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Commit 9905ce8a authored by Rabin Vincent's avatar Rabin Vincent Committed by Steven Rostedt
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ftrace/recordmcount: Avoid STT_FUNC symbols as base on ARM 



While find_secsym_ndx often finds the unamed local STT_SECTION, if a
section has only one function in it, the ARM toolchain generates the
STT_FUNC symbol before the STT_SECTION, and recordmcount finds this
instead.

This is problematic on ARM because in ARM ELFs, "if a [STT_FUNC] symbol
addresses a Thumb instruction, its value is the address of the
instruction with bit zero set (in a relocatable object, the section
offset with bit zero set)".  This leads to incorrect mcount addresses
being recorded.

Fix this by not using STT_FUNC symbols as the base on ARM.

Signed-off-by: default avatarRabin Vincent <rabin@rab.in>
Link: http://lkml.kernel.org/r/1305134631-31617-1-git-send-email-rabin@rab.in


Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 4d7a2fa8

scripts/recordmcount.h

+8 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#undef ELF_R_INFO

#undef Elf_r_info

#undef ELF_ST_BIND

#undef ELF_ST_TYPE

#undef fn_ELF_R_SYM

#undef fn_ELF_R_INFO

#undef uint_t
@@ -76,6 +77,7 @@ 
# define ELF_R_INFO		ELF64_R_INFO

# define Elf_r_info		Elf64_r_info

# define ELF_ST_BIND		ELF64_ST_BIND

# define ELF_ST_TYPE		ELF64_ST_TYPE

# define fn_ELF_R_SYM		fn_ELF64_R_SYM

# define fn_ELF_R_INFO		fn_ELF64_R_INFO

# define uint_t			uint64_t
@@ -108,6 +110,7 @@ 
# define ELF_R_INFO		ELF32_R_INFO

# define Elf_r_info		Elf32_r_info

# define ELF_ST_BIND		ELF32_ST_BIND

# define ELF_ST_TYPE		ELF32_ST_TYPE

# define fn_ELF_R_SYM		fn_ELF32_R_SYM

# define fn_ELF_R_INFO		fn_ELF32_R_INFO

# define uint_t			uint32_t
@@ -427,6 +430,11 @@ static unsigned find_secsym_ndx(unsigned const txtndx, 
		if (txtndx == w2(symp->st_shndx)

			/* avoid STB_WEAK */

		    && (STB_LOCAL == st_bind || STB_GLOBAL == st_bind)) {

			/* function symbols on ARM have quirks, avoid them */

			if (w2(ehdr->e_machine) == EM_ARM

			    && ELF_ST_TYPE(symp->st_info) == STT_FUNC)

				continue;



			*recvalp = _w(symp->st_value);

			return symp - sym0;

		}