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authorNathan Lynch <ntl@pobox.com>2008-07-22 04:48:46 +1000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2008-07-25 15:44:39 +1000
commit483fad1c3fa1060d7e6710e84a065ad514571739 (patch)
tree98c2da31a58c71d1ae9c808bdf232cbbbe060550 /fs/binfmt_elf.c
parente9f76354ce83a20c7768ad37caa033f6506b4f96 (diff)
downloadconfigs-483fad1c3fa1060d7e6710e84a065ad514571739.tar.gz
ELF loader support for auxvec base platform string
Some IBM POWER-based platforms have the ability to run in a mode which mostly appears to the OS as a different processor from the actual hardware. For example, a Power6 system may appear to be a Power5+, which makes the AT_PLATFORM value "power5+". This means that programs are restricted to the ISA supported by Power5+; Power6-specific instructions are treated as illegal. However, some applications (virtual machines, optimized libraries) can benefit from knowledge of the underlying CPU model. A new aux vector entry, AT_BASE_PLATFORM, will denote the actual hardware. For example, on a Power6 system in Power5+ compatibility mode, AT_PLATFORM will be "power5+" and AT_BASE_PLATFORM will be "power6". The idea is that AT_PLATFORM indicates the instruction set supported, while AT_BASE_PLATFORM indicates the underlying microarchitecture. If the architecture has defined ELF_BASE_PLATFORM, copy that value to the user stack in the same manner as ELF_PLATFORM. Signed-off-by: Nathan Lynch <ntl@pobox.com> Acked-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'fs/binfmt_elf.c')
-rw-r--r--fs/binfmt_elf.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 639d2d8b571..742c8f53048 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -131,6 +131,15 @@ static int padzero(unsigned long elf_bss)
#define STACK_ALLOC(sp, len) ({ sp -= len ; sp; })
#endif
+#ifndef ELF_BASE_PLATFORM
+/*
+ * AT_BASE_PLATFORM indicates the "real" hardware/microarchitecture.
+ * If the arch defines ELF_BASE_PLATFORM (in asm/elf.h), the value
+ * will be copied to the user stack in the same manner as AT_PLATFORM.
+ */
+#define ELF_BASE_PLATFORM NULL
+#endif
+
static int
create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
unsigned long load_addr, unsigned long interp_load_addr)
@@ -142,7 +151,9 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
elf_addr_t __user *envp;
elf_addr_t __user *sp;
elf_addr_t __user *u_platform;
+ elf_addr_t __user *u_base_platform;
const char *k_platform = ELF_PLATFORM;
+ const char *k_base_platform = ELF_BASE_PLATFORM;
int items;
elf_addr_t *elf_info;
int ei_index = 0;
@@ -172,6 +183,19 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
return -EFAULT;
}
+ /*
+ * If this architecture has a "base" platform capability
+ * string, copy it to userspace.
+ */
+ u_base_platform = NULL;
+ if (k_base_platform) {
+ size_t len = strlen(k_base_platform) + 1;
+
+ u_base_platform = (elf_addr_t __user *)STACK_ALLOC(p, len);
+ if (__copy_to_user(u_base_platform, k_base_platform, len))
+ return -EFAULT;
+ }
+
/* Create the ELF interpreter info */
elf_info = (elf_addr_t *)current->mm->saved_auxv;
/* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */
@@ -209,6 +233,10 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec,
NEW_AUX_ENT(AT_PLATFORM,
(elf_addr_t)(unsigned long)u_platform);
}
+ if (k_base_platform) {
+ NEW_AUX_ENT(AT_BASE_PLATFORM,
+ (elf_addr_t)(unsigned long)u_base_platform);
+ }
if (bprm->interp_flags & BINPRM_FLAGS_EXECFD) {
NEW_AUX_ENT(AT_EXECFD, bprm->interp_data);
}