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powerpc/ftrace: Ignore weak functions

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Extend commit b39181f7c6 ("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: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220809105425.424045-1-naveen.n.rao@linux.vnet.ibm.com
This commit is contained in:
Naveen N. Rao 2022-08-09 16:24:25 +05:30 committed by Michael Ellerman
parent 14b5d59a26
commit 7af82ff90a
1 changed files with 7 additions and 0 deletions
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7
arch/powerpc/include/asm/ftrace.h
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@ -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);