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[Qemu-devel] [PATCH for-2.11] linux-user: Fix calculation of auxv length
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [PATCH for-2.11] linux-user: Fix calculation of auxv length |
Date: |
Tue, 7 Nov 2017 18:25:18 +0000 |
In commit 7c4ee5bcc82e643 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
Signed-off-by: Peter Maydell <address@hidden>
---
linux-user/elfload.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/linux-user/elfload.c b/linux-user/elfload.c
index 3b857fb..20f3d8c 100644
--- a/linux-user/elfload.c
+++ b/linux-user/elfload.c
@@ -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);
--
2.7.4
- [Qemu-devel] [PATCH for-2.11] linux-user: Fix calculation of auxv length,
Peter Maydell <=