From a6db407f15ab7d0dbfd83a48173343654106510e Mon Sep 17 00:00:00 2001 From: John Baldwin Date: Thu, 10 Mar 2022 15:39:53 -0800 Subject: [PATCH] libpmcstat: Fix a few ARM-specific issues with function symbols. - Refine the checks for ARM mapping symbols and apply them on arm64 as well as 32-bit arm. In particular, mapping symbols can have additional characters and are not strictly limited to just "$a" but can append additional characters (e.g. "$a.1"). Add "$x" to the list of mapping symbol prefixes. - Clear the LSB of function symbol addresses. Thumb function addresses set the LSB to enable Thumb mode. However, the actual function starts at the aligned address with LSB clear. Not clearing the LSB can cause pmcannotate to pass misaligned addresses to objdump when extracting disassembly. Reviewed by: andrew Obtained from: CheriBSD Sponsored by: University of Cambridge, Google, Inc. Differential Revision: https://reviews.freebsd.org/D34416 --- lib/libpmcstat/libpmcstat_image.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/lib/libpmcstat/libpmcstat_image.c b/lib/libpmcstat/libpmcstat_image.c index 97109f203806..c63f00e03253 100644 --- a/lib/libpmcstat/libpmcstat_image.c +++ b/lib/libpmcstat/libpmcstat_image.c @@ -119,13 +119,23 @@ pmcstat_image_add_symbols(struct pmcstat_image *image, Elf *e, if ((fnname = elf_strptr(e, sh->sh_link, sym.st_name)) == NULL) continue; -#ifdef __arm__ - /* Remove spurious ARM function name. */ + +#if defined(__aarch64__) || defined(__arm__) + /* Ignore ARM mapping symbols. */ if (fnname[0] == '$' && (fnname[1] == 'a' || fnname[1] == 't' || - fnname[1] == 'd') && - fnname[2] == '\0') + fnname[1] == 'd' || fnname[1] == 'x')) continue; + + /* + * Clear LSB from starting addresses for functions + * which execute in Thumb mode. We should perhaps + * only do this for functions in a $t mapping symbol + * range, but parsing mapping symbols would be a lot + * of work and function addresses shouldn't have the + * LSB set otherwise. + */ + sym.st_value &= ~1; #endif symptr->ps_name = pmcstat_string_intern(fnname);