ia64 fix ptrace patch4.15-8

1 files changed, 87 insertions, 0 deletions

diff --git a/1700_ia64_fix_ptrace.patch b/1700_ia64_fix_ptrace.patch
new file mode 100644
index 00000000..6173b053
--- /dev/null
+++ b/1700_ia64_fix_ptrace.patch
@@ -0,0 +1,87 @@
+From patchwork Fri Feb  2 22:12:24 2018
+Content-Type: text/plain; charset="utf-8"
+MIME-Version: 1.0
+Content-Transfer-Encoding: 8bit
+Subject: ia64: fix ptrace(PTRACE_GETREGS) (unbreaks strace, gdb)
+From: Sergei Trofimovich <slyfox@gentoo.org>
+X-Patchwork-Id: 10198159
+Message-Id: <20180202221224.16597-1-slyfox@gentoo.org>
+To: Tony Luck <tony.luck@intel.com>, Fenghua Yu <fenghua.yu@intel.com>,
+ linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
+Cc: Sergei Trofimovich <slyfox@gentoo.org>
+Date: Fri,  2 Feb 2018 22:12:24 +0000
+
+The strace breakage looks like that:
+./strace: get_regs: get_regs_error: Input/output error
+
+It happens because ia64 needs to load unwind tables
+to read certain registers. Unwind tables fail to load
+due to GCC quirk on the following code:
+
+    extern char __end_unwind[];
+    const struct unw_table_entry *end = (struct unw_table_entry *)table_end;
+    table->end = segment_base + end[-1].end_offset;
+
+GCC does not generate correct code for this single memory
+reference after constant propagation (see https://gcc.gnu.org/PR84184).
+Two triggers are required for bad code generation:
+- '__end_unwind' has alignment lower (char), than
+  'struct unw_table_entry' (8).
+- symbol offset is negative.
+
+This commit workarounds it by fixing alignment of '__end_unwind'.
+While at it use hidden symbols to generate shorter gp-relative
+relocations.
+
+CC: Tony Luck <tony.luck@intel.com>
+CC: Fenghua Yu <fenghua.yu@intel.com>
+CC: linux-ia64@vger.kernel.org
+CC: linux-kernel@vger.kernel.org
+Bug: https://github.com/strace/strace/issues/33
+Bug: https://gcc.gnu.org/PR84184
+Reported-by: Émeric Maschino <emeric.maschino@gmail.com>
+Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
+Tested-by: stanton_arch@mail.com
+---
+ arch/ia64/include/asm/sections.h |  1 -
+ arch/ia64/kernel/unwind.c        | 15 ++++++++++++++-
+ 2 files changed, 14 insertions(+), 2 deletions(-)
+
+diff --git a/arch/ia64/include/asm/sections.h b/arch/ia64/include/asm/sections.h
+index f3481408594e..0fc4f1757a44 100644
+--- a/arch/ia64/include/asm/sections.h
++++ b/arch/ia64/include/asm/sections.h
+@@ -24,7 +24,6 @@ extern char __start_gate_mckinley_e9_patchlist[], __end_gate_mckinley_e9_patchli
+ extern char __start_gate_vtop_patchlist[], __end_gate_vtop_patchlist[];
+ extern char __start_gate_fsyscall_patchlist[], __end_gate_fsyscall_patchlist[];
+ extern char __start_gate_brl_fsys_bubble_down_patchlist[], __end_gate_brl_fsys_bubble_down_patchlist[];
+-extern char __start_unwind[], __end_unwind[];
+ extern char __start_ivt_text[], __end_ivt_text[];
+ 
+ #undef dereference_function_descriptor
+diff --git a/arch/ia64/kernel/unwind.c b/arch/ia64/kernel/unwind.c
+index e04efa088902..025ba6700790 100644
+--- a/arch/ia64/kernel/unwind.c
++++ b/arch/ia64/kernel/unwind.c
+@@ -2243,7 +2243,20 @@ __initcall(create_gate_table);
+ void __init
+ unw_init (void)
+ {
+-	extern char __gp[];
++	#define __ia64_hidden __attribute__((visibility("hidden")))
++	/*
++	 * We use hidden symbols to generate more efficient code using
++	 * gp-relative addressing.
++	 */
++	extern char __gp[] __ia64_hidden;
++	/*
++	 * Unwind tables need to have proper alignment as init_unwind_table()
++	 * uses negative offsets against '__end_unwind'.
++	 * See https://gcc.gnu.org/PR84184
++	 */
++	extern const struct unw_table_entry __start_unwind[] __ia64_hidden;
++	extern const struct unw_table_entry __end_unwind[] __ia64_hidden;
++	#undef __ia64_hidden
+ 	extern void unw_hash_index_t_is_too_narrow (void);
+ 	long i, off;
+