Commit 7af82ff9 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman

powerpc/ftrace: Ignore weak functions

Extend commit b39181f7 ("ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to
avoid adding weak function") to ppc32 and ppc64 -mprofile-kernel by
defining FTRACE_MCOUNT_MAX_OFFSET.

For ppc64 -mprofile-kernel ABI, we can have two instructions at function
entry for TOC setup followed by 'mflr r0' and 'bl _mcount'. So, the
mcount location is at most the 4th instruction in a function. For ppc32,
mcount location is always the 3rd instruction in a function, preceded by
'mflr r0' and 'stw r0,4(r1)'.

With this patch, and with ppc64le_guest_defconfig and some ftrace/bpf
config items enabled:
  # grep __ftrace_invalid_address available_filter_functions | wc -l
  79
Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220809105425.424045-1-naveen.n.rao@linux.vnet.ibm.com
parent 14b5d59a
......@@ -10,6 +10,13 @@
#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
/* Ignore unused weak functions which will have larger offsets */
#ifdef CONFIG_MPROFILE_KERNEL
#define FTRACE_MCOUNT_MAX_OFFSET 12
#elif defined(CONFIG_PPC32)
#define FTRACE_MCOUNT_MAX_OFFSET 8
#endif
#ifndef __ASSEMBLY__
extern void _mcount(void);
......
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