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pmcstat: fix PPC kernel symbol resolution

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PowerPC kernel is of DYN type and it has a base address where it is
initially loaded, before being relocated. As the start address passed to
pmcstat_image_link() is where the kernel was relocated to, but the symbols
always use the original base address, we need to subtract it to get the
correct offset.

Reviewed by:	jhibbits
Sponsored by:	Eldorado Research Institute (eldorado.org.br)
Differential Revision:	https://reviews.freebsd.org/D26114
This commit is contained in:
Leandro Lupori 2020-11-05 16:47:23 +00:00
parent 5cebdfc072
commit 926da0492a
1 changed files with 25 additions and 0 deletions
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25
lib/libpmcstat/libpmcstat_image.c
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@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/endian.h>
#include <sys/pmc.h>
#include <sys/sysctl.h>
#include <sys/imgact_aout.h>
#include <sys/imgact_elf.h>
@ -176,6 +177,10 @@ pmcstat_image_link(struct pmcstat_process *pp, struct pmcstat_image *image,
{
struct pmcstat_pcmap *pcm, *pcmnew;
uintfptr_t offset;
#ifdef __powerpc__
unsigned long kernbase;
size_t kernbase_len;
#endif
assert(image->pi_type != PMCSTAT_IMAGE_UNKNOWN &&
image->pi_type != PMCSTAT_IMAGE_INDETERMINABLE);
@ -183,6 +188,26 @@ pmcstat_image_link(struct pmcstat_process *pp, struct pmcstat_image *image,
if ((pcmnew = malloc(sizeof(*pcmnew))) == NULL)
err(EX_OSERR, "ERROR: Cannot create a map entry");
/*
* PowerPC kernel is of DYN type and it has a base address
* where it is initially loaded, before being relocated.
* As the address in 'start' is where the kernel was relocated to,
* but the symbols always use the original base address, we need to
* subtract it to get the correct offset.
*/
#ifdef __powerpc__
if (pp->pp_pid == -1) {
kernbase = 0;
kernbase_len = sizeof(kernbase);
if (sysctlbyname("kern.base_address", &kernbase, &kernbase_len,
NULL, 0) == -1)
warnx(
"WARNING: Could not retrieve kernel base address");
else
start -= kernbase;
}
#endif
/*
* Adjust the map entry to only cover the text portion
* of the object.