From a376e11d84ba7ea8cc7333c77043e20c7b0cfc91 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Thu, 26 Apr 2018 13:01:26 +0100 Subject: [PATCH] Fix calling ifunc functions when resolver has debug info and different name Currently, on Fedora 27 (glibc 2.26), if you try to call strlen in the inferior you get: (gdb) p strlen ("hello") $1 = (size_t (*)(const char *)) 0x7ffff554aac0 <__strlen_avx2> strlen is an ifunc function, and what we see above is the result of calling the ifunc resolver in the inferior. That returns a pointer to the actual target function that implements strlen on my machine. GDB should have turned around and called the resolver automatically without the user noticing. This is was caused by commit: commit bf223d3e808e6fec9ee165d3d48beb74837796de Date: Mon Aug 21 11:34:32 2017 +0100 Handle function aliases better (PR gdb/19487, errno printing) which added the find_function_alias_target call to c-exp.y, to try to find an alias with debug info for a minsym. For ifunc symbols, that finds the ifunc's resolver if it has debug info (in the example it's called "strlen_ifunc"), with the result that GDB calls that as a regular function. After this commit, we get now get: (top-gdb) p strlen ("hello") '__strlen_avx2' has unknown return type; cast the call to its declared return type Which is correct, because __strlen_avx2 is written in assembly. That'll be improved in a following patch, though. gdb/ChangeLog: 2018-04-26 Pedro Alves * c-exp.y (variable production): Skip finding an alias for ifunc symbols. --- gdb/ChangeLog | 5 +++++ gdb/c-exp.y | 4 +++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 3266d7fc621..e23eeee0d07 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2018-04-26 Pedro Alves + + * c-exp.y (variable production): Skip finding an alias for ifunc + symbols. + 2018-04-26 Pedro Alves * elfread.c (elf_rel_plt_read): Look for relocations for .got.plt too. diff --git a/gdb/c-exp.y b/gdb/c-exp.y index 8dc3c068a5e..e2ea07cd792 100644 --- a/gdb/c-exp.y +++ b/gdb/c-exp.y @@ -1081,7 +1081,9 @@ variable: name_not_typename is important for example for "p *__errno_location()". */ symbol *alias_target - = find_function_alias_target (msymbol); + = (msymbol.minsym->type != mst_text_gnu_ifunc + ? find_function_alias_target (msymbol) + : NULL); if (alias_target != NULL) { write_exp_elt_opcode (pstate, OP_VAR_VALUE); -- 2.39.2