commit: e08bdc6ca7fec4ff403493157ca3ae663bace3a6 Author: Alice Ferrazzi <alicef <AT> gentoo <DOT> org> AuthorDate: Wed Feb 28 20:06:15 2018 +0000 Commit: Alice Ferrazzi <alicef <AT> gentoo <DOT> org> CommitDate: Wed Feb 28 20:06:15 2018 +0000 URL: https://gitweb.gentoo.org/proj/linux-patches.git/commit/?id=e08bdc6c
ia64 fix ptrace patch 1700_ia64_fix_ptrace.patch | 87 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) diff --git a/1700_ia64_fix_ptrace.patch b/1700_ia64_fix_ptrace.patch new file mode 100644 index 0000000..6173b05 --- /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 <[email protected]> +X-Patchwork-Id: 10198159 +Message-Id: <[email protected]> +To: Tony Luck <[email protected]>, Fenghua Yu <[email protected]>, + [email protected], [email protected] +Cc: Sergei Trofimovich <[email protected]> +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 <[email protected]> +CC: Fenghua Yu <[email protected]> +CC: [email protected] +CC: [email protected] +Bug: https://github.com/strace/strace/issues/33 +Bug: https://gcc.gnu.org/PR84184 +Reported-by: Émeric Maschino <[email protected]> +Signed-off-by: Sergei Trofimovich <[email protected]> +Tested-by: [email protected] +--- + 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; +
