6 +8,7 @@ SECTIONS . = + SIZEOF_HEADERS; .interp : { *(.interp) } .hash : { *(.hash) } + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .rel.text : { *(.rel.text) } diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S index 2517ecb8bf..68ed24df5c 100644 --- a/arch/um/kernel/dyn.lds.S +++ b/arch/um/kernel/dyn.lds.S @@ -26,6 +26,7 @@ SECTIONS /* Read-only sections, merged into text segment: */ .hash : { *(.hash) } + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .gnu.version : { *(.gnu.version) } diff --git a/arch/x86_64/ia32/Makefile b/arch/x86_64/ia32/Makefile index 62bc5f56da..cdae36435e 100644 --- a/arch/x86_64/ia32/Makefile +++ b/arch/x86_64/ia32/Makefile @@ -23,6 +23,7 @@ targets := $(foreach F,sysenter syscall,vsyscall-$F.o vsyscall-$F.so) # The DSO images are built using a special linker script quiet_cmd_syscall = SYSCALL $@ cmd_syscall = $(CC) -m32 -nostdlib -shared -s \ + $(call ld-option, -Wl$(comma)--hash-style=sysv) \ -Wl,-soname=linux-gate.so.1 -o $@ \ -Wl,-T,$(filter-out FORCE,$^) diff --git a/arch/x86_64/ia32/vsyscall.lds b/arch/x86_64/ia32/vsyscall.lds index f2e75ed4c6..1dc86ff5bc 100644 --- a/arch/x86_64/ia32/vsyscall.lds +++ b/arch/x86_64/ia32/vsyscall.lds @@ -11,6 +11,7 @@ SECTIONS . = VSYSCALL_BASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text + .gnu.hash : { *(.gnu.hash) } .dynsym : { *(.dynsym) } .dynstr : { *(.dynstr) } .gnu.version : { *(.gnu.version) } diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include index 2180c88cfe..f011322635 100644 --- a/scripts/Kbuild.include +++ b/scripts/Kbuild.include @@ -85,6 +85,13 @@ cc-version = $(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-version.sh \ cc-ifversion = $(shell if [ $(call cc-version, $(CC)) $(1) $(2) ]; then \ echo $(3); fi;) +# ld-option +# Usage: ldflags += $(call ld-option, -Wl$(comma)--hash-style=both) +ld-option = $(shell if $(CC) $(1) \ + -nostdlib -o ldtest$$$$.out -xc /dev/null \ + > /dev/null 2>&1; then echo "$(1)"; else echo "$(2)"; fi; \ + rm -f ldtest$$$$.out) + ### # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj= # Usage: