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linux-user: Fix calculation of auxv length

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In commit 7c4ee5bcc8 we changed the order in which we construct
the AUXV, but forgot to adjust the calculation of the length. The
result is that we set info->auxv_len to a bogus and negative value,
and then later on the code in open_self_auxv() gets confused and
ends up presenting the guest with an empty file.

Since we now have to calculate the auxv length up-front as part
of figuring out how much we're going to put on the stack, set
info->auxv_len then; this allows us to assert that we put the
same number of entries into auxv as we pre-calculated, rather
than merely having a comment saying we need to do that.

Fixes: https://bugs.launchpad.net/qemu/+bug/1728116

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>
This commit is contained in:
Peter Maydell 2017-11-07 18:25:18 +00:00 committed by Riku Voipio
parent 78bfef72fb
commit f516511ea8
1 changed files with 9 additions and 2 deletions
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11
linux-user/elfload.c
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@ -1732,6 +1732,8 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
#ifdef ELF_HWCAP2
size += 2;
#endif
info->auxv_len = size * n;
size += envc + argc + 2;
size += 1; /* argc itself */
size *= n;
@ -1760,7 +1762,6 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
put_user_ual(val, u_auxv); u_auxv += n; \
} while(0)
/* There must be exactly DLINFO_ITEMS entries here. */
#ifdef ARCH_DLINFO
/*
* ARCH_DLINFO must come first so platform specific code can enforce
@ -1768,6 +1769,9 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
*/
ARCH_DLINFO;
#endif
/* There must be exactly DLINFO_ITEMS entries here, or the assert
* on info->auxv_len will trigger.
*/
NEW_AUX_ENT(AT_PHDR, (abi_ulong)(info->load_addr + exec->e_phoff));
NEW_AUX_ENT(AT_PHENT, (abi_ulong)(sizeof (struct elf_phdr)));
NEW_AUX_ENT(AT_PHNUM, (abi_ulong)(exec->e_phnum));
@ -1793,7 +1797,10 @@ static abi_ulong create_elf_tables(abi_ulong p, int argc, int envc,
NEW_AUX_ENT (AT_NULL, 0);
#undef NEW_AUX_ENT
info->auxv_len = u_argv - info->saved_auxv;
/* Check that our initial calculation of the auxv length matches how much
* we actually put into it.
*/
assert(info->auxv_len == u_auxv - info->saved_auxv);
put_user_ual(argc, u_argc);